Overview

Programming C++ Gauges

The recommended method of creating gauges is to use the XML based system, refer to the document, Creating XML gauges. However, if the flexibility of this system does not meet your requirements, gauges can be created programmatically using C++. This document describes a number of samples that show how to do this.

Note

Gauges.h has been updated for the release of the ESP SDK. To use the samples and updated header file, C++, rather than C, must be used as the development language. There is also an additional sample that shows how to link an XML gauge with C++ code (see the section Creating a Gauge using XML and C++).

See Also

• SDK Overview
• Creating XML Gauges
• HelpIDs
• Panel Configuration Files
• Tooltips
• Token Variables

Table of Contents

• Sample Code for C++ Gauges
• Tutorial: Creating a C++ Gauge File
• Step 1: Defining Variables and Resources
• Step 2: Setting up the Gauge Header
• Step 3: Simulating System Failures
• Step 4: Using the Gauge Macros
• Step 5: Making the Background Image
• Step 6: Defining Mouse Rectangles
• Step 7: Compiling and Using Your Gauges
• C++ Gauge Reference
• Using Token Variables
• Accessing Token Variables
• Gauge Macros and Drawing Elements
• Shared Data Elements
• Drawing Element Header
• Drawing Element Structures
• Gauge Macros
• Drawing Element Macros
• String Element Macros
• Draw Flags
• Aircraft Special Instrumentation
• Custom Events
• C++ Gauge Function Reference
• Creating a Gauge using XML and C++
• Running the Cabin Comfort sample
• Key steps in creating the Cabin Comfort sample

Sample Code for C++ Gauges

This SDK includes source code for several sample gauges, along with their associated resources. Use these samples to learn how to build gauges and feel free to modify them in creating your own gauges and panels. The following table shows the samples provided and a brief description.

SDKSample.vcproj	Visual Studio project file. Select this to open up the whole project in Visual Studio.
\inc\gauges.h	Contains the variables, macros, and other structures used by the panel and gauge system. You must #INCLUDE this file when building gauges.
\inc\gps_info.h	Header file used with GPS systems.
\C-Gauge Samples\makefile	Used to build the sample code from the command line.
\C-Gauge Samples\SDK.h \C-Gauge Samples\SDK.rc	Define gauge constants, variables, and resources used by the sample gauges code.
\C-Gauge Samples\SDK.cpp	The main source file for the project.
\C-Gauge Samples\SDK.attitude.cpp	Contains the Attitude Indicator source and provides a sprite example.
\C-Gauge Samples\SDK.control_surfaces.cpp	Contains the Control surfaces source and provides a slider example.
\C-Gauge Samples\SDK.fuel.cpp	Contains the Fuel gauge source and provides a needle example.
\C-Gauge Samples\SDK.fuel_selector.cpp	Contains the Fuel Selector source and provides an icon-based example.
\C-Gauge Samples\SDK.temperature.cpp	Contains the Temperature display source and provides a string and icon example.
\C-Gauge Samples\SDK.wiskey.cpp	Contains the Whiskey compass source and provides a moving image example.
\C-Gauge Samples\SDK.FlightMap.cpp	Contains a simple GPS-like gauge and provides an example of implementing “owner draw” gauges.
\C-Gauge Samples\res	Contains the resource bitmaps used with the sample gauges.
\C-Gauge Samples\SDK.FlightInfo.xml	XML Gauge string.

Tutorial: Creating a C++ Gauge File

The goal of the sample is to create a file called SDK.gau. This is a gauge file for use by the panel system. A gauge file is a Windows DLL with the extension .gau, which is loaded by the panel system. A gauge file can contain one or more individual gauges within the panel. The panel system interacts with each gauge using the exported interface defined by the gauge header file (Gauges.h). The interface used by a gauge consists of a list of drawing elements and the exported functions used to manage the gauge. All .gau files reside within the Gauges folder. When compiled, the sample code generates a single SDK.gau containing six different gauges, each illustrating a different type.

Step 1: Defining Variables and Resources

Your gauges will need access to various resources and variables to function properly. The sample code provided with this SDK accomplishes these key definitions in three files (found in the \C-Gauge Samples folder):
SDK.h
SDK.cpp
SDK.rc
Make sure to go through the following sections carefully because they describe what’s happening within each file. Read through the sources as you go through this information as well. ******

SDK.h: Defining Gauge Resources

When you open SDK.h you’ll first see a series of #define directives that set version information as well as some constants within the C++ preprocessor.

#define         VERSION_MAJOR           1
#define         VERSION_MINOR           0
#define         VERSION_BUILD           0
// magic to get the preprocessor to do what we want
#define     lita(arg) #arg
#define     xlita(arg) lita(arg)
#define     cat3(w,x,z) w##.##x##.##z##\000
#define     xcat3(w,x,z) cat3(w,x,z)
#define     VERSION_STRING xlita(xcat3 (VERSION_MAJOR,VERSION_MINOR,VERSION_BUILD))
#ifndef           VS_VERSION_INFO
#define           VS_VERSION_INFO         0x0001

Depending on which C++ compiler you are using, you may need to tweak the preprocessor information somewhat, but otherwise, you won’t need to modify the #define directives. The primary task you’ll need to accomplish inside SDK.h is to define the various resources (bitmaps) used by all the gauges you are building into the target .gau file. The following code fragment defines the constants used for resources (i.e., the resource_id) associated with the Attitude Indicator sample (SDK.attitude.cpp):

// Attitude Bitmaps
//
#define           BMP_ATTITUDE_SMALL_BACKGROUND       0x1000
#define           BMP_ATTITUDE_SMALL_CARD1            0x1100
#define           BMP_ATTITUDE_SMALL_MASK1            0x1101
#define           BMP_ATTITUDE_SMALL_CARD2            0x1200
#define           BMP_ATTITUDE_SMALL_MASK2            0x1201

The actual linking of these constants to specific .bmp files happens in SDK.rc as described later in this document. There are some rules associated with setting these constants:

• You can identify lower-resolution and higher-resolution bitmaps by incrementing the hex value by 500. For example, you could set your defines for two different resolutions as follows:

#define BMP_1024_AIRSPEED_BACKGROUND        1000
#define BMP_1280_AIRSPEED_BACKGROUND        1500

• Bitmaps that you intend to apply as masks over other bitmaps should increment by 1 as in this example.

#define  BMP_ATTITUDE_SMALL_CARD1            0x1100
#define  BMP_ATTITUDE_SMALL_MASK1            0x1101

The sample SDK.h provided defines constant values for all the bitmap resources used by the sample gauge files.

SDK.rc: Associating Resource IDs with .bmp Files

The sample resource file associates the resource_id for all the resources in all the gauges with the corresponding .bmp file. First, note that the SDK.rc file contains an include directive for SDK.h near the top:

#include “sdk.h”

You’ll need to adjust this for whatever you name your gauge header file. Just below this, you’ll find more versioning information, along with a block entitled “StringFileInfo” as shown below:

BEGIN
    BLOCK "StringFileInfo"
    BEGIN
        BLOCK "040904b0"
        BEGIN
            VALUE "CompanyName", "Your Company\0"
            VALUE "FileDescription", "Gauge\0"
            VALUE "FileVersion", VERSION_STRING
            VALUE "LegalCopyright", "Your Copyright.\0"
            VALUE "ProductName", "Your Product\0"
            VALUE "ProductVersion", VERSION_STRING
        END
    END
    BLOCK "VarFileInfo"
    BEGIN
        VALUE "Translation", 0x409, 1200
    END
END

In the string values for “CompanyName”, “FileDescription”, “LegalCopyright”, and “ProductName” replace the placeholder text with information appropriate for you. This information will appear whenever anyone checks the properties for the .gau file you create. The next section is where each resource_id defined in SDK.h gets associated with the appropriate .bmp file:

// Attitude Bitmaps
//
BMP_ATTITUDE_SMALL_BACKGROUND BITMAP      DISCARDABLE       "res\\SDK.Attitude.bg.BMP"
BMP_ATTITUDE_SMALL_CARD1      BITMAP      DISCARDABLE       "res\\SDK.Attitude.card1.BMP"
BMP_ATTITUDE_SMALL_MASK1      BITMAP      DISCARDABLE       "res\\SDK.Attitude.mask1.BMP"
BMP_ATTITUDE_SMALL_CARD2      BITMAP      DISCARDABLE       "res\\SDK.Attitude.card2.BMP"
BMP_ATTITUDE_SMALL_MASK2      BITMAP      DISCARDABLE       "res\\SDK.Attitude.mask2.BMP"

You’ll need to create similar resource_id assignments for all resource files used by your gauges.

SDK.cpp: Naming and Positioning Gauges, Including Source Files, and Exporting Pointers for Gauges

The SDK.cpp file included with this SDK enables you to manage the various gauges from a single file while still separating the individual gauge source files for easier maintenance. You don’t necessarily have to create a corresponding SDK.cpp file for your gauges, but there are some specific things you need to do within your gauge code as explained below. First, notice that SDK.cpp has #include statements for both Gauges.h and SDK.h. Make sure you include Gauges.h and SDK.h in your gauge code as well. SDK.cpp then breaks out into sections for each individual gauge, finishing up with a series of gauge table entries. Each individual gauge section contains the following coding:

/////////////////////////////////////////////////////////////////////////////
// Attitude
/////////////////////////////////////////////////////////////////////////////
#define           GAUGE_NAME        "Attitude"
#define           GAUGEHDR_VAR_NAME gaugehdr_attitude
#define           GAUGE_W                 100

#include "SDK.Attitude.cpp"
/////////////////////////////////////////////////////////////////////////////
// Control Surfaces
/////////////////////////////////////////////////////////////////////////////
#define           GAUGE_NAME        "Control_Surfaces"
#define           GAUGEHDR_VAR_NAME gaugehdr_control_surfaces
#define           GAUGE_W                 100

#include "SDK.Control_Surfaces.cpp"
/////////////////////////////////////////////////////////////////////////////
// Fuel
/////////////////////////////////////////////////////////////////////////////
#define           GAUGE_NAME        "Fuel"
#define           GAUGEHDR_VAR_NAME gaugehdr_fuel
#define           GAUGE_W                 100

#include "SDK.Fuel.cpp"

This code is then repeated for the remaining gauges. Here’s what’s happening with each assignment: GAUGE_NAME is assigned the string that becomes the gauge’s name. This gauge name is used in the Panel.cfg file under the [windowXX] section where each gauge is defined. For the fragment above, panel.cfg would identify these gauges as:

gauge00=SDK!Attitude, 247, 58
gauge01=SDK!Control_Surfaces, 370, 160
gauge02=SDK!Fuel, 146, 57

GAUGEHDR_VAR_NAME is assigned the gauge name used by the Gauge Table (the module’s export table). The Gauge Table gets defined at the end of SDK.cpp. GAUGE_W is assigned a value for the number of X-axis design units used by the gauge. Note that the units used by the gauge correspond to the units used by the panel background. For example, if your panel is 1000 units and a gauge is 100 units, then that gauge will be 1/10 the size of the panel. (You can override this ratio in the Panel.cfg file.)

#include “SDK_xxx.cpp” simply includes the specific gauge code file for each gauge in the compilation.

This code repeats for each gauge within SDK.cpp. Accordingly, each of the gauge code files (SDK_xxx.cpp) ends with #undef for GAUGE_NAME, GAUGEHDR_VAR_NAME, and GAUGE_W so they’re ready to reset with new values for the next gauge.

Finally, at the end of SDK.cpp, the Gauge Table assignments are made. The Gauge Table in the sample file looks like this:

/////////////////////////////////////////////////////////////////////////////
// Gauge table entries
/////////////////////////////////////////////////////////////////////////////
GAUGE_TABLE_BEGIN()
      GAUGE_TABLE_ENTRY(&gaugehdr_attitude)
      GAUGE_TABLE_ENTRY(&gaugehdr_control_surfaces)
      GAUGE_TABLE_ENTRY(&gaugehdr_fuel)
      GAUGE_TABLE_ENTRY(&gaugehdr_fuel_selector)
      GAUGE_TABLE_ENTRY(&gaugehdr_temperature)
      GAUGE_TABLE_ENTRY(&gaugehdr_wiskey)
      GAUGE_TABLE_ENTRY(&gaugehdr;_flightmap) 
GAUGE_TABLE_END()

You’ll need a GAUGE_TABLE_ENTRY for each gauge identified by GAUGEHDR_VAR_NAME, so the gauge table can export a pointer. These names must match as shown in the sample code.

The Sample Gauges

Now that we’ve covered some of the basic constant and variable assignments for gauges, we’ll move on to code for the sample gauges. This SDK includes sample code for the following gauges.

SDK.Attitude.cpp	Attitude indicator, sprite example.
SDK.Control_surfaces.cpp	Control Surfaces, slider example.
SDK.FlightMap.cpp	Simple GPS-like gauge, example of implementing  “owner draw” gauges.
SDK.Fuel.cpp	Fuel gauge, needle example.
SDK.Fuel_selector.cpp	Fuel Selector, icon example.
SDK.Temperature.cpp	Temperature gauge, string and icon examples.
SDK.Whiskey.cpp	Whiskey Compass, moving image example.

All of these files contain static image examples. The following sections describe the basic calls made within a gauge source file, pointing out the individual distinctions for each gauge type.

Step 2: Setting up the Gauge Header

At the beginning of each sample gauge source file, you’ll see a code fragment like this:

//    Set up gauge header

char attitude_gauge_name[]    = GAUGE_NAME;
extern PELEMENT_HEADER        attitude_list;
extern MOUSERECT        attitude_mouse_rect[];

First, the code assigns values for the following variables used by the gauge header:

PELEMENT_HEADER	Identifies which gauge macro forms the background
MOUSERECT	Identifies mouse rectangle

Then the code fills in values for GAUGE_HEADER_FS700, the gauge header macro. The gauge header is a structure that defines the interface used by the panel system to control the gauge DLL. You must export the gauge header to expose the gauge interface to the panel system.

GAUGE_HEADER_FS700

Use the GAUGE_HEADER_FS700 macro to create and export the gauge header (GAUGEHDR). The GAUGE_HEADER_FS700 macro creates GAUGEHDR, filling in the unique members of the GAUGEHDR structure (see the full definition of this structure in gauges.h).

The following example shows how to use the GAUGE_HEADER_FS700 macro in code:

GAUGE_HEADER_FS700(GAUGE_W, attitude_gauge_name, &attitude_list, attitude_mouse_rect, 0, 0, 0, 0);

Here’s the syntax for the GAUGE_HEADER_FS700 macro:

#define GAUGE_HEADER_FS700(default_size_mm, gauge_name, element_list, pmouse_rect, pgauge_callback, user_data, parameters, usage)

The GAUGE_HEADER_FS700 macro has these members:

default_size_mm	The default X axis size of the gauge in design units. This value is set as GAUGE_W in SDK.cpp.
gauge_name	The name of the gauge as defined in SDK.cpp as GAUGE_NAME.
element_list	A pointer to the first drawing element in the list of elements.
pmouse_rect	A pointer to the mouse rectangle drawn over the gauge.
pgauge_callback	A pointer to a function for the entire gauge. This will pass a message to the system. Use 0 if none.
user_data	A 32-bit space you can use for any data you want. Use 0 if none.
parameters	A field that contains a string. A pointer to this string is placed in the gauge header for use in the gauge callback function (or wherever might be appropriate). Use 0 if none.
usage	Not used. Use 0.

The GAUGE_HEADER_FS700 macro creates the GAUGEHDR structure and an exported variable, gauge_header. The panel system uses the gauge_header variable to initialize each of the drawing elements. Most of the Panel API functions use gauge_header as one parameter to be passed. You will use this variable often.

Step 3: Simulating System Failures

Several types of aircraft system failures can be simulated. Almost all of the sample gauge source files contain code that illustrates how to set up a simulated system failure.

FAILURE_RECORD

You’ll use the FAILURE_RECORD structure to identify the systems that—should they fail—would need to be reflected by the gauge. The structure inside Gauges.h looks like this:

typedef     struct      FAILURE_RECORD
{
      FAILURE_KEY       key;
      FAILURE_ACTION    action;
      PVOID             reserved;
}
FAILURE_RECORD, *PFAILURE_RECORD, **PPFAILURE_RECORD;

The following code illustrates how you can build FAILURE_RECORD for a Fuel gauge:

FAILURE_RECORD    fuel_fail[] =
{
      {FAIL_SYSTEM_ELECTRICAL_PANELS,   FAIL_ACTION_ZERO},
      {FAIL_GAUGE_FUEL_INDICATORS,      FAIL_ACTION_FREEZE},
      {FAIL_NONE,                       FAIL_ACTION_NONE}
}

This code creates a FAILURE_RECORD called fuel_fail. Each FAILURE_KEY enum value identifies the system undergoing failure; its associated FAILURE_ACTION identifies what happens in the event of that failure. The final FAILURE_KEY and FAILURE_ACTION pair is always FAIL_NONE, FAIL_ACTION_NONE. The failure record can contain any number of failure keys and actions.

FAILURE_KEY

System failures are listed in the FAILURE_KEY enum values defined in gauges.h, and described below:

FAIL_NONE	Marks the end of a failure record.
OLD_FAIL_SYSTEM_ ELECTRICAL	Is obsolete. Don’t use it in new gauges; use FAIL_SYSTEM_ELECTRICAL_PANELS instead.
FAIL_SYSTEM_ENGINE	Specifies an engine system failure.
FAIL_SYSTEM_PITOT_STATIC	Specifies a pitot-static system failure.
FAIL_SYSTEM_VACUUM	Specifies a vacuum system failure.
FAIL_GAUGE_ADF	Specifies an ADF gauge system failure.
FAIL_GAUGE_AIRSPEED	Specifies an airspeed gauge system failure.
FAIL_GAUGE_ALTIMETER	Specifies an altimeter gauge system failure.
FAIL_GAUGE_ATTITUDE	Specifies an attitude gauge system failure.
FAIL_GAUGE_COMMUNICATIONS	Specifies a COM1 communication gauge system failure.
FAIL_GAUGE_FUEL_INDICATORS	Specifies a fuel indicators gauge system failure.
FAIL_GAUGE_GYRO_HEADING	Specifies a gyro heading gauge system failure.
FAIL_GAUGE_MAGNETIC_COMPASS	Specifies a magnetic compass gauge system failure.
FAIL_GAUGE_NAVIGATION_VOR1	Specifies a navigation VOR1 gauge system failure.
FAIL_GAUGE_NAVIGATION_VOR2	Specifies a navigation VOR2 gauge system failure.
FAIL_GAUGE_ TRANSPONDER	Specifies a transponder gauge system failure.
FAIL_GAUGE_TURN_COORDINATOR	Specifies a turn coordinator gauge system failure.
FAIL_GAUGE_VERTICAL_SPEED	Specifies a vertical speed indicator gauge system failure.
FAIL_SYSTEM_ELECTRICAL_PANELS	Specifies a failure of the electrical panel.
FAIL_SYSTEM_ELECTRICAL_AVIONICS	Specifies a failure of the electrical avionics.
FAIL_GAUGE_COMMUNICATIONS_COM2	Specifies a COM2 communication gauge system failure.

FAILURE_ACTION

You can set up a gauge element to react to one or more of the system failures shown in the FAILURE_RECORD by using one of the defined FAILURE_ACTION enum values:

FAIL_ACTION_NONE = 0	Takes no action. This type of failure record is typically used as the background static image for covering a gauge.
FAIL_ACTION_FREEZE	Freezes the gauge element at its last updated position. The element’s MODULE_VAR variable(s) will not be updated. (MODULE_VAR relates to the various gauge token variables accessible to the panel system from the simulation engine. See the section on Token Variables for more information.)
FAIL_ACTION_ZERO	Sets the element MODULE_VAR variable(s) to 0.
FAIL_ACTION_NO_DRAW	Erases the element and doesn't draw it again.

Step 4: Using the Gauge Macros

Moving a little further down in the sources for the various sample gauges, you’ll see different macros being used to pass parameters between the gauge and the panel system. These macros are defined in Gauges.h, and you can use them to create various types of gauges. Let’s continue through the code to where macros first start appearing—we’ll look specifically at the sliders example and then cover all the gauge macros in detail later on.

Sliders Example

The SDK.control_surfaces.cpp example shows how to build a gauge using sliders that move over a static image in the background. The code that follows uses the bitmaps listed in the table below as resources:

	SDK.Control_Surfaces.Ailerons.BMP	A slider (down pointer).
	SDK.Control_Surfaces.Elevator.BMP	A slider (left pointer).
	SDK.Control_Surfaces.Rudder.BMP	A slider (up pointer).
	SDK.Control_Surfaces.Trim.BMP	A slider (right pointer).

To create a slider use the MAKE_SLIDER macro:

#define     MAKE_SLIDER(      NAME,                         \
                              RES_ID,                       \
                              NEXT_LIST,                    \
                              FAILURE,                      \
                              DRAW_FLAGS,                   \
                              ASI_FLAGS,                    \
                              POSITION_X, POSITION_Y,       \
                              SOURCE_VAR_X, CALLBACK_X, SCALE_X,  \
                              SOURCE_VAR_Y, CALLBACK_Y, SCALE_Y )

Fill the structure out with slider-specific information, such as the following from SDK.Control_Surfaces.cpp:

MAKE_SLIDER
(
      cs_slider_trim,
      BMP_CS_SMALL_TRIM,
      NULL,
      0,
      IMAGE_USE_ERASE | IMAGE_USE_TRANSPARENCY,
      0,
      20,44,
      MODULE_VAR_NONE, NULL, 0,
      ELEVATOR_TRIM, NULL, -100
)

Refer to the MAKE_SLIDER macro for an explanation of each of these properties. The code in SDK.control_surfaces.cpp contains four separate MAKE_SLIDER macros, one for each of the different sliders used.

PELEMENT_HEADER

After the final MAKE_SLIDER macro has been defined, you’ll see the following code:

PELEMENT_HEADER         cs_sliders_list[] =
{
      &cs_slider_trim.header,
      &cs_slider_ailerons.header,
      &cs_slider_elevator.header,
      &cs_slider_rudder.header,
      NULL
};

This PELEMENT_HEADER code signals the end of the series of macros and sets the order in which these different parts of the gauge appear. The display order goes from top to bottom. This works very well here since the various sliders do not overlap one another. Note that every macro you define must have an associated PELEMENT_HEADER somewhere, and it must end with a NULL. The specific code fragment above sets the order for all sliders simultaneously. In cases where sliders or other resources overlap, you could instead break these out separately. For example:

MAKE_SLIDER
(
       cs_slider_ailerons,
       BMP_CS_SMALL_AILERONS,
       NULL,
       0,
       IMAGE_USE_ERASE | IMAGE_USE_TRANSPARENCY,
       0,
       95, 6,        AILERON_DEFLECTION, NULL, 100,
       MODULE_VAR_NONE, NULL, 0
)

PELEMENT_HEADER            cs_sliders_list1[] =
{
       &cs_slider_ailerons.header,
       NULL
};    \\ END OF FIRST SLIDER MACRO
 

MAKE_SLIDER(
       cs_slider_elevator,
       BMP_CS_SMALL_ELEVATOR,
       &cs_sliders_list1,
       0,
       IMAGE_USE_ERASE | IMAGE_USE_TRANSPARENCY,
       0,
       98, 46,
       MODULE_VAR_NONE, NULL, 0,
       ELEVATOR_DEFLECTION, NULL, -70
)

PELEMENT_HEADER            cs_sliders_list2[] =
{
       &cs_slider_elevator.header,
       NULL
};    \\ END OF SECOND SLIDER MACRO

MAKE_SLIDER
(
       cs_slider_rudder,
       BMP_CS_SMALL_RUDDER,
       &cs_sliders_list2,
       0,
       IMAGE_USE_ERASE | IMAGE_USE_TRANSPARENCY,
       0,
       94, 83,
       RUDDER_DEFLECTION, NULL, 80,
       MODULE_VAR_NONE, NULL, 0
)

PELEMENT_HEADER            cs_sliders_list3[] =
{
       &cs_slider_rudder.header,
       NULL
};     \\ END OF THIRD SLIDER MACRO

Note that the NEXT LIST parameter for the second slider references &cs_sliders_list1, &cs_sliders_list2, and so forth, indicating the links between each MAKE_SLIDER instance.

Step 5: Making the Background Image

To set the background image for the gauge, use the MAKE_STATIC macro. You will always use this macro with every gauge you create. First, here’s the background resource used by Control_surfaces.cpp:

	SDK.Control_Surfaces.bg.BMP	A static background against which the sliders will move up/down/left/right.

You’ll create the static background image with the MAKE_STATIC macro. As an example, here’s the macro structure from Gauges.h:

#define     MAKE_STATIC(      NAME,                   \
                              RES_ID,                 \
                              NEXT_LIST,              \
                              FAILURE,                \
                              DRAW_FLAGS,             \
                              ASI_FLAGS,              \
                              POSITION_X, POSITION_Y )\

And here’s the code fragment from Control_surfaces.cpp that uses MAKE_STATIC:

MAKE_STATIC
(
      cs_background,
      BMP_CS_SMALL_BACKGROUND,
      &cs_sliders_list,
      NULL,
      IMAGE_USE_TRANSPARENCY,
      0,
      0,0
)
PELEMENT_HEADER         cs_list     = &cs_background.header;

PELEMENT_HEADER         cs_list     = &cs_background.header;

Refer to the MAKE_STATIC reference for descriptions of each field.

Finally, the PELEMENT_HEADER for the macro gets set to identify this image as the gauge background:

PELEMENT_HEADER         cs_list     = &cs_background.header;

If you look back near the top of the code, you’ll see:

EXTERN PELEMENT_HEADER cs_list;

Here, the initial assignment of cs_list identifies this specific macro with the background image for the gauge. We’re pretty much nearing the end of our sample code inside the Control_surfaces.cpp file. Let’s wrap up with a discussion of how to tell the mouse the gauge exists.

Step 6: Defining Mouse Rectangles

By using mouse rectangles, you can specify how a gauge will interact with the mouse pointer (i.e., mouse movement and mouse button clicks). For example, you can change the cursor or display a ToolTip as the mouse enters the area you've defined as a mouse rectangle; you can also trigger a simulation event or execute a callback function. Note that the mouse rectangle you define is specific to the gauge itself—it works off the gauge coordinates, not the panel background coordinates. This allows you to move the gauge around the panel, while keeping the mouse rectangle intact.

To define a mouse rectangle, you use a combination of the mouse definition macros, as shown in the following code example from the SDK.control_surfaces.cpp file:

MOUSE_BEGIN( cs_mouse_rect, HELP_NONE, 0, 0 )
  MOUSE_PARENT( 0,0,44,94, HELPID_GAUGE_PITCH_TRIM) 
  MOUSE_PARENT( 60,0,76,16, HELPID_GAUGE_ROLL_TRIM) 
  MOUSE_PARENT( 82,16,32,62, HELPID_GAUGE_PITCH_TRIM) 
  MOUSE_PARENT( 60,78,76,16, HELPID_GAUGE_YAW_TRIM) 
MOUSE_END

MOUSE_BEGIN, MOUSE_PARENT, and MOUSE_END are all macros you can use when defining mouse rectangles. You should look inside the Gauges.h file to get a detailed understanding of how these macros are defined. MOUSE_BEGIN uses the following parameters.

name	Contains the name of the MOUSERECT you’ve assigned to the rectangle.
helpid	Contains the Help ID of the ToolTip message you want to appear when a mouse cursor enters the rectangle. For foreign versions, the Help IDs point to localized strings. There is currently no way to add more ToolTip ID’s.
x, y	Specifies the upper-left corner of the rectangle. For MOUSE_BEGIN, this value will always be 0, 0.

MOUSE_END ends the definition of the rectangle. You can also create rectangles within rectangles by using the capabilities of MOUSE_PARENT_* and MOUSE_CHILD_*.

Rectangles within Rectangles

You can also define sub-rectangles within the gauge rectangle using the MOUSE_PARENT and MOUSE_PARENT_BEGIN macros. Both of these macros use the following parameters.

x, y	Specifies the X and Y position from the 0,0 position of the gauge.
w, h	Specifies the width and height of the rectangle.
Help ID	Specifies theHelp ID of the ToolTip text to display for the rectangle. For foreign versions, the Help IDs point to localized strings. There is currently no way to add more ToolTip IDs.

The only difference between MOUSE_PARENT and MOUSE_PARENT_BEGIN is that MOUSE_PARENT includes both MOUSE_PARENT_BEGIN and MOUSE_PARENT_END.

Generating Events

The MOUSE_CHILD_EVENT macro defines a sub-rectangle of the rectangle created by MOUSE_PARENT_BEGIN. Using this macro, you can generate panel system events (such as KEY_SMOKE_TOGGLE, which toggles the smoke system ON/OFF) from a mouse rectangle. This macro uses the following syntax:

MOUSE_CHILD_EVENT(x, y, w, h, cursor, mouse_flags, event_id)

MOUSE_CHILD_EVENT uses the following parameters.

x, y	Specifies the upper-left corner of the rectangle.
w, h	Specifies the width and height of rectangle.
Cursor	Specifies the cursor shown when the mouse is in the mouse rectangle. This parameter can be set to one of the following: CURSOR_NONE CURSOR_NORMAL CURSOR_UPARROW CURSOR_DOWNARROW CURSOR_LEFTARROW CURSOR_RIGHTARROW CURSOR_HAND CURSOR_CROSSHAIR CURSOR_GRAB
mouse_flags	Specifies under what conditions the event will be generated. It can be set to one of the following values: MOUSE_NONE MOUSE_RIGHTSINGLE MOUSE_MIDDLESINGLE MOUSE_LEFTSINGLE MOUSE_RIGHTDOUBLE MOUSE_MIDDLEDOUBLE MOUSE_LEFTDOUBLE MOUSE_RIGHTDRAG MOUSE_MIDDLEDRAG MOUSE_LEFTDRAG MOUSE_MOVE MOUSE_DOWN_REPEAT MOUSE_RIGHTRELEASE MOUSE_MIDDLERELEASE MOUSE_LEFTRELEASE MOUSE_WHEEL_FLIP (reverse direction of mouse wheel) MOUSE_WHEEL_SKIP MOUSE_WHEEL_UP MOUSE_WHEEL_DOWN MOUSE_MOVE_REPEAT MOUSE_LEAVE MOUSE_GETALL MOUSE_LEFTALL (equivalent to MOUSE_LEFTSINGLE | MOUSE_LEFTDRAG | MOUSE_LEFT_RELEASE) MOUSE_RIGHTALL (equivalent to MOUSE_RIGHTSINGLE | MOUSE_RIGHTDRAG | MOUSE_RIGHT_RELEASE) MOUSE_MIDDLEALL (equivalent to MOUSE_MIDDLESINGLE | MOUSE_MIDDLEDRAG | MOUSE_MIDDLE_RELEASE) MOUSE_WHEEL (equivalent to MOUSE_WHEEL_DOWN | MOUSE_WHEEL_UP )
event_id	Specifies the simulation event to be sent by the mouse event. For a complete list of events, see the associated file EventIDs documentation.

The following is an example of mouse rectangle setup code that generates the KEY_FLAPS_DECR and KEY_FLAPS_INCR events:

MOUSE_BEGIN(mouse_rect, HELPID_B737_FLAPS, 0, 0) 
MOUSE_CHILD_EVENT(0,0,44,85, CURSOR_DOWNARROW, MOUSE_LEFTSINGLE, KEY_FLAPS_DECR) 
MOUSE_CHILD_EVENT(44,0,44,85, CURSOR_UPARROW, MOUSE_LEFTSINGLE, KEY_FLAPS_INCR) 
MOUSE_END

Using Callback Functions

You can use the MOUSE_CHILD_FUNCT macro to specify a callback function when an event specified by the mouse_flags parameter is triggered. You will need to define the callback function with the mouse_child_funct function. The trigger_key_event and panel_window_toggle functions are often used in the mouse event callback functions. For information on all the functions available, refer to the C++ Gauges Function Reference section. The syntax for MOUSE_CHILD_FUNCT is as follows:

MOUSE_CHILD_FUNCT(x, y, w, h, cursor, mouse_flags, function)

MOUSE_CHILD_FUNCT uses the following parameters:

x, y	Specifies the upper-left corner of the rectangle.
w, h	Specifies the width and height of the rectangle.
cursor	Specifies the type of cursor that is shown when the mouse is in the mouse rectangle.
mouse_flags	Specifies under what mouse conditions the callback function will be executed.
function	Specifies the callback function executed by the mouse event. You must define this function using mouse_child_funct.

Here’s a code snippet showing how you would use the MOUSE_CHILD_FUNCT macro to designate a callback function:

MOUSE_TOOLTIP_ARGS (GPS_Args)
      MOUSE_TOOLTIP_ARG (MODULE_VAR_NONE, 0, NULL, NULL, NULL, GPSARG_Get_GroundSpeed, NULL, NULL)
      MOUSE_TOOLTIP_ARG (MODULE_VAR_NONE, 0, NULL, NULL, NULL, GPSARG_Get_Track, NULL, NULL)
      MOUSE_TOOLTIP_ARG (MODULE_VAR_NONE, 0, NULL, NULL, NULL, NULL, NULL, GPSARG_Get_WP_ID)
      MOUSE_TOOLTIP_ARG (MODULE_VAR_NONE, 0, NULL, NULL, NULL, GPSARG_Get_WP_Distance, NULL, NULL)
MOUSE_TOOLTIP_ARGS_END

Creating Dynamic Mouse ToolTips

The SDK.FlightMap.cpp file contains the following code example of how you can use dynamic ToolTips (that is, ToolTips where the text changes depending on the state of the gauge):

MOUSE_TOOLTIP_TEXT_STRING ("Ground Speed: %1!d! knots, Track: %2!d!°, Next Waypoint: %3!s!, Distance: %4!.1f! nm", GPS_Args)

The first argument in MOUSE_TOOLTIP_TEXT_STRING above is the ToolTip text. Note that changeable parts of the ToolTip text are specified by constructs such as “%1!d!”. These constructs always start with a percent sign (“%”), followed by the argument number (in the arguments array, GPS_Args). The argument number starts at 1 and increases sequentially. This argument number is followed by a formatting argument. The formatting argument is placed between exclamation marks (“!”), for example, !d!. This formatting argument is similar to the arguments of the printf function (from the C Standard Library), where “d” (in the formatting argument) prints an integer and “f” (in printf) prints a floating point number. GPS_Args, in the code example above, is the name of the argument’s array. The code below, taken from the sample file, illustrates how this array is defined.

MOUSE_TOOLTIP_ARGS (GPS_Args)
      MOUSE_TOOLTIP_ARG (MODULE_VAR_NONE, 0, NULL, NULL, NULL, GPSARG_Get_GroundSpeed, NULL, NULL)
      MOUSE_TOOLTIP_ARG (MODULE_VAR_NONE, 0, NULL, NULL, NULL, GPSARG_Get_Track, NULL, NULL)
      MOUSE_TOOLTIP_ARG (MODULE_VAR_NONE, 0, NULL, NULL, NULL, NULL, NULL, GPSARG_Get_WP_ID)
      MOUSE_TOOLTIP_ARG (MODULE_VAR_NONE, 0, NULL, NULL, NULL, GPSARG_Get_WP_Distance, NULL, NULL)
MOUSE_TOOLTIP_ARGS_END

Arguments in the MOUSE_TOOLTIP_ARG macro follow this order:

• First, the MODULE_VAR enum, which defines a module variable from which to get the value.
• Second, a scaling number which can be applied to the value of the module variable.
• Next, pointers to three different lookup tables. If you don’t want to use them, just use NULL pointers. The three tables are for numbers, ids and strings.
• Finally, the pointers to three callback functions, to use with numbers, ids and strings, respectively.

All functions have the same argument but have a return result of different types. The arguments are:

• The numeric value of the module variable after scaling and lookup in the numeric lookup table.
• The id, which is the value from the id lookup table.
• A string pointer, from the string lookup table.
• The pointer to the MODULE_VAR structure initialized to the first argument of the MOUSE_TOOLTIP_ARG macro.
• The pointer to the gauge header.

These functions can return: a numeric value, used together with numeric formats “d” or “f”; the id value used as a HELPID enum; or a string value used with “s” format. For details, see the SDK.FlightMap.cpp example.

Step 7: Compiling and Using Your Gauges

Once you’ve finished defining the mouse rectangles for your gauges, you can compile the files and start the process of testing, debugging, and rebuilding—until you wind up with gauges you’re happy with. You can create gauges using the Visual C++ compiler, version 4.0 or later. The process used for compiling gauges with other compilers should be similar. To compile and view your new gauges, complete these steps:

• If you are using Visual Studio, load and run the SDKSample project. This will create a file sdk.dll. Rename this sdk.gau. If you are using the command line, change to the sample directory (\sample) and type nmake. This will build the Sdk.gau file.
• Copy Sdk.gau to the root \ESP\Gauges directory.
• Make sure you have the Panel.cfg file properly set up with the gauges positioned where you want them.
• Make sure you have your aircraft container system properly configured (pointing to the right .air file, panel folder, and so on).
• Start ESP, load your aircraft, and check out your new panel.

C++ Gauge Reference

• Using Token Variables
• Accessing Token Variables
• Gauge Macros and Drawing Elements
• Shared Data Elements
• Drawing Element Header
• Drawing Element Structures
• Gauge Macro Reference

Using Token Variables

Gauges have access to information about the simulation state. You can access state information through a set of token variables. The state information provided to the token variables depends on the aircraft’s .air file. Each .air file provides access to different token variables. For example, the Cessna 182 provides access to GROUND_ALTITUDE, as does every other aircraft. The Cessna 182, however, doesn’t provide access to the TURB_ENGINE_1_VIBRATION variable because the Cessna 182’s .air file specifies that this aircraft has a reciprocating engine, not a turbine engine. Therefore, it’s important to make sure that the .air file you’re using for your aircraft and gauges supports the token variables those gauges require.

UNIVERSAL_VAR Types

Each token variable returns a specific type of data. The following structure shows how the UNIVERSAL_VAR variable is defined and the types that could be returned:

typedef union UNIVERSAL_VAR {
    FLOAT64 n; // any number.
    BOOL b; // any boolean
    ENUM e; // any enumerated value
    FLAGS f;// any flags field
    PVOID p;// any pointer
    VAR32 d;// any binary coded decimal
    VAR32 o;// any binary coded octal
} UNIVERSAL_VAR, *PUNIVERSAL_VAR, **PPUNIVERSAL_VAR;

The table in the Token Variables document lists the module variable name and specifies which UNIVERSAL_VAR union member to use with each variable.

Accessing Token Variables

You can access token variables in three ways:

1. From various Gauge macros as described earlier.
2. Through drawing elements. In the element structure, you can specify which variable controls the element. For example, you may have a needle (ELEMENT_NEEDLE) that is controlled by the variable VERTICAL_SPEED. As the needle is updated, it will refer to the variable VERTICAL_SPEED to determine the angle at which it will be displayed. For details, see the section Gauge Macros and Drawing Elements.
3. Through the Panel API, using the following procedure:

To access a tokenized variable through the Panel API

• Instantiate a MODULE_VAR variable initializing the GAUGE_TOKEN ID structure member. You can set the ID to one of the token variables provided in the Token Variables document. For example:

  typedef struct MODULE_VAR
  {
  GAUGE_TOKEN id;
  PVOID var_ptr;
  VAR_TYPE var_type;
  UNIVERSAL_VAR var_value;
  UNIVERSAL_VAR var_old;
  } MODULE_VAR, *PMODULE_VAR, **PPMODULE_VAR;
  

• To update the contents of the variable from state information, use lookup_var:

   lookup_var(PMODULE_VAR module_var )

After the lookup_var function is called, the value of a MODULE_VAR variable is stored in the var_value member of the structure.
Important: Token variables are read-only. Any attempt to set these variables through the var_ptr variable may result in unpredictable behavior. The following code example shows how the MODULE_VAR variable is used. Note that this is a callback function and, in this specific example, it is for a sprite element.

MODULE_VAR  attitude_bank     = { ATTITUDE_INDICATOR_BANK_DEGREES };

FLOAT64     flight_director_bank_cb( PELEMENT_SPRITE pelement )
{
      lookup_var(&attitude_bank);

      // Offset by attitude card's bank
      return attitude_bank.var_value.n - pelement->source_var_0.var_value.n;
} 

Gauge Macros and Drawing Elements

Each of the Gauge macros makes use of the drawing elements available. These drawing elements are part of the macro definition in Gauges.h. Here is each macro and its associated element.

MAKE_STATIC	ELEMENT_STATIC_IMAGE
MAKE_NEEDLE	ELEMENT_NEEDLE
MAKE_STRING	ELEMENT_STRING
MAKE_SLIDER	ELEMENT_SLIDER
MAKE_ICON	ELEMENT_ICON
MAKE_MOVING	ELEMENT_MOVING_IMAGE
MAKE_SPRITE	ELEMENT_SPRITE

Shared Data Elements

Each macro has twelve shared data elements, which aren't included in the declaration of each structure. Instead, a #define HEADER is present that, when expanded, produces the twelve data members. The following code examples show the drawing element ELEMENT_NEEDLE before and after expansion. Before expansion:

typedef struct ELEMENT_NEEDLE 
{ 
    HEADER; 
    'Needle-specific data members 
};

After expansion:

typedef struct ELEMENT_NEEDLE 
{ 
    ELEMENT_TYPE_ENUM element_type; 
    ID resource_id; 
    PIXPOINT position; 
    PIXPOINT previous_position; 
    PIXPOINT ofs; 
    PGAUGEHDR gauge_header; 
    struct ELEMENT_HEADER previous_element; 
    struct ELEMENT_HEADER next_element; 
    PFAILURE_RECORD failure_systems; 
    FLAGS image_flags; 
    FLAGS aircraft_special_instrumentation; 
    FLAGS reserved; 
    'Needle-specific data members. 
};

Drawing Element Header

The first twelve data members are the same for all the drawing element structures. The data members are described in the following table.

element_type	Specifies the element type. Set this member to be one of the following elements: ELEMENT_TYPE_STATIC_IMAGE ELEMENT_TYPE_NEEDLE ELEMENT_TYPE_STRING ELEMENT_TYPE_SLIDER ELEMENT_TYPE_ICON ELEMENT_TYPE_MOVING_IMAGE ELEMENT_TYPE_SPRITE
resource_id	Specifies the resource ID of an 8-bit or 24-bit bitmap resource. All element types, with the exception of ELEMENT_STRING (which ignores this value), use this value.
position	Specifies the point that the drawing element pivots around. This value is used by ELEMENT_NEEDLE and ELEMENT_SPRITE and ignored by the other elements.
previous_position	Specifies the previous position of the element relative to the gauge position. Used by the panel system. This value is ignored during initialization.
ofs	Specifies an offset (pivot point) for an element to rotate around. This value is used by ELEMENT_NEEDLE and ELEMENT_SPRITE and ignored by the other elements.
gauge_header	Points to the gauge header file.
previous_element	Points to the previous element. This value is set by the panel system. This value is ignored during initialization.
next_element	Points to a list of graphical elements. The elements are drawn after the current element. This value is used to determine the drawing order of all the elements in your gauge.
failure_systems	Points to a FAILURE_RECORD list. This list defines how an element will react during simulated aircraft system failure.
image_flags	Specifies how the element image will be rendered, with one or more DRAW_FLAGS.
aircraft_special_instrumentation	Specifies the Aircraft Special Instrumentation flags.
reserved	This value is reserved and must be set to 0.

Drawing Element Structures

Each drawing element structure has one or more MODULE_VAR members. You can initialize these members to one of the token variable values. Call the function element_install or element_list_install to initialize the MODULE_VAR element(s). The element_update or element_list_update function can be used to update the contents of the MODULE_VAR. The elements themselves use the MODULE_VAR information at render time to determine in what state they'll be rendered.

Graphical elements can use the MODULE_VAR structure member to determine the state in which the element will be rendered. Sometimes, however, MODULE_VAR may not be a useful value. You can get around this problem by using callbacks. For each of the MODULE_VAR structures listed in the element structure, you can set an associated PMODULE_VAR_CB pointer. The pointer points to a callback function that you can use to set the variable to a useful value. The callback function is called by the panel system after the variable has been updated from the simulation state information. The callback function is generally used to normalize or scale the MODULE_VAR value into a valid range. You can also use the callback function to convert enumerated values, interpret a flag's variable, and so on. For example, the following code uses a callback routine to clip the airspeed to a useful range that can be used by the airspeed gauge. All elements use the same style callback routine in which the argument to the function acts as a pointer to that element.

FLOAT64 convert_var_aspeed(PMODULE_VAR var) 
{ 
    if (var->var_value.n > GAUGE_MAX_AIRSPEED) 
    var->var_value.n = GAUGE_MAX_AIRSPEED; 
    if (var->var_value.n < 60) 
    var->var_value.n = 60; 
    return var->var_value.n; 
}

You can set any callback pointer to NULL so that no call will occur. Any assignments to the MODULE_VAR in a callback routine are discarded. The final value set in MODULE_VAR is the return value of the callback function.

Drawing Element Lists

In code, the drawing elements are organized (using the next_element data member) in a tree structure (the element list). This element list defines the drawing order of the gauge elements:

• The first element in the list in the gauge header is drawn first.
• Each subsequent element in the list is drawn in the order it appears in the list.
• Before drawing the next element in the list, the current element’s element-list pointer is examined. If the pointer is not NULL, the element’s element list is drawn using the same logic.

You don't need to set the previous_element pointer. This pointer is initialized by the panel system when the gauge is initialized.

Gauge Macros

This section describes each of the following gauge macros:

• MAKE_STATIC
• MAKE_NEEDLE
• MAKE_STRING
• MAKE_SLIDER
• MAKE_MOVING
• MAKE_ICON
• MAKE_SPRITE
• Drawing Element Macros
• String Element Macros
• Draw Flags
• Aircraft Specific Information Flags

MAKE_STATIC

The MAKE_STATIC macro draws the simplest type of graphical element. Use MAKE_STATIC to draw an image that never changes.
Here’s the macro structure from Gauges.h:

#define     MAKE_STATIC(      NAME,                   \
                              RES_ID,                 \
                              NEXT_LIST,              \
                              FAILURE,                \
                              DRAW_FLAGS,             \
                              ASI_FLAGS,              \
                              POSITION_X, POSITION_Y )\

And here’s the code fragment from Control_surfaces.cpp that uses MAKE_STATIC:

MAKE_STATIC
(
      cs_background,
      BMP_CS_SMALL_BACKGROUND,
      &cs_sliders_list,
      NULL,
      IMAGE_USE_TRANSPARENCY,
      0,
      0,0
)
PELEMENT_HEADER         cs_list     = &cs_background.header;

PELEMENT_HEADER         cs_list     = &cs_background.header;

The following table explains the different fields in MAKE_STATIC.

NAME	cs_background	Contains the unique name you assign to the macro—this specific name applies to the static background image.
RES_ID	BMP_CS_SMALL_BACKGROUND	Contains the name of the resource file used by the macro as identified earlier by SDK.h.
NEXT_LIST	&cs_sliders_list	Sets the order in which parts of the gauge get drawn. The example identifies the sliders.
FAILURE	NULL	References a FAILURE_RECORD or NULL.
DRAW_FLAGS	IMAGE_USE_TRANSPARENCY	One or more DRAW_FLAGS.
ASI_FLAGS	0	Specifies the Aircraft Special Instrumentation flags.
POSITION_X, POSITION_Y	0,0	Specifies the X,Y coordinates, in display units relative to the background image (i.e., static image), at which to initially place the bitmap. Since this is the background image, always set the X,Y coordinates to 0,0.

MAKE_NEEDLE

Use MAKE_NEEDLE to draw an image that pivots around a specific point in another image. MAKE_NEEDLE supports transparency and nonlinear gauges. For MAKE_NEEDLE, POS (position) is the center of rotation in the background image; OFS (offset) is the center of rotation in the needle image.
Here’s the macro structure from Gauges.h:

#define     MAKE_NEEDLE(      NAME,                               \
                              RES_ID,                             \
                              NEXT_LIST,                          \
                              FAILURE,                            \
                              DRAW_FLAGS,                         \
                              ASI_FLAGS,                          \
                              BKND_POSITION_X, BKND_POSITION_Y,   \
                              NDL_POSITION_X, NDL_POSITION_Y,     \
                              SOURCE_VAR, CALLBACK,               \
                              NONLINEARITY_TABLE,                 \
                              MAX_DEG_PER_SEC )                   \
                              

And here’s the code fragment from SDK.fuel.cpp that uses this macro:

MAKE_NEEDLE
(
      fuel_needle,
      BMP_FUEL_SMALL_NEEDLE,
      NULL,
      fuel_fail,
      IMAGE_USE_TRANSPARENCY | IMAGE_USE_ERASE,
      0,
      150, 150,
      6, 12,
      FUEL_QUANTITY_CENTER,fuel_needle_cb,
      fuel_nonlinearity,
      6
)

The following table explains the different fields in MAKE_NEEDLE.

NAME	fuel_needle	Contains the unique name you assign to the macro—this specific name applies to the static background image.
RES_ID	BMP_FUEL_SMALL_NEEDLE	Contains the name of the resource file used by the needle as identified earlier by SDK.h.
NEXT_LIST	NULL	Sets the order in which parts of the gauge get drawn.
FAILURE	fuel_fail	References a FAILURE_RECORD or NULL.
DRAW_FLAGS	IMAGE_USE_TRANSPARENCY | IMAGE_USE_ERASE	One or more DRAW_FLAGS.
ASI_FLAGS	0	Specifies the Aircraft Special Instrumentation flags.
BKND_POSITION_X, BKND_POSITION_Y	150, 150	The X and Y coordinates on the background image around which the needle rotates.
NDL_POSITION_X, NDL_POSITION_Y	6, 12	The X and Y coordinates of the needle itself around which the needle revolves—the fix point of the needle. In general, bitmaps for needles should be drawn horizontally.
SOURCE_VAR	FUEL_QUANTITY_ CENTER	Token Variable used to drive the needle. You can enter MODULE_VAR_NONE if you want to set your variable values.
CALLBACK	fuel_needle_cb	Callback function associated with the needle.
NONLINEARITY_ TABLE	fuel_nonlinearity	Name of the non-linearity table used by the needle.
MAX_DEG_PER_SEC	6	Determines the refresh rate for the macro. Gauges are refreshed 18 times per second, so a value of 0 means update every cycle; a value of 6 means update every third of a second. You trade off gauge display quality versus frame rate—lower numbers give smoother display but worse frame rate.

Using Non-Linearity Tables

In some cases, you might want a needle to move in a nonlinear manner. For example, an airspeed gauge sometimes shows a greater angle between 0 and 50 knots than the angle between 100 and 150 knots. You can specify this behavior by using a non-linearity table. A non-linearity table is an array of NONLINEARITY structures. Each element in the array represents a discrete point on a gauge where the value is known. For example, your gauge might show airspeed as values from 0 to 160 knots, with tick marks every 20 knots. You could create an entry for each tick, filling in the pt and value member variables of the NONLINEARITY structure.

A NONLINEARITY structure uses the following members.

pt	Specifies the X, Y point in the background bitmap.
value	Contains the readout of the gauge at that point.
degrees	Used internally by the panel system: do not use. Must be set to 0.

In SDK.Fuel.cpp, the linearity table deals with the fuel quantity, which ranges from 0 to 75. Here’s the non-linearity table it uses:

NONLINEARITY  fuel_nonlinearity[] =
{
      {{30, 182}, 0, 0},
      {{119, 47}, 25, 0},
      {{246, 93}, 50, 0},
      {{241, 221}, 75, 0}
};

At runtime, the value of the needle is examined and the angle to be drawn is interpolated from the non-linearity table. Values are listed in the table as they appear on the gauge (clockwise around the face). If gauge values increase when rotating clockwise, values in the non-linearity table will start at the minimum and increase. If gauge values decrease when rotating clockwise, then values in the table will start with the maximum and decrease.

MAKE_STRING

Use MAKE_STRING to display text on a gauge. MAKE_STRING is particularly useful when you have a string that changes as the gauge is updated; the string can be automatically updated by setting up the MODULE_VAR elements and using callback functions. Using MAKE_STRING, you can specify the font name, weight, and the background and foreground colors of the text. You can also specify a highlight text color to use when the string is selected.
Here’s the macro structure from Gauges.h:

#define     MAKE_NEEDLE(      NAME,                               \
                              RES_ID,                             \
                              NEXT_LIST,                          \
                              FAILURE,                            \
                              DRAW_FLAGS,                         \
                              ASI_FLAGS,                          \
                              BKND_POSITION_X, BKND_POSITION_Y,   \
                              NDL_POSITION_X, NDL_POSITION_Y,     \
                              SOURCE_VAR, CALLBACK,               \
                              NONLINEARITY_TABLE,                 \
                              MAX_DEG_PER_SEC )                   \

Here’s the code fragment from SDK.Temperature.cpp that uses the MAKE_STRING macro:

MAKE_NEEDLE
(
      fuel_needle,
      BMP_FUEL_SMALL_NEEDLE,
      NULL,
      fuel_fail,
      IMAGE_USE_TRANSPARENCY | IMAGE_USE_ERASE,
      0,
      150, 150,
      6, 12,
      FUEL_QUANTITY_CENTER,fuel_needle_cb,
      fuel_nonlinearity,
      6
)

The following table explains the different fields in MAKE_STRING.

NAME	temperature_string	Contains the unique name you assign to the macro—this specific name applies to the static background image.
RES_ID	NULL	Contains the name of the resource file used by the macro.
NEXT_LIST	NULL	Sets the order in which parts of the gauge are drawn.
FAILURE	temperature_fail	References a FAILURE_RECORD or NULL.
DRAW_FLAGS	IMAGE_USE_ERASE | IMAGE_USE_BRIGHT	One or more DRAW_FLAGS.
ASI_FLAGS	0	Specifies the Aircraft Special Instrumentation flags.
POSITION_X, POSITION_Y	28, 9	Specifies the X and Y coordinates on the background image where you want the text to display.
SIZE_X, SIZE_Y	60, 29	Defines the height and width of each character.
NUMCHARS	3	Specifies the number of characters to use in the string. The optimal font size is calculated using the information passed to the macro.
SOURCE_VAR_1	TOTAL_AIR_TEMP	Contains the token variable used to update the string. The string can contain numbers, characters, or both. If you want to set your variable values, enter MODULE_VAR_NONE.
SOURCE_VAR_2	DISPLAY_UNITS	Used to look up multiple token variables to update the string. (e.g., Hours, Minutes, Seconds). Sequence them inside the callback function.
SOURCE_VAR_3	MODULE_VAR_NONE	Contains the token variable used to update the string.
FORECOLOR	RGB(255,0,0),	Defines the foreground (or daylight) color of the string display.
BACKCOLOR	RGB(0,0,0),	Defines the background color of the string display.
HILITECOLOR	RGB(92,92,92),	Defines the highlight color for the selected area.
FONT_NAME	GAUGE_FONT_DEFAULT	Contains the font name of the string. For more information, see “Defining the Font Type” below.
FONT_WEIGHT	GAUGE_WEIGHT_DEFAULT	Contains the font weight of the string. (The sample code sets the value of GAUGE_WEIGHT_DEFAULT to FW_NORMAL.) Specifies the weight of the font in the range 0 through 1000. For example, 400 is normal and 700 is bold. If this value is zero, a default weight is used. The following values are defined for convenience. Value Weight FW_DONTCARE 0 FW_THIN 100 FW_EXTRALIGHT 200 FW_ULTRALIGHT 200 FW_LIGHT 300 FW_NORMAL 400 FW_REGULAR 400 FW_MEDIUM 500 FW_SEMIBOLD 600 FW_DEMIBOLD 600 FW_BOLD 700 FW_EXTRABOLD 800 FW_ULTRABOLD 800 FW_HEAVY 900 FW_BLACK 900
FONT_CHARSET	GAUGE_CHARSET	Specifies the font character set for the string. A list of valid values can be found in the CreateFont Win32 API.
FONT_SIZE	0	Specifies the font size for the string. A value of zero (0) means scale so that NUMCHARS capital W's fit into SIZE_X. A non-zero FONT_SIZE means fixed height.
DRAW_TEXT_ FLAGS	DT_CENTER | DT_VCENTER | DT_SINGLELINE	Sets how to draw the text. There are three valid entries: DT_CENTER DT_VCENTER DT_SINGLELINE
HILITE_LIST	NULL	Lists gauge selection states. For a table listing all gauge selection states, see Selecting a String by KEY_EVENT below. (You can also find examples of gauge selection states in Gauges.h.)
CALLBACK	temperature_string_cb	Updates the string. The callback function updates the string member variable. The string member variable is the character string data that's used to render this drawing element.

Defining the Font Type

To define the font type you must place #define statements (after the initial #include) in your gauge code. For example, SDK.Temperature.cpp looks like this:

#define GAUGE_CHARSET               DEFAULT_CHARSET
#define GAUGE_FONT_DEFAULT          "Courier New"
#define GAUGE_WEIGHT_DEFAULT        FW_NORMAL

The first line in the code above is the default character set for English (UK and US). Most instruments are labeled in English. The second line defines the font set name. You want to define a font that will, with almost certainty, exist on your user’s PC. Therefore, choose one of the following fonts: Courier New, Arial, Times New Roman, or Helvetica. The third line defines how the font will display. Here are the available options:

FW_THINFW_EXTRALIGHT
FW_LIGHT
FW_NORMAL
FW_MEDIUM
FW_SEMIBOLD
FW_BOLD
FW_EXTRABOLD
FW_HEAVY

Selecting a String by KEY_EVENT

You can use the SEQ_REC table to select a string automatically on certain KEY_EVENTs. The user can select certain gauge elements by using different keyboard combinations. The SEQ_REC structure sets up the relationship between the current selection state and the characters that can be selected for that state. The following code shows the SEQ_REC structure definition (from gauges.h):

typedef struct SEQ_REC 
{ 
    int seq_id; 
    int sel_str; 
    int sel_end; 
} SEQ_REC, *PSEQ_REC, **PPSEQ_REC;

SEQ_REQ uses the following members.

seq_id	Specifies the selection state.
sel_str	Specifies the first character to select when the selection state is equal to the seq_id state.
sel_end	Specifies the last character to select.

To mark the end of the array you must add one blank record that sets seq_id, sel_str, and sel_end to SELECT_NONE, 0, and 0, respectively. The following code example shows a sample SEQ_REC definition:

SEQ_REC seq_com[]  = 
{ 
    {SELECT_COM_WHOLE, 0, 2}, 
    {SELECT_COM_FRACTION, 4, 5}, 
    {SELECT_NONE, 0, 0} 
};

The following table shows the gauge selection states available.

SEQ Record ID
SELECT_NONE	No selection
SELECT_1	Unused
SELECT_ZOOM	Zoom
SELECT_MAGNETO	Magneto
SELECT_COM_WHOLE	COM1 communication frequency, whole number
SELECT_COM_FRACTION	COM1 communication frequency, fractional number
SELECT_NAV1_WHOLE	Navigation radio frequency #1, whole number
SELECT_NAV1_FRACTION	Navigation radio frequency #1, fractional number
SELECT_NAV2_WHOLE	Navigation radio frequency #2, whole number
SELECT_NAV2_FRACTION	Navigation radio frequency #2, fractional number
SELECT_XPNDR_1000	Transponder frequency fourth digit
SELECT_XPNDR_0100	Transponder frequency third digit
SELECT_XPNDR_0010	Transponder frequency second digit
SELECT_XPNDR_0001	Transponder frequency first digit
SELECT_VOR1	Toggle to VOR1 selection
SELECT_VOR2	Toggle to VOR2 selection
SELECT_ENGINE	Toggle engine selection
SELECT_DME1	Toggle to DME1 selection
SELECT_DME2	Toggle to DME2 selection
SELECT_ADF_100	ADF frequency third digit
SELECT_ADF_010	ADF frequency second digit
SELECT_ADF_001	ADF frequency first digit
SELECT_EGT_BUG	EGT bug
SELECT_SIM_RATE	Simulation rate
SELECT_CLOCK_HOURS	Clock hours
SELECT_CLOCK_MINUTES	Clock minutes
SELECT_CLOCK_SECONDS	Clock seconds
SELECT_COM2_WHOLE	COM2 communication frequency, whole number
SELECT_COM2_FRACTION	COM2 communication frequency, fractional number
SELECT_ADF_TENTHS	ADF tenths

MAKE_SLIDER

Use MAKE_SLIDER to move a drawing element around a gauge on the X and Y axes. You can use MAKE_SLIDER to move an image in only one direction as well. Just set the MODULE_VAR, for either X or Y, to MODULE_VAR_NONE. Here’s the macro structure from Gauges.h:

#define     MAKE_SLIDER(      NAME,                         \
                              RES_ID,                       \
                              NEXT_LIST,                    \
                              FAILURE,                      \
                              DRAW_FLAGS,                   \
                              ASI_FLAGS,                    \
                              POSITION_X, POSITION_Y,       \
                              SOURCE_VAR_X, CALLBACK_X, SCALE_X,  \
                              SOURCE_VAR_Y, CALLBACK_Y, SCALE_Y )

You’ll need to fill this structure out with slider-specific information, such as the following from SDK.Control_Surfaces.cpp:

MAKE_SLIDER
(
      cs_slider_trim,
      BMP_CS_SMALL_TRIM,
      NULL,
      0,
      IMAGE_USE_ERASE | IMAGE_USE_TRANSPARENCY,
      0,
      20,44,

      MODULE_VAR_NONE, NULL, 0,
      ELEVATOR_TRIM, NULL, -100
)

The following table explains the different fields in MAKE_SLIDER.

NAME	cs_slider_trim	Contains the unique name you assign to the macro—this specific name applies to the trim slider. A gauge can have multiple sliders, but each one must have a unique name
RES_ID	BMP_CS_SMALL_TRIM	Contains the name of the resource file used by the slider as identified earlier by SDK.h.
NEXT_LIST	NULL	Sets the order in which parts of the gauge get drawn. Set to NULL as this is a simple gauge where the sliders do not overlap.
FAILURE	0	References a FAILURE_RECORD or NULL.
DRAW_FLAGS	IMAGE_USE_ERASE | IMAGE_USE_TRANSPARENCY	One or more DRAW_FLAGS.
ASI_FLAGS	0	Specifies the Aircraft Special Instrumentation flags.
POSITION_X, POSITION_Y	20,44	Specifies the X,Y coordinates, in display units relative to the background image (i.e., static image), at which to initially place the slider bitmap.
SOURCE_VAR_X, CALLBACK_X, SCALE_X	MODULE_VAR_NONE, NULL, 0	Set the X or Y axis (you can move a slider on the X or Y axis). SOURCE_VAR_X identifies the token variable the slider will use. Since Trim only goes up and down, there’s no token variable so use MODULE_VAR_NONE. CALLBACK_X identifies the modifying callback if any. None is needed so set to NULL. SCALE_X sets the scaling value for the range of X-axis movement of the variable across the background image. Here it’s 0. A slider moves from left to right unless this value is preceded by a minus (-) sign.
SOURCE_VAR_Y, CALLBACK_Y, SCALE_Y	ELEVATOR_TRIM, NULL, -100	Set Y-axis values. Here the Trim slider does move on the Y-axis. SOURCE_VAR_Y uses the ELEVATOR_TRIM token variable. See the discussion of token variables later in this section. CALLBACK_Y identifies the modifying callback, which isn’t used here. SCALE_Y is the scaling value of the Y-axis movement of the slider across the background image. Divide the token variable value returned by the range of movement in pixels, and then multiply by the units of measure. A slider moves from left to right unless this value is preceded by a minus (-) sign.

MAKE_MOVING

MAKE_MOVING, like MAKE_SLIDER, moves an image around on a gauge on the X and Y axes. The difference is that MAKE_MOVING specifies a mask, which does not move, and is used to hide parts of the image. The moving image moves in reference to where the mask is placed. Whiskey compasses are drawn using MAKE_MOVING. Here’s the macro structure from Gauges.h:

#define     MAKE_MOVING(            NAME,                  \
                                    RES_ID,                 \
                                    NEXT_LIST,              \
                                    FAILURE,                \
                                    DRAW_FLAGS,             \
                                    ASI_FLAGS,              \
                                    POSITION_X, POSITION_Y, \
                                    SOURCE_VAR_X, CALLBACK_X,     \
                                    MIN_X, MAX_X,                 \
                                    SOURCE_VAR_Y, CALLBACK_Y,     \
                                    MIN_Y, MAX_Y )

You’ll need to fill this structure out with specific information, such as the following from SDK.Wiskey.cpp:

MAKE_MOVING
(
      wiskey_moving_card,
      BMP_COMPASS_SMALL_CARD,
      NULL,
      wiskey_fail,
      IMAGE_USE_ERASE | IMAGE_USE_TRANSPARENCY,
      0,
      22,41,
      WHISKEY_COMPASS_DEGREES, wiskey_moving_card_x_cb,
      0, 360,
      MODULE_VAR_NONE, wiskey_moving_card_y_cb,
      0, 0
)

The following table explains the different fields in MAKE_MOVING.

NAME	wiskey_moving_card	Contains the unique name you assign to the macro.
RES_ID	BMP_COMPASS_SMALL_CARD	Contains the name of the resource file used by the gauge as identified earlier by SDK.h. This is the moving image.
NEXT_LIST	NULL	Sets the order in which parts of the gauge are drawn.
FAILURE	wiskey_fail	References a FAILURE_RECORD or NULL.
DRAW_FLAGS	IMAGE_USE_ERASE | IMAGE_USE_TRANSPARENCY	One or more DRAW_FLAGS.
ASI_FLAGS	0	Specifies the Aircraft Special Instrumentation flags.
POSITION_X, POSITION_Y	20,44	Specifies the X,Y coordinates, in display units relative to the background image (i.e., static image), at which to initially place the mask.
SOURCE_VAR_X, CALLBACK_X	WHISKEY_COMPASS_DEGREES, wiskey_moving_card_x_cb	Specifies the token variable to use and a callback function to control the image in the X direction.
MIN_X, MAX_X	0,360	Specifies the minimum and maximum values expected from the callback for the X direction.
SOURCE_VAR_Y, CALLBACK_Y	MODULE_VAR_NONE, wiskey_moving_card_y_cb	Specifies the token variable to use and a callback function to control the image in the Y direction.
MIN_Y, MAX_Y	0,0	Specifies the minimum and maximum values expected from the callback for the Y direction.

When you specify a mask with MAKE_MOVING, you’re actually specifying the area within which another part of the gauge can move and appear. Once that other part moves outside of that area (as defined by MIN_X, MAX_X, MIN_Y, and MAX_Y) it won’t display. These fields identify the top left and bottom right corners of this area within the gauge background.

MAKE_ICON

Use MAKE_ICON to toggle between one of several images at a static location on a gauge. The RES_ID member of the structure specifies the first icon image. The panel system loads the first icon image using RES_ID. The panel system loads the next icon image by adding 1 to the RES_ID. It then adds 1 more to RES_ID and loads the next image, and so on. The panel system continues this process as many times as NUM_ICONS specifies. Icon images can be any size, although all images in the same MAKE_ICON have the same upper left location. If you specify IMAGE_USE_ERASE in the image flags for MAKE_ICON, the save buffer will only be as large as the first image. If source_var is set to -1, the icon image is automatically hidden.

Here’s the MAKE_ICON structure as defined ingauges.h:

#define     MAKE_ICON(              NAME,            \
                                    RES_ID,          \
                                    NEXT_LIST,       \
                                    FAILURE,         \
                                    DRAW_FLAGS,      \
                                    ASI_FLAGS,       \
                                    POSITION_X, POSITION_Y,\
                                    SOURCE_VAR, CALLBACK,  \
                                    SWITCH_TYPE,     \
                                    NUM_ICONS,       \
                                    SCALE,           \
                                    OFFSET )         \

You’ll need to fill this structure out with specific information, such as the following from SDK.Fuel_Selector.cpp:

MAKE_ICON
(
      fuel_selector_icon,
      BMP_FUEL_SELECTOR_OFF,
      NULL,
      NULL,
      IMAGE_USE_ERASE | IMAGE_USE_TRANSPARENCY,
      0,
      0,0,
      FUEL_TANK_SELECTOR,fuel_selector_icon_cb,
      ICON_SWITCH_TYPE_STEP_TO,
      4,
      0,
      0
)

The following table explains the different fields in MAKE_ICON.

NAME	fuel_selector_icon	Contains the unique name you assign to the macro.
RES_ID	BMP_FUEL_SELECTOR_OFF	Contains the name of the resource file used by the gauge as identified earlier by SDK.h.
NEXT_LIST	NULL	Sets the order in which parts of the gauge get drawn.
FAILURE	NULL	References a FAILURE_RECORD or NULL.
DRAW_FLAGS	IMAGE_USE_ERASE | IMAGE_USE_TRANSPARENCY	One or more DRAW_FLAGS.
ASI_FLAGS	0	Specifies the Aircraft Special Instrumentation flags.
POSITION_X, POSITION_Y	0,0	Defines the upper-left X,Y coordinate in display units to initially place the image.
SOURCE_VAR, CALLBACK	FUEL_TANK_SELECTOR, fuel_selector_icon_cb	Specifies the token variable to use and a callback function to control the image in the X direction.
SWITCH_TYPE	ICON_SWITCH_TYPE_SET_CUR_ICON	The switch type of the icon. There are four types: ICON_SWITCH_TYPE_SET_CUR_ICON: Simple on-off functions. The value is interpreted as an index to the current icon, where 0 is the first icon and the number of icons minus one is the last icon. ICON_SWITCH_TYPE_SET_CUR_USING_RANGE: The value is subtracted from offset and divided by scale to get the current index. You can specify a range that is linearly interpolated into the valid range of icon index. ICON_SWITCH_TYPE_STEP_TO: Steps through a series of icons—such as a key switch. This is the same as ICON_SWITCH_TYPE_SET_CUR_ICON except that it will step through (animate) each icon. ICON_SWITCH_TYPE_STEP_TO_USING_RANGE: This is the same as ICON_SWITCH_TYPE_SET_CUR_USING_RANGE except that it will step through (animate) each icon.
NUM_ICONS	4	Specifies the number of icon bitmaps in the gauge.
SCALE	0	Specifies the scale of the icon. This value is only used if SWITCH_TYPE is: ICON_SWITCH_TYPE_SET_CUR_USING_RANGE or ICON_SWITCH_TYPE_STEP_TO_USING_RANGE.
OFFSET	0	Specifies the offset of the icon. This value is only used if switch type is: ICON_SWITCH_TYPE_SET_CUR_USING_RANGE or ICON_SWITCH_TYPE_STEP_TO_USING_RANGE

MAKE_SPRITE

MAKE_SPRITE, like MAKE_MOVING_IMAGE, moves an element in X and Y directions and uses a mask to hide parts of the element. The difference is that MAKE_SPRITE can rotate an element around a pivot point. For MAKE_SPRITE, TEXTURE_CENTER_X and TEXTURE_CENTER_Y identify the center of the sprite—the center of the texture maps to this point. Textures used for ELEMENT_SPRITE must be 256 x 256. When the gauge is loaded, the RES_ID specifies the image to use for the texture. RES_ID + 1 specifies the mask image. The mask doesn't have to be a specific size. The mask is placed on the gauge using the position member. The texture slides and rotates underneath the mask. Element transformations occur in the following order:

• Rotate, based on SOURCE_VAR_0.
• Scale, based on TEXTURE_SCALE_X and TEXTURE_SCALE_Y.
• Transpose, based on SOURCE_VAR_X and SOURCE_VAR_Y.

Here’s the MAKE_SPRITE structure as defined in gauges.h:

#define     MAKE_SPRITE(            NAME,      \
                                    RES_ID,    \
                                    NEXT_LIST,  \
                                    FAILURE,    \
                                    DRAW_FLAGS, \
                                    ASI_FLAGS,  \
                                    BKND_POSITION_X, BKND_POSITION_Y,   \
                                    TEXTURE_CENTER_X, TEXTURE_CENTER_Y, \
                                    TEXTURE_SCALE_X, TEXTURE_SCALE_Y,   \
                                    SOURCE_VAR_X, CALLBACK_X, SCALE_X,  \
                                    SOURCE_VAR_Y, CALLBACK_Y, SCALE_Y,  \
                                    SOURCE_VAR_0, CALLBACK_0, SCALE_0 ) \

You’ll need to fill this structure out with specific information, such as the following from SDK.Attitude.cpp:

MAKE_SPRITE
(
      attitude_sprite_outer,
      BMP_ATTITUDE_SMALL_CARD2,
      NULL,
      (PFAILURE_RECORD)&attitude_fail,
      IMAGE_USE_TRANSPARENCY,
      0,
      16, 13,
      137,134,
      1.05, 1.05,
      MODULE_VAR_NONE, NULL, 0,
      MODULE_VAR_NONE, NULL, 0,
      ATTITUDE_INDICATOR_BANK_DEGREES, NULL, -1
)

The following table explains the different fields in MAKE_SPRITE.

NAME	attitude_sprite_outer	Contains the unique name you assign to the macro.
RES_ID	BMP_ATTITUDE_SMALL_CARD2	Contains the name of the resource file used by the sprite as identified earlier by SDK.h.
NEXT_LIST	NULL	Sets the order in which parts of the gauge get drawn.
FAILURE	(PFAILURE_RECORD)&attitude_fail	References a FAILURE_RECORD or NULL.
DRAW_FLAGS	IMAGE_USE_TRANSPARENCY	One or more DRAW_FLAGS.
ASI_FLAGS	0	Specifies the Aircraft Special Instrumentation flags.
BKND_POSITION_X, BKND_POSITION_Y	16, 13	Specifies the X and Y coordinates for the top left corner of the mask against the gauge background.
TEXTURE_CENTER_X, TEXTURE_CENTER_Y	137,134	Specifies the X and Y coordinates of the center of the bitmap that moves behind the mask.
TEXTURE_SCALE_X, TEXTURE_SCALE_Y	1.05, 1.05	Specifies the X and Y scaling factor for the sprite. X value can differ from Y value.
SOURCE_VAR_X, CALLBACK_X, SCALE_X	MODULE_VAR_NONE, NULL, 0	Specifies the token variable to be read, callback function, and scaling factor for X direction (this value has no effect if equal to 1).
SOURCE_VAR_Y, CALLBACK_Y, SCALE_Y	MODULE_VAR_NONE, NULL, 0	Specifies the token variable to be read, callback function, and scaling factor for Y direction (this value has no effect if equal to 1).
SOURCE_VAR_0, CALLBACK_0, SCALE_0	ATTITUDE_INDICATOR_BANK_DEGREES, NULL, -1	Specifies the token variable to be read, callback function, and scaling factor for 0 direction (this value has no effect if equal to 1).

Drawing Element Macros

The following macros have been defined to manipulate drawing elements:

#define GET_IMAGE_HIDDEN( element)      (element->image_flags & IMAGE_HIDDEN)
#define SHOW_IMAGE( element)            (element->image_flags &= ~IMAGE_HIDDEN)
#define HIDE_IMAGE( element)            (element->image_flags |= IMAGE_HIDDEN)
#define GET_IMAGE_HIDDEN_TREE( element) (element->image_flags & IMAGE_HIDDEN_TREE)
#define SHOW_IMAGE_TREE( element)       (element->image_flags &= ~IMAGE_HIDDEN_TREE)
#define HIDE_IMAGE_TREE( element)       (element->image_flags |= IMAGE_HIDDEN_TREE)
#define GET_USE_TRANSPARENCY( element)  (element->image_flags & IMAGE_USE_TRANSPARENCY)
#define GET_USE_ERASE( element)         (element->image_flags & IMAGE_USE_ERASE)
#define GET_USE_BRIGHT( element)        (element->image_flags & IMAGE_USE_BRIGHT)
#define GET_ERASE_ON_FAILURE( element)  (element->image_flags & IMAGE_ERASE_ON_FAILURE)

#define GET_ON_SCREEN( element)         (element->image_flags & IMAGE_ON_SCREEN)
#define SET_ON_SCREEN( element)         (element->image_flags |= IMAGE_ON_SCREEN)
#define SET_OFF_SCREEN( element)        (element->image_flags &= ~IMAGE_ON_SCREEN)

#define GET_FAILED( element)            (element->image_flags & GAUGE_FAILURE)
#define SET_GAUGE_FAILED( element)      (element->image_flags |= GAUGE_FAILURE)
#define SET_GAUGE_NOT_FAILED( element)  (element->image_flags &= ~GAUGE_FAILURE)

String Element Macros

The following macros have been defined to manipulate string elements:

#define STR_UNSEL( ELEment)           (ELEMENT->sel_end = -1; ELEMENT->sel_str = -1;)
#define STR_SEL( ELEMENT, STR, END)   (ELEMENT->sel_end = END; ELEMENT->sel_str = STR;) 
#define IS_STR_SEL( ELEment)          (ELEMENT->sel_end != -1 && ELEMENT->sel_str != -1)

DRAW_FLAGS

The DRAW_FLAGS field is a combination of one or more of the following flags (combine them using the | operator):

IMAGE_USE_TRANSPARENCY	This flag is used by C-style gauges for all element types; it has nothing to do with the transparency of a mask image used with an element. When black (pure black, or an RGB value of 0,0,0) is anywhere in a mask image, it is transparent, regardless of whether or not this image flag is set. Renders the image using transparency. If this flag is set, RGB color (0,0,0) is treated as transparent in a 24-bit bitmap. Because non-transparent rendering is faster than transparent rendering, you can use this flag to enhance performance.
IMAGE_USE_ERASE	Use the access buffer for resource. Note: there is a cost in memory and CPU usage. Before the graphical element is rendered, a "snapshot" of the background is saved. As a result, the panel system can erase the element as needed by plotting the contents of the save buffer to the screen. You can use this flag to increase performance and save memory if an element never needs to be erased. Static images use this flag extensively.
IMAGE_USE_BRIGHT	Use this to make the image appear lit at night. Maps the element’s image colors to the section of the palette that doesn't change during the transition from day to night. The image colors will not change.
IMAGE_CREATE_DIBSECTION	Creates a new static image as a dibsection.
IMAGE_BILINEAR_GRAY
IMAGE_BILINEAR_COLOR
IMAGE_PRESERVE_COLOR_IN_HUD
IMAGE_CONTAINS_NO_MASK
IMAGE_BLT_MASK_ONLY
IMAGE_CONTAINS_MASK	Image contains mask bits.
IMAGE_USE_ALPHA	Image contains alpha channel.
IMAGE_USE_LUMINOUS	Image is bright when the interior light is on.
IMAGE_USE_LUMINOUS_PARTIAL	Parts of image are lit by interior light (alpha channel).
IMAGE_HIDDEN_TREE	Do not show this image, and all images in the resource tree above it, until the gauge code specifically calls for it.
IMAGE_NO_STRETCH
IMAGE_HUD_COLOR_MAP
IMAGE_NO_TRANSLATION
IMAGE_HIDDEN	Do not show this image until the gauge code specifically calls for it. These change dynamically.
IMAGE_ON_SCREEN	Status bit to say whether element is on the screen. You force a gauge to re-plot by setting it off-screen.

Aircraft Special Instrumentation

These flags specify how the element will react in a special instrument situation. Currently this is used only with autopilot. This member can have the following values:

ASI_ALT_MANUALLY_TUNABLE	Sets a global flag indicating that autopilot altitude hold is manually tunable. If this flag isn't set, turning on altitude hold maintains the current altitude instead of the currently set altitude.
ASI_HEADING_MANUALLY_TUNABLE	Sets a global flag indicating that autopilot heading hold is manually tunable. If this flag isn't set, turning on heading hold would maintain the current heading instead of the currently set heading.

Custom Events

Third parties can use custom events with ID numbers in the following range to communicate between 3D virtual cockpits and 2D C++ gauges. See the example code for the function register_key_event_handler.

#define THIRD_PARTY_EVENT_ID_MIN 0x00011000
#define THIRD_PARTY_EVENT_ID_MAX 0x0001FFFF

Refer also the documentation on the function SimConnect_MapClientEventToSimEvent.

C++ Gauges Function Reference

The following functions can be used in combination with various gauge and mouse rectangle macros. Note that you will not see many of these functions in the samples provided, because they are encapsulated in the macros and there is no need to call them explicitly if the macros are used.

aircraft_varget	Retrieves the value of an aircraft simulation variable.
check_named_variable	Retrieves the ID number of a named local variable, if it exists.
element_list_erase	Used before redrawing a gauge.
element_list_generate	Regenerates a the effects mask and images for a gauge.
element_list_initialize	Prepares a gauge before being redrawn.
element_list_install	Used to install a gauge during initialization of a panel.
element_list_kill	Used to remove a gauge completely, for example when changing user aircraft.
element_list_plot	Redraws a gauge.
element_list_query	Used to register the failure conditions for a gauge.
element_list_update	Calculates new values for each gauge element.
element_use_color	Selects the text color for string elements.
execute_calculator_code	Evaluates a coded calculator string.
format_calculator_string	Evaluates a formatted calculator string.
gauge_calculator_code_precompile	Compresses a calculator string into a more efficient internal format.
get_aircraft_var_enum	Retrieves the enum value for a simulation variable, given the string name of that variable.
get_gauge_flags	Retrieves the flags set on a gauge.
get_name_of_named_variable	Retrieves the name of a local variable, given an ID number.
get_named_variable_typed_value	Retrieves the value of a named local variable, in the specified units.
get_named_variable_value	Retrieves the value of a local variable, given and ID.
get_units_enum	Retrieves the enum value for units, given the string name of the units.
initialize_var	Initializes a token variable.
initialize_var_by_name	Initializes a MODULE_VAR structure, given the name of a token variable.
is_master	Returns true if the aircraft is the master aircraft of a shared cockpit.
is_panel_window_visible_ident	Returns true if the specified panel window is visible.
lookup_var	Updates the contents of a token variable.
mouse_list_install	Creates the mouse rectangles for a gauge.
mouse_list_register	Registers the mouse windows.
mouse_list_unregister	Unregisters the mouse windows.
panel_get_aircraft_c_callback	Retrieves a pointer to the aircraft callback function.
panel_get_registered_c_callback	Retrieves a pointer to the registered callback function.
panel_register_c_callback	Description
panel_resource_string_get	Retrieves the resource string, given an ID.
panel_window_close_ident	Closes the specified panel window.
panel_window_open_ident	Displays the specified panel window.
panel_window_toggle	Toggles the visible state of a panel window.
panel_window_toggle_hud_color	Changes the global HUD color to the next in the list.
panel_window_toggle_hud_units	Toggles the HUD units between metric and imperial.
panel_window_toggle_menu_id	Selects a menu item given an ID.
process_shared_event_out	Sends data to the other aircraft, in a multiplayer shared cockpit scenario.
radio_stack_autoclose	Closes the radio stack, if it was opened with radio_stack_popup.
radio_stack_popup	Displays the radio stack
register_key_event_handler	Registers a key event callback function.
register_named_variable	Registers a local variable name.
register_var_by_name	Registers a variable from another gauge, for use by this gauge.
send_key_event	Transmits a WM_COMMAND application event.
set_gauge_flags	Used to specify the flags for a gauge.
set_named_variable_typed_value	Specifies a local variable should be set to the given value with the given units.
set_named_variable_value	Sets a local variable to a given value.
tooltip_units_getset	Specifies or retrieves the tooltip units (metric or US).
trigger_key_event	Initiates the action of a key event.
unregister_all_named_vars	Unregisters all token variables, and frees up the memory used.
unregister_key_event_handler	Unregisters the key event handler.
unregister_var_by_name	Unregisters a named variable from another gauge, and frees up the memory used.

See Also

• Structures

aircraft_varget

The aircraft_varget function retrieves the value of an aircraft simulation variable.

Syntax

FLOAT64 aircraft_varget(
  ENUM  simvar,
  ENUM  units,
  SINT32  index
);

Parameters

simvar
  [in]  Specifies a simulation variable enum value. Use get_aircraft_var_enum to retrieve the enum value from a string.
units
  [in]  Specifies the units enum value the returned value should have. Use get_units_enum to retrieve the enum value from a string.
index
  [in]  Specifies an index number, which is required for some engine and communication data. Refer to the Simulation Variables document for details.

Return Values

The function returns the value in a FLOAT64. If the simulation variable is not found, zero will be returned.

Example

See Cabin_Comfort.cpp for an example of the use of this function, and refer to Creating a Gauge using XML and C++ for a description of this sample

Remarks

None.

See Also

• C++ Gauges Function Reference
• get_aircraft_var_enum
• get_units_enum

check_named_variable

The check_named_variable function retrieves the ID number of a named local variable, if it exists.

Syntax

ID check_named_variable(
  PCSTRINGZ  name
);

Parameters

name
  [in]  Specifies the variable name.

Return Values

The function returns an ID number if the variables exists, or -1 if it does not.

Remarks

Local variable names are case-insensitive.

See Also

• C++ Gauges Function Reference
• register_named_variable

element_list_erase

The element_list_erase function is used before redrawing a gauge.

Syntax

void element_list_erase(
  PELEMENT_HEADER  element
);

Parameters

element
  [in]  A pointer to the element header.

Return Values

This function does not return a value.

Remarks

It is not necessary to call this function if the redrawing of the gauge is handled by element_list_plot.

See Also

• C++ Gauges Function Reference
• element_list_install

element_list_generate

The element_list_generate function is regenerates a the effects mask and images for a gauge.

Syntax

void element_list_generate(
  PELEMENT_HEADER  element,
  GENERATE_PHASE  phase
);

Parameters

element
  [in]  A pointer to the element header.
phase
  [in]  Unused, enter zero.

Return Values

This function does not return a value.

Remarks

See the remarks for element_list_plot.

See Also

• C++ Gauges Function Reference

element_list_initialize

The element_list_initialize function prepares a gauge before being redrawn.

Syntax

void element_list_initialize(
  PELEMENT_HEADER  element
);

Parameters

element
  [in]  A pointer to the element header.

Return Values

This function does not return a value.

Remarks

See the remarks for element_list_plot.

See Also

• C++ Gauges Function Reference

element_list_install

The element_list_install function is used to install a gauge during initialization of a panel.

Syntax

void element_list_install(
  PELEMENT_HEADER  element,
  PVOID  resource_file_handle
);

Parameters

element
  [in]  A pointer to the element header.
resource_file_handle
  [in]  Specifies the resource file handle.

Return Values

This function does not return a value.

Remarks

Use this function before calling any of the other element_list functions. A gauge is defined by an element list, however the macros used to create gauges described in the tutorial mean that in many cases these functions do not need to be called directly.

See Also

• C++ Gauges Function Reference

element_list_kill

The element_list_kill function is used to remove a gauge completely, for example when changing user aircraft.

Syntax

void element_list_kill(
  PELEMENT_HEADER  element
);

Parameters

element
  [in]  A pointer to the element header.

Return Values

This function does not return a value.

Remarks

None.

See Also

• C++ Gauges Function Reference
• element_list_install

element_list_plot

The element_list_plot function redraws a gauge.

Syntax

void element_list_plot(
  PELEMENT_HEADER  element
);

Parameters

element
  [in]  A pointer to the element header.

Return Values

This function does not return a value.

Remarks

Before calling this function, each and every time, call the following functions in this order:

1. element_list_initialize
2. element_list_update
3. element_list_generate
4. element_list_plot

See Also

• C++ Gauges Function Reference
• element_list_install

element_list_query

The element_list_query function used to register the failure conditions for a gauge.

Syntax

void element_list_query(
  PELEMENT_HEADER  element
);

Parameters

element
  [in]  A pointer to the element header.

Return Values

This function does not return a value.

Remarks

Call this function once, after element_list_install.

See Also

• C++ Gauges Function Reference

element_list_update

The element_list_update function calculates new values for each gauge element.

Syntax

void element_list_update(
  PELEMENT_HEADER  element
);

Parameters

element
  [in]  A pointer to the element header.

Return Values

This function does not return a value.

Remarks

See the remarks for element_list_plot.

See Also

• C++ Gauges Function Reference

element_use_color

The element_use_color function selects the text color for string elements.

Syntax

void element_use_color(
  PELEMENT_HEADER  element,
  BOOL  override,
  UINT32  color
);

Parameters

element
  [in]  A pointer to the element header.
override
  [in]  Specifies if a color selected by the user should be overridden..
color
  [in]   RGB value for the color.

Return Values

This function does not return a value.

Remarks

None.

See Also

• C++ Gauges Function Reference

execute_calculator_code

The execute_calculator_code function evaluates a coded calculator string.

Syntax

BOOL execute_calculator_code(
  PCSTRINGZ  code,
  FLOAT64*  fvalue,
  SINT32*  ivalue,
  PCSTRINGZ*  svalue
);

Parameters

code
  [in]  Specifies the calculator code.
fvalue
  [out]  Pointer to a float. Returns the result of the calculation, if it is a floating point value.
ivalue
  [out]  Pointer to an integer. Returns the result of the calculation, if it is an integer value.
svalue
  [out]  Pointer to a string. Returns the result of the calculation, if it is a string.

Return Values

If the function succeeds, it returns a non-zero value. If it fails, it returns zero.

Example

FLOAT64 att_pitch = 0;
FLOAT64 att_bank = 0;
execute_calculator_code ("(A:ATTITUDE INDICATOR PITCH DEGREES:2, degrees)", &att_pitch, NULL, NULL);
execute_calculator_code ("(A:ATTITUDE INDICATOR BANK DEGREES:2, degrees)", &att_bank, NULL, NULL);

Remarks

None.

See Also

• C++ Gauges Function Reference
• format_calculator_string
• gauge_calculator_code_precompile

format_calculator_string

The format_calculator_string function evaluates a formatted calculator string.

Syntax

BOOL format_calculator_string(
  PSTRINGZ  result,
  UINT32  resultsize,
  PCSTRINGZ  format
);

Parameters

result
  [out]  Returns the formatted string.
resultsize
  [out]  Returns the length of the formatted string.
format
  [in]  Specifies the calculator string to format.

Return Values

If the function succeeds, it returns a non-zero value. If it fails, it returns zero.

Remarks

None.

See Also

• C++ Gauges Function Reference
• execute_calculator_code
• gauge_calculator_code_precompile

gauge_calculator_code_precompile

The gauge_calculator_code_precompile function compresses a calculator string into a more efficient internal format.

Syntax

BOOL gauge_calculator_code_precompile(
  PCSTRINGZ*  pCompiled,
  UINT32*  pCompiledSize,
  PCSTRINGZ  source
);

Parameters

pCompiled
  [out]  Pointer to a string, which will contain the compiled string if the function call is successful.
pCompiledSize
  [out]  Pointer to an integer, which will contain the length of the compiled string if the function call is successful.
source
  [in]  Specifies the source calculator string. Refer to the Creating XML Gauges document for details on format strings.

Return Values

If the function succeeds, it returns a non-zero value. If it fails, it returns zero.

Remark

A precompiled (compressed) calculator string can be used as input to the execute_calculator_code and format_calculator_string functions.

See Also

• C++ Gauges Function Reference
• execute_calculator_code
• format_calculator_string

get_aircraft_var_enum

The get_aircraft_var_enum function retrieves the enum value for a simulation variable, given the string name of that variable.

Syntax

ENUM get_aircraft_var_enum(
  PCSTRINGZ  simvar
);

Parameters

simvar
  [in]  Specifies the simulation variable name.

Return Values

The function returns the ENUM value of the simulation variable, or SIMVAR_NONE (-1) if the variable name is not found.

Example

See Cabin_Comfort.cpp for an example of the use of this function, and refer to Creating a Gauge using XML and C++ for a description of this sample

Remarks

Use this function before calling aircraft_varget.

See Also

• C++ Gauges Function Reference
• aircraft_varget
• get_units_enum

get_gauge_flags

The get_gauge_flags function is used to retrieve the flags set on a gauge.

Syntax

FLAGS32 get_gauge_flags(
  PCSTRINGZ  name
);

Parameters

name
  [in]  Specifies the name of the gauge.

Return Values

The function returns a FLAGS32 value containing the flags that are set. See set_gauge_flags for a table of gauge flags.

Remarks

None.

See Also

• set_gauge_flags
• C++ Gauges Function Reference

get_name_of_named_variable

The get_name_of_named_variable function retrieves the name of a local variable, given an ID number.

Syntax

PCSTRINGZ get_name_of_named_variable(
  ID  id
);

Parameters

id
  [in]  Specifies the ID of the variable.

Return Values

The function returns the name in a PCSTRINGZ, or NULL if the name is not found.

Remarks

None.

See Also

• C++ Gauges Function Reference

get_named_variable_typed_value

The get_named_variable_typed_value function retrieves the value of a named local variable, in the specified units.

Syntax

FLOAT64 get_named_variable_typed_value(
  ID  id,
  ENUM  units
);

Parameters

id
  [in]  Specifies the ID of the variable.
units
  [in]  Specifies the enum value of the units required. Use get_units_enum to retrieve the enum value from a string.

Return Values

The function returns the value in a FLOAT64. Zero is returned if the variable ID is not found.

Remarks

None.

See Also

• get_named_variable_value
• set_named_variable_typed_value
• set_named_variable_value
• C++ Gauges Function Reference

get_named_variable_value

The get_named_variable_value function retrieves the value of a local variable, given an ID.

Syntax

FLOAT64 get_named_variable_value(
  ID  id
);

Parameters

id
  [in]  Specifies the ID of the variable.

Return Values

The function returns the value in a FLOAT64. Zero is returned if the variable ID is not found.

Remarks

None.

See Also

• get_named_variable_typed_value
• set_named_variable_typed_value
• set_named_variable_value
• C++ Gauges Function Reference

get_units_enum

The get_units_enum function retrieves the enum value for units, given the string name of the units.

Syntax

ENUM get_units_enum(
  PCSTRINGZ  unitname
);

Parameters

unitname
  [in]  Specifies the string name of the units.

Return Values

The function returns the ENUM. value for the units, or UNITS_UNKNOWN (-1) if the string name is not found.

Example

See Cabin_Comfort.cpp for an example of the use of this function, and refer to Creating a Gauge using XML and C++ for a description of this sample

Remarks

Use this function before calling aircraft_varget.

See Also

• C++ Gauges Function Reference
• aircraft_varget
• get_aircraft_var_enum

initialize_var

The initialize_var function initializes a token variable.

Syntax

void initialize_var(
  PMODULE_VAR  module_var
);

Parameters

module_var
  [in]  Specifies a pointer to a MODULE_VAR structure, containing the token variable to initialize.

Return Values

This function does not return a value.

Example

MODULE_VAR gs_var = {VOR1_GS_FLAG}; 
void install_routine(HINSTANCE resource_file_handle) 
{ 
initialize_var(&gs_var);
'Include other initialization code. 
}

Remarks

Before a token variable can be used, you must initialize it with a call to this function.

See Also

• initialize_var_by_name
• C++ Gauges Function Reference

initialize_var_by_name

The initialize_var_by_name function initializes a MODULE_VAR structure, given the name of a token variable.

Syntax

void initialize_var_by_name(
  PMODULE_VAR  module_var,
  PSTRINGZ  name
);

Parameters

module_var
  [in]  Specifies the address of the MODULE_VAR structure that will receive information about the variable.
name
  [in] Specifies the name of the variable (the same name used in register_var_by_name).

Return Values

This function does not return a value.

Example

MODULE_VAR var;
initialize_var_by_name (&var, GPS_INFO_PANEL_VARIABLE_NAME);

Also see SDK.FlightMap.cpp for an example of the use of this function.

Remarks

None.

See Also

• initialize_var
• C++ Gauges Function Reference

is_master

The is_master function returns true if the aircraft is the master aircraft of a shared cockpit.

Syntax

BOOL is_master();

Parameters

This function takes no parameters.

Return Values

If the aircraft is the master aircraft, it returns a non-zero value. If it is not, it returns zero.

Remarks

This function is used in the multiplayer scenario of a shared cockpit. One aircraft is the master and one is not. There is a maximum of two users in this scenario.

See Also

• process_shared_event_out
• C++ Gauges Function Reference

is_panel_window_visible_ident

The is_panel_window_visible_ident function returns true if the specified panel window is visible.

Syntax

BOOL is_panel_window_visible_ident(
  UINT32  panel_id
);

Parameters

panel_id
  [in]  Specifies the identification number of the window to query. The identification number is specified in the Panel.cfg file in the [WindowXX] section by the variable ident.

Return Values

If the function succeeds, it returns a non-zero value. If it fails, it returns zero.

Remarks

None.

See Also

• C++ Gauges Function Reference

lookup_var

The lookup_var function updates the contents of a token variable.

Syntax

void lookup_var(
  PMODULE_VAR  module_var
);

Parameters

module_var
  [in]  Pointer to a MODULE_VAR structure, containing the token variable to update.

Return Values

This function does not return a value.

Example

MODULE_VAR gs_var = {VOR1_GS_FLAG}; 
Void update_routine() 
{ 
  lookup_var(&gs_var); 
  if(gs_var.var_value.n == 0) 
  { 
    HIDE_IMAGE((&gs_slider)); 
    HIDE_IMAGE((&gs_background)); 
  } 
  else 
  { 
    SHOW_IMAGE((&gs_slider)); 
    SHOW_IMAGE((&gs_background)); 
  } 
'Include other update code
}

Remarks

Before using the contents of a module variable, you must call the lookup_var function.

See Also

• C++ Gauges Function Reference

mouse_list_install

The mouse_list_install function creates the mouse rectangles for a gauge.

Syntax

void mouse_list_install(
  PMOUSERECT  rect,
  PGAUGEHDR  gauge_header,
  PPIXPOINT  size
);

Parameters

rect
  [in, out]  Specifies a pointer to a list of MOUSERECT structures. The first rectangle in the list is the main box. The rectangles are scaled according to the settings in the gauge_header. The last rectangle structure in the list should have the type MOUSE_RECT_EOL.
gauge_header
  [in]  Specifies a pointer to a gauge_header structure (defined in gauges.h).
size
  [in]  Specifies a pointer to a PIXPOINT structure, which contains an x and y value, defining the size of the rectangle.

Return Values

This function does not return a value.

Remarks

Call mouse_list_register after setting up the mouse rectangles with this function. Note that the mouse rectangle creation macros can be used instead of these low level function calls.

See Also

• C++ Gauges Function Reference
• mouse_list_register
• mouse_list_unregister

mouse_list_register

The mouse_list_register function registers the mouse windows.

Syntax

void mouse_list_register(
  PMOUSERECT  rect,
  PGAUGEHDR  gauge_header
);

Parameters

rect
  [in]  Specifies a pointer to a MOUSERECT structure.
gauge_header
  [in]  Specifies a pointer to a gauge_header structure (defined in gauges.h).

Return Values

This function does not return a value.

Remarks

None.

See Also

• C++ Gauges Function Reference
• mouse_list_install
• mouse_list_unregister

mouse_list_unregister

The mouse_list_unregister function unregisters the mouse windows.

Syntax

void mouse_list_unregister(
  PMOUSERECT  rect,
  PGAUGEHDR  gauge_header
);

Parameters

rect
  [in]  Specifies a pointer to a MOUSERECT structure.
gauge_header
  [in]  Specifies a pointer to a gauge_header structure (defined in gauges.h).

Return Values

This function does not return a value.

Remarks

None.

See Also

• C++ Gauges Function Reference
• mouse_list_install
• mouse_list_register

panel_get_aircraft_c_callback

The panel_get_aircraft_c_callback function retrieves a pointer to the aircraft callback function.

Syntax

IAircraftCCallback* panel_get_aircraft_c_callback(
  PCSTRINGZ  name
);

Parameters

name
  [in]  Specifies the name of the callback function.

Return Values

The function returns a pointer to the IAircraftCCallback function, or NULL if the name is not found.

Remarks

None.

See Also

• C++ Gauges Function Reference

panel_get_registered_c_callback

The panel_get_registered_c_callback function retrieves a pointer to the registered callback function.

Syntax

IPanelCCallback* panel_get_registered_c_callback(
  PCSTRINGZ  name
);

Parameters

name
 [in]  Specifies the name of the module, "CABIN" in the Cabin_Comfort.cpp example.

Return Values

The function returns a pointer to an IPanelCCallback function.

Remarks

None.

See Also

• C++ Gauges Function Reference
• panel_register_c_callback

panel_register_c_callback

The panel_register_c_callback function specifies the registered callback function.

Syntax

BOOL panel_register_c_callback(
  PCSTRINGZ  name,
  IPanelCCallback*  pcallback
);

Parameters

name
  [in]  Specifies the name of the module, "CABIN" in the Cabin_Comfort.cpp example.
pcallback
  [in]  Specifies a pointer to the IPanelCCallback function.

Return Values

If the function succeeds, it returns a non-zero value. If it fails, it returns zero.

Example

See Cabin_Comfort.cpp for an example of the use of this function, and refer to Creating a Gauge using XML and C++ for a description of this sample

Remarks

None.

See Also

• C++ Gauges Function Reference
• panel_get_registered_c_callback

panel_resource_string_get

The panel_resource_string_get function retrieves the resource string, given an ID.

Syntax

PCSTRINGZ panel_resource_string_get(
  ID32  id
);

Parameters

id
  [in]  Specifies the resource ID.

Return Values

The function returns the resource string in a PCSTRINGZ , or NULL if the ID is not found.

Remarks

None.

See Also

• C++ Gauges Function Reference

panel_window_close_ident

The panel_window_close_ident function closes the specified panel window.

Syntax

BOOL panel_window_close_ident(
  UINT32  panel_id
);

Parameters

panel_id
  [in]  Specifies the identification number of the window to close. The identification number is specified in the Panel.cfg file in the [WindowXX] section by the variable ident.

Return Values

If the function succeeds, it returns a non-zero value. If it fails, it returns zero.

Remarks

None.

See Also

• panel_window_open_ident
• C++ Gauges Function Reference

panel_window_open_ident

The panel_window_open_ident function displays the specified panel window.

Syntax

BOOL panel_window_open_ident(
  UINT32  panel_id
);

Parameters

panel_id
  [in]  Specifies the identification number of the window to open. The identification number is specified in the Panel.cfg file in the [WindowXX] section by the variable ident.

Return Values

If the function succeeds, it returns a non-zero value. If it fails, it returns zero.

Remarks

None.

See Also

• panel_window_close_ident
• C++ Gauges Function Reference

panel_window_toggle

The panel_window_toggle function toggles the visible state of a panel window.

Syntax

BOOL panel_window_toggle(
  UINT32  panel_id
);

Parameters

panel_id
  [in]  Specifies the identification number of the window to toggle. The identification number is specified in the Panel.cfg file in the [WindowXX] section by the variable ident.

Return Values

If the function succeeds, it returns a non-zero value. If it fails, it returns zero.

Example

BOOL window_open_cb(PPIXPOINT relative_point, FLAGS32 mouse_flags) 
{ 
  return panel_window_toggle(50);
}

Remarks

None.

See Also

• panel_window_toggle_hud_color
• panel_window_toggle_hud_units
• panel_window_toggle_menu_id
• C++ Gauges Function Reference

panel_window_toggle_hud_color

The panel_window_toggle_hud_color function changes the global HUD color to the next in the list.

Syntax

void panel_window_toggle_hud_color();

Parameters

This function takes no parameters.

Return Values

This function does not return a value.

Remarks

This function cycles through the range of HUD colors (green, dark green, blue, dark blue, red, dark red, black, white), setting the global HUD color to the next in the list..

See Also

• panel_window_toggle
• panel_window_toggle_hud_units
• panel_window_toggle_menu_id
• C++ Gauges Function Reference

panel_window_toggle_hud_units

The panel_window_toggle_hud_units function toggles the HUD units between metric and imperial.

Syntax

void panel_window_toggle_hud_units();

Parameters

This function takes no parameters.

Return Values

This function does not return a value.

Remarks

None.

See Also

• panel_window_toggle
• panel_window_toggle_hud_color
• panel_window_toggle_menu_id
• C++ Gauges Function Reference

panel_window_toggle_menu_id

The panel_window_toggle_menu_id function selects a menu item given an ID.

Syntax

BOOL panel_window_toggle_menu_id(
  ID32  menu_id
);

Parameters

menu_id
  [in]  Specifies the menu ID

Return Values

If the function succeeds, it returns a non-zero value. If it fails, it returns zero.

Example

panel_window_toggle_menu_id( IDM_MAIN_PANEL_OFF );

Remarks

This function does not "toggle", but rather "selects", but the name is left unchanged for backwards compatibility.

See Also

• panel_window_toggle
• panel_window_toggle_hud_color
• panel_window_toggle_hud_units
• C++ Gauges Function Reference

process_shared_event_out

The process_shared_event_out function sends data to the other aircraft, in a multiplayer shared cockpit scenario.

Syntax

BOOL process_shared_event_out(
  PGAUGEHDR  gauge_header,
  BYTE  *pBuf,
  UINT32  nSize
);

Parameters

gauge_header
  [in]  Specifies the gauge header, which is used to identify the gauge that the event applies to.

pBuf
  [in]  A pointer to an array of data.

nSize
  [in]  The length of the data array, in bytes.

Return Values

If the function succeeds, it returns a non-zero value. If it fails, it returns zero.

Remarks

This function is used to send data from one aircraft to another in the shared cockpit scenario of multiplayer operations. Only two aircraft can share a cockpit, one is the master and the other is not. This function can be used to send data from either one to the other.

See Also

• is_master
• C++ Gauges Function Reference

radio_stack_autoclose

The radio_stack_autoclose function closes the radio stack, if it was opened with radio_stack_popup.

Syntax

void radio_stack_autoclose();

Parameters

This function takes no parameters.

Return Values

This function does not return a value.

Remarks

None.

See Also

• C++ Gauges Function Reference
• radio_stack_popup

radio_stack_popup

The radio_stack_popup function displays the radio stack

Syntax

void radio_stack_popup();

Parameters

This function takes no parameters.

Return Values

This function does not return a value.

Remarks

This function has no effect if the radio stack is already displayed.

See Also

• C++ Gauges Function Reference
• radio_stack_autoclose

register_key_event_handler

The register_key_event_handler function registers a key event callback function.

Syntax

void register_key_event_handler(
  GAUGE_KEY_EVENT_HANDLER  handler,
  PVOID  userdata
);

Parameters

handler
  [in]  Specifies the handler function, which should match the following definition:
typedef void (*GAUGE_KEY_EVENT_HANDLER) (ID32 event, UINT32 evdata, PVOID userdata);
userdata
  [in]  Specifies an optional value for use by the gauge developer. This value will be returned to the key event handler function, whenever it is called.

Return Values

This function does not return a value.

Example

This example shows how to receive custom numeric events from part animations (refer to the Creating a New Animation section of the Using Modeling Tools document).

Defined in gauges.h:

const int EVENT_BUTTON_PUSH = 0x11000; //THIRD_PARTY_EVENT_ID_MIN

Code in the gauge handler:

bool g_ButtonState = false;

//GAUGE_KEY_EVENT_HANDLER
void EventHandler(ID32 event, UINT32 evdata, PVOID userdata)
{
     switch(event)
    {
         case EVENT_BUTTON_PUSH:
             g_ButtonState = !g_ButtonState;
             break;
         default:
             break;
     }
}

void FSAPI module_init(void)
{
     if (NULL != Panels)
     {
         ImportTable.PANELSentry.fnptr = (PPANELS)Panels;
             PanelCallbackInit();
     }
    register_key_event_handler((GAUGE_KEY_EVENT_HANDLER)EventHandler, NULL);
} 

Remarks

None.

See Also

• C++ Gauges Function Reference
• unregister_key_event_handler

register_named_variable

The register_named_variable function registers a local variable name.

Syntax

ID register_named_variable(
  PCSTRINGZ  name
);

Parameters

name
  [in]  Specifies the variable name.

Return Values

The function returns an ID. If the named variable already exists, its existing ID will be returned. If it does not exist, a new registered variable is created.

Remarks

Local variable names are case-insensitive. The value of the variable is set to zero, and the units to UNITS_UNKNOWN, on creation.

See Also

• C++ Gauges Function Reference
• check_named_variable

register_var_by_name

The register_var_by_name function registers a variable from another gauge, for use by this gauge.

Syntax

  PVOID  var,
  VAR_TYPE  var_type,
  PSTRINGZ  name
);

Parameters

var
  [in]  Specifies the address of the variable.
var_type
  [in]  Specifies the type of the variable, one of the following enum:

typedef enum VAR_TYPE {
    VAR_TYPE_NONE,
    TYPE_BOOL8,
    TYPE_UINT8,
    TYPE_SINT8,
    TYPE_FLAGS8,
    TYPE_ENUM8,
    TYPE_BOOL16,
    TYPE_ANGL16,
    TYPE_UINT16,
    TYPE_SINT16,
    TYPE_UIF16,
    TYPE_SIF16,
    TYPE_FLAGS16,
    TYPE_ENUM16,
    TYPE_BCD16,
    TYPE_BCO16,
    TYPE_VAR16,
    TYPE_BOOL32,
    TYPE_ANGL32,
    TYPE_UINT32,
    TYPE_SINT32,
    TYPE_UIF32,
    TYPE_SIF32,
    TYPE_FLAGS32,
    TYPE_ENUM32,
    TYPE_VAR32,
    TYPE_ANGL48,
    TYPE_SINT48,
    TYPE_UIF48,
    TYPE_SIF48,
    TYPE_UINT64,
    TYPE_SINT64,
    TYPE_SIF64,
    TYPE_FLOAT64,
    TYPE_BOOL,
    TYPE_FLAGS,
    TYPE_ENUM,
    TYPE_VOID,
    TYPE_PVOID,
    TYPE_PUINT32,
    TYPE_PSINT32,
    TYPE_PFLOAT64,
    VAR_TYPE_MAX
} VAR_TYPE;

name
  [in]  Specifies the name of the variable. Specify a unique and descriptive name for the variable, such as "gaugename.variablename".

Return Values

This function does not return a value.

Example

static GPS_INFO gps_data;
static TVector<GPS_WP_INFO> *gps_wps;
static GPS_INFO gps_data_request;
static GPS_WP_INFO gps_wps_request[MAX_GPS_WAYPOINTS];

// In the gauge initialization code....

if (!gps_wps)
    gps_wps = new TVector<GPS_WP_INFO>;
init_gps_var (&gps_data, gps_wps->Address ());
init_gps_var (&gps_data_request, gps_wps_request);

register_var_by_name (&gps_data, TYPE_PVOID, GPS_INFO_PANEL_VARIABLE_NAME);
register_var_by_name (&gps_data_request, TYPE_PVOID, GPS_REQUEST_PANEL_VARIABLE_NAME);

// In the gauge closing code....

unregister_var_by_name (GPS_REQUEST_PANEL_VARIABLE_NAME);
unregister_var_by_name (GPS_INFO_PANEL_VARIABLE_NAME);
if (gps_wps) {
    delete gps_wps;
    gps_wps = NULL;
}

Remarks

You can use named variables to enable communication between two or more gauges. To establish communication between gauges, a “server” and “client” gauge needs to be defined. The terms “server” and “client” just distinguish between variable ownership and variable usage:

• The server gauges provides one or more named variables for other gauges to access.
• The client gauges accesses one or more named variables from the server gauges.

A single gauge can be both a server (by providing one or more variables) and a client (by accessing another gauge's variables) at the same time. Use the register_var_by_name, unregister_var_by_name, and initialize_var_by_name functions with named variables. The server gauge uses the register_var_by_name function to register a named variable with the panel system at startup, so create a callback for your gauge as part of the gauge_header structure. You can set this so it performs at startup, on shutdown, etc.

When using named variables, don’t call the lookup_var function (as you would with the standard panel system variables). Afterinitialize_var_by_name is called, the var_ptr field of the MODULE_VAR structure contains a pointer to the named variable. The panel system doesn’t recognize named variables, per se, but the system does maintain the name to the pointer link for gauges to query. As a result, you can’t use a named variable as a controlling variable for an ELEMENT structure directly. Instead, use a MODULE_VAR_NONE structure and provide a callback function that can query the variable’s value using the var_ptr field of the MODULE_VAR structure.

Because named variables work via direct pointers between gauges, make sure that the server gauge is loaded before, or at the same time as, the client gauge. You can make sure this happens by either putting both gauges on the same panel window or by putting the server gauge on the main panel window. This ensures that the server gauge is loaded and the named variable is registered before the client gauge tries to connect to it. Alternatively, you can check the returned var_ptr for NULL and the returned var_type (both in the MODULE_VAR structure) for VAR_TYPE_NONE and execute (in the ELEMENT callback function) the initialize_var_by_name function until it returns valid information. (You can also call theinitialize_var_by_name function every time you want to access the variable, but this approach is a little slower than caching the information once it's received.). The server gauge must keep checking the current value of the variable(s) it has made available, if the current state/value of that variable has any effect.

You can use named variables at any point in the simulation when you want to pass information between two or more gauges. Because named variables are shared by direct pointer access, you can also share out an entire data structure using one named variable, as long as the server and client gauges interpret the same data format.

You can place these gauges anywhere on a panel, as long as the server gauge is guaranteed to load before or at the same time as the client gauge.

See Also

• C++ Gauges Function Reference
• initialize_var_by_name
• unregister_var_by_name

send_key_event

The send_key_event function transmits a WM_COMMAND application event.

Syntax

void send_key_event(
  ID32  event_id,
  UINT32  value
);

Parameters

event_id
  [in]  Specifies a WM_COMMAND event ID.
value
  [in]  Specifies a value to be transmitted along with the event ID. Can be set to zero.

Return Values

This function does not return a value.

Remarks

This function transmits a message with the following syntax:

PostMessage(hwndMain, WM_COMMAND, event_id, (LPARAM) value);

See Also

• C++ Gauges Function Reference
• trigger_key_event

set_gauge_flags

The set_gauge_flags function is used to specify the flags for a gauge.

Syntax

void set_gauge_flags(
  PCSTRINGZ  name,
  FLAGS32  newflags
);

Parameters

name
  [in]  Specifies the name of the gauge.
newflags
  [in]   One or more of the following flags:

GAUGE_FLAG_NORMAL	0
GAUGE_FLAG_HIDDEN	0x1
GAUGE_FLAG_BLINKING	0x2
GAUGE_FLAG_GRAYED	0x4
GAUGE_FLAG_HILIGHTED	0x8

Return Values

This function does not return a value.

Remarks

None.

See Also

• get_gauge_flags
• C++ Gauges Function Reference

set_named_variable_typed_value

The set_named_variable_typed_value function specifies a local variable should be set to the given value with the given units.

Syntax

void set_named_variable_typed_value(
  ID  id,
  FLOAT64  value,
  ENUM  units
);

Parameters

id
  [in]  Specifies the ID of the variable.
value
  [in]  Specifies the value the variable should be set to.
units
  [in]  Specifies the units of the value.

Return Values

This function does not return a value.

Remarks

None.

See Also

• get_named_variable_typed_value
• get_named_variable_value
• set_named_variable_value
• C++ Gauges Function Reference

set_named_variable_value

The set_named_variable_value function sets a local variable to a given value.

Syntax

void set_named_variable_value(
  ID  id,
  FLOAT64  value
);

Parameters

id
  [in]  Specifies the ID of the variable.
value
  [in]  Specifies the value the variable should be set to.

Return Values

This function does not return a value.

Remarks

None.

See Also

• get_named_variable_typed_value
• get_named_variable_value
• set_named_variable_typed_value
• C++ Gauges Function Reference

tooltip_units_getset

The tooltip_units_getset function specifies or retrieves the tooltip units (metric or US).

Syntax

ENUM tooltip_units_getset(
  int  action,
  ENUM  type
);

Parameters

action
  [in]  Specifies the action. If this value is less than zero, the units are toggled (between metric and US imperial). If this value equals zero, the enum value for the units is returned. If this value is greater than zero, the units are set to the value of the type parameter.
type
  [in]  The enum value to set the tooltip units to, one of:

enum TOOLTIP_UNITS_TYPE {
  TOOLTIP_UNITS_TYPE_DEFAULT,
  TOOLTIP_UNITS_TYPE_METRIC,
  TOOLTIP_UNITS_TYPE_US,
};

Return Values

The function returns one member of the TOOLTIPS_UNITS_TYPE enumeration.

Remarks

None.

See Also

• C++ Gauges Function Reference

trigger_key_event

The trigger_key_event function initiates the action of a key event.

Syntax

ERR trigger_key_event(
  ID32  event_id,
  UINT32  value
);

Parameters

event_id
  [in]  Specifies the event ID. Refer to the list of key events in the EventIDs document, and the **#define KEY_**events in gauges.h.
value
  [in]  Specifies an additional integer value. Set this to zero if it is not required.

Return Values

The function returns an ERR, which is usually ignored. If the event requested is not appropriate, it simply will not happen.

Example

static MODULE_VAR nav_light;
lookup_var( &nav_light);
trigger_key_event( KEY_TOGGLE_NAV_LIGHTS, 0 );

Also see the SDK.Fuel_Selector.cpp sample.

Remarks

None.

See Also

• C++ Gauges Function Reference
• send_key_event

unregister_all_named_vars

The unregister_all_named_vars function unregisters all token variables, and frees up the memory used.

Syntax

void unregister_all_named_vars();

Parameters

This function takes no parameters.

Return Values

This function does not return a value.

Remarks

None.

See Also

• C++ Gauges Function Reference

unregister_key_event_handler

The unregister_key_event_handler function unregisters the key event handler.

Syntax

void unregister_key_event_handler(
  GAUGE_KEY_EVENT_HANDLER  handler,
  PVOID  userdata
);

Parameters

handler
  [in]  Specifies the handler function.
userdata
  [in]  Specifies the user data value specified when creating the handler function.

Return Values

This function does not return a value.

Remarks

None.

See Also

• C++ Gauges Function Reference
• register_key_event_handler

unregister_var_by_name

The unregister_var_by_name function unregisters a named variable from another gauge, and frees up the memory used.

Syntax

void unregister_var_by_name(
  PSTRINGZ  name
);

Parameters

name
  [in]  Specifies the name of the variable.

Return Values

This function does not return a value.

Example

See register_var_by_name for an example of the use of this function.

Remarks

None.

See Also

• C++ Gauges Function Reference
• register_var_by_name

Structures

The following structures are useful when creating gauges.

MOUSERECT	Defines a mouse rectangle, with associated cursor, help ID, and actions.

MOUSERECT

The MOUSERECT structure defines a mouse rectangle, with associated cursor, help ID, and actions.

Syntax

typedef struct MOUSERECT{
  MOUSE_RECT_TYPE  rect_type;
  PIXBOX  relative_box;
  CURSOR_TYPE  cursor;
  ID  help_id;
  FLAGS  mouse_flags;
  ID  event_id;
  PMOUSE_FUNCTION  mouse_function;
  PVOID  api_data;
};

Members

rect_type
   Type of mouse rectangle, one of:

typedef enum
{
    MOUSE_RECT_EOL,
    MOUSE_RECT_PARENT,
    MOUSE_RECT_CHILD,
    MOUSE_RECT_END_PARENT,
    MOUSE_RECT_USER,


} MOUSE_RECT_TYPE;

relative_box
   relative sense rectangle (relative to parameter to register function) .
cursor
   Cursor to display when over this window.
help_id
   Pop-up Help Id.
mouse_flags
  One or more mouse flags.
event_id
   Event to generate if mouse_flags conditions met.
mouse_function
   Function to call if mouse_flags conditions met.
api_data
  Unused.

Example

See SDK.Attitude.cpp for an example of the use of this structure.

Remarks

None.

See Also

• C++ Gauges Function Reference
• Structures

Creating a Gauge using XML and C++

The Cabin Comfort sample demonstrates how to link an XML definition of a gauge with underlying C++ code. The advantage of this approach is that you can use the ACE tool to build most of the gauge (described in the Creating XML Gauges document) and yet access the power and flexibility of a programming language.

The sample itself uses some artificial methods of judging passenger comfort in an aircraft. The judgement is based on cabin temperature, the aircraft bank angle, and the status of the attendants and restrooms. These of course are bogus measurements, but the temperature is chosen as it can be set from the gauge, showing how to increment and decrement values using buttons (mouse rectangles) on the gauge, and that information needs to be communicated to the C++ code. The bank angle gives an example of how to access a simulation variable, and the status settings are examples of values that are entirely calculated from within the C++ code. The gauge is shown in the image below. Note the red and blue rectangles are used to increment and decrement the cabin temperature.

Running the Cabin Comfort sample

To get the sample to work go through the following steps:

1. Navigate to the Panels and Gauges SDK\Mixed Mode Sample folder.

2. Open up the Cabin_Comfort solution in Visual Studio, and build the project. Copy the CabinComfort.dll from the Release or Debug folder (whichever you selected to build) to the Microsoft ESP\1.0\ root folder.

3. Copy the CabinComfort.cab file to the ESP\Gauges folder. The cabinet file simply contains the XML description of the gauge Cabin_Comfort.xml, and the background image -- Stone.bmp.

4. Either copy the sample panel.cfg file to the SimObjects\Airplanes\C208B\panel folder, to add the sample gauge to the Cessna C208B Grand Caravan. Alternatively, to add the gauge to any other aircraft, open up the panel.cfg folder for that aircraft and add the lines shown in the following table:

   [Window Titles] Window00=Main Panel Window01=Radio Stack Window02=GPS Window03=Throttle Quadrant Window04=Engine Gauges Window05=Fuel Control Window06=Electrical Window07=Compass Window08=Landing View Window09=Outside Air Temp Window10=Mini Panel Window11=Cabin	Add the line in bold to the [Window Titles] section, though note that the Window number (Window11 in this case) may be different.
   //-- Cabin --------------------------- [Window11] size_mm=225,145 position=6 visible=1 no_luminous=1 gauge01=CabinComfort!CabinComfort, 0,0	Add this entire section to the configuration file. Change the Window number if necessary.

5. Edit the dll.xml file. For Windows XP this is in the Documents and Settings\<user>\Application Data\Microsoft\ESP folder, for Windows Vista this is in the C:\Users\<username>\AppData\Roaming\Microsoft\ESP folder. Add the following to dll.xml:

   <Launch.Addon> <Name>Cabin Comfort</Name> <Disabled>False</Disabled> <ManualLoad>False</ManualLoad> <Path>Cabin_Comfort.dll</Path> <DllStartName>module_init</DllStartName> <DllStopName>module_deinit</DllStopName> </Launch.Addon>

   Note in particular the use of the DllStartName and DllStopName entries. These are necessary to provide the entry and exit functions to the DLL launch code of ESP. For a description of the rest of the parameters, refer to the DLL.XML section of the SimConnect documentation.

6. Now the sample is ready to test. Load up ESP and select the Cessna C208B Grand Caravan.

7. From the Views/Instrument Panel menu select Cabin, and you should see a screen similar to the following image:

Key Steps in Creating the Cabin Comfort sample

The steps in building a gauge system combining XML and C++ can be done in a different order than described here, but the following steps provide a logical process to go about creating such a gauge. One of the advantages of combining XML and C++ is that the gauge graphics can be created with the assistance of the ACE tool, described in the Creating XML Gauges document, which considerably speeds up the trial and error process.

Step 1: Create the XML component of the gauge

Use the ACE tool to help create a great looking gauge. The only parts of the XML gauge that communicate with the C++ component are the evaluated strings. A name for the C++ component needs to be decided upon (the word "CABIN" in the sample), and also names for the variables that are going to be communicated (either read or write). For the Cabin Comfort sample, the evaluated strings are the following:

<GaugeString>%((C:CABIN:CabinTemperature))%!2.2f!</GaugeString>	Displays the cabin temperature as a float, with two decimal places. Note in particular the double brackets surrounding the custom variable. The cabin temperature is set from the gauge - see the two mouse click scripts below.
<GaugeString>%((C:CABIN:BankAngle))%!2.2f!</GaugeString>	Displays the bank angle, again to two decimal places.
<GaugeString>%((C:CABIN:FlightAttendants))%!s!</GaugeString>	Displays a string indicating the current activity of the flight attendants.
<GaugeString>%((C:CABIN:Restroom))%!s!</GaugeString>	Displays the state of the restroom.
<GaugeString>%((C:CABIN:PassengerComfort))%!3.0f!</GaugeString>	Displays the Passenger Comfort setting, with no decimal places.
<Script>(C:CABIN:CabinTemperature) 50 &lt; if{ (C:CABIN:CabinTemperature) 1 + (&gt;C:CABIN:CabinTemperature) }</Script>	If the cabin temperature is less than 50 degrees, 1 is added to the current temperature and the result written back to the cabin temperature variable.
<Script>(C:CABIN:CabinTemperature) 0 &gt; if{ (C:CABIN:CabinTemperature) 1 - (&gt;C:CABIN:CabinTemperature) }</Script>	If the cabin temperature is greater than 0 degrees, 1 is subtracted from the current temperature and the result written back to the cabin temperature variable.

Test and refine the XML as much as possible before coding the C++ component.

Step 2: Creating a property table for the gauge variables

In the code snippets shown below, from the Cabin_Comfort.cpp file, note the definition of the callback name "CABIN", and the names of all the variables, exactly match those in the XML code from Step 1.

struct PROPERTY_TABLE
{
   PCSTRINGZ szPropertyName;
   PCSTRINGZ szUnitsName;
   ENUM units;
};
   
static const char CABIN_CALLBACK_NAME[] = "CABIN";

static PROPERTY_TABLE CABIN_PROPERTY_TABLE[] = 
{
   { "CabinTemperature",	"Celcius",	UNITS_UNKNOWN}, 
   { "BankAngle",	"Degrees", UNITS_UNKNOWN}, 
   { "FlightAttendants",	"String", UNITS_STRING}, 
   { "Restroom",	"String", UNITS_STRING}, 
   { "PassengerComfort",	"Number", UNITS_UNKNOWN},
};
// Enum that contains the properties 
enum CABIN_VAR
{
   CABIN_VAR_CABIN_TEMPERATURE,
   CABIN_VAR_BANK_ANGLE,
   CABIN_VAR_FLIGHT_ATTENDANTS,
   CABIN_VAR_RESTROOM,
   CABIN_VAR_PASSENGER_COMFORT,
};

Step 3: Initialize the variables and the property table

Examine the CABINGaugeCallback class, which inherits the IGaugeCCallback class defined in gauges.h. The simplest way of initializing any variables is to do it in the creation function of this class.

CABINGaugeCallback::CABINGaugeCallback(UINT32 containerId)
: m_RefCount(1),
m_containerId(containerId)
{
   // Initialize aircraft variables
   cabin_temperature	= ROOM_TEMPERATURE;
   flight_attendant_state	= PASSIVE;
   restroom_state	= VACANT;
}

Notice though that the property table defined in Step 2 is initialized in the creation function for CABINPanelCallback. If a string is the units of a variable, set the value to UNITS_STRING in the property table, otherwise set it to UNITS_UNKNOWN. The following code then finds all the unknown units and finds the enumeration value for the units. This is necessary as the actual enumeration values for any units are not exposed, and may change in future versions. By calling get_units_enum this initialization code is made more robust.

CABINPanelCallback::CABINPanelCallback()
{
   // init property table
   for (int n = 0; n < LENGTHOF(CABIN_PROPERTY_TABLE); n++)
   {
      if (ImportTable.PANELSentry.fnptr != NULL &&
      CABIN_PROPERTY_TABLE[n].units == UNITS_UNKNOWN)
      {
         CABIN_PROPERTY_TABLE[n].units = get_units_enum ( CABIN_PROPERTY_TABLE[n].szUnitsName );
      }
   }
}

Step 4: Getting and Setting variables

Notice there are two methods for both getting and setting property table values. One method handles strings, the other numerical values. The CabinTemperature property is the only one that can be set from the gauge controls in the Cabin Comfort sample, and the code to do this follows:

bool CABINGaugeCallback::SetPropertyValue (SINT32 id, FLOAT64 value)
{
   CABIN_VAR eCABINVar = (CABIN_VAR)id;
   switch(eCABINVar)
   {
      case CABIN_VAR_CABIN_TEMPERATURE:
         setCabinTemperature(value);
         break;
      default:
         return false;
   }
   return true; 
}

Step 5: Updating Variables

The CABINGaugeCallback::Update() method is called optimally on a cycle of 18Hz (18 times per second), however it should be pointed out that the actual frequency can be somewhat lower than this, as optimizations are made to maintain frame rates. This function is the right place to put code to change variables that is not dependant on a get or set call. For some gauges this method may well not contain any code at all.

Step 6: Handle the modules initialization and termination

Two very important methods are module_init and module_deinit. The code for these is shown below. These methods are called when the dll is created and removed respectively. Notice in particular the Panels pointer, shown in bold, that is set to NULL. This value is set by the DLL launch code.

void CABINPanelCallbackInit()
{
   CABINPanelCallback *pPanelCallback = new CABINPanelCallback();
   if(pPanelCallback)
   {
      bool b = panel_register_c_callback(CABIN_CALLBACK_NAME, pPanelCallback);
      pPanelCallback->Release();
   } 
}
void CABINPanelCallbackDeInit()
{
   panel_register_c_callback(CABIN_CALLBACK_NAME, NULL);
}

PPANELS Panels = NULL;

GAUGESIMPORT ImportTable = 
{ 
   { 0x0000000F, (PPANELS)NULL }, 
   { 0x00000000, NULL } 
}; 

void FSAPI module_init(void)
{
   if (NULL != Panels)
   {
      ImportTable.PANELSentry.fnptr = (PPANELS)Panels;
      CABINPanelCallbackInit();
   }
} 
// This is the module's export table.
GAUGESLINKAGE Linkage = 
{ 
   0x00000013, 
   module_init, 
   module_deinit, 
   0, 
   0, 
   FS9LINK_VERSION, { 0 }
};

Step 7: Export the initialization, termination and Panels pointer correctly

A key component of the gauge project is the Cabin_Comfort_Def.def definition file. This contains the following:

LIBRARY "Cabin_Comfort" EXPORTS module_init module_deinit Panels DATA

This small piece is vital, as it exports the initialization and termination method names in an undecorated format, and provides the pointer to the Panels data that is absolutely required to be set when the dll is loaded.

Step 8: Compile, Run and Test the DLL gauge

The C++ project should compile into a dll. Follow the steps for running the Cabin Comfort sample to test your own gauge, including adding a <Launch.Addon> section for it to the DLL.XML file. Make sure to place all the different components in the correct folders.