LPTEXTOUTPROC

Artikkeli
03/10/2023

When the user executes a source control operation from inside the integrated development environment (IDE), the source control plug-in might want to convey error or status messages relating to the operation. The plug-in can display its own message boxes for this purpose. However, for more seamless integration, the plug-in can pass strings to the IDE, which then displays them in its native way of displaying status information. The mechanism for this is the LPTEXTOUTPROC function pointer. The IDE implements this function (described in more detail below) for displaying error and status.

The IDE passes to the source control plug-in a function pointer to this function, as the lpTextOutProc parameter, when calling the SccOpenProject. During an SCC operation, for example, in the middle of a call to the SccGet involving many files, the plug-in can call the LPTEXTOUTPROC function, periodically passing strings to display. The IDE may display these strings on a status bar, in an output window, or in a separate message box, as appropriate. Optionally, the IDE may be able to display certain messages with a Cancel button. This enables the user to cancel the operation, and it gives the IDE the ability to pass this information back to the plug-in.

Signature

The IDE's output function has the following signature:

typedef LONG (*LPTEXTOUTPROC) (
   LPSTR display_string,
   LONG mesg_type
);

Parameters

display_string

A text string to display. This string should not be terminated with a carriage return or a line feed.

mesg_type

The type of message. The following table lists the supported values for this parameter.

Value	Description
`SCC_MSG_INFO, SCC_MSG_WARNING, SCC_MSG_ERROR`	The message is considered Information, Warning, or Error.
`SCC_MSG_STATUS`	The message shows status and can be displayed in the status bar.
`SCC_MSG_DOCANCEL`	Sent with no message string.
`SCC_MSG_STARTCANCEL`	Begins displaying a Cancel button.
`SCC_MSG_STOPCANCEL`	Stops displaying a Cancel button.
`SCC_MSG_BACKGROUND_IS_CANCELLED`	Asks IDE if the background operation is to be cancelled: IDE returns `SCC_MSG_RTN_CANCEL` if operation was cancelled; otherwise, returns `SCC_MSG_RTN_OK`. The `display_string` parameter is cast as an SccMsgDataIsCancelled structure, which is supplied by the source control plug-in.
`SCC_MSG_BACKGROUND_ON_BEFORE_GET_FILE`	Tells the IDE about a file before it is retrieved from version control. The `display_string` parameter is cast as an SccMsgDataOnBeforeGetFile structure, which is supplied by the source control plug-in.
`SCC_MSG_BACKGROUND_ON_AFTER_GET_FILE`	Tells the IDE about a file after it has been retrieved from version control. The `display_string` parameter is cast as an SccMsgDataOnAfterGetFile structure, which is supplied by the source control plug-in.
`SCC_MSG_BACKGROUND_ON_MESSAGE`	Tells the IDE of the current status of a background operation. The `display_string` parameter is cast as an SccMsgDataOnMessage structure, which is supplied by the source control plug-in.

Return value

Value	Description
SCC_MSG_RTN_OK	The string was displayed or the operation was completed successfully.
SCC_MSG_RTN_CANCEL	The user wants to cancel the operation.

Example

Suppose the IDE calls the SccGet with twenty file names. The source control plug-in wants to prevent canceling the operation in the middle of a file get. After getting each file, it calls lpTextOutProc, passing it the status information on each file, and sends a SCC_MSG_DOCANCEL message if it has no status to report. If at any time the plug-in receives a return value of SCC_MSG_RTN_CANCEL from the IDE, it cancels the get operation immediately, so that no more files are retrieved.

Structures

SccMsgDataIsCancelled

typedef struct {
   DWORD dwBackgroundOperationID;
} SccMsgDataIsCancelled;

This structure is sent with the SCC_MSG_BACKGROUND_IS_CANCELLED message. It is used to communicate the ID of the background operation that was canceled.

SccMsgDataOnBeforeGetFile

typedef struct {
   DWORD dwBackgroundOperationID;
   PCSTR szFile;
} SccMsgDataOnBeforeGetFile;

This structure is sent with the SCC_MSG_BACKGROUND_ON_BEFORE_GET_FILE message. It is used to communicate the name of the file about to be retrieved and the ID of the background operation that is doing the retrieving.

SccMsgDataOnAfterGetFile

typedef struct {
   DWORD dwBackgroundOperationID;
   PCSTR szFile;
   SCCRTN sResult;
} SccMsgDataOnAfterGetFile;

This structure is sent with the SCC_MSG_BACKGROUND_ON_AFTER_GET_FILE message. It is used to communicate the result of retrieving the specified file as well as the ID of the background operation that did the retrieving. See the return values for the SccGet for what can be given as a result.

SccMsgDataOnMessage

typedef struct {
   DWORD dwBackgroundOperationID;
   PCSTR szMessage;
   BOOL bIsError;
} SccMsgDataOnMessage;

This structure is sent with the SCC_MSG_BACKGROUND_ON_MESSAGE message. It is used to communicate the current status of a background operation. The status is expressed as a string to be displayed by the IDE, and bIsError indicates the severity of the message (TRUE for an error message; FALSE for a warning or for an informational message). The ID of the background operation sending the status is also given.

Code example

Here is a brief example of calling LPTEXTOUTPROC to send the SCC_MSG_BACKGROUND_ON_MESSAGE message, showing how to cast the structure for the call.

LONG SendStatusMessage(
    LPTEXTOUTPROC pTextOutProc,
    DWORD         dwBackgroundID,
    LPCTSTR       pStatusMsg,
    BOOL          bIsError)
{
    SccMsgDataOnMessage msgData = { 0 };
    LONG                result  = 0;

    msgData.dwBackgroundOperationID = dwBackgroundID;
    msgData.szMessage               = pStatusMsg;
    msgData.bIsError                = bIsError;

    result = pTextOutProc(reinterpret_cast<LPCTSTR>(&msgData), SCC_MSG_BACKGROUND_ON_MESSAGE);
    return result;
}

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