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IWiaUIExtension COM interface

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If you implement the IWiaUIExtension interface, you can implement none, some, or all the IWiaUIExtension methods.

If a particular method returns E_NOTIMPL, the system-provided alternative, and one is available, it is used instead.

The IWiaUIExtension interface provides the following methods:P

Method Description
IWiaUIExtension::DeviceDialog Provides a custom user interface that replaces the default system user interface.
IWiaUIExtension::GetDeviceBitmapLogo Gets a custom bitmap logo for the device.
IWiaUIExtension::GetDeviceIcon Gets a custom device icon.

IWiaUIExtension::DeviceDialog accepts a pointer to a DEVICEDIALOGDATA structure (declared in wiadevd.h), which contains all the data needed to implement the device dialog box.

The device dialog must be implemented as a modal Win32 dialog box, subject to the following four constraints:

  1. The array of items returned in pDeviceDialogData-->ppWiaItems must be allocated using CoTaskMemAlloc, and is freed by the application using CoTaskMemFree (see the Microsoft Windows SDK documentation for both functions).

  2. You must not destroy or release the root item stored in pDeviceDialogData -->pIWiaItemRoot. You also must not cause the root item to become invalid. For instance, you must not call the WIA_CMD_SYNCHRONIZE device command.

  3. Return S_OK to indicate that the user requested a data transfer, and S_FALSE to indicate that the user canceled the transfer.

  4. Take care to ensure that memory or resource leaks are not introduced in this component, because it runs in-process in the application.

IWiaUIExtension::GetDeviceIcon allows the application to use a driver-specified icon. To avoid resource leaks, this icon should be loaded with LoadImage, using the LR_SHARED flag (see the Windows SDK documentation).

IWiaUIExtension::GetDeviceBitmapLogo allows the application to present device and vendor logos as appropriate. Currently, no system components use this method. The bitmap should be a DIB-allocated bitmap using CreateDIBSection, or loaded using LoadImage with the LR_CREATEDIBSECTION flag (see the Windows SDK documentation for more information). This allows the application to extract any palette information and adapt to the current or changing display color depths.

To implement a custom scanning dialog box in a WIA scanner driver, use the IWiaUIExtension::DeviceDialog method (with the four constraints listed above) to create a Win32 modal dialog box and pass the DEVICEDIALOGDATA structure to the dwInitParam parameter of the DialogBoxParam function as an LPARAM.

It is important to remember that the device dialog box itself does not manage the data transfers. The dialog box merely returns a pointer to an array of IWiaItem interface pointers (with properties set) from the driver to the application. It is then up to the application to negotiate the transfer mechanism and format.