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Add UI to a WIA Minidriver

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You can add extended UI or replace UI components for a WIA minidriver by installing a separate DLL with the WIA minidriver. Unlike a TWAIN driver, a WIA driver's UI component is separate from the actual WIA minidriver. The UI components run in the application's process, while the WIA minidriver runs in the WIA service's process. So, a WIA driver might not directly show UI; only the WIA UI extension modules of the driver might show UI.

WIA allows you to add property pages to the system-provided dialog boxes, provide custom icon images, or completely replace the system-provided dialog box. The property page extension mechanism is based on the shell definition of the IShellPropSheetExt COM interface (described in the Microsoft Windows SDK documentation). This mechanism is registered under the property sheet handlers (HKCR\Clsid\<Clsid of the device UI>\shellex\PropertySheetHandlers).

All device dialog box extensions, except property pages, require that the IWiaUIExtension Interface be implemented.

If you implement the IWiaUIExtension interface and do not wish to replace the system UI, you must return E_NOTIMPL for the IWiaUIExtension::DeviceDialog method. Any other return value suppresses the device dialog box for the device.

The device dialog box must be implemented as a modal dialog in an in-process COM server, passing pDeviceDialogData ->hwndParent for the parent to the DialogBoxParam function (described in the Windows SDK documentation). The device dialog box must return S_OK for success, S_FALSE if the user cancels the dialog box, or a COM error HRESULT for other errors.

The DEVICEDIALOGDATA structure contains all of the data needed to implement a custom device dialog.

To provide a custom icon for a device, implement the IWiaUIExtension::GetDeviceIcon method. The icon is destroyed by the caller using DestroyIcon (described in the Windows SDK documentation).

Note   WIA has very limited scripting support. So, while it is possible to replace the UI, it is not possible to merely suppress it in a script.

The rest of this section includes:

Create a "Hello World" WIA Minidriver UI Extension, a complete example of how to implement your own custom UI.