The client application sends the ICM_ABOUT message to display your driver’s About dialog box. The client application sets dwParam1 to -1; the application is querying whether your driver supports display of an About box. Your driver returns ICERR_OK if it does, and it returns ICERR_UNSUPPORTED if it does not. Your driver should only display an About box if the client application specifies a window handle in dwParam1. The window handle indicates the parent of the dialog box.
The client application uses the ICM_GETINFO message to obtain a description of your driver. Your driver should respond to this message by filling in the ICINFO structure it receives with the message. The flags your driver sets in the structure tell the client application which capabilities the driver supports. Your driver will not typically use the szDriver[128] member. This member is used to specify the module that contains the driver. Set the flags corresponding to the capabilities of your driver in the low-ordered word of the dwFlags member. You can use the high-ordered word for driver-specific flags.