Writing the Main Message Loop

The main message loop of an MDI application is similar to that of a non-MDI application handling accelerator keys. The difference is that the MDI message loop calls the TranslateMDISysAccel function before checking for application-defined accelerator keys or before dispatching the message.

The following example shows the message loop of a typical MDI application.

while (GetMessage(&msg, (HWND) NULL, 0, 0)) 
{ 
    if (!TranslateMDISysAccel(hwndMDIClient, &msg) && 
            !TranslateAccelerator(hwndFrame, hAccel, &msg))
    { 
        TranslateMessage(&msg); 
        DispatchMessage(&msg); 
    } 
} 
 

The TranslateMDISysAccel function translates WM_KEYDOWN messages into WM_SYSCOMMAND messages and sends them to the active MDI child window. If the message is not an MDI accelerator message, the function returns FALSE, in which case the application uses the TranslateAccelerator function to determine whether any of the application-defined accelerator keys were pressed. If not, the loop dispatches the message to the appropriate window procedure.