DOCUMENT:Q121330  06-NOV-1999  [win16sdk]
TITLE   :BUG: MCIWndClass Popup Window Palette Flashes
PRODUCT :Microsoft Windows Software Development Kit
PROD/VER:WINDOWS:1.1,3.1
OPER/SYS:
KEYWORDS:kbmmkbbuglist

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The information in this article applies to:

 - Microsoft Windows Software Development Kit (SDK) 3.1 
 - Microsoft Video for Windows, version 1.1 
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SYMPTOMS
========

An MCIWndClass popup window realizes its logical palette in the foreground
instead of the background as requested in a call to MCIWndRealize() with the
fBkgnd flag set to TRUE. The foreground palette realization is seen as a flash.

The following code demonstrates the setting that results in the flash. The flash
occurs when the popup window receives the input focus from another application
using a different logical palette.

   hwndPanel = MCIWndCreate(hwndParent, hInst,
         MCIWNDF_NOAUTOSIZEMOVIE | MCIWNDF_NOMENU |
         WS_OVERLAPPED | WS_BORDER | WS_CAPTION |
         WS_SYSMENU | WS_POPUP, NULL);
      MCIWndOpen(hwndPanel, fname, 0);
      MCIWndRealize(hwndPanel, TRUE);
      SetWindowPos(hwndPanel, HWND_TOP, X, Y, 0, 0,
         SWP_NOSIZE | SWP_DRAWFRAME | SWP_SHOWWINDOW);
      MCIWndPlay(hwndPanel);

CAUSE
=====

When the MCIWndClass popup window receives the input focus from another
application that uses a different logical palette, the popup window receives a
WM_QUERYNEWPALETTE message that is processed for the popup window by the
MCIWndProc() procedure. In the MCIWndProc() procedure, the "case
WM_QUERYNEWPALETTE:" results in a call to MCIWndRealize() with the flag fBkgnd
set to FALSE. This occurs even if the popup window's palette was originally
realized in the background.

STATUS
======

Microsoft has confirmed this to be a bug in Microsoft Video for Windows Version
1.1. We are researching this problem and will post new information as it becomes
available in the Microsoft Knowledge Base.

MORE INFORMATION
================

The problem described in the SYMPTOMS section occurs only with popup windows. It
does not arise when the window style is WS_CHILD. When the window is a child
window, the WM_QUERYNEWPALETTE messages are processed by the parent window's
callback procedure instead of the MCIWndProc() procedure.

When the window involved is a popup window, you can avoid the flash by
subclassing the MCIWndProc() procedure and allowing the subclassing application
to process the WM_QUERYNEWPALETTE message directly by calling MCIWndRealize()
with the fBkgnd flag set to TRUE. The following code demonstrates this
workaround:

   // MakeProcInstance() is called once in a convenient place such
   // as the application's InitInstance() procedure. RealizeProc()
   // is the procedure that subclasses MCIWndProc(). RealizeProc()
   // will process WM_QUERYNEWPALETTE messages on behalf of
   // MCIWndProc(). In the Module Definition File, list the
   // RealizeProc() procedure under EXPORTS.

      lpfnRealizeProc = MakeProcInstance((FARPROC)
         RealizeProc, hinstCurrent);

   // In the application's MainWndProc() under "case WM_DESTROY:",
   // call FreeProcInstance().

      FreeProcInstance(lpfnRealizeProc);

   // Add the next two function calls to the code shown in the
   // Symptoms section just after the call to MCIWndCreate(). The
   // GetWindowLong() call returns a pointer to the popup window's
   // original window procedure, namely MCIWndProc(). The
   // SetWindowLong() procedure specifies that the RealizeProc()
   // procedure is the new window procedure for the popup window.

      lpfnOldRealizeProc = (FARPROC)GetWindowLong(hwndPanel,

         GWL_WNDPROC);

      SetWindowLong(hwndPanel, GWL_WNDPROC, (LONG)
         lpfnRealizeProc);

   // The following procedure subclasses MCIWndProc(). It processes
   // the WM_QUERYNEWPALETTE messages. All other messages
   // are sent to MCIWndProc(), which is pointed to by the
   // parameter lpfnOldRealizeProc.

   long FAR PASCAL RealizeProc(HWND hwndPanel, UINT message, WPARAM
                  wParam, LPARAM lParam)
   {
      switch (message)
      {
         case WM_QUERYNEWPALETTE:
            return (MCIWndRealize(hwndPanel, TRUE));

         default:
             return (CallWindowProc((WNDPROC)lpfnOldRealizeProc,
               hwndPanel, message, wParam, lParam));
      }
   }

Additional query words: 3.10 1.10 mci buglist3.10 buglist1.10

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Keywords          : kbmm kbbuglist
Technology        : kbAudDeveloper kbWin3xSearch kbVideoSearch kbSDKSearch kbWinSDKSearch kbWinSDK310 kbVideo110
Version           : WINDOWS:1.1,3.1

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