Producing translucent dialog boxes and windows without flickering

• Download demo project - 12 Kb
• Download source - 18 Kb

Problem

1. Text and ListView controls (and several others) aren't rendered correctly during fade-in.
2. You cannot specify a translucency for the window, i.e., after the animation is over, the window is opaque.

Workaround?

Solution

INT_PTR CALLBACK DialogProc(
  HWND hwndDlg,  // handle to dialog box
  UINT uMsg,     // message
  WPARAM wParam, // first message parameter
  LPARAM lParam  // second message parameter
  ) 
{
   RECT rcDesktop;
   RECT rcMe;

   BYTE bTranslucency;

   const DWORD ANIMATION_MILLIS = 200;
   const BYTE TRANSLUCENCY = 192;
   const BYTE TRANSLUCENCY_STEP = 16;
   const DWORD TRANSLUCENCY_TIMEOUT 
      = TRANSLUCENCY_STEP * ANIMATION_MILLIS / TRANSLUCENCY;

   switch (uMsg) {
   case WM_INITDIALOG:
      // Make it a layered window.
      ::SetWindowLong(hwndDlg, GWL_EXSTYLE,
         ::GetWindowLong(hwndDlg, GWL_EXSTYLE) | WS_EX_LAYERED);

      // Completely transparent window - note the third parameter
      ::SetLayeredWindowAttributes(hwndDlg, 0, 0, LWA_ALPHA);

      // Show it _first_
      ::ShowWindow(hwndDlg, SW_SHOW);

      // Redraw contents NOW - no flickering since the window's not visible
      ::RedrawWindow(hwndDlg, NULL, NULL, RDW_UPDATENOW); 

      // Normally, you would use a timer here...
      for (bTranslucency = 0; bTranslucency < TRANSLUCENCY;
      bTranslucency+=TRANSLUCENCY_STEP) {
         // Adjust the translucency
         ::SetLayeredWindowAttributes(hwndDlg, 0, bTranslucency, LWA_ALPHA);

         // Wait
         ::Sleep(TRANSLUCENCY_TIMEOUT);
      }

      // Set the final translucency
      ::SetLayeredWindowAttributes(hwndDlg, 0, bTranslucency, LWA_ALPHA);
      break;
   }

   return 0;
}

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