drawing under icons on desktop

Question

I wrote a program who paints widget on desktop wallpaper, under desktop icons, and all was good. But I reveal a strange bug - my program was not works on some other computers - they displays the same desktop without widget after start.

So, have anybody any expirience, some knowledge in this area? Please, help me! :)

(I can't find any computers near, where widget not works, in my computer all works well. I wrote a lot of test programs, whose tries draw anything on desktop with rather methods, but test displays nothing too in my friends computers.)

Drawing method:

I wrote a dll, who finds desktop window (progman->child->child )) and creates a hook and install own window procedure for desktop. In window procedure i hook WM_ERASEBKGND:

case WM_ERASEBKGND:
  HDC hdc = (HDC)wparam;
  PaintDesktop(hdc);
  WidgetPaint(hdc);
  return 1;

// I skip in this code getting and setting clipping areas for fast drawing. (I tried all combinations with clipping and without clipping)

And in tests I also trying to paint widget in WM_PAINT message with same results -- all already works at me, but works not at all my friends.

upd: I solved it! :)

Answer 1

I solved it! It's simple was a 64-bit machines) So I compile my code for 64-bit and widget start work pretty good!

And, also -

PaintDesktop(hdc);

will produce very bright wallpaper in Windows7 (and Vista) with Aero. (User's wallpaper comes brighten). Must be

CallWindowProc(OldWndProc, WM_ERASEBKGND, wparam, lparam);

Cause of this - Aero treats PaintDesktop() as usual paint (over virtual screen wallpaper, that is the same as on desktop) with color summation.

Regards! :)