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! 🙂