Re: AW: [Visualoberon-win32] Bitmaps

[Stewart G. <sgr...@ip...>]

tim...@ma... wrote:
> 
> Hallo!
> 
> > For me, colours drawn into bitmaps don't come out when copied into a
> > window.
> 
> I didn't have that problems when checking functionality using the WireFrame
> stuff in XTest, but it only uses black and white.
> 
> Perhaps a color allocation problem? But colors aren't bitmap local, they are
> global
> to the programm!?

After a lot of detective work, I finally found the problem. Its rather
subtle.

It seems that CreateCompatibleBitmap requires the handle on the original
DC, *not* the compatible DC returned by CreateCompatibleDC. The bitmap
created with the compatible DC appears to be monochrome so when it it
blitted into the window DC the result is a dithered image that maps
black/white to the default foreground/background colour. I guess Windows
does not regard "compatibility" as transitive.

The attached Display.Mod corrects the problem in CreateBitmap.

Cheers,
  Stewart