gdk-win32: forced 24bpp causing slowness?

[Peter Zelezny <pzel dodo com au>]

Hi All,

Running gtk-win32 on a 32bit color  display seems to be a little slow. If you
manipulate GdkImages and then blit them to windows, it's noticably slower than
at 24bpp. I think I have found the cause, this peice of code around
gdkvisual-win32.c line 237

  else if (bitspixel == 24 || bitspixel == 32)
    {
      bitspixel = 24;
      system_visual->type = GDK_VISUAL_TRUE_COLOR;

Does someone remember why it's always forced back to 24bpp? I *think* the
slowness might come from blitting a 24bpp DIB into a window that's running
natively at 32bpp, where Windows has to do an on-the-fly conversion.

Removing the "bitspixel = 24;" line fixed the noticable slowness, but what
other side effects will it have on gdk? I suppose pixmaps/images will take a
little more memory (*4/3), but I havn't noticed any other problems.

-- 
Peter.