Allegro 4.2 Slow on Windows 7

no-reply@allegro.cc (Mike Geig) — Fri, 25 Feb 2011 09:53:30 +0000

Hello everyone, I need to run Allegro 4.2 for legacy and I am running Windows 7 32-bit. The programs run super slow and are prone to crashing. The same programs run fine in Windows XP and on another Windows 7 box (64 bit). Any ideas what I can do to fix my issue?

no-reply@allegro.cc (LennyLen) — Fri, 25 Feb 2011 13:03:51 +0000

The problem might be caused by badly written code, so perhaps you should post it.

no-reply@allegro.cc (Mike Geig) — Fri, 25 Feb 2011 21:21:32 +0000

Well, I doubt it since it is a simple demo app:

#SelectExpand
  1#include 
  2#include 
  3
  4int main(void)
  5{
  6  allegro_init();
  7  set_gfx_mode(GFX_AUTODETECT_WINDOWED, 640, 480, 0, 0);
  8  install_keyboard();
  9
 10  while(!key[KEY_ESC])
 11  {
 12    rectfill(screen, 320, 240, 340, 360, 15);
 13  }
 14  allegro_exit();
 15}
 16END_OF_MAIN();

no-reply@allegro.cc (Matthew Leverton) — Fri, 25 Feb 2011 21:24:43 +0000

How do you know that runs slowly? It's not doing anything... Does it crash?

Do you always use 8-bit graphics? Those are known to not work well under Windows 7.

The best way to get good performance is:

set_color_depth(desktop_color_depth());

Also, Allegro 4.4 might work better. It's source compatible with 4.2.

One last thing, make sure the Allegro libraries/binaries you use are for your specific compiler version (not a problem if you built it yourself) and that you use the same C or assembly settings during build, as mixing those can cause crashes.

no-reply@allegro.cc (Mike Geig) — Fri, 25 Feb 2011 22:11:07 +0000

Thanks Matthew, setting the color depth made the program work great. The only problem there is that my primitives are rendered a very dark, almost black color no matter what color I pass in for them.

Any ideas?

no-reply@allegro.cc (Edgar Reynaldo) — Fri, 25 Feb 2011 22:19:14 +0000

Try using makecol instead of passing 15 as the color?

no-reply@allegro.cc (Matthew Leverton) — Fri, 25 Feb 2011 22:44:49 +0000

When using anything higher than 8-bit color depth, you have to use makecol to get the proper integer representation of a color. (8-bit uses an indexed palette.)

makecol(255,255,255) is white.

As an aside, when using 8-bit mode under Windows, the GFX_GDI driver is probably the most compatible.