Fixed bug #33 Mike Frysinger wrote: > with libsdl-1.2.9, some games (like bomberclone) started > segfaulting in Gentoo [...snip...] > the last change in the last hunk: [...snip...] > if i change the statement to read: > (table[which].blit_features & GetBlitFeatures()) == GetBlitFeatures() > bomberclone no longer segfaults on my box Alex Volkov wrote: > The test "(table[which].blit_features & GetBlitFeatures()) == > table[which].blit_features)" is correct, and the previous > "(table[which].cpu_mmx == SDL_HasMMX())" was actually broken. I think there is potentially a slightly different cause of the above problem. During the introduction of the Altivec code, the blit_table struct field 'alpha' got changed from a straightforward enum to a bitmask, which makes perfect sense by itself. However, now the table driven blitter selection code in SDL_CalculateBlitN() can choose the wrong blitters when searching for a NO_ALPHA blitter because of the following code: int a_need = 0; ... (a_need & table[which].alpha) == a_need && When searching through the normal_blit_2[] table, a SET_ALPHA blitter (like Blit_RGB565_ARGB8888) can now be selected instead of a NO_ALPHA one, causing alpha channel bits to appear in a non-alpha destination surface. I suppose this could theoretically be an indirect cause of the segfault mentioned above. I *think* this can be fixed by changing to int a_need = NO_ALPHA;

.TH "SDL_VideoModeOK" "3" "Tue 11 Sep 2001, 23:01" "SDL" "SDL API Reference" 
.SH "NAME"
SDL_VideoModeOK\- Check to see if a particular video mode is supported\&.
.SH "SYNOPSIS"
.PP
\fB#include "SDL\&.h"
.sp
\fBint \fBSDL_VideoModeOK\fP\fR(\fBint width, int height, int bpp, Uint32 flags\fR);
.SH "DESCRIPTION"
.PP
\fBSDL_VideoModeOK\fP returns \fB0\fR if the requested mode is not supported under any bit depth, or returns the bits-per-pixel of the closest available mode with the given width, height and requested \fIsurface\fR flags (see \fI\fBSDL_SetVideoMode\fP\fR)\&.
.PP
The bits-per-pixel value returned is only a suggested mode\&. You can usually request and bpp you want when \fIsetting\fR the video mode and SDL will emulate that color depth with a shadow video surface\&.
.PP
The arguments to \fBSDL_VideoModeOK\fP are the same ones you would pass to \fISDL_SetVideoMode\fR
.SH "EXAMPLE"
.PP
.nf
\f(CWSDL_Surface *screen;
Uint32 bpp;
\&.
\&.
\&.
printf("Checking mode 640x480@16bpp\&.
");
bpp=SDL_VideoModeOK(640, 480, 16, SDL_HWSURFACE);

if(!bpp){
  printf("Mode not available\&.
");
  exit(-1);
}

printf("SDL Recommends 640x480@%dbpp\&.
", bpp);
screen=SDL_SetVideoMode(640, 480, bpp, SDL_HWSURFACE);
\&.
\&.\fR
.fi
.PP
.SH "SEE ALSO"
.PP
\fI\fBSDL_SetVideoMode\fP\fR, \fI\fBSDL_GetVideoInfo\fP\fR
...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:01