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_GL_SetAttribute" "3" "Tue 11 Sep 2001, 23:01" "SDL" "SDL API Reference" 
.SH "NAME"
SDL_GL_SetAttribute\- Set a special SDL/OpenGL attribute
.SH "SYNOPSIS"
.PP
\fB#include "SDL\&.h"
.sp
\fBint \fBSDL_GL_SetAttribute\fP\fR(\fBSDL_GLattr attr, int value\fR);
.SH "DESCRIPTION"
.PP
Sets the OpenGL \fIattribute\fR \fBattr\fR to \fBvalue\fR\&. The attributes you set don\&'t take effect until after a call to \fI\fBSDL_SetVideoMode\fP\fR\&. You should use \fI\fBSDL_GL_GetAttribute\fP\fR to check the values after a \fBSDL_SetVideoMode\fP call\&.
.SH "RETURN VALUE"
.PP
Returns \fB0\fR on success, or \fB-1\fR on error\&.
.SH "EXAMPLE"
.PP
.nf
\f(CWSDL_GL_SetAttribute( SDL_GL_RED_SIZE, 5 );
SDL_GL_SetAttribute( SDL_GL_GREEN_SIZE, 5 );
SDL_GL_SetAttribute( SDL_GL_BLUE_SIZE, 5 );
SDL_GL_SetAttribute( SDL_GL_DEPTH_SIZE, 16 );
SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 );
if ( (screen=SDL_SetVideoMode( 640, 480, 16, SDL_OPENGL )) == NULL ) {
  fprintf(stderr, "Couldn\&'t set GL mode: %s
", SDL_GetError());
  SDL_Quit();
  return;
}\fR
.fi
.PP
.PP
.RS
\fBNote:  
.PP
The \fBSDL_DOUBLEBUF\fP flag is not required to enable double buffering when setting an OpenGL video mode\&. Double buffering is enabled or disabled using the SDL_GL_DOUBLEBUFFER attribute\&.
.RE
.SH "SEE ALSO"
.PP
\fI\fBSDL_GL_GetAttribute\fP\fR, \fIGL Attributes\fR
...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:01