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Date: Sat, 10 Apr 2004 02:25:33 -0400 From: Glenn Maynard To: sdl@libsdl.org Subject: [SDL] SDL_SetVideoMode() failing and not setting an error (patch) Running an OpenGL SDL application off 1.2.7, at SDL_InitSubSystem(SDL_INIT_VIDEO) time: Warning: Unable to initialize AAlib mouseUsing AAlib driver: Slang driver 1.0 (slang) SDL_SetVideoMode then fails; SDL_GetError() returns "". The installation problem is straightforward: X (the higher priority driver) isn't running, so SDL is falling back on aalib. However, no error is being set when aalib fails to initialize. This also happens with the svgalib driver. SDL_video.c line ~653 sets mode to NULL, since aalib didn't return an OpenGL surface. Line ~711 ("failed setting a video mode") returns NULL. The attached patch sets an error. It's a horrible, useless error message--it should really say eg. "aalib does not support OpenGL"; this should probably be done earlier in the individual drivers, too.
author Sam Lantinga <slouken@libsdl.org>
date Sun, 11 Apr 2004 19:54:40 +0000
parents 355632dca928
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><H1
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>SDL_GL_SetAttribute</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN2742"
></A
><H2
>Name</H2
>SDL_GL_SetAttribute&nbsp;--&nbsp;Set a special SDL/OpenGL attribute</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN2745"
></A
><H2
>Synopsis</H2
><DIV
CLASS="FUNCSYNOPSIS"
><A
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></A
><P
></P
><PRE
CLASS="FUNCSYNOPSISINFO"
>#include "SDL.h"</PRE
><P
><CODE
><CODE
CLASS="FUNCDEF"
>int <B
CLASS="FSFUNC"
>SDL_GL_SetAttribute</B
></CODE
>(SDL_GLattr attr, int value);</CODE
></P
><P
></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN2752"
></A
><H2
>Description</H2
><P
>Sets the OpenGL <A
HREF="sdlglattr.html"
>attribute</A
> <TT
CLASS="PARAMETER"
><I
>attr</I
></TT
> to <TT
CLASS="PARAMETER"
><I
>value</I
></TT
>. The attributes you set don't take effect until after a call to <A
HREF="sdlsetvideomode.html"
><TT
CLASS="FUNCTION"
>SDL_SetVideoMode</TT
></A
>. You should use <A
HREF="sdlglgetattribute.html"
><TT
CLASS="FUNCTION"
>SDL_GL_GetAttribute</TT
></A
> to check the values after a <TT
CLASS="FUNCTION"
>SDL_SetVideoMode</TT
> call.</P
></DIV
><DIV
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><A
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></A
><H2
>Return Value</H2
><P
>Returns <SPAN
CLASS="RETURNVALUE"
>0</SPAN
> on success, or <SPAN
CLASS="RETURNVALUE"
>-1</SPAN
> on error.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN2768"
></A
><H2
>Example</H2
><PRE
CLASS="PROGRAMLISTING"
>SDL_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\n", SDL_GetError());
  SDL_Quit();
  return;
}</PRE
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><B
>Note: </B
>The <TT
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>SDL_DOUBLEBUF</TT
> 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.</P
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>See Also</H2
><P
><A
HREF="sdlglgetattribute.html"
><TT
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>SDL_GL_GetAttribute</TT
></A
>,
<A
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>GL Attributes</A
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