Re: quesa/Development/Source/Renderers/Common GLDrawContext.c, 1.63, 1.64

[James W. <ja...@fr...>]

Jose' Cruanyes wrote:
> Il giorno 24/mag/07, alle ore 00:51, James W. Walker ha scritto:
> 
>> Update of /cvsroot/quesa/quesa/Development/Source/Renderers/Common
>> In directory sc8-pr-cvs16.sourceforge.net:/tmp/cvs-serv18759/quesa/ 
>> Development/Source/Renderers/Common
>>
>> Modified Files:
>> 	GLDrawContext.c
>> Log Message:
>> In gldrawcontext_win_new, try to fail more gracefully when  
>> SetPixelFormat fails to change the pixel format.
>>
>> Index: GLDrawContext.c
>> ===================================================================
>> RCS file: /cvsroot/quesa/quesa/Development/Source/Renderers/Common/ 
>> GLDrawContext.c,v
>> retrieving revision 1.63
>> retrieving revision 1.64
>> diff -C2 -d -r1.63 -r1.64
>> *** GLDrawContext.c	18 May 2007 23:47:36 -0000	1.63
>> --- GLDrawContext.c	23 May 2007 22:51:11 -0000	1.64
>> ***************
>> *** 1615,1618 ****
>> --- 1615,1620 ----
>>   		goto fail;
>>
>> + 	int	prevPixelFormat = GetPixelFormat( theContext->theDC );
>> + 	
>>       if (!SetPixelFormat(theContext->theDC, pixelFormat,  
>> &pixelFormatDesc))
>>   	{
>> ***************
>> *** 1623,1628 ****
>>   		E3Assert( __FILE__, __LINE__, theString );
>>   	#endif
>> ! 		Q3Error_PlatformPost(error);
>> !     	goto fail;
>>   	}
>>
>> --- 1625,1640 ----
>>   		E3Assert( __FILE__, __LINE__, theString );
>>   	#endif
>> ! 		
>> ! 		// The docs on SetPixelFormat say that "Once a window's pixel  
>> format is
>> ! 		// set, it cannot be changed".  In that case, try falling back  
>> to the
>> ! 		// previous format.
>> ! 		
>> ! 		pixelFormat = prevPixelFormat;
>> ! 		
>> ! 		if ( (pixelFormat == 0) || !SetPixelFormat(theContext->theDC,  
>> pixelFormat, &pixelFormatDesc) )
>> ! 		{
>> ! 			Q3Error_PlatformPost(error);
>> ! 	    	goto fail;
>> ! 		}
>>   	}
> 
> 
> We've found that this change (or another triggered by this) cause  
> crashes on certain machines, when rebuilding the drawContext...
> 
> if we open a window, print it (creating a pixmap DC), when rebuilding  
> the window, quesa crashes when trying to swap buffers at the end of  
> the first, render loop
> 
> the machine has an onboard SIS video adaptor, so I think it's using  
> the software renderer
> 
> throwing an error if SetPixelFormat fails, solves the problem (my  
> program tries to rebuild the Drawcontext in the next update event and  
> then it works)
> 
> any ideas?

I don't know why this change would cause a problem, but if you want to 
revert it, I won't be upset.

As I recall, I noticed a problem with SetPixelFormat when switching to 
shadow rendering in Geom Test.  That requires a stencil buffer, where 
none had been requested before, hence a change in pixel format.  Of 
course my change did not actually solve that problem.  One really needs 
to request a stencil buffer at the beginning if there is any chance that 
a stencil buffer will be needed later.

If you do revert the change, please leave a comment that a window's 
pixel format cannot be set more than once, so that the next time 
SetPixelFormat fails, I won't have to figure it out again.
-- 
   James W. Walker, Innoventive Software LLC
   <http://www.frameforge3d.com/>