Re: [Qemu-devel] Updated BGR vs. RGB vga patch...

[Leonardo E. Reiter]

You can definitely figure it out by asking the X server or SDL.  I don't 
know enough SDL to have hacked it in myself.  X is pretty simple on the 
other hand.

As for where to add it, I agree that the low level conversions are not a 
great place to add this.  I didn't originate the patch, I just updated 
it.  Unfortunately none of the VGA is optimized - everything happens 
pixel by pixel already.  Adding what probably amounts to 2 instructions 
(probably a couple of clock cycles) per pixel doesn't seem to do 
anything for performance really.  The VGA is already slow.

Unfortunately X11 will not allow you to force a certain color order in 
24-bit mode.  You can tell it to force byte-order but this only affects 
16-bit blits - it's ignored for 24-bit since the individual components 
of the 24-bit blits, even if packed into 32-bits, are still 8-bits long. 
 That's what the color masks are for.  There is no efficient way to do 
this at the server level that I can see.  If you find a better way 
(within the current scope of the VGA architecture), I'd be glad to try 
to implement it.  I was just sharing something that was useful to me.

Thanks,

Leo Reiter

Paul Brook wrote:
> On Monday 10 April 2006 17:25, Leonardo E. Reiter wrote:
>
> > Hello,
> >
> > attached is an updated version (against today's CVS) of a patch to
> > enable B/G/R color encoding rather than R/G/B with the command-line
> > option -bgr.  I found the original here (post by Martin Bochnig):
>
>
> Shouldn't we be able to figure this out by asking SDL and/or the X server?
> Also, adding an if to the low-level conversion routines seems a bad idea for 
> performance.
>
> Paul

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Leonardo E. Reiter
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