Question about XRender specification

[Peter Harris]

Helge Bahmann wrote:
>> 				XRenderCompositeTrapezoids(display,
>> 					PictOpOver, red_transp, picture, 0,
>> 					0, 0, &trap, 2);
> 
> the way you are calling, they are drawn independently, this means the first 
> trapezoid covers the pixel by 1/2, the second gets drawn over and now the 
> pixel is covered by 3/4 and NOT 1 !
> 
> The solution is to use PictOpDisjointOver; possibly to have to composite your 
> figure into a temporary mask and then use this pre-composited shape in a 
> second rendering step

Alternatively, you could specify a maskFormat other than NULL when you 
call XRenderCompositeTrapezoids.

Peter Harris
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