[cairo] Best strategy for complex screen drawing

[Timothée Lecomte]

MenTaLguY wrote:

>On Sat, 2005-11-26 at 14:52 +0100, Timothée Lecomte wrote:
>  
>
>>It gives no seam, and it is much quicker (400 ms to draw the 10000
>>polygons on a generic image surface, instead of 1500 ms).
>>Unfortunately, there are some unwanted side effects, because I have to
>>draw polygons over already existing polygons, and with
>>CAIRO_OPERATOR_ADD this leads to some transparency effects. Here is a
>>screenshot :
>>
>>http://tipote.free.fr/wxt16.png
>>    
>>
>
>Maybe you want to use SATURATE rather than ADD?
>
>-mental
>  
>
By looking at http://cairographics.org/samples/operator_saturate.html ,
I would say yes, but when I choose it instead of add in my code, I don't
get the desired output :

http://tipote.free.fr/wxt17.png

As you can see, this time polygons which should overwrite previous ones
(like with CAIRO_OPERATOR_OVER) simply don't appear.

Timothée Lecomte