Rendering, something wrong between cairo and soft

Hello,

Something wrong between cairo and soft rendering

with pacman2.sif from this post

With cairo render on workspace (canevas)
Pacman-Cairo-ok.png

Without cairo render (internal software render) on workspace (canevas)
Pacman-noCairo-KO.png

Preview with cairo
Pacman-Preview-Cairo.png

Preview without cairo
Pacman-Preview-Soft.png

Development version: Revision: 20130916 Branch: master Revision ID: 6444ec Built on Sep 18 2013

The workarea renderer uses Tile Render when the zoom is far from certain value. Tile render in Software render has some tricks to avoid render things that aren’t visible when rendering using Straight methods. Looks like there is a bug (or I introduced a bug) in the software renderer that makes the tile render do its work wrong in the tiles where there is not intersection between the circle and the background.
In Cairo render I don’t do those tricks and that’s the reason it doesn’t happen.
In Software preview it doesn’t happen because preview doesn’t use tile render at all (it is a full frame render)
-G

Straight methods were extremely crash prone while I was working with that file. I was using the tar’d version of synfigstudio:
synfigstudio-0.64.0-20130509.master.8.i386.tar.bz2
synfigstudio-0.64.0-20130909.master.8.i386.tar.bz2
synfigstudio-0.64.0-20130916.morevna.8.i386.tar.bz2

All of them were experiencing crashes whenever I used Straight or Straight Onto blend methods.

I have played a little without crash ( 0.64.1 dev ) i hope that announce that the release will be more stable…