[cairo] in_fill hit test and matrix transforms

Donn donn.ingle at gmail.com
Wed Nov 21 23:43:06 PST 2007

> Just move the matrixend call before the in_fill call.  
For what I am doing this might not be possible. In my app I am wrapping 
transforms within transforms because I have a parent/child situation going. 
All cairo commands are drawn from absolute 0,0 and then their actual 
positions are set by each matrix. So, to stop the matrix for the in_fill() is 
going to cause trouble.
 I will experiment. Perhaps I'll stop it then start it again after in_fill, 
ready for the next child to be drawn, I just worry a little about speed.

> Note that in_fill 
> transforms your event x,y according to the current transform matrix
> (ctm) too.  
That's dark voodoo that I will have to face soon, but I am not mathematically 
gifted. This is all seat-of-pants stuff.

> So, you need to get to an identity ctm before doing it for 
> your use case.
Er... I confess that I don't savvy what you mean, but I'll go look up the 
terms and tweak.

Thanks, at least there's light at the end of the tunnel now.


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