Fixed origin zoom with goocanvas

[Bernhard Schuster <schuster bernhard googlemail com>]

I am trying to create zoomable goocanvas, which zooms towards the current pointer position instead of the 
center of the visible part of the goocanvas. Unfortunately my correction offset seems to be correct 
mathematically but does not work if I implement it.

As the implementation spans some lines of C-code, I created a structured question at stackoverflow 
http://stackoverflow.com/questions/15212219/goocanvas-coordinate-systems-and-zooming
I hope this kind of pointer is acceptable for this mailinglist.

Thanks for your time, I'd appreciate any kind of tip or pointer.

Best regards,

Bernhard