Newly added simple support to the gtk3 vclplug for "canvas" support which is the thing we draw onto for presentations. Which means the gtk3 vclplug now supports full screen presentations. Which required a whole massive pile of reorganization of the existing canvas backends to move them from their own per-platform concept in canvas to the per-desktop concept in vcl.
So now rather than having only one cairo canvas backend based on the xlib apis which is for "Linux" we have a cairo canvas for each vcl plug. The old school xlib one is moved from inside its #ifdef LINUX in canvas to the shared base of the gtk2, kde, etc backends in vcl, and there is now a new one for gtk3
Presumably there are lots of performance gains to be made to the new canvas backend seeing as I'm just invalidating the whole slide window when the canvas declares that it's flush time but slides appear to appear instantaneously for me and fly ins and move around a patch effects are smooth even in -O0 debug mode so I'll hold back on any optimizations efforts for now.