Regarding the GUI part, I had tested Jabier's branch, and one thing that hindered the drawing process was heavy onscreen display while rotating.
In my opinion there is no need to show the circular disc and clipping the canvas into that disc while rotating. a simple on-screen notification showing the degree of rotation is enough.
May be a small rectangle notification box with degrees. This is just my opinion. The previous rotation HUD kind of display was a bit distracting.

+1 for GUI notifications for rotation but with subtlety.

I get what you say and I tend to agree. The problem is that Inkscape falls behind with redrawing on such intensive calculations such as this one. Jabier did a clever thing. He copied bitmap of what's currently on canvas and rotated just that image, which is fairly cheap operation when done once. That was precisely the reason why it was so fast. Only after user released MMB the whole canvas was redrawn. If we can grab bigger rectangle, I guess we can rotate that one instead and ensure that there are no gaps drawn on screen, since no panning, or any other operation for that matter, can occur while rotating (while MMB is down and we are in rotation mode, that is).

Vlada
 

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Raghavendra Kamath
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