Bill Baxter said:
Actually I think the way to go for the UI is not keys for rotate left
and right, but key to go into rotate mode then drag to rotate around the current center of the screen.
With a modal keyboard shortcut, you now have to have an additional indicator on screen that you are in a new "mode," something beyond a cursor or toolbar icon. This could over-complicate the interface for what is really a simple operation.
I think we should try and make canvas rotation work the same as zoom. Since both affect the "camera" that looks upon the Inkscape document, they should function the same, as well.
You can set the zoom precisely, or you can use the Zoom tool for a balance between speed and precision, but if you're aiming for pure speed (like how I work), using the keyboard with preset angles, or a modifier on the scroll wheel as buila suggested, gets you close enough for most purposes.
Having a keyboard shortcut to perform a rotation at a set increment (10-15 degrees) would be sufficient for most purposes, since perfect precision of the rotate angle isn't necessary for most illustration work. This would work the same as the +/- keys or [ctrl]-wheel. The next step would be having something to allow setting the rotation "free hand" as you've described, by holding some key down and dragging the mouse. This is similar to the Zoom tool. Finally, having a widget/dialog to set the canvas rotation the same way that the zoom can be set would take care of the precision aspect.
By the way, canvas rotation is something I infinitely miss from Toon Boom when I'm working in Inkscape. :)
John