OpenGL object selection

[Michael Goffioul]

Hi,

For people interested, I've started to implement object selection for the OpenGL renderer. This is one of the missing piece in the OpenGL-based backends. It allows to select objects with the mouse and trigger the appropriate callbacks. At the moment, the code is in QtHandles, but eventually the plan will be to move the opengl_selector class in main octave source tree.

It's still in development (and probably buggy), but it's already usable and I created a simple test script to demonstrate the "picking" capability (see https://github.com/goffioul/QtHandles/blob/master/tests/test1.m).

Feedback and suggestions welcome.

Michael.