GLMixer Code

fixed bug tooltip mixing presets

Complete reimplementation of the Layers View :
- picking using FBO and depth map
- selection area (sub-classed)
- zoom best fit
+ coherent implementation for other View

Improved GUI glmixer
added butons to add date and list of sources in the bloc notes.

Bugs fixed:
- no effect on zoom action for RenderView
- stop / play of a video source paused: keep the pause state
- no reset of the video_current_pts time on start video file
- disable action 'delete' when no current source available
- restored shadow of frame in Geometry and Layers view
- improved layout of SessionSwitcherWidget

Improved rendering of the groups in mixing view

Fixed rendering bug in Mxing View (missing shadows) : generalized the
fix to all similar cases (reset the vertex array).

changed menu action 'toggle modifiable' to the check box action
'Unchangeable'

Implementation of source menu actions for aspect ratio manipulation:
fix, set to original and set to rendering

Improvement of Fragment Code Plugin (shader toy compatible GLSL)

Finished implementation of resize tools in layout toolbox