Clicking on GUI elements picks 3D mesh elements under them.

[gloook]

The paint attribute tool continues to paint across the GUI: when changing tool parameters, the surface is painted behind the widgets (when clicking on a window, it clicks through the window)

[BrunoLevy]

Committed a fix, you'll need to update geogram.

[BrunoLevy]

Problem still exists when Undo/Redo is activated. See #26 for the explanation (fix is on its way...)