Description:
In an Impress slide show when the GTK3 overlay is active, holding a left click on a slide opens the right-click context menu after a few seconds.  This is annoying when drawing on a slide, as if I leave the pen down too long, then move, I often trigger a random menu option (most often advance to next slide).

A secondary effect is that if I release, without triggering a menu option, but then click somewhere else, a line is draw between the two click points.

Neither of these behaviors occurs if GTK3 is not being used, with an otherwise entirely identical install and profile.

Obviously this could be worked around by not holding the left click so long, but as I am usually drawing while presenting to a live audience and using the pointer also to point to objects, I trigger this bug fairly frequently.  I only recently worked out that it is GTK3-specific.

Steps to Reproduce:
1. For simplicity of demonstration, disable advance slide on click.
2. Start slide show.
3. Left click and hold.  See contex menu appear.
4. Turn on pen.
5. Left click and hold.  Release without trigger menu.
6. Left click briefly somewhere else.  See line appear between points.

Actual Results:
Right-click menu is opened by left click, and random lines are drawn.

Expected Results:
No context menu on left click and no random lines.


Reproducible: Always


User Profile Reset: Yes


OpenGL enabled: Yes

Additional Info:
Appears to affect all versions since introduction of GTK3 but I have not tested extensively.