Created attachment 141329 [details] Preview update with the G'MIC-Qt plug-in for GIMP Testing G'MIC plug-in with Krita 5.0-beta1 (appimage for Linux). When selecting a filter in G'MIC-Qt that has movable control points over the preview window, there is a clear difference on the preview update behavior between the plug-in for Krita and GIMP. I've recorded two videos of the same filter (Deformations / Perspective) to show the difference.
Created attachment 141330 [details] G'MIC-Qt plug-in running on Krita 5.0-beta1
Amyspark, can you take a look?
A quick debug session (hampered by GDB struggling to keep up with the debugging symbols) shows that GMic-Qt drops almost all of the mouse events because the preview widget is always at "max zoom". I'll continue tracing things later, with an update to 2.9.9, but please be aware that the preview widget code wasn't altered by my plugin porting.
Updated to 2.9.9 and compiled both v4 and v5 hosts. Both show the same unresponsiveness and event dropping on the preview widget. As the Krita host has been essentially unaltered since my port, and I've not changed anything regarding rendering in the plugin-based host, I'm inclined to believe this is a bug for Sébastien's repo.