SUMMARY If you bind "Sample Foreground Color from Merged Image" to "alt+left button", and try to sample colour off canvas immediately after interacting with a docker, the color sampler does not activate and the canvas becomes unresponsive to panning and zooming until you switch focus out of Krita and back again. If you wait about a second after interacting with the docker, before trying to sample a colour off canvas, the issue does not appear. I have tested this on 5.1.0-RC1 on Linux Mint and 4.3.0 on Windows 10, both have the same issue STEPS TO REPRODUCE 1. Bind "Sample Foreground Color from Merged Image" to "alt+left button" 2. Create a document with two layers 3. In the layer docker, use the cursor to switch to another layer 4. Immediately after switching, in less than a second, move the cursor over your canvas and press alt to bring up the color sampler. OBSERVED RESULT The colour sampler does not appear, and the canvas can no longer be navigated. SOFTWARE/OS VERSIONS Windows: Windows 10 macOS: Linux: Linux Mint 20.2 Cinnamon
In further testing, I find this happens even if the colour sampler tool is not mapped to "alt". Simply pressing "alt" quickly after interacting with a docker seems to be enough to trigger this, although of course that's not something a user usually would do. This also may explain why, similarly, I sometimes get canvas input freezes when alt-tabbing out of Krita. It seems this issue becomes more prominent when using a plugin, such as pigment.O, that does refreshes in the background. I suspect in the case of pigment.O, the docker the plugin creates gets activated periodically. This should be undetectable to the user, but it means that if the user presses "Alt" at the "wrong" time, canvas inputs become frozen.
*** This bug has been marked as a duplicate of bug 440399 ***