Bug 515623

Summary:	Cannot interact with canvas when selection on canvas is active and and switching back to its tab
Product:	[Applications] krita	Reporter:	krichbanana
Component:	General	Assignee:	Krita Bugs <krita-bugs-null>
Status:	REPORTED ---
Severity:	normal	Keywords:	regression
Priority:	NOR
Version First Reported In:	nightly build (please specify the git hash!)
Target Milestone:	---
Platform:	Arch Linux
OS:	Linux
Latest Commit:	6685687bd6	Version Fixed/Implemented In:
Sentry Crash Report:

Description krichbanana 2026-02-06 14:14:20 UTC

SUMMARY
Krita 5.4.0 prealpha @6685687bd6, also present on 5.3.0 beta (both AppImage). Multi-canvas usage is incredibly broken, with canvases no longer becoming editable after switching away, but triggering the breakage is a bit random.

STEPS TO REPRODUCE
1. Open a large canvas (mine was 2.7G, at around 10k x 7k pixels
2. Open a second canvas. (can be a backup, newer version, or a png, or blank canvas)
3. Switch away from the affected canvas (via tab bar)
4. Switch back, and attempt to paint or pan/zoom the canvas
4b. Alternatively, try to toggle visibility of a layer and mouse back over the canvas.

It seems like it affects the save files randomly.

OBSERVED RESULT
Using tools switches the canvas back to another tab (with three tabs, it seems to switch back to the same tab regardless of tab order or visit order). Attempting to pan or zoom does nothing. On Wayland, the cursor is not visible over the canvas. Toggling a layer visibility seems to work, but mousing back to the canvas warps back to another canvas.

EXPECTED RESULT
I should be able to switch to another canvas freely (to e.g. colorpick) and switch back without worry of the canvas being no longer paintable or navigatable.

SOFTWARE/OS VERSIONS
KDE Plasma Version: 6.5.5
KDE Frameworks Version: 6.22.0
Qt Version: 6.10.2/5.15.18
Kernel Version: 6.18.7-arch1-1 (64-bit)
Graphics Platform: Wayland

(I also replicated this on X11/MATE on another system with the beta)

ADDITIONAL INFORMATION
(trying the qt6 appimage version locked up on F4, and the qt6 git version had an uninteractable UI, so cannot test those)

Comment 1 krichbanana 2026-02-07 18:26:36 UTC

I've identified the cause and a better repro method:

TO REPRODUCE:
1. Open a canvas
2. Make a selection, keep it active
3. Open a second canvas (tab)
4. Click the first tab, with the canvas that has the selection

CAUSE:
It appears to have been first introduced with commit 433d716688f0a157079eeac129ae4ef94ae636a8, and boils down to a branch in KisSelectionActionsPanel::eventFilter that marks all FocusIn events as handled. Removing the FocusIn case from the 6.0 beta code prevents the bug from triggering. Interestingly, with the bug, deselecting the selection when the bugged tab is active restores access to the canvas.