SUMMARY ``` WARNING: idle task consumed more than 200ms, it can cause visible distractions to the user WARNING: time consumed in "layer-thumbnails-stroke" is 1000ms ``` https://invent.kde.org/graphics/krita/-/blob/87ec67592d6fc7ed15a1b19d40e3a520738d29e9/libs/ui/KisIdleTaskStrokeStrategy.cpp#L51-65 is consistently triggered by "layer-thumbnails-stroke" action, when user have any non-trivial layer setup such as filter layers with many layers. Krita becomes unresponsive and blocks user input, resulting in a poor user experience. A typical scenario looks like this When the thumbnail computation is running, krita become unresponsive and blocks user input, causing bad user experience. Typical scenario: 1. User make a stroke 2. User thinks briefly to decide if the stroke is good or not, for 200ms (`4 * preferredIdleWatcherInterval()`). 3. "layer-thumbnails-stroke" KisIdleTaskStrokeStrategy starts running, blocks user input, sometimes more than 1000ms. 4. User presses undo while the thumbnail update is still running, and krita just ignores it. (Not even undoing after it unblocks) I don't know if there is a valid reason for this thumbnail update to block user input or the event loop. Since it’s a low-priority background task, it should be possible to offload the computation. A cheap workaround is to turn up `preferredIdleWatcherInterval()` to lower the chance of user hitting this. STEPS TO REPRODUCE 1. Run something like https://gist.github.com/sifmelcara/987e0c3a2eee82ad5bd58dc3e4ec00f4 to get a non-trivial layer setup 2. Paint on the inner most paint layer while the layers docker is visible, observe the extreme lag 3. Paint in fullscreen mode, observe that the lag caused by thumbnail update is gone You can also try change `preferredIdleTaskMaximumTime()` to lower the threshold of warning, to make the issue more visible in log. SOFTWARE/OS VERSIONS Note that this is a regression introduced to master branch, not in 5.2.13 release ADDITIONAL INFORMATION
Extra note: 07:41:16 < sifmelcara[M]> Hmm just found https://invent.kde.org/graphics/krita/-/commit/572c64858d1b506ca1500b776cc49dfd65105ddd and realize that the delay was actually reduced in order to speed up overview docker update. The time-consuming layer thumbnails update scenario wasn't considered
Git commit 00e1b0fe9e5ba7c7b06599cd4f4892b469fd3b19 by Dmitry Kazakov. Committed on 28/01/2026 at 12:24. Pushed by dkazakov into branch 'master'. Switch to coarse layer thumbnails when generation is slow When a layer has vast areas of empty pixels, it may be slow to calculate its exactBounds(). In this case, if thumbnail generation takes more than 40ms, Krita will automatically switch the layer into "coarse thumbnail generation mode" and use extent() instead. The status bar will also show a warning symbol and list the "slow layers" in a tooltip. A proper solution to this problem will come later in this MR: https://invent.kde.org/graphics/krita/-/merge_requests/2578 M +6 -6 benchmarks/kis_thumbnail_benchmark.cpp M +25 -4 libs/image/kis_base_node.cpp M +30 -2 libs/image/kis_base_node.h M +7 -10 libs/image/kis_layer.cc M +2 -2 libs/image/kis_layer.h M +2 -4 libs/image/kis_mask.cc M +1 -1 libs/image/kis_mask.h M +11 -6 libs/image/kis_paint_device.cc M +5 -2 libs/image/kis_paint_device.h M +26 -7 libs/image/kis_paint_device_cache.h M +2 -4 libs/image/kis_selection_based_layer.cpp M +1 -1 libs/image/kis_selection_based_layer.h M +8 -0 libs/image/kis_types.h M +1 -1 libs/image/tests/kis_paint_device_test.cpp M +16 -2 libs/ui/KisLayerThumbnailCache.cpp M +10 -0 libs/ui/kis_config.cc M +9 -0 libs/ui/kis_config.h M +1 -1 libs/ui/kis_custom_pattern.cc M +1 -1 libs/ui/kis_node_model.cpp M +49 -2 libs/ui/kis_statusbar.cc M +1 -1 libs/ui/utils/KisFileIconCreator.cpp M +1 -1 plugins/dockers/advancedcolorselector/kis_common_colors.cpp M +1 -1 plugins/dockers/animation/KisAnimTimelineFramesModel.cpp M +1 -3 plugins/dockers/historydocker/KisUndoModel.cpp M +1 -1 plugins/dockers/widegamutcolorselector/WGCommonColorsCalculationRunner.cpp M +1 -1 plugins/tools/tool_transform2/kis_tool_transform.cc https://invent.kde.org/graphics/krita/-/commit/00e1b0fe9e5ba7c7b06599cd4f4892b469fd3b19
Git commit a059548b007f99e32533c77e26f0d25650998027 by Dmitry Kazakov. Committed on 28/01/2026 at 12:24. Pushed by dkazakov into branch 'master'. Add Image->Purge Unused Image Data Under some conditions it might happen that some layers and/or projections will contain vast areas of fully transparent data. It can cause a lot of undesirable side-effects, like layer thumbnails recalculating too slowly or image compositing being extremely slow. This patch adds a new user-faced action Image->Purge Unused Image Data, which iterated through all existing layers and removing all fully transparent areas. Just a mere calling to this action can workaround the "slow thumbnail generation" issue as reported in bug 510627. Hence calling to that also switches all the layers back into "precise" thumbnail generation mode. WARNING: calling this action can potentially break Undo/Redo for your image. Please take that into account until the feature is fully tested. CC:kimageshop@kde.org M +2 -1 krita/krita5.xmlgui M +12 -0 krita/kritamenu.action M +68 -13 libs/image/kis_image.cc M +14 -0 libs/image/kis_transaction.h M +11 -0 libs/ui/kis_layer_manager.cc M +1 -0 libs/ui/kis_layer_manager.h M +2 -1 libs/ui/kis_statusbar.cc https://invent.kde.org/graphics/krita/-/commit/a059548b007f99e32533c77e26f0d25650998027