Created attachment 190358 [details] Screenshot showing a layer with three black question marks at 64% opacity, with the other document (a chibi drawing) visible. SUMMARY When multiple documents are open in Krita, and the current document contains a layer at low opacity with no solid pixels to fill the canvas behind it, the other document is visible. STEPS TO REPRODUCE 1. Set Krita's Multiple Document Mode to Tabs in Configure Krita > General > Window. 2. Create or open a document. You can leave it empty, but some distinctive content would make the problem easier to see. 3. Create a new document with a transparent background, i.e. background opacity set to 0 in the Content tab (it's possible deleting the background layer works too, but I no longer have 6.0.0 installed to check) 4. Create a second layer, and draw or paste something in it, ideally with a large-ish solid shape. I initially noticed it while working with photos, but brush strokes "work" too. 5. Set that layer's opacity to below 100%. Around 50% should make the problem clearly visible. OBSERVED RESULT The other document tab is visible in the translucent portions of the layer. You may need to zoom in and/or pan around the image so that the translucent pixels overlap recognizable parts of the other tab, such as a distinctive element or the image border. EXPECTED RESULT The other document should not be visible, the translucent portions of the layer should blend only with the transparency checkerboard. SOFTWARE/OS VERSIONS Windows: 10 Qt Version: 6.x ADDITIONAL INFORMATION I was not able to reproduce this in 5.3.0-beta2, so this is likely a Qt6 issue. I tested with graphics acceleration enabled, renderr: Direct3D via ANGLE. I did not think to try other rendering options before installing 5.3.0-beta2, oops.
Thanks for the report!
I can confirm the issue on Windows. The problem happens in both modes, ANGLE and openGL. Might be related to bug 517248
This is a qt6-only bug
*** Bug 518116 has been marked as a duplicate of this bug. ***
*** Bug 518331 has been marked as a duplicate of this bug. ***
Git commit 4e44f0958ebe5b8cfcfb484f8bf9dcc4568aa44e by Dmitry Kazakov. Committed on 02/07/2026 at 17:18. Pushed by dkazakov into branch 'master'. [win][qt6] Fix transparent canvas widget issue It seems like Qt6 properly supports transparent widget textures, so, if we write non-opaque pixels over it, the widget also becomes transparent. To fix the issue, we should use a blend function with explicit switch to avoid writing into the alpha channel of the final widget texture. M +3 -3 libs/ui/opengl/KisOpenGLCanvasRenderer.cpp https://invent.kde.org/graphics/krita/-/commit/4e44f0958ebe5b8cfcfb484f8bf9dcc4568aa44e
Git commit fc7a7f797a1b165107ce454ba7aecad2809a5c4e by Dmitry Kazakov. Committed on 02/07/2026 at 17:21. Pushed by dkazakov into branch 'krita/6.0'. [win][qt6] Fix transparent canvas widget issue It seems like Qt6 properly supports transparent widget textures, so, if we write non-opaque pixels over it, the widget also becomes transparent. To fix the issue, we should use a blend function with explicit switch to avoid writing into the alpha channel of the final widget texture. M +3 -3 libs/ui/opengl/KisOpenGLCanvasRenderer.cpp https://invent.kde.org/graphics/krita/-/commit/fc7a7f797a1b165107ce454ba7aecad2809a5c4e