Created attachment 127011 [details] ^ gif-animation of the bug, inverting selection on the silhouettes of characters. Hi, I'm not sure if this one is a regression or have been around all this time; I remember seeing tiny glitch (eg. a single horyzontal line) but it looks like this is another level now. The marching-ants decoration on inverted selection has many articfacts: clusters of black&white noises; many horyzontal lines crossing the canvas, etc... (gif in attachement) To reproduce: ============= 1. Open a new canvas on Krita, create an empty transparent layer. 2. Take a brush with a texture, paint a shape and fill it manually. 3. Over the layer stack docker, right click on the layer with the painted shape and select "Select Opaque (Replace)" feature. 4. Go to the top menu; Select > Invert Selection 5. If no effect happens, switch between discrete zoom (33%,50%,67%,25%, back and forth) with mouse wheel until glitch appears. Observed: ========= While the original selection of the shape with ant-marching decoration was comfortable to work with; the inverted representation makes it difficult: clusters of black&white noises; many horyzontal lines crossing the canvas, etc... (gif in attachement)
Created attachment 127015 [details] inverted-ragged-selection I can reproduce this for the 4.2.9 beta1 appimage and the 4.2.8 appimage. It seems to be caused by the complexity/raggedness of the selection outline. See attachment "inverted-ragged-selection". It can be stopped by re-inverting the selection. It can be stopped by turning Graphics Acceleration off but not by turning Instant Preview off.
It looks like a bug in Qt's code in rendering dashes pens with multiple subpaths. Splitting the path into subpolygons fixes the issue.
*** This bug has been marked as a duplicate of bug 413220 ***
Git commit c15d8888c3d793a31c914ffb80a5b38a1f2846ad by Dmitry Kazakov. Committed on 08/05/2020 at 17:18. Pushed by dkazakov into branch 'master'. Fix artifacts when rendering complex selection outlines It happens because of a bug in opengl-based stroking algorithm in Qt. And it happens only when one tries to draw a path with multiple subpaths. The easiest workaround for this bug without patching Qt is to manually split a multi-subpath path into QPainterPath objects with only one subpath in each. It might happen that the resulting subpath generated by the QDashStroker will have no lines at all. It happens when further LineToElement items compare as equal to the starting MoveToElement when compared in 'float' space. In such case QTriangulatingStroker::process() skips LineTo elements and the vertexBuffer ends up with unconnected vertices, which generate unwanted triangles. Related: bug 413220 A +80 -0 3rdparty/ext_qt/0100-Fix-artifacts-when-rendering-multisubpath-dashed-QPa.patch M +5 -0 3rdparty/ext_qt/CMakeLists.txt https://invent.kde.org/kde/krita/commit/c15d8888c3d793a31c914ffb80a5b38a1f2846ad
Git commit 8208fa254321232105a231fc517541e98c747216 by Dmitry Kazakov. Committed on 08/05/2020 at 17:19. Pushed by dkazakov into branch 'krita/4.3'. Fix artifacts when rendering complex selection outlines It happens because of a bug in opengl-based stroking algorithm in Qt. And it happens only when one tries to draw a path with multiple subpaths. The easiest workaround for this bug without patching Qt is to manually split a multi-subpath path into QPainterPath objects with only one subpath in each. It might happen that the resulting subpath generated by the QDashStroker will have no lines at all. It happens when further LineToElement items compare as equal to the starting MoveToElement when compared in 'float' space. In such case QTriangulatingStroker::process() skips LineTo elements and the vertexBuffer ends up with unconnected vertices, which generate unwanted triangles. Related: bug 413220 A +80 -0 3rdparty/ext_qt/0100-Fix-artifacts-when-rendering-multisubpath-dashed-QPa.patch M +5 -0 3rdparty/ext_qt/CMakeLists.txt https://invent.kde.org/kde/krita/commit/8208fa254321232105a231fc517541e98c747216