See attachment for picture The lines appear on 512x512 tiles -- the maximum size of updated area in a single thread. This bug affects QPainter canvas only.
Created attachment 65839 [details] Screenshot
Git commit 8e65448dec295c31aa92acd3c29807c98049c135 by Dmitry Kazakov. Committed on 19/11/2011 at 17:18. Pushed by dkazakov into branch 'master'. Fixed lines appearing on a canvas on non-integer zooms This happens because for scaling we may need some areas outside current update rect. And these external areas may not be prepared yet by other threads. So our current thread reads empty (not-yet-updated) areas and uses them for scaling. This causes while lines. Now the problem is solved like it is solved in KisLayer::needRect/changeRect. The update, updates it's own rect, and small adjoining areas around which depent on it, that may be called "changeRect". Then the patch (KisImagePatch) requests even more pixels to make the scaling right (that may be called "needRect"). BUG:286985 M +1 -1 krita/ui/canvas/kis_image_patch.h M +14 -3 krita/ui/canvas/kis_prescaled_projection.cpp http://commits.kde.org/calligra/8e65448dec295c31aa92acd3c29807c98049c135