From 29d29cb250c043eeefbac59f94813dcb5e21ec03 Mon Sep 17 00:00:00 2001 From: Eirik Aavitsland Date: Fri, 18 Aug 2017 10:19:48 +0200 Subject: Fix huge painting artefact of certain dashed lines The artefacts appeared for square-capped dashed pens when the end of the line fell a tiny fraction into the start of a new dash. At that point in the dashing algorithm, accumulated precision errors in the 'length' variable could make it slightly differ from the actual length between the start and end points of the line fragment. Although both values would be "almost zero", the rasterizeLine() function's square capping would make the error very visible; see the bug report. Fix by calculating the precise length of the last line fragment. Task-number: QTBUG-56969 Change-Id: I7b69c0d465649be61fb87ac7b8348f0c299486ee Reviewed-by: Lars Knoll (cherry picked from commit 73573fce295caef35da706a8c8c796ec18e6baf1) --- src/gui/painting/qpaintengine_raster.cpp | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/gui/painting/qpaintengine_raster.cpp b/src/gui/painting/qpaintengine_raster.cpp index 6a5bf4d537..6ad8533481 100644 --- a/src/gui/painting/qpaintengine_raster.cpp +++ b/src/gui/painting/qpaintengine_raster.cpp @@ -3164,7 +3164,7 @@ void QRasterPaintEnginePrivate::rasterizeLine_dashed(QLineF line, QLineF l = line; if (dash >= length) { - dash = length; + dash = line.length(); // Avoid accumulated precision error in 'length' *dashOffset += dash / width; length = 0; } else { -- cgit v1.2.3