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QPainter cosmetic stroker: Fix painting error for FlatCap lines 

Initialize the lastDir properly, to avoid the stroking algorithm doing
direction-change handling for a single line. That could cause a cap to
be painted for a single FlatCap line.

Also fixes a bug in tst_qpainter, revealed by the above fix. The
result drawPolyline was erroneously compared to the result of drawing
the lines individually, for a case where the former correctly paints
the pixel of the join point in the corner, while the latter by
coincidence used to paint the same pixel as a cap because of the bug
above.

Task-number: QTBUG-70101
Change-Id: Ie20eda33214cfe9e7627f17ef4c7a5b3835c9c24
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
bb10
Eirik Aavitsland 2018-08-31 15:13:28 +02:00
parent 213cfc3fae
commit b233ce66d3
2 changed files with 3 additions and 2 deletions
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3
src/gui/painting/qcosmeticstroker_p.h
View File

@ -85,6 +85,7 @@ public:
// used to avoid drop outs or duplicated points
enum Direction {
NoDirection = 0,
TopToBottom = 0x1,
BottomToTop = 0x2,
LeftToRight = 0x4,
@ -104,7 +105,7 @@ public:
patternOffset(0),
legacyRounding(false),
current_span(0),
lastDir(LeftToRight),
lastDir(NoDirection),
lastAxisAligned(false)
{ setup(); }

2
tests/auto/gui/painting/qpainter/tst_qpainter.cpp
View File

@ -5024,7 +5024,7 @@ void tst_QPainter::drawPolyline_data()
{
QTest::addColumn< QVector<QPointF> >("points");
QTest::newRow("basic") << (QVector<QPointF>() << QPointF(10, 10) << QPointF(20, 10) << QPointF(20, 20) << QPointF(10, 20));
QTest::newRow("basic") << (QVector<QPointF>() << QPointF(10, 10) << QPointF(20, 10) << QPointF(20, 20));
QTest::newRow("clipped") << (QVector<QPointF>() << QPoint(-10, 100) << QPoint(-1, 100) << QPoint(-1, -2) << QPoint(100, -2) << QPoint(100, 40)); // QTBUG-31579
QTest::newRow("shortsegment") << (QVector<QPointF>() << QPoint(20, 100) << QPoint(20, 99) << QPoint(21, 99) << QPoint(21, 104)); // QTBUG-42398
QTest::newRow("edge") << (QVector<QPointF>() << QPointF(4.5, 121.6) << QPointF(9.4, 150.9) << QPointF(14.2, 184.8) << QPointF(19.1, 130.4));