From 19f29802bf7daafacd0fd824c2a1349e80eac536 Mon Sep 17 00:00:00 2001
From: Eirik Aavitsland <eirik.aavitsland@qt.io>
Date: Thu, 17 Oct 2019 13:25:06 +0200
Subject: Fix: QPainter off-by-one clipping for some non-integer scalings

For some scalings, setClipRect(QRect) would produce a clip one pixel
different from setClipRect(QRectF) because of different
rounding. Ditto for setClipRegion. Fix by making sure to transform
QRectFs instead of QRects.

Fixes: QTBUG-78962
Fixes: QTBUG-78963
Change-Id: I0be721133858c30769ec6d81e978962a3d6b70cf
Reviewed-by: Christoph Cullmann <cullmann@kde.org>
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
---
 tests/auto/gui/painting/qpainter/tst_qpainter.cpp | 49 ++++++++++++++++++++++-
 1 file changed, 48 insertions(+), 1 deletion(-)

(limited to 'tests/auto/gui/painting/qpainter/tst_qpainter.cpp')

diff --git a/tests/auto/gui/painting/qpainter/tst_qpainter.cpp b/tests/auto/gui/painting/qpainter/tst_qpainter.cpp
index d2a4dfc3e9..6e48439944 100644
--- a/tests/auto/gui/painting/qpainter/tst_qpainter.cpp
+++ b/tests/auto/gui/painting/qpainter/tst_qpainter.cpp
@@ -157,10 +157,10 @@ private slots:
     void clippedLines();
     void clippedPolygon_data();
     void clippedPolygon();
-
     void clippedText();
 
     void clipBoundingRect();
+    void transformedClip();
 
     void setOpacity_data();
     void setOpacity();
@@ -4589,6 +4589,53 @@ void tst_QPainter::clipBoundingRect()
 
 }
 
+void tst_QPainter::transformedClip()
+{
+    QImage img(8, 4, QImage::Format_ARGB32_Premultiplied);
+    QImage img2(img.size(), img.format());
+    QRect clip(0, 0, 2, 1);
+    QTransform xf;
+    xf.translate(0.2, 0);
+    xf.scale(2.2, 1);
+    // setClipRect(QRectF)
+    {
+        img.fill(Qt::green);
+        QPainter p(&img);
+        p.setTransform(xf);
+        p.setClipRect(QRectF(clip));
+        p.fillRect(img.rect(), Qt::white);
+    }
+    // setClipRect(QRect)
+    {
+        img2.fill(Qt::green);
+        QPainter p(&img2);
+        p.setTransform(xf);
+        p.setClipRect(clip);
+        p.fillRect(img2.rect(), Qt::white);
+        QCOMPARE(img, img2);
+    }
+    // setClipRegion
+    {
+        img2.fill(Qt::green);
+        QPainter p(&img2);
+        p.setTransform(xf);
+        p.setClipRegion(QRegion(clip) + QRect(0, 3, 1, 1));  // dummy extra rect to avoid single-rect codepath
+        p.fillRect(img2.rect(), Qt::white);
+        QCOMPARE(img.copy(0, 0, 8, 2), img2.copy(0, 0, 8, 2));
+    }
+    // setClipPath
+    {
+        img2.fill(Qt::green);
+        QPainter p(&img2);
+        p.setTransform(xf);
+        QPainterPath path;
+        path.addRect(clip);
+        p.setClipPath(path);
+        p.fillRect(img2.rect(), Qt::white);
+        QCOMPARE(img, img2);
+    }
+}
+
 #if defined(Q_OS_MAC)
 // Only Mac supports sub pixel positions in raster engine currently
 void tst_QPainter::drawText_subPixelPositionsInRaster_qtbug5053()
-- 
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