Fix QPainter save/restore of clipping enabled state

Clipping enabled state would not always be correctly restored for the
raster engine (other engines work fine). The raster engine's QClipData
object is sometimes shared between painter state objects on the
save/restore stack. QClipData has its own enabled flag, and this could
then come out of sync. Fix by making sure we sync the enabled state on
restore.

Task-number: QTBUG-58789
Change-Id: I81e6254ebb93df6e153bbef58e32a885273e3224
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

2 files changed, 35 insertions, 0 deletions

diff --git a/src/gui/painting/qpaintengine_raster.cpp b/src/gui/painting/qpaintengine_raster.cpp
index 33fde8c61a..6336b2943e 100644
--- a/src/gui/painting/qpaintengine_raster.cpp
+++ b/src/gui/painting/qpaintengine_raster.cpp
@@ -698,6 +698,11 @@ void QRasterPaintEngine::setState(QPainterState *s)
 {
     Q_D(QRasterPaintEngine);
     QPaintEngineEx::setState(s);
+    QRasterPaintEngineState *t = state();
+    if (t->clip && t->clip->enabled != t->clipEnabled) {
+        // Since we do not "detach" clipdata when changing only enabled state, we need to resync state here
+        t->clip->enabled = t->clipEnabled;
+    }
     d->rasterBuffer->compositionMode = s->composition_mode;
 }
 
diff --git a/tests/auto/gui/painting/qpainter/tst_qpainter.cpp b/tests/auto/gui/painting/qpainter/tst_qpainter.cpp
index 8dfaa6f5cd..ba405e2860 100644
--- a/tests/auto/gui/painting/qpainter/tst_qpainter.cpp
+++ b/tests/auto/gui/painting/qpainter/tst_qpainter.cpp
@@ -153,6 +153,7 @@ private slots:
     void setEqualClipRegionAndPath();
 
     void clipRectSaveRestore();
+    void clipStateSaveRestore();
 
     void clippedFillPath_data();
     void clippedFillPath();
@@ -3425,6 +3426,35 @@ void tst_QPainter::clipRectSaveRestore()
     QCOMPARE(img.pixel(0, 0), QColor(Qt::black).rgba());
 }
 
+void tst_QPainter::clipStateSaveRestore()
+{
+    QImage img(16, 16, QImage::Format_RGB32);
+    img.fill(Qt::blue);
+    {
+        QPainter p(&img);
+        p.setClipRect(QRect(5, 5, 10, 10));
+        p.save();
+        p.setClipping(false);
+        p.restore();
+        p.fillRect(0, 0, 16, 16, Qt::red);
+        p.end();
+        QCOMPARE(img.pixel(0, 0), QColor(Qt::blue).rgb());
+    }
+
+    img.fill(Qt::blue);
+    {
+        QPainter p(&img);
+        p.setClipRect(QRect(5, 5, 10, 10));
+        p.setClipping(false);
+        p.save();
+        p.setClipping(true);
+        p.restore();
+        p.fillRect(0, 0, 16, 16, Qt::red);
+        p.end();
+        QCOMPARE(img.pixel(0, 0), QColor(Qt::red).rgb());
+    }
+}
+
 void tst_QPainter::clippedImage()
 {
     QImage img(16, 16, QImage::Format_ARGB32_Premultiplied);