QBackingStore: Take DPR into account when resizing with static contents

The plumbing from QBackingStore::resize to the platform backing store
was missing a high-DPI conversion for the backing store's static
contents, which is also expressed in the QtGui coordinate system.

Pick-to: 6.7 6.6 6.5 6.2
Change-Id: Ifaac916cbf184b9386aa5feca1577a53bf2906ed
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

1 files changed, 76 insertions, 0 deletions

diff --git a/tests/auto/gui/kernel/qbackingstore/tst_qbackingstore.cpp b/tests/auto/gui/kernel/qbackingstore/tst_qbackingstore.cpp
index 7e2b9198d2..9fdf566988 100644
--- a/tests/auto/gui/kernel/qbackingstore/tst_qbackingstore.cpp
+++ b/tests/auto/gui/kernel/qbackingstore/tst_qbackingstore.cpp
@@ -30,6 +30,8 @@ private slots:
 
     void scroll();
     void flush();
+
+    void staticContents();
 };
 
 void tst_QBackingStore::initTestCase_data()
@@ -267,5 +269,79 @@ void tst_QBackingStore::flush()
     QTRY_VERIFY(window.isExposed());
 }
 
+void tst_QBackingStore::staticContents()
+{
+#if !defined(Q_OS_WIN)
+    QSKIP("Platform does not support static backingstore content");
+#endif
+
+    QWindow window;
+    window.create();
+
+    const auto dpr = window.devicePixelRatio();
+
+    QBackingStore backingStore(&window);
+
+    QRect initialRect(0, 0, 100, 100);
+
+    // Static contents without paint first should not crash
+    backingStore.setStaticContents(initialRect);
+    backingStore.resize(initialRect.size());
+    QCOMPARE(backingStore.size(), initialRect.size());
+    backingStore.beginPaint(QRect(0, 0, 50, 50));
+    backingStore.endPaint();
+    backingStore.handle()->toImage();
+
+    {
+        backingStore.setStaticContents(QRect());
+        backingStore.beginPaint(initialRect);
+        QPainter p(backingStore.paintDevice());
+        p.fillRect(initialRect, Qt::green);
+        p.end();
+        backingStore.endPaint();
+
+        QImage image = backingStore.handle()->toImage();
+        if (image.isNull())
+            QSKIP("Platform backingstore does not implement toImage");
+
+        QCOMPARE(image.pixelColor(initialRect.topLeft() * dpr), Qt::green);
+        QCOMPARE(image.pixelColor(initialRect.bottomLeft() * dpr), Qt::green);
+        QCOMPARE(image.pixelColor(initialRect.topRight() * dpr), Qt::green);
+        QCOMPARE(image.pixelColor(initialRect.bottomRight() * dpr), Qt::green);
+    }
+
+    {
+        backingStore.setStaticContents(initialRect);
+
+        QRect resizedRect(0, 0, 200, 200);
+        backingStore.resize(resizedRect.size());
+
+        QRegion repaintRegion = QRegion(resizedRect) - QRegion(initialRect);
+
+        backingStore.beginPaint(repaintRegion);
+        QPainter p(backingStore.paintDevice());
+        for (auto repaintRect : repaintRegion)
+            p.fillRect(repaintRect, Qt::red);
+        p.end();
+        backingStore.endPaint();
+
+        QImage image = backingStore.handle()->toImage();
+        if (image.isNull())
+            QSKIP("Platform backingstore does not implement toImage");
+
+        QCOMPARE(image.pixelColor(initialRect.topLeft() * dpr), Qt::green);
+        QCOMPARE(image.pixelColor(initialRect.bottomLeft() * dpr), Qt::green);
+        QCOMPARE(image.pixelColor(initialRect.topRight() * dpr), Qt::green);
+        QCOMPARE(image.pixelColor(initialRect.bottomRight() * dpr), Qt::green);
+
+        for (auto repaintRect : repaintRegion) {
+            QCOMPARE(image.pixelColor(repaintRect.topLeft() * dpr), Qt::red);
+            QCOMPARE(image.pixelColor(repaintRect.bottomLeft() * dpr), Qt::red);
+            QCOMPARE(image.pixelColor(repaintRect.topRight() * dpr), Qt::red);
+            QCOMPARE(image.pixelColor(repaintRect.bottomRight() * dpr), Qt::red);
+        }
+    }
+}
+
 #include <tst_qbackingstore.moc>
 QTEST_MAIN(tst_QBackingStore);