4 files changed, 31 insertions, 0 deletions
diff --git a/src/gui/image/qpixmap_raster.cpp b/src/gui/image/qpixmap_raster.cpp
index 5c188f0362..30463f3c0d 100644
--- a/src/gui/image/qpixmap_raster.cpp
+++ b/src/gui/image/qpixmap_raster.cpp
@@ -353,7 +353,9 @@ void QRasterPlatformPixmap::createPixmapForImage(QImage &sourceImage, Qt::ImageC
     is_null = (w <= 0 || h <= 0);
 
     image.d->devicePixelRatio = sourceImage.devicePixelRatio();
+    //ensure the pixmap and the image resulting from toImage() have the same cacheKey();
     setSerialNumber(image.cacheKey() >> 32);
+    setDetachNumber(image.d->detach_no);
 }
 
 QImage* QRasterPlatformPixmap::buffer()
diff --git a/src/gui/image/qplatformpixmap.cpp b/src/gui/image/qplatformpixmap.cpp
index 2e12ae2e91..1d147e3d3c 100644
--- a/src/gui/image/qplatformpixmap.cpp
+++ b/src/gui/image/qplatformpixmap.cpp
@@ -173,6 +173,11 @@ void QPlatformPixmap::setSerialNumber(int serNo)
     ser_no = serNo;
 }
 
+void QPlatformPixmap::setDetachNumber(int detNo)
+{
+    detach_no = detNo;
+}
+
 QImage QPlatformPixmap::toImage(const QRect &rect) const
 {
     if (rect.contains(QRect(0, 0, w, h)))
diff --git a/src/gui/image/qplatformpixmap.h b/src/gui/image/qplatformpixmap.h
index af3abecaf8..d54f31099e 100644
--- a/src/gui/image/qplatformpixmap.h
+++ b/src/gui/image/qplatformpixmap.h
@@ -132,6 +132,7 @@ public:
 protected:
 
     void setSerialNumber(int serNo);
+    void setDetachNumber(int detNo);
     int w;
     int h;
     int d;
diff --git a/tests/auto/gui/image/qpixmap/tst_qpixmap.cpp b/tests/auto/gui/image/qpixmap/tst_qpixmap.cpp
index 576519e2ca..e204da059d 100644
--- a/tests/auto/gui/image/qpixmap/tst_qpixmap.cpp
+++ b/tests/auto/gui/image/qpixmap/tst_qpixmap.cpp
@@ -114,6 +114,7 @@ private slots:
 
     void convertFromImageNoDetach();
     void convertFromImageDetach();
+    void convertFromImageCacheKey();
 
 #if defined(Q_OS_WIN)
     void toWinHBITMAP_data();
@@ -779,6 +780,28 @@ void tst_QPixmap::convertFromImageDetach()
     QVERIFY(copy.isDetached());
 }
 
+void tst_QPixmap::convertFromImageCacheKey()
+{
+    QPixmap randomPixmap(10, 10);
+    if (randomPixmap.handle()->classId() != QPlatformPixmap::RasterClass)
+        QSKIP("Test only valid for raster pixmaps");
+
+    //first get the screen format
+    QImage::Format screenFormat = randomPixmap.toImage().format();
+    QVERIFY(screenFormat != QImage::Format_Invalid);
+
+    QImage orig(100,100, screenFormat);
+    orig.fill(0);
+
+    QPixmap pix = QPixmap::fromImage(orig);
+    QImage copy = pix.toImage();
+
+    QVERIFY(copy.format() == screenFormat);
+
+    QCOMPARE(orig.cacheKey(), pix.cacheKey());
+    QCOMPARE(copy.cacheKey(), pix.cacheKey());
+}
+
 #if defined(Q_OS_WIN)
 
 QT_BEGIN_NAMESPACE