Fix hidpi support for opengl window grabbing

Now set the QImage devicePixelRatio so the content is correct on all
screens.

Task-number: QTBUG-53795
Change-Id: Ic92eee98f691ebb1e0212498c1ae13ede74bca93
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

2 files changed, 4 insertions, 1 deletions

diff --git a/src/gui/kernel/qopenglwindow.cpp b/src/gui/kernel/qopenglwindow.cpp
index e1bd3d11b2..5170c7ab63 100644
--- a/src/gui/kernel/qopenglwindow.cpp
+++ b/src/gui/kernel/qopenglwindow.cpp
@@ -528,7 +528,9 @@ QImage QOpenGLWindow::grabFramebuffer()
         return QImage();
 
     makeCurrent();
-    return qt_gl_read_framebuffer(size() * devicePixelRatio(), false, false);
+    QImage img = qt_gl_read_framebuffer(size() * devicePixelRatio(), false, false);
+    img.setDevicePixelRatio(devicePixelRatio());
+    return img;
 }
 
 /*!
diff --git a/tests/auto/gui/qopengl/tst_qopengl.cpp b/tests/auto/gui/qopengl/tst_qopengl.cpp
index 44921f68aa..4cdd8202e9 100644
--- a/tests/auto/gui/qopengl/tst_qopengl.cpp
+++ b/tests/auto/gui/qopengl/tst_qopengl.cpp
@@ -381,6 +381,7 @@ static bool fuzzyComparePixels(const QRgb testPixel, const QRgb refPixel, const
 
 static void fuzzyCompareImages(const QImage &testImage, const QImage &referenceImage, const char* file, int line)
 {
+    QCOMPARE(testImage.devicePixelRatio(), referenceImage.devicePixelRatio());
     QCOMPARE(testImage.width(), referenceImage.width());
     QCOMPARE(testImage.height(), referenceImage.height());