QOpenGLWidget: Fix grabbing multisample framebuffers

Task-number: QTBUG-48450
Change-Id: I0a680e0d682c7c08c3aea40d922bbf2ad66c1de0
Reviewed-by: Joni Poikelin <joni.poikelin@theqtcompany.com>
Reviewed-by: Paul Olav Tvete <paul.tvete@theqtcompany.com>

1 files changed, 13 insertions, 2 deletions

diff --git a/src/widgets/kernel/qopenglwidget.cpp b/src/widgets/kernel/qopenglwidget.cpp
index ee0543ceda..65a70ceb02 100644
--- a/src/widgets/kernel/qopenglwidget.cpp
+++ b/src/widgets/kernel/qopenglwidget.cpp
@@ -877,11 +877,22 @@ QImage QOpenGLWidgetPrivate::grabFramebuffer()
     if (!inPaintGL)
         render();
 
-    resolveSamples();
-    q->makeCurrent();
+    if (resolvedFbo) {
+        resolveSamples();
+        resolvedFbo->bind();
+    } else {
+        q->makeCurrent();
+    }
+
     QImage res = qt_gl_read_framebuffer(q->size() * q->devicePixelRatioF(), false, false);
     res.setDevicePixelRatio(q->devicePixelRatioF());
 
+    // While we give no guarantees of what is going to be left bound, prefer the
+    // multisample fbo instead of the resolved one. Clients may continue to
+    // render straight after calling this function.
+    if (resolvedFbo)
+        q->makeCurrent();
+
     return res;
 }