3 files changed, 34 insertions, 6 deletions

diff --git a/src/widgets/kernel/qopenglwidget.cpp b/src/widgets/kernel/qopenglwidget.cpp
index 1d86d2e8d9..68e3082c14 100644
--- a/src/widgets/kernel/qopenglwidget.cpp
+++ b/src/widgets/kernel/qopenglwidget.cpp
@@ -228,6 +228,18 @@ QT_BEGIN_NAMESPACE
   regarding stacking orders for example. QOpenGLWidget avoids this by not
   creating a separate native window.
 
+  \section1 Multisampling
+
+  To enable multisampling, set the number of requested samples on the
+  QSurfaceFormat that is passed to setFormat(). On systems that do not support
+  it the request may get ignored.
+
+  Multisampling support requires support for multisampled renderbuffers and
+  framebuffer blits. On OpenGL ES 2.0 implementations it is likely that these
+  will not be present. This means that multisampling will not be available. With
+  modern OpenGL versions and OpenGL ES 3.0 and up this is usually not a problem
+  anymore.
+
   \section1 Threading
 
   Performing offscreen rendering on worker threads, for example to generate
@@ -435,6 +447,7 @@ public:
     void beginCompose() Q_DECL_OVERRIDE;
     void endCompose() Q_DECL_OVERRIDE;
     void resizeViewportFramebuffer() Q_DECL_OVERRIDE;
+    void resolveSamples() Q_DECL_OVERRIDE;
 
     QOpenGLContext *context;
     QOpenGLFramebufferObject *fbo;
@@ -491,9 +504,11 @@ void QOpenGLWidgetPrivate::recreateFbo()
     context->makeCurrent(surface);
 
     delete fbo;
+    fbo = 0;
     delete resolvedFbo;
+    resolvedFbo = 0;
 
-    int samples = get(q->window())->shareContext()->format().samples();
+    int samples = context->format().samples();
     QOpenGLExtensions *extfuncs = static_cast<QOpenGLExtensions *>(context->functions());
     if (!extfuncs->hasOpenGLExtension(QOpenGLExtensions::FramebufferMultisample))
         samples = 0;
@@ -570,6 +585,16 @@ void QOpenGLWidgetPrivate::initialize()
     q->initializeGL();
 }
 
+void QOpenGLWidgetPrivate::resolveSamples()
+{
+    Q_Q(QOpenGLWidget);
+    if (resolvedFbo) {
+        q->makeCurrent();
+        QRect rect(QPoint(0, 0), fbo->size());
+        QOpenGLFramebufferObject::blitFramebuffer(resolvedFbo, rect, fbo, rect);
+    }
+}
+
 void QOpenGLWidgetPrivate::invokeUserPaint()
 {
     Q_Q(QOpenGLWidget);
@@ -577,11 +602,6 @@ void QOpenGLWidgetPrivate::invokeUserPaint()
     f->glViewport(0, 0, q->width() * q->devicePixelRatio(), q->height() * q->devicePixelRatio());
 
     q->paintGL();
-
-    if (resolvedFbo) {
-        QRect rect(QPoint(0, 0), fbo->size());
-        QOpenGLFramebufferObject::blitFramebuffer(resolvedFbo, rect, fbo, rect);
-    }
 }
 
 void QOpenGLWidgetPrivate::render()
@@ -605,6 +625,7 @@ QImage QOpenGLWidgetPrivate::grabFramebuffer()
         return QImage();
 
     render();
+    resolveSamples();
     q->makeCurrent();
     QImage res = qt_gl_read_framebuffer(q->size() * q->devicePixelRatio(), false, false);
 
diff --git a/src/widgets/kernel/qwidget.cpp b/src/widgets/kernel/qwidget.cpp
index 95964bfb9d..57169edb9d 100644
--- a/src/widgets/kernel/qwidget.cpp
+++ b/src/widgets/kernel/qwidget.cpp
@@ -5595,6 +5595,11 @@ void QWidgetPrivate::sendPaintEvent(const QRegion &toBePainted)
     Q_Q(QWidget);
     QPaintEvent e(toBePainted);
     QCoreApplication::sendSpontaneousEvent(q, &e);
+
+#ifndef QT_NO_OPENGL
+    if (renderToTexture)
+        resolveSamples();
+#endif // QT_NO_OPENGL
 }
 
 void QWidgetPrivate::render(QPaintDevice *target, const QPoint &targetOffset,
diff --git a/src/widgets/kernel/qwidget_p.h b/src/widgets/kernel/qwidget_p.h
index 011d456a39..1a34ee504c 100644
--- a/src/widgets/kernel/qwidget_p.h
+++ b/src/widgets/kernel/qwidget_p.h
@@ -653,6 +653,8 @@ public:
     // filtered away from the widget. This is fine for QGLWidget but bad for QOpenGLWidget
     // since the fbo must be resized. We need an alternative way to notify.
     virtual void resizeViewportFramebuffer() { }
+    // Called after each paint event.
+    virtual void resolveSamples() { }
 #endif
 
     // Variables.