stdin.patch

diff --git i/examples/gui/openglwindow/main.cpp w/examples/gui/openglwindow/main.cpp
index aa1c6d7..d2a4d4a 100644
--- i/examples/gui/openglwindow/main.cpp
+++ w/examples/gui/openglwindow/main.cpp
@@ -139,7 +139,7 @@ void TriangleWindow::render()
     const qreal retinaScale = devicePixelRatio();
     glViewport(0, 0, width() * retinaScale, height() * retinaScale);
 
-    glClear(GL_COLOR_BUFFER_BIT);
+    //glClear(GL_COLOR_BUFFER_BIT);
 
     m_program->bind();
 
diff --git i/examples/gui/openglwindow/openglwindow.cpp w/examples/gui/openglwindow/openglwindow.cpp
index afebf52..029cb5c 100644
--- i/examples/gui/openglwindow/openglwindow.cpp
+++ w/examples/gui/openglwindow/openglwindow.cpp
@@ -52,6 +52,7 @@ OpenGLWindow::OpenGLWindow(QWindow *parent)
     , m_update_pending(false)
     , m_animating(false)
     , m_context(0)
+    , m_context2(0)
     , m_device(0)
 {
     setSurfaceType(QWindow::OpenGLSurface);
@@ -77,13 +78,26 @@ void OpenGLWindow::render()
     if (!m_device)
         m_device = new QOpenGLPaintDevice;
 
-    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
+//    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
 
     m_device->setSize(size());
 
     QPainter painter(m_device);
     render(&painter);
 }
+
+void OpenGLWindow::render2()
+{
+    if (!m_device)
+        m_device = new QOpenGLPaintDevice;
+    
+//    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
+    
+    m_device->setSize(size());
+    
+    QPainter painter(m_device);
+    painter.fillRect(QRect(0, 0, 100, 100), Qt::red);
+}
 //! [2]
 
 //! [3]
@@ -127,9 +141,23 @@ void OpenGLWindow::renderNow()
     if (!m_context) {
         m_context = new QOpenGLContext(this);
         m_context->setFormat(requestedFormat());
+        
+        m_context2 = new QOpenGLContext(this);
+        m_context2->setFormat(requestedFormat());
+        m_context2->setShareContext(m_context);
+        
+        m_context->setShareContext(m_context2);
+        
         m_context->create();
 
         needsInitialize = true;
+        
+     
+        m_context2->create();
+        
+        m_context2->makeCurrent(this);
+        initializeOpenGLFunctions();
+        initialize();
     }
 
     m_context->makeCurrent(this);
@@ -143,6 +171,10 @@ void OpenGLWindow::renderNow()
 
     m_context->swapBuffers(this);
 
+    m_context2->makeCurrent(this);
+    render2();
+    m_context2->swapBuffers(this);
+    
     if (m_animating)
         renderLater();
 }
@@ -158,3 +190,4 @@ void OpenGLWindow::setAnimating(bool animating)
 }
 //! [5]
 
+
diff --git i/examples/gui/openglwindow/openglwindow.h w/examples/gui/openglwindow/openglwindow.h
index f6b53e3..20595cb 100644
--- i/examples/gui/openglwindow/openglwindow.h
+++ w/examples/gui/openglwindow/openglwindow.h
@@ -57,6 +57,7 @@ public:
 
     virtual void render(QPainter *painter);
     virtual void render();
+        virtual void render2();
 
     virtual void initialize();
 
@@ -76,6 +77,7 @@ private:
     bool m_animating;
 
     QOpenGLContext *m_context;
+    QOpenGLContext *m_context2;
     QOpenGLPaintDevice *m_device;
 };
 //! [1]
diff --git i/src/plugins/platforms/ios/qioscontext.h w/src/plugins/platforms/ios/qioscontext.h
index 52357a5..93be4cb 100644
--- i/src/plugins/platforms/ios/qioscontext.h
+++ w/src/plugins/platforms/ios/qioscontext.h
@@ -88,7 +88,7 @@ private:
         bool isComplete;
     };
 
-    static void deleteBuffers(const FramebufferObject &framebufferObject);
+    void deleteBuffers(const FramebufferObject &framebufferObject);
 
     FramebufferObject &backingFramebufferObjectFor(QPlatformSurface *) const;
     mutable QHash<QIOSWindow *, FramebufferObject> m_framebufferObjects;
diff --git i/src/plugins/platforms/ios/qioscontext.mm w/src/plugins/platforms/ios/qioscontext.mm
index 1ea0403..ddee521 100644
--- i/src/plugins/platforms/ios/qioscontext.mm
+++ w/src/plugins/platforms/ios/qioscontext.mm
@@ -140,17 +140,22 @@ void QIOSContext::swapBuffers(QPlatformSurface *surface)
     if (surface->surface()->surfaceClass() == QSurface::Offscreen)
         return; // Nothing to do
 
-    Q_ASSERT(surface->surface()->surfaceClass() == QSurface::Window);
-    QIOSWindow *window = static_cast<QIOSWindow *>(surface);
-    Q_ASSERT(m_framebufferObjects.contains(window));
+    FramebufferObject &framebufferObject = backingFramebufferObjectFor(surface);
 
     [EAGLContext setCurrentContext:m_eaglContext];
-    glBindRenderbuffer(GL_RENDERBUFFER, m_framebufferObjects[window].colorRenderbuffer);
+    glBindRenderbuffer(GL_RENDERBUFFER, framebufferObject.colorRenderbuffer);
     [m_eaglContext presentRenderbuffer:GL_RENDERBUFFER];
 }
 
 QIOSContext::FramebufferObject &QIOSContext::backingFramebufferObjectFor(QPlatformSurface *surface) const
 {
+    // We keep track of default-FBOs in the root context of a share-group. This assumes
+    // that the contexts form a tree, where leaf nodes are always destroyed before their
+    // parents. If that assumption (based on the current implementation) doesn't hold we
+    // should probably use QOpenGLMultiGroupSharedResource to track the shared default-FBOs.
+    if (m_sharedContext)
+        return m_sharedContext->backingFramebufferObjectFor(surface);
+
     Q_ASSERT(surface && surface->surface()->surfaceClass() == QSurface::Window);
     QIOSWindow *window = static_cast<QIOSWindow *>(surface);