4 files changed, 29 insertions, 2 deletions
diff --git a/src/gui/kernel/qclipboard.cpp b/src/gui/kernel/qclipboard.cpp
index 21127eebbd..f14355bc01 100644
--- a/src/gui/kernel/qclipboard.cpp
+++ b/src/gui/kernel/qclipboard.cpp
@@ -425,8 +425,9 @@ void QClipboard::setPixmap(const QPixmap &pixmap, Mode mode)
 /*!
     \fn QMimeData *QClipboard::mimeData(Mode mode) const
 
-    Returns a reference to a QMimeData representation of the current
-    clipboard data.
+    Returns a pointer to a QMimeData representation of the current
+    clipboard data (can be NULL if the given \a mode is not
+    supported by the platform).
 
     The \a mode argument is used to control which part of the system
     clipboard is used.  If \a mode is QClipboard::Clipboard, the
diff --git a/src/gui/kernel/qguiapplication.cpp b/src/gui/kernel/qguiapplication.cpp
index d8457bc041..7beab72ab0 100644
--- a/src/gui/kernel/qguiapplication.cpp
+++ b/src/gui/kernel/qguiapplication.cpp
@@ -351,6 +351,16 @@ void QWindowGeometrySpecification::applyTo(QWindow *window) const
 static QWindowGeometrySpecification windowGeometrySpecification = Q_WINDOW_GEOMETRY_SPECIFICATION_INITIALIZER;
 
 /*!
+    \macro qGuiApp
+    \relates QGuiApplication
+
+    A global pointer referring to the unique application object.
+    Only valid for use when that object is a QGuiApplication.
+
+    \sa QCoreApplication::instance(), qApp
+*/
+
+/*!
     \class QGuiApplication
     \brief The QGuiApplication class manages the GUI application's control
     flow and main settings.
diff --git a/src/gui/kernel/qplatformscreen.cpp b/src/gui/kernel/qplatformscreen.cpp
index 3c1552c31e..1d519e84f9 100644
--- a/src/gui/kernel/qplatformscreen.cpp
+++ b/src/gui/kernel/qplatformscreen.cpp
@@ -342,6 +342,10 @@ void QPlatformScreen::resizeMaximizedWindows()
     for (int i = 0; i < windows.size(); ++i) {
         QWindow *w = windows.at(i);
 
+        // Skip non-platform windows, e.g., offscreen windows.
+        if (!w->handle())
+            continue;
+
         if (platformScreenForWindow(w) != this)
             continue;
 
diff --git a/src/gui/kernel/qsurfaceformat.cpp b/src/gui/kernel/qsurfaceformat.cpp
index d7dc0faceb..000d727380 100644
--- a/src/gui/kernel/qsurfaceformat.cpp
+++ b/src/gui/kernel/qsurfaceformat.cpp
@@ -41,6 +41,8 @@
 
 #include <QtCore/qatomic.h>
 #include <QtCore/QDebug>
+#include <QOpenGLContext>
+#include <QtGui/qguiapplication.h>
 
 #ifdef major
 #undef major
@@ -761,6 +763,16 @@ Q_GLOBAL_STATIC(QSurfaceFormat, qt_default_surface_format)
  */
 void QSurfaceFormat::setDefaultFormat(const QSurfaceFormat &format)
 {
+#ifndef QT_NO_OPENGL
+    if (qApp) {
+        QOpenGLContext *globalContext = QOpenGLContext::globalShareContext();
+        if (globalContext && globalContext->isValid()) {
+            qWarning("Warning: Setting a new default format with a different version or profile "
+                     "after the global shared context is created may cause issues with context "
+                     "sharing.");
+        }
+    }
+#endif
     *qt_default_surface_format() = format;
 }