Windows: Synthesize expose event for shrinking windows.

Synthesize expose events for all Windows except ANGLE-windows.

Task-number: QTBUG-32121

Change-Id: Ifbff2730ec8f2e8cfe23eeb4022b76a6e432598e
Reviewed-by: Oliver Wolff <oliver.wolff@digia.com>
Reviewed-by: Gunnar Sletta <gunnar.sletta@digia.com>

2 files changed, 25 insertions, 13 deletions

diff --git a/src/plugins/platforms/windows/qwindowswindow.cpp b/src/plugins/platforms/windows/qwindowswindow.cpp
index c3ec949eef..dc51dbfc88 100644
--- a/src/plugins/platforms/windows/qwindowswindow.cpp
+++ b/src/plugins/platforms/windows/qwindowswindow.cpp
@@ -808,8 +808,12 @@ QWindowsWindow::QWindowsWindow(QWindow *aWindow, const WindowData &data) :
     const Qt::WindowType type = aWindow->type();
     if (type == Qt::Desktop)
         return; // No further handling for Qt::Desktop
-    if (aWindow->surfaceType() == QWindow::OpenGLSurface)
+    if (aWindow->surfaceType() == QWindow::OpenGLSurface) {
         setFlag(OpenGLSurface);
+#ifdef QT_OPENGL_ES_2
+        setFlag(OpenGL_ES2);
+#endif
+    }
     if (aWindow->isTopLevel()) {
         switch (type) {
         case Qt::Window:
@@ -1233,9 +1237,16 @@ void QWindowsWindow::handleGeometryChange()
     //Prevent recursive resizes for Windows CE
     if (testFlag(WithinSetStyle))
         return;
+    const QRect previousGeometry = m_data.geometry;
     m_data.geometry = geometry_sys();
     QPlatformWindow::setGeometry(m_data.geometry);
     QWindowSystemInterface::handleGeometryChange(window(), m_data.geometry);
+    // QTBUG-32121: OpenGL/normal windows (with exception of ANGLE) do not receive
+    // expose events when shrinking, synthesize.
+    if (!testFlag(OpenGL_ES2) && isExposed()
+        && !(m_data.geometry.width() > previousGeometry.width() || m_data.geometry.height() > previousGeometry.height())) {
+        fireExpose(QRegion(m_data.geometry), true);
+    }
     if (testFlag(SynchronousGeometryChangeEvent))
         QWindowSystemInterface::flushWindowSystemEvents();
 
diff --git a/src/plugins/platforms/windows/qwindowswindow.h b/src/plugins/platforms/windows/qwindowswindow.h
index 07f3976d87..996542f92a 100644
--- a/src/plugins/platforms/windows/qwindowswindow.h
+++ b/src/plugins/platforms/windows/qwindowswindow.h
@@ -124,18 +124,19 @@ public:
         WithinSetParent = 0x2,
         FrameDirty = 0x4,            //! Frame outdated by setStyle, recalculate in next query.
         OpenGLSurface = 0x10,
-        OpenGLDoubleBuffered = 0x20,
-        OpenGlPixelFormatInitialized = 0x40,
-        BlockedByModal = 0x80,
-        SizeGripOperation = 0x100,
-        FrameStrutEventsEnabled = 0x200,
-        SynchronousGeometryChangeEvent = 0x400,
-        WithinSetStyle = 0x800,
-        WithinDestroy = 0x1000,
-        TouchRegistered = 0x2000,
-        AlertState = 0x4000,
-        Exposed = 0x08000,
-        WithinCreate = 0x10000
+        OpenGL_ES2 = 0x20,
+        OpenGLDoubleBuffered = 0x40,
+        OpenGlPixelFormatInitialized = 0x80,
+        BlockedByModal = 0x100,
+        SizeGripOperation = 0x200,
+        FrameStrutEventsEnabled = 0x400,
+        SynchronousGeometryChangeEvent = 0x800,
+        WithinSetStyle = 0x1000,
+        WithinDestroy = 0x2000,
+        TouchRegistered = 0x4000,
+        AlertState = 0x8000,
+        Exposed = 0x10000,
+        WithinCreate = 0x20000
     };
 
     struct WindowData