Fix crash when handling WM_PAINT during COM operations

Synchronous expose corrupts painter state if it is done during existing
paint operation, which can happen e.g. when requesting some value from
dumpcpp generated wrapper inside a slot.

Fixed by implementing support for setting asynchronous expose and
doing expose according to the setting in handleWmPaint().

Task-number: QTBUG-27209
Change-Id: I89b5aa823fda947d26b1a4757f129e7c31ea408b
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/src/plugins/platforms/windows/qwindowsintegration.cpp b/src/plugins/platforms/windows/qwindowsintegration.cpp
index f95fbf4b34..b7309c3f7c 100644
--- a/src/plugins/platforms/windows/qwindowsintegration.cpp
+++ b/src/plugins/platforms/windows/qwindowsintegration.cpp
@@ -96,6 +96,7 @@ QT_BEGIN_NAMESPACE
 class QWindowsNativeInterface : public QPlatformNativeInterface
 {
     Q_OBJECT
+    Q_PROPERTY(bool asyncExpose READ asyncExpose WRITE setAsyncExpose)
 public:
 #ifndef QT_NO_OPENGL
     virtual void *nativeResourceForContext(const QByteArray &resource, QOpenGLContext *context);
@@ -106,6 +107,8 @@ public:
     Q_INVOKABLE void *createMessageWindow(const QString &classNameTemplate,
                                           const QString &windowName,
                                           void *eventProc) const;
+    bool asyncExpose() const;
+    void setAsyncExpose(bool value);
 };
 
 void *QWindowsNativeInterface::nativeResourceForWindow(const QByteArray &resource, QWindow *window)
@@ -183,6 +186,16 @@ void *QWindowsNativeInterface::createMessageWindow(const QString &classNameTempl
     return hwnd;
 }
 
+bool QWindowsNativeInterface::asyncExpose() const
+{
+    return QWindowsContext::instance()->asyncExpose();
+}
+
+void QWindowsNativeInterface::setAsyncExpose(bool value)
+{
+    QWindowsContext::instance()->setAsyncExpose(value);
+}
+
 /*!
     \class QWindowsIntegration
     \brief QPlatformIntegration implementation for Windows.