Windows: Generate expose events for layered transient children.

Layered (translucent/non-opaque) windows do not receive WM_PAINT,
expose events need to be generated. Improve
6800728d091e5122e6d93675db84ee028221d161 to handle transient
children as well.

Task-number: QTBUG-17548
Change-Id: Id113604512692dfbea1f2b10d0db3068213cf599
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>

2 files changed, 29 insertions, 6 deletions

diff --git a/src/plugins/platforms/windows/qwindowswindow.cpp b/src/plugins/platforms/windows/qwindowswindow.cpp
index 8ec10294a2..401fa67c4b 100644
--- a/src/plugins/platforms/windows/qwindowswindow.cpp
+++ b/src/plugins/platforms/windows/qwindowswindow.cpp
@@ -1408,14 +1408,27 @@ void QWindowsWindow::handleWindowStateChange(Qt::WindowState state)
         handleHidden();
         QWindowSystemInterface::flushWindowSystemEvents(); // Tell QQuickWindow to stop rendering now.
         break;
-    case Qt::WindowNoState:
+    case Qt::WindowNoState: {
         // QTBUG-17548: We send expose events when receiving WM_Paint, but for
-        // layered windows, we won't receive any WM_Paint.
-        if (GetWindowLongPtr(m_data.hwnd, GWL_EXSTYLE) & WS_EX_LAYERED) {
-            fireExpose(QRegion(0, 0, window()->width(), window()->height()));
-            if (!QWindowsContext::instance()->asyncExpose())
-                QWindowSystemInterface::flushWindowSystemEvents();
+        // layered windows and transient children, we won't receive any WM_Paint.
+        QWindow *w = window();
+        bool exposeEventsSent = false;
+        if (isLayered()) {
+            fireExpose(QRegion(0, 0, w->width(), w->height()));
+            exposeEventsSent = true;
         }
+        foreach (QWindow *child, QGuiApplication::allWindows()) {
+            if (child != w && child->isVisible() && child->transientParent() == w) {
+                QWindowsWindow *platformWindow = QWindowsWindow::baseWindowOf(child);
+                if (platformWindow->isLayered()) {
+                    platformWindow->fireExpose(QRegion(0, 0, child->width(), child->height()));
+                    exposeEventsSent = true;
+                }
+            }
+        }
+        if (exposeEventsSent && !QWindowsContext::instance()->asyncExpose())
+            QWindowSystemInterface::flushWindowSystemEvents();
+    }
         break;
     default:
         break;
diff --git a/src/plugins/platforms/windows/qwindowswindow.h b/src/plugins/platforms/windows/qwindowswindow.h
index f7d142fc36..afcfa8b821 100644
--- a/src/plugins/platforms/windows/qwindowswindow.h
+++ b/src/plugins/platforms/windows/qwindowswindow.h
@@ -229,6 +229,7 @@ public:
     static inline void setUserDataOf(HWND hwnd, void *ud);
 
     static bool setWindowLayered(HWND hwnd, Qt::WindowFlags flags, bool hasAlpha, qreal opacity);
+    bool isLayered() const;
 
     HDC getDC();
     void releaseDC();
@@ -375,6 +376,15 @@ inline void QWindowsWindow::destroyIcon()
     }
 }
 
+inline bool QWindowsWindow::isLayered() const
+{
+#ifndef Q_OS_WINCE
+    return GetWindowLongPtr(m_data.hwnd, GWL_EXSTYLE) & WS_EX_LAYERED;
+#else
+    return false;
+#endif
+}
+
 QT_END_NAMESPACE
 
 Q_DECLARE_METATYPE(QMargins)