Windows: Prevent hidden transient children from being re-shown by Windows.

Bring back code from Qt 4 to handle WM_SHOWWINDOW / SW_PARENTOPENING
correctly.

Task-number: QTBUG-40696
Change-Id: If018bf90573f495dbe32d0c46f522ccde0691ebb
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>

src/plugins/platforms/windows/qtwindowsglobal.h

@@ -77,6 +77,7 @@ enum WindowsEventType // Simplify event types
     LeaveEvent = WindowEventFlag + 5,
     CloseEvent = WindowEventFlag + 6,
     ShowEvent = WindowEventFlag + 7,
+    ShowEventOnParentRestoring = WindowEventFlag + 20,
     HideEvent = WindowEventFlag + 8,
     DestroyEvent = WindowEventFlag + 9,
     MoveEvent = WindowEventFlag + 10,
@@ -128,7 +129,7 @@ enum ProcessDpiAwareness
 
 } // namespace QtWindows
 
-inline QtWindows::WindowsEventType windowsEventType(UINT message, WPARAM wParamIn)
+inline QtWindows::WindowsEventType windowsEventType(UINT message, WPARAM wParamIn, LPARAM lParamIn)
 {
     switch (message) {
     case WM_PAINT:
@@ -156,7 +157,9 @@ inline QtWindows::WindowsEventType windowsEventType(UINT message, WPARAM wParamI
     case WM_MOVE:
         return QtWindows::MoveEvent;
     case WM_SHOWWINDOW:
-        return wParamIn ? QtWindows::ShowEvent : QtWindows::HideEvent;
+        if (wParamIn)
+            return lParamIn == SW_PARENTOPENING ? QtWindows::ShowEventOnParentRestoring : QtWindows::ShowEvent;
+        return QtWindows::HideEvent;
     case WM_SIZE:
         return QtWindows::ResizeEvent;
     case WM_NCCALCSIZE:

src/plugins/platforms/windows/qwindowscontext.cpp

@@ -1052,6 +1052,12 @@ bool QWindowsContext::windowsProc(HWND hwnd, UINT message,
     case QtWindows::FocusOutEvent:
         handleFocusEvent(et, platformWindow);
         return true;
+    case QtWindows::ShowEventOnParentRestoring: // QTBUG-40696, prevent Windows from re-showing hidden transient children (dialogs).
+        if (!platformWindow->window()->isVisible()) {
+            *result = 0;
+            return true;
+        }
+        break;
     case QtWindows::HideEvent:
         platformWindow->handleHidden();
         return false;// Indicate transient children should be hidden by windows (SW_PARENTCLOSING)
@@ -1243,7 +1249,7 @@ void QWindowsContext::setAsyncExpose(bool value)
 extern "C" LRESULT QT_WIN_CALLBACK qWindowsWndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
 {
     LRESULT result;
-    const QtWindows::WindowsEventType et = windowsEventType(message, wParam);
+    const QtWindows::WindowsEventType et = windowsEventType(message, wParam, lParam);
     const bool handled = QWindowsContext::instance()->windowsProc(hwnd, message, et, wParam, lParam, &result);
     if (QWindowsContext::verbose > 1 && lcQpaEvents().isDebugEnabled()) {
         if (const char *eventName = QWindowsGuiEventDispatcher::windowsMessageName(message)) {

tests/auto/gui/kernel/qwindow/tst_qwindow.cpp

@@ -39,10 +39,11 @@
 **
 ****************************************************************************/
 
-#include <qwindow.h>
+#include <qrasterwindow.h>
 #include <qpa/qwindowsysteminterface.h>
 #include <qpa/qplatformintegration.h>
 #include <private/qguiapplication_p.h>
+#include <QtGui/QPainter>
 
 #include <QtTest/QtTest>
 
@@ -51,6 +52,8 @@
 
 #if defined(Q_OS_QNX)
 #include <QOpenGLContext>
+#elif defined(Q_OS_WIN) && !defined(Q_OS_WINCE) && !defined(Q_OS_WINRT)
+#  include <QtCore/qt_windows.h>
 #endif
 
 // For QSignalSpy slot connections.
@@ -94,6 +97,7 @@ private slots:
     void modalWithChildWindow();
     void modalWindowModallity();
     void modalWindowPosition();
+    void windowsTransientChildren();
     void initTestCase();
     void cleanup();
 
@@ -1539,6 +1543,59 @@ void tst_QWindow::modalWindowPosition()
     QCOMPARE(window.geometry(), origGeo);
 }
 
+class ColoredWindow : public QRasterWindow {
+public:
+    explicit ColoredWindow(const QColor &color, QWindow *parent = 0) : QRasterWindow(parent), m_color(color) {}
+    void paintEvent(QPaintEvent *) Q_DECL_OVERRIDE
+    {
+        QPainter p(this);
+        p.fillRect(QRect(QPoint(0, 0), size()), m_color);
+    }
+
+private:
+    const QColor m_color;
+};
+
+static bool isNativeWindowVisible(const QWindow *window)
+{
+#if defined(Q_OS_WIN) && !defined(Q_OS_WINCE) && !defined(Q_OS_WINRT)
+    return IsWindowVisible(reinterpret_cast<HWND>(window->winId()));
+#else
+    Q_UNIMPLEMENTED();
+    return window->isVisible();
+#endif
+}
+
+void tst_QWindow::windowsTransientChildren()
+{
+    if (QGuiApplication::platformName().compare(QStringLiteral("windows"), Qt::CaseInsensitive))
+        QSKIP("Windows only test");
+
+    ColoredWindow mainWindow(Qt::yellow);
+    mainWindow.setGeometry(QRect(m_availableTopLeft + QPoint(100, 100), m_testWindowSize));
+    mainWindow.setTitle(QStringLiteral("Main"));
+    ColoredWindow child(Qt::blue, &mainWindow);
+    child.setGeometry(QRect(QPoint(0, 0), m_testWindowSize / 2));
+
+    ColoredWindow dialog(Qt::red);
+    dialog.setGeometry(QRect(m_availableTopLeft + QPoint(200, 200), m_testWindowSize));
+    dialog.setTitle(QStringLiteral("Dialog"));
+    dialog.setTransientParent(&mainWindow);
+
+    mainWindow.show();
+    child.show();
+    dialog.show();
+
+    QVERIFY(QTest::qWaitForWindowExposed(&dialog));
+    mainWindow.setWindowState(Qt::WindowMinimized);
+    QVERIFY(!isNativeWindowVisible(&dialog));
+    dialog.hide();
+    mainWindow.setWindowState(Qt::WindowNoState);
+    // QTBUG-40696, transient children hidden by Qt should not be re-shown by Windows.
+    QVERIFY(!isNativeWindowVisible(&dialog));
+    QVERIFY(isNativeWindowVisible(&child)); // Real children should be visible.
+}
+
 #include <tst_qwindow.moc>
 QTEST_MAIN(tst_QWindow)