QPA: Introduce QPlatformWindow::normalGeometry().

QWidgetWindow stores the normal geometry obtained from the widget when
transiting to other states. This does not work reliably on Windows,
where this geometry is already that of the new state. Instead,
introduce  QPlatformWindow::normalGeometry(), add implementation
for Windows and use that in QWidgetWindow.

Task-number: QTBUG-21371

Change-Id: I3819ebaf55b4e7d2f7eef1affe6c20712ba45d7c
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>

src/gui/kernel/qplatformwindow.cpp

@@ -127,6 +127,18 @@ QRect QPlatformWindow::geometry() const
     return d->rect;
 }
 
+/*!
+    Returns the geometry of a window in 'normal' state
+    (neither maximized, fullscreen nor minimized) for saving geometries to
+    application settings.
+
+    \since 5.3
+*/
+QRect QPlatformWindow::normalGeometry() const
+{
+    return QRect();
+}
+
 QMargins QPlatformWindow::frameMargins() const
 {
     return QMargins();

src/gui/kernel/qplatformwindow.h

@@ -84,6 +84,7 @@ public:
 
     virtual void setGeometry(const QRect &rect);
     virtual QRect geometry() const;
+    virtual QRect normalGeometry() const;
 
     virtual QMargins frameMargins() const;
 

src/plugins/platforms/windows/qwindowswindow.cpp

@@ -1234,6 +1234,28 @@ void QWindowsWindow::handleCompositionSettingsChanged()
         applyBlurBehindWindow(handle());
 }
 
+static QRect normalFrameGeometry(HWND hwnd)
+{
+#ifndef Q_OS_WINCE
+    WINDOWPLACEMENT wp;
+    wp.length = sizeof(WINDOWPLACEMENT);
+    if (GetWindowPlacement(hwnd, &wp))
+        return qrectFromRECT(wp.rcNormalPosition);
+#else
+    Q_UNUSED(hwnd)
+#endif
+    return QRect();
+}
+
+QRect QWindowsWindow::normalGeometry() const
+{
+    // Check for fake 'fullscreen' mode.
+    const bool fakeFullScreen = m_savedFrameGeometry.isValid() && window()->windowState() == Qt::WindowFullScreen;
+    const QRect frame = fakeFullScreen ? m_savedFrameGeometry : normalFrameGeometry(m_data.hwnd);
+    const QMargins margins = fakeFullScreen ? QWindowsGeometryHint::frame(m_savedStyle, 0) : frameMargins();
+    return frame.isValid() ? frame.marginsRemoved(margins) : frame;
+}
+
 void QWindowsWindow::setGeometry(const QRect &rectIn)
 {
     QRect rect = rectIn;
@@ -1593,10 +1615,9 @@ void QWindowsWindow::setWindowState_sys(Qt::WindowState newState)
                 m_savedStyle = style();
 #ifndef Q_OS_WINCE
                 if (oldState == Qt::WindowMinimized) {
-                    WINDOWPLACEMENT wp;
-                    wp.length = sizeof(WINDOWPLACEMENT);
-                    if (GetWindowPlacement(m_data.hwnd, &wp))
-                        m_savedFrameGeometry = qrectFromRECT(wp.rcNormalPosition);
+                    const QRect nf = normalFrameGeometry(m_data.hwnd);
+                    if (nf.isValid())
+                        m_savedFrameGeometry = nf;
                 } else {
 #endif
                     m_savedFrameGeometry = frameGeometry_sys();

src/plugins/platforms/windows/qwindowswindow.h

@@ -162,6 +162,7 @@ public:
     virtual QSurfaceFormat format() const { return m_format; }
     virtual void setGeometry(const QRect &rect);
     virtual QRect geometry() const { return m_data.geometry; }
+    QRect normalGeometry() const Q_DECL_OVERRIDE;
 
     virtual void setVisible(bool visible);
     bool isVisible() const;

src/widgets/kernel/qwidgetwindow.cpp

@@ -50,6 +50,7 @@
 #include <private/qwidgetbackingstore_p.h>
 #include <qpa/qwindowsysteminterface_p.h>
 #include <qpa/qplatformtheme.h>
+#include <qpa/qplatformwindow.h>
 #include <private/qgesturemanager_p.h>
 
 QT_BEGIN_NAMESPACE
@@ -547,6 +548,24 @@ void QWidgetWindow::updateGeometry()
     m_widget->data->fstrut_dirty = false;
 }
 
+Qt::WindowState effectiveState(Qt::WindowStates state);
+
+// Store normal geometry used for saving application settings.
+void QWidgetWindow::updateNormalGeometry()
+{
+    QTLWExtra *tle = m_widget->d_func()->maybeTopData();
+    if (!tle)
+        return;
+     // Ask platform window, default to widget geometry.
+    QRect normalGeometry;
+    if (const QPlatformWindow *pw = handle())
+        normalGeometry = pw->normalGeometry();
+    if (!normalGeometry.isValid() && effectiveState(m_widget->windowState()) == Qt::WindowNoState)
+        normalGeometry = m_widget->geometry();
+    if (normalGeometry.isValid())
+        tle->normalGeometry = normalGeometry;
+}
+
 void QWidgetWindow::handleMoveEvent(QMoveEvent *event)
 {
     updateGeometry();
@@ -692,8 +711,6 @@ void QWidgetWindow::handleExposeEvent(QExposeEvent *event)
     }
 }
 
-Qt::WindowState effectiveState(Qt::WindowStates state);
-
 void QWidgetWindow::handleWindowStateChangedEvent(QWindowStateChangeEvent *event)
 {
     // QWindow does currently not know 'active'.
@@ -712,16 +729,12 @@ void QWidgetWindow::handleWindowStateChangedEvent(QWindowStateChangeEvent *event
         widgetState |= Qt::WindowMinimized;
         break;
     case Qt::WindowMaximized:
-        if (effectiveState(widgetState) == Qt::WindowNoState)
-            if (QTLWExtra *tle = m_widget->d_func()->maybeTopData())
-                tle->normalGeometry = m_widget->geometry();
+        updateNormalGeometry();
         widgetState |= Qt::WindowMaximized;
         widgetState &= ~(Qt::WindowMinimized | Qt::WindowFullScreen);
         break;
     case Qt::WindowFullScreen:
-        if (effectiveState(widgetState) == Qt::WindowNoState)
-            if (QTLWExtra *tle = m_widget->d_func()->maybeTopData())
-                tle->normalGeometry = m_widget->geometry();
+        updateNormalGeometry();
         widgetState |= Qt::WindowFullScreen;
         widgetState &= ~(Qt::WindowMinimized);
         break;

src/widgets/kernel/qwidgetwindow_qpa_p.h

@@ -104,6 +104,7 @@ private slots:
 
 private:
     void updateGeometry();
+    void updateNormalGeometry();
 
     enum FocusWidgets {
         FirstFocusWidget,