Windows QPA: Fix restore geometry after dragging from maximised

Start tracking the window geometry before a mouse drag, so that we can
revert back to that geometry when we restore from maximised. Previously,
when dragging from maximised to maximised, the restore geometry would
end up being the final drag place before snapping to maximised, instead
of where the window was before the first maximised.

Fixes: QTBUG-112814
Pick-to: 6.5 6.2
Change-Id: Ic2ddf29d6c4abdc9e8b0c5161b17aa6ee9474ea3
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>

src/plugins/platforms/windows/qwindowscontext.cpp

@@ -1219,11 +1219,15 @@ bool QWindowsContext::windowsProc(HWND hwnd, UINT message,
         break;
     case QtWindows::EnterSizeMoveEvent:
         platformWindow->setFlag(QWindowsWindow::ResizeMoveActive);
+        if (!IsZoomed(hwnd))
+            platformWindow->updateRestoreGeometry();
         return true;
     case QtWindows::ExitSizeMoveEvent:
         platformWindow->clearFlag(QWindowsWindow::ResizeMoveActive);
         platformWindow->checkForScreenChanged();
         handleExitSizeMove(platformWindow->window());
+        if (!IsZoomed(hwnd))
+            platformWindow->updateRestoreGeometry();
         return true;
     case QtWindows::ScrollEvent:
         if (!(d->m_systemInfo & QWindowsContext::SI_SupportsPointer))

src/plugins/platforms/windows/qwindowswindow.cpp

@@ -932,6 +932,7 @@ QWindowsWindowData
     QRect obtainedGeometry(context->obtainedPos, context->obtainedSize);
 
     result.geometry = obtainedGeometry;
+    result.restoreGeometry = frameGeometry(result.hwnd, topLevel);
     result.fullFrameMargins = context->margins;
     result.embedded = embedded;
     result.hasFrame = hasFrame;
@@ -1972,6 +1973,11 @@ void QWindowsWindow::handleDpiScaledSize(WPARAM wParam, LPARAM lParam, LRESULT *
         // are currently doing.
         m_data.customMargins *= scale;
     }
+    if (!m_data.restoreGeometry.isEmpty()) {
+        m_data.restoreGeometry.setWidth(m_data.restoreGeometry.width() * scale);
+        m_data.restoreGeometry.setHeight(m_data.restoreGeometry.height() * scale);
+    }
+
     const QSize windowSize = (geometry().size() * scale).grownBy(margins + customMargins());
     SIZE *size = reinterpret_cast<SIZE *>(lParam);
     size->cx = windowSize.width();
@@ -2435,6 +2441,14 @@ void QWindowsWindow::handleWindowStateChange(Qt::WindowStates state)
         handleHidden();
         QWindowSystemInterface::flushWindowSystemEvents(QEventLoop::ExcludeUserInputEvents); // Tell QQuickWindow to stop rendering now.
     } else {
+        if (state & Qt::WindowMaximized) {
+            WINDOWPLACEMENT windowPlacement{};
+            windowPlacement.length = sizeof(WINDOWPLACEMENT);
+            GetWindowPlacement(m_data.hwnd, &windowPlacement);
+            const RECT geometry = RECTfromQRect(m_data.restoreGeometry);
+            windowPlacement.rcNormalPosition = geometry;
+            SetWindowPlacement(m_data.hwnd, &windowPlacement);
+        }
         // QTBUG-17548: We send expose events when receiving WM_Paint, but for
         // layered windows and transient children, we won't receive any WM_Paint.
         QWindow *w = window();
@@ -2458,6 +2472,11 @@ void QWindowsWindow::handleWindowStateChange(Qt::WindowStates state)
     }
 }
 
+void QWindowsWindow::updateRestoreGeometry()
+{
+    m_data.restoreGeometry = normalFrameGeometry(m_data.hwnd);
+}
+
 void QWindowsWindow::setWindowState(Qt::WindowStates state)
 {
     if (m_data.hwnd) {

src/plugins/platforms/windows/qwindowswindow.h

@@ -78,6 +78,7 @@ struct QWindowsWindowData
 {
     Qt::WindowFlags flags;
     QRect geometry;
+    QRect restoreGeometry;
     QMargins fullFrameMargins; // Do not use directly for windows, see FrameDirty.
     QMargins customMargins;    // User-defined, additional frame for NCCALCSIZE
     HWND hwnd = nullptr;
@@ -218,6 +219,8 @@ public:
     void setGeometry(const QRect &rect) override;
     QRect geometry() const override { return m_data.geometry; }
     QRect normalGeometry() const override;
+    QRect restoreGeometry() const { return m_data.restoreGeometry; }
+    void updateRestoreGeometry();
 
     void setVisible(bool visible) override;
     bool isVisible() const;