Windows QPA: Fix broken frame geometry when moving windows with native menus

QWindowsWindow::updateFullFrameMargins() which is called
from the screen changed handling does not take native menus
into account.

Since the size of the menu is not known when using
EnableNonClientDpiScaling(), obtaining the correct frame
size requires triggering a WM_NCCALCSIZE message. Extract
the helper forceNcCalcSize() from QWindowsMenu and
use that from updateFullFrameMargins() in case menus are present.

Amends d2fd9b1b9818b3ec88487967e010f66e92952f55.

Fixes: QTBUG-82580
Change-Id: I306f1faf84e26c88608cb22ffd42eccc848905c3
Reviewed-by: André de la Rocha <andre.rocha@qt.io>

5 files changed, 23 insertions, 10 deletions

diff --git a/src/plugins/platforms/windows/qwindowscontext.cpp b/src/plugins/platforms/windows/qwindowscontext.cpp
index d31352b854..293faf8a53 100644
--- a/src/plugins/platforms/windows/qwindowscontext.cpp
+++ b/src/plugins/platforms/windows/qwindowscontext.cpp
@@ -978,6 +978,13 @@ QByteArray QWindowsContext::comErrorString(HRESULT hr)
     return result;
 }
 
+void QWindowsContext::forceNcCalcSize(HWND hwnd)
+{
+    // Force WM_NCCALCSIZE to adjust margin
+    SetWindowPos(hwnd, nullptr, 0, 0, 0, 0,
+                 SWP_FRAMECHANGED | SWP_NOACTIVATE | SWP_NOMOVE | SWP_NOSIZE | SWP_NOZORDER | SWP_NOOWNERZORDER);
+}
+
 bool QWindowsContext::systemParametersInfo(unsigned action, unsigned param, void *out,
                                            unsigned dpi)
 {
diff --git a/src/plugins/platforms/windows/qwindowscontext.h b/src/plugins/platforms/windows/qwindowscontext.h
index 8027f09389..07398bd61c 100644
--- a/src/plugins/platforms/windows/qwindowscontext.h
+++ b/src/plugins/platforms/windows/qwindowscontext.h
@@ -246,6 +246,8 @@ public:
     bool asyncExpose() const;
     void setAsyncExpose(bool value);
 
+    static void forceNcCalcSize(HWND hwnd);
+
     static bool systemParametersInfo(unsigned action, unsigned param, void *out, unsigned dpi = 0);
     static bool systemParametersInfoForScreen(unsigned action, unsigned param, void *out,
                                               const QPlatformScreen *screen = nullptr);
diff --git a/src/plugins/platforms/windows/qwindowsmenu.cpp b/src/plugins/platforms/windows/qwindowsmenu.cpp
index d20edd685e..221e4ff6ec 100644
--- a/src/plugins/platforms/windows/qwindowsmenu.cpp
+++ b/src/plugins/platforms/windows/qwindowsmenu.cpp
@@ -794,20 +794,13 @@ QWindowsMenuBar *QWindowsMenuBar::menuBarOf(const QWindow *notYetCreatedWindow)
         ? qobject_cast<QWindowsMenuBar *>(menuBarV.value<QObject *>()) : nullptr;
 }
 
-static inline void forceNcCalcSize(HWND hwnd)
-{
-    // Force WM_NCCALCSIZE to adjust margin: Does not appear to work?
-    SetWindowPos(hwnd, nullptr, 0, 0, 0, 0,
-                 SWP_FRAMECHANGED | SWP_NOACTIVATE | SWP_NOMOVE | SWP_NOSIZE | SWP_NOZORDER | SWP_NOOWNERZORDER);
-}
-
 void QWindowsMenuBar::install(QWindowsWindow *window)
 {
     const HWND hwnd = window->handle();
     const BOOL result = SetMenu(hwnd, m_hMenuBar);
     if (result) {
         window->setMenuBar(this);
-        forceNcCalcSize(hwnd);
+        QWindowsContext::forceNcCalcSize(hwnd);
     }
 }
 
@@ -817,7 +810,7 @@ void QWindowsMenuBar::removeFromWindow()
         const HWND hwnd = window->handle();
         SetMenu(hwnd, nullptr);
         window->setMenuBar(nullptr);
-        forceNcCalcSize(hwnd);
+        QWindowsContext::forceNcCalcSize(hwnd);
     }
 }
 
diff --git a/src/plugins/platforms/windows/qwindowswindow.cpp b/src/plugins/platforms/windows/qwindowswindow.cpp
index a11da598fc..04478d5f1f 100644
--- a/src/plugins/platforms/windows/qwindowswindow.cpp
+++ b/src/plugins/platforms/windows/qwindowswindow.cpp
@@ -2431,7 +2431,17 @@ void QWindowsWindow::setFullFrameMargins(const QMargins &newMargins)
 
 void QWindowsWindow::updateFullFrameMargins()
 {
-    // Normally obtained from WM_NCCALCSIZE
+    // QTBUG-82580: If a native menu is present, force a WM_NCCALCSIZE.
+    if (GetMenu(m_data.hwnd))
+        QWindowsContext::forceNcCalcSize(m_data.hwnd);
+    else
+        calculateFullFrameMargins();
+}
+
+void QWindowsWindow::calculateFullFrameMargins()
+{
+    // Normally obtained from WM_NCCALCSIZE. This calculation only works
+    // when no native menu is present.
     const auto systemMargins = testFlag(DisableNonClientScaling)
         ? QWindowsGeometryHint::frameOnPrimaryScreen(m_data.hwnd)
         : frameMargins_sys();
diff --git a/src/plugins/platforms/windows/qwindowswindow.h b/src/plugins/platforms/windows/qwindowswindow.h
index 1f8800272b..aaf02d2a81 100644
--- a/src/plugins/platforms/windows/qwindowswindow.h
+++ b/src/plugins/platforms/windows/qwindowswindow.h
@@ -370,6 +370,7 @@ private:
     void handleWindowStateChange(Qt::WindowStates state);
     inline void destroyIcon();
     void fireExpose(const QRegion &region, bool force=false);
+    void calculateFullFrameMargins();
 
     mutable QWindowsWindowData m_data;
     QPointer<QWindowsMenuBar> m_menuBar;