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;