Windows QPA: Fix cursors getting out of sync after restoring override cursors on native windows

Introduce a flag to QWindowsWindow which forces the cursor to be applied
after restoring override cursors.

Fixes: QTBUG-98856
Pick-to: 6.2 5.15
Change-Id: Id62cdc2dd01f45324503a542446b1c11a1fe6f44
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Keith Kyzivat <keith.kyzivat@qt.io>
Reviewed-by: André de la Rocha <andre.rocha@qt.io>

src/plugins/platforms/windows/qwindowscontext.cpp

@@ -181,14 +181,12 @@ QWindowsContext *QWindowsContext::m_instance = nullptr;
     \internal
 */
 
-typedef QHash<HWND, QWindowsWindow *> HandleBaseWindowHash;
-
 struct QWindowsContextPrivate {
     QWindowsContextPrivate();
 
     unsigned m_systemInfo = 0;
     QSet<QString> m_registeredWindowClassNames;
-    HandleBaseWindowHash m_windows;
+    QWindowsContext::HandleBaseWindowHash m_windows;
     HDC m_displayContext = nullptr;
     int m_defaultDPI = 96;
     QWindowsKeyMapper m_keyMapper;
@@ -460,6 +458,11 @@ QList<int> QWindowsContext::possibleKeys(const QKeyEvent *e) const
     return d->m_keyMapper.possibleKeys(e);
 }
 
+QWindowsContext::HandleBaseWindowHash &QWindowsContext::windows()
+{
+    return d->m_windows;
+}
+
 QSharedPointer<QWindowCreationContext> QWindowsContext::setWindowCreationContext(const QSharedPointer<QWindowCreationContext> &ctx)
 {
     const QSharedPointer<QWindowCreationContext> old = d->m_creationContext;

src/plugins/platforms/windows/qwindowscontext.h

@@ -86,6 +86,7 @@ class QWindowsContext
 {
     Q_DISABLE_COPY_MOVE(QWindowsContext)
 public:
+    using HandleBaseWindowHash = QHash<HWND, QWindowsWindow *>;
 
     enum SystemInfoFlags
     {
@@ -168,6 +169,8 @@ public:
     bool useRTLExtensions() const;
     QList<int> possibleKeys(const QKeyEvent *e) const;
 
+    HandleBaseWindowHash &windows();
+
     static bool isSessionLocked();
 
     QWindowsMimeConverter &mimeConverter() const;

src/plugins/platforms/windows/qwindowscursor.cpp

@@ -652,6 +652,11 @@ void QWindowsCursor::clearOverrideCursor()
         SetCursor(m_overriddenCursor);
         m_overriddenCursor = m_overrideCursor = nullptr;
     }
+    auto &windows = QWindowsContext::instance()->windows();
+    for (auto it = windows.cbegin(), end = windows.cend(); it != end; ++it) {
+        if (it.value()->screen() == m_screen)
+            it.value()->setFlag(QWindowsWindow::RestoreOverrideCursor);
+    }
 }
 
 QPoint QWindowsCursor::mousePosition()

src/plugins/platforms/windows/qwindowswindow.cpp

@@ -2894,7 +2894,14 @@ void QWindowsWindow::applyCursor()
 void QWindowsWindow::setCursor(const CursorHandlePtr &c)
 {
 #ifndef QT_NO_CURSOR
-    if (c->handle() != m_cursor->handle()) {
+    bool changed = c->handle() != m_cursor->handle();
+    // QTBUG-98856: Cursors can get out of sync after restoring override
+    // cursors on native windows. Force an update.
+    if (testFlag(RestoreOverrideCursor)) {
+        clearFlag(RestoreOverrideCursor);
+        changed = true;
+    }
+    if (changed) {
         const bool apply = applyNewCursor(window());
         qCDebug(lcQpaWindows) << window() << __FUNCTION__
             << c->handle() << " doApply=" << apply;

src/plugins/platforms/windows/qwindowswindow.h

@@ -238,7 +238,8 @@ public:
         VulkanSurface = 0x400000,
         ResizeMoveActive = 0x800000,
         DisableNonClientScaling = 0x1000000,
-        Direct3DSurface = 0x2000000
+        Direct3DSurface = 0x2000000,
+        RestoreOverrideCursor = 0x4000000
     };
 
     QWindowsWindow(QWindow *window, const QWindowsWindowData &data);