add isFixedSize implementation

Yuhang Zhao

2023-12-05 d02f3b0bc32f711bf33a7fd288185963e9e96189

 src/core/contexts/win32windowcontext.cpp

@@ -1143,7 +1143,7 @@
                QPoint qtScenePos = fromNativeLocalPosition(
                    m_windowHandle, QPoint(nativeLocalPos.x, nativeLocalPos.y));

                bool isFixedSize = /*isWindowFixedSize()*/ false; // ### FIXME
                bool isFixedSize = m_delegate->isHostSizeFixed(m_host);
                bool isTitleBar = isInTitleBarDraggableArea(qtScenePos);
                bool dontOverrideCursor = false;                  // ### TODO