Windows QPA: Improve handling of windows of type Qt::ForeignWindow.

Extract a base class QWindowsBaseWindow from QWindowsWindow that provides
_sys() getters for geometry and margin calculation and implements
QPlatformWindow::geometry()/ frameMargins() to be calculated from the
HWND.

Implement a QWindowsDesktopWindow class directly inheriting
QWindowsBaseWindow which does not allow any manipulation.

Add a thin QWindowsForeignWindow class that wraps a foreign window id and
always returns correct geometry/margin information when queried. Simple
reparenting and manipulation of geometry for child windows is also implemented,
allowing for embedding foreign windows into Qt. When calling other setters on
it, the unimplemented warnings of QPlatformWindow will trigger.

Remove the special casing for foreign/desktop window from QWindowsWindow.
The existing mechanism to cache the geometry/margin values in QWindowsWindow
remains as is.

Rename the existing QWindowsWindow::baseWindowOf() and add checks there.

Task-number: QTBUG-50206
Task-number: QTBUG-41186
Change-Id: Ib57cb87e3981312d32920fe3e49f0b1c4ad516a3
Reviewed-by: Joerg Bornemann <joerg.bornemann@theqtcompany.com>

1 files changed, 5 insertions, 4 deletions

diff --git a/src/plugins/platforms/windows/qwindowsmousehandler.cpp b/src/plugins/platforms/windows/qwindowsmousehandler.cpp
index 2bc9527b1b..c8b18f3b57 100644
--- a/src/plugins/platforms/windows/qwindowsmousehandler.cpp
+++ b/src/plugins/platforms/windows/qwindowsmousehandler.cpp
@@ -267,7 +267,7 @@ bool QWindowsMouseHandler::translateMouseEvent(QWindow *window, HWND hwnd,
             // Capture is necessary so we don't get WM_MOUSELEAVEs to confuse matters.
             // This autocapture is released normally when button is released.
             if (!platformWindow->hasMouseCapture()) {
-                QWindowsWindow::baseWindowOf(window)->applyCursor();
+                platformWindow->applyCursor();
                 platformWindow->setMouseGrabEnabled(true);
                 platformWindow->setFlag(QWindowsWindow::AutoMouseCapture);
                 qCDebug(lcQpaEvents) << "Automatic mouse capture for missing buttondown event" << window;
@@ -355,7 +355,7 @@ bool QWindowsMouseHandler::translateMouseEvent(QWindow *window, HWND hwnd,
                 m_trackedWindow = 0;
                 // We are not officially in any window, but we need to set some cursor to clear
                 // whatever cursor the left window had, so apply the cursor of the capture window.
-                QWindowsWindow::baseWindowOf(window)->applyCursor();
+                platformWindow->applyCursor();
             }
         }
         // Enter is needed if:
@@ -367,7 +367,8 @@ bool QWindowsMouseHandler::translateMouseEvent(QWindow *window, HWND hwnd,
             || (m_previousCaptureWindow && window != m_previousCaptureWindow && currentWindowUnderMouse
                 && currentWindowUnderMouse != m_previousCaptureWindow)) {
             qCDebug(lcQpaEvents) << "Entering " << currentWindowUnderMouse;
-            QWindowsWindow::baseWindowOf(currentWindowUnderMouse)->applyCursor();
+            if (QWindowsWindow *wumPlatformWindow = QWindowsWindow::windowsWindowOf(currentWindowUnderMouse))
+                wumPlatformWindow->applyCursor();
             QWindowSystemInterface::handleEnterEvent(currentWindowUnderMouse,
                                                      currentWindowUnderMouse->mapFromGlobal(globalPosition),
                                                      globalPosition);
@@ -392,7 +393,7 @@ static bool isValidWheelReceiver(QWindow *candidate)
 {
     if (candidate) {
         const QWindow *toplevel = QWindowsWindow::topLevelOf(candidate);
-        if (const QWindowsWindow *ww = QWindowsWindow::baseWindowOf(toplevel))
+        if (const QWindowsWindow *ww = QWindowsWindow::windowsWindowOf(toplevel))
             return !ww->testFlag(QWindowsWindow::BlockedByModal);
     }