Set window screen from wl_surface.enter and leave events

Removes the pointer mScreen, which would previously cause a crash if the screen
was removed.

Ensures that QWindow::screen() is correct, except in the cases where:

- The compositor has not yet sent enter and leave events (in which case the
  primary output is returned).
- The compositor is not sending enter and leave events (although this is
  mandatory, some compositors don't do this).
- The application developer has tried to move the window with
  QWindow::setScreen(QScreen *). Since there is no way for a client to ask to
  be moved to a specific monitor in windowed mode, we return the requested
  screen until a new enter or leave event is received.

This will also be useful when implementing/fixing features where the current
screen matters. Examples are QT_AUTO_SCREEN_SCALE_FACTOR and the optional
output parameter to wl_shell_surface.set_fullscreen.

Task-number: QTBUG-62044
Change-Id: Iafde2e278fbc8876e8dafe5b2a4d2482fdc7961a
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>

1 files changed, 9 insertions, 2 deletions

diff --git a/src/client/qwaylandwindow_p.h b/src/client/qwaylandwindow_p.h
index e7b9e3d38..bd4a35909 100644
--- a/src/client/qwaylandwindow_p.h
+++ b/src/client/qwaylandwindow_p.h
@@ -142,7 +142,7 @@ public:
     QWaylandDisplay *display() const { return mDisplay; }
     QWaylandShellSurface *shellSurface() const;
     QWaylandSubSurface *subSurfaceWindow() const;
-    QWaylandScreen *screen() const { return mScreen; }
+    QWaylandScreen *screen() const;
 
     void handleContentOrientationChange(Qt::ScreenOrientation orientation) override;
     void setOrientationMask(Qt::ScreenOrientations mask);
@@ -209,7 +209,10 @@ public slots:
     void requestResize();
 
 protected:
-    QWaylandScreen *mScreen;
+    void surface_enter(struct ::wl_output *output) override;
+    void surface_leave(struct ::wl_output *output) override;
+
+    QVector<QWaylandScreen *> mScreens; //As seen by wl_surface.enter/leave events. Chronological order.
     QWaylandDisplay *mDisplay;
     QWaylandShellSurface *mShellSurface;
     QWaylandSubSurface *mSubSurfaceWindow;
@@ -244,6 +247,9 @@ protected:
 
     QWaylandShmBackingStore *mBackingStore;
 
+private slots:
+    void handleScreenRemoved(QScreen *qScreen);
+
 private:
     bool setWindowStateInternal(Qt::WindowState flags);
     void setGeometry_helper(const QRect &rect);
@@ -254,6 +260,7 @@ private:
     void reset();
     void sendExposeEvent(const QRect &rect);
     static void closePopups(QWaylandWindow *parent);
+    QWaylandScreen *calculateScreenFromSurfaceEvents() const;
 
     void handleMouseEventWithDecoration(QWaylandInputDevice *inputDevice, const QWaylandPointerEvent &e);