Compositor: make XdgShellV6 reconfigure clients on mode-change

[ChangeLog][Compositor] Made the zxdg_shell_v6 compositor protocol
implementation re-issue configure requests with updated sizes when
the size or available geometry changes on an output used by a
maximized or fullscreen surface.

Change-Id: Ia446511f123e831b2d0a35ba202a6d092a841569
Reviewed-by: Johan Helsing <johan.helsing@qt.io>

2 files changed, 48 insertions, 4 deletions

diff --git a/src/compositor/extensions/qwaylandxdgshellv6integration.cpp b/src/compositor/extensions/qwaylandxdgshellv6integration.cpp
index 769b426c9..c3cd140e1 100644
--- a/src/compositor/extensions/qwaylandxdgshellv6integration.cpp
+++ b/src/compositor/extensions/qwaylandxdgshellv6integration.cpp
@@ -74,6 +74,7 @@ XdgToplevelV6Integration::XdgToplevelV6Integration(QWaylandQuickShellSurfaceItem
         handlePopupCreated(item, popup);
     });
     connect(m_xdgSurface->surface(), &QWaylandSurface::sizeChanged, this, &XdgToplevelV6Integration::handleSurfaceSizeChanged);
+    connect(m_toplevel, &QObject::destroyed, this, &XdgToplevelV6Integration::handleToplevelDestroyed);
 }
 
 bool XdgToplevelV6Integration::mouseMoveEvent(QMouseEvent *event)
@@ -145,8 +146,21 @@ void XdgToplevelV6Integration::handleSetMaximized()
         windowedGeometry.initialPosition = m_item->moveItem()->position();
     }
 
-    QWaylandOutput *output = m_item->view()->output();
-    m_toplevel->sendMaximized(output->availableGeometry().size() / output->scaleFactor());
+    // Any prior output-resize handlers are irrelevant at this point.
+    disconnect(nonwindowedState.sizeChangedConnection);
+    nonwindowedState.output = m_item->view()->output();
+    nonwindowedState.sizeChangedConnection = connect(nonwindowedState.output, &QWaylandOutput::availableGeometryChanged, this, &XdgToplevelV6Integration::handleMaximizedSizeChanged);
+    handleMaximizedSizeChanged();
+}
+
+void XdgToplevelV6Integration::handleMaximizedSizeChanged()
+{
+    // Insurance against handleToplevelDestroyed() not managing to disconnect this
+    // handler in time.
+    if (m_toplevel == nullptr)
+        return;
+
+    m_toplevel->sendMaximized(nonwindowedState.output->availableGeometry().size() / nonwindowedState.output->scaleFactor());
 }
 
 void XdgToplevelV6Integration::handleUnsetMaximized()
@@ -179,8 +193,21 @@ void XdgToplevelV6Integration::handleSetFullscreen()
         windowedGeometry.initialPosition = m_item->moveItem()->position();
     }
 
-    QWaylandOutput *output = m_item->view()->output();
-    m_toplevel->sendFullscreen(output->geometry().size() / output->scaleFactor());
+    // Any prior output-resize handlers are irrelevant at this point.
+    disconnect(nonwindowedState.sizeChangedConnection);
+    nonwindowedState.output = m_item->view()->output();
+    nonwindowedState.sizeChangedConnection = connect(nonwindowedState.output, &QWaylandOutput::geometryChanged, this, &XdgToplevelV6Integration::handleFullscreenSizeChanged);
+    handleFullscreenSizeChanged();
+}
+
+void XdgToplevelV6Integration::handleFullscreenSizeChanged()
+{
+    // Insurance against handleToplevelDestroyed() not managing to disconnect this
+    // handler in time.
+    if (m_toplevel == nullptr)
+        return;
+
+    m_toplevel->sendFullscreen(nonwindowedState.output->geometry().size() / nonwindowedState.output->scaleFactor());
 }
 
 void XdgToplevelV6Integration::handleUnsetFullscreen()
@@ -221,6 +248,13 @@ void XdgToplevelV6Integration::handleSurfaceSizeChanged()
     }
 }
 
+void XdgToplevelV6Integration::handleToplevelDestroyed()
+{
+    // Disarm any handlers that might fire on the now-stale toplevel pointer
+    nonwindowedState.output = nullptr;
+    disconnect(nonwindowedState.sizeChangedConnection);
+}
+
 XdgPopupV6Integration::XdgPopupV6Integration(QWaylandQuickShellSurfaceItem *item)
     : m_item(item)
     , m_xdgSurface(qobject_cast<QWaylandXdgSurfaceV6 *>(item->shellSurface()))
diff --git a/src/compositor/extensions/qwaylandxdgshellv6integration_p.h b/src/compositor/extensions/qwaylandxdgshellv6integration_p.h
index afb4964b9..5b56af89b 100644
--- a/src/compositor/extensions/qwaylandxdgshellv6integration_p.h
+++ b/src/compositor/extensions/qwaylandxdgshellv6integration_p.h
@@ -77,6 +77,9 @@ private Q_SLOTS:
     void handleFullscreenChanged();
     void handleActivatedChanged();
     void handleSurfaceSizeChanged();
+    void handleToplevelDestroyed();
+    void handleMaximizedSizeChanged();
+    void handleFullscreenSizeChanged();
 
 private:
     QWaylandQuickShellSurfaceItem *m_item = nullptr;
@@ -110,6 +113,13 @@ private:
         QSize initialWindowSize;
         QPointF initialPosition;
     } windowedGeometry;
+
+    struct {
+        QWaylandOutput *output = nullptr;
+        QMetaObject::Connection sizeChangedConnection; // Depending on whether maximized or fullscreen,
+                                                       // will be hooked to geometry-changed or available-
+                                                       // geometry-changed.
+    } nonwindowedState;
 };
 
 class XdgPopupV6Integration : public QWaylandQuickShellIntegration