Emit a signal when QWaylandXdgSurface changes window type

This allows compositors to track when a window changes type and
act accordingly (for example do a different show animation).

Compositors might also want to keep track of the window type in
order to filter out windows when presenting them to the user,
think of a spread windows effect that only shows top level windows.

Change-Id: I13c0ed3db2bdc6318ff1f4345d065e188b7c2435
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>

3 files changed, 50 insertions, 5 deletions

diff --git a/src/compositor/extensions/qwaylandxdgshell.cpp b/src/compositor/extensions/qwaylandxdgshell.cpp
index 8b07283e7..137f3ec31 100644
--- a/src/compositor/extensions/qwaylandxdgshell.cpp
+++ b/src/compositor/extensions/qwaylandxdgshell.cpp
@@ -221,6 +221,7 @@ QWaylandXdgSurfacePrivate::QWaylandXdgSurfacePrivate()
     , xdg_surface()
     , m_surface(nullptr)
     , m_parentSurface(nullptr)
+    , m_windowType(UnknownWindowType)
     , m_unsetWindowGeometry(true)
     , m_lastAckedConfigure({{}, QSize(0, 0), 0})
 {
@@ -346,12 +347,22 @@ void QWaylandXdgSurfacePrivate::xdg_surface_set_parent(Resource *resource, wl_re
                     QWaylandXdgSurfacePrivate::Resource::fromResource(parent)->xdg_surface_object)->q_func();
     }
 
-    if (m_parentSurface == parentSurface)
-        return;
-
     Q_Q(QWaylandXdgSurface);
-    m_parentSurface = parentSurface;
-    emit q->parentSurfaceChanged();
+
+    if (m_parentSurface != parentSurface) {
+        m_parentSurface = parentSurface;
+        emit q->parentSurfaceChanged();
+    }
+
+    if (m_parentSurface && m_windowType != TransientWindowType) {
+        // There's a parent now, which means the surface is transient
+        m_windowType = TransientWindowType;
+        emit q->setTransient();
+    } else if (!m_parentSurface && m_windowType != TopLevelWindowType) {
+        // When the surface has no parent it is toplevel
+        m_windowType = TopLevelWindowType;
+        emit q->setTopLevel();
+    }
 }
 
 void QWaylandXdgSurfacePrivate::xdg_surface_set_app_id(Resource *resource, const QString &app_id)
@@ -611,6 +622,20 @@ void QWaylandXdgShell::handleFocusChanged(QWaylandSurface *newSurface, QWaylandS
  */
 
 /*!
+ * \qmlsignal QtWaylandCompositor::XdgSurface::setTopLevel()
+ *
+ * This signal is emitted when the parent surface is unset, effectively
+ * making the window top level.
+ */
+
+/*!
+ * \qmlsignal QtWaylandCompositor::XdgSurface::setTransient()
+ *
+ * This signal is emitted when the parent surface is set, effectively
+ * making the window transient.
+ */
+
+/*!
  * Constructs a QWaylandXdgSurface.
  */
 QWaylandXdgSurface::QWaylandXdgSurface()
@@ -704,12 +729,22 @@ QWaylandSurface *QWaylandXdgSurface::surface() const
  * \qmlproperty object QtWaylandCompositor::XdgSurface::parentSurface
  *
  * This property holds the XdgSurface parent of this XdgSurface.
+ * When a parent surface is set, the parentSurfaceChanged() signal
+ * is guaranteed to be emitted before setTopLevel() and setTransient().
+ *
+ * \sa QtWaylandCompositor::XdgSurface::setTopLevel()
+ * \sa QtWaylandCompositor::XdgSurface::setTransient()
  */
 
 /*!
  * \property QWaylandXdgSurface::surface
  *
  * This property holds the XdgSurface parent of this XdgSurface.
+ * When a parent surface is set, the parentSurfaceChanged() signal
+ * is guaranteed to be emitted before setTopLevel() and setTransient().
+ *
+ * \sa QWaylandXdgSurface::setTopLevel()
+ * \sa QWaylandXdgSurface::setTransient()
  */
 QWaylandXdgSurface *QWaylandXdgSurface::parentSurface() const
 {
diff --git a/src/compositor/extensions/qwaylandxdgshell.h b/src/compositor/extensions/qwaylandxdgshell.h
index 2da7f3d3d..a12d16480 100644
--- a/src/compositor/extensions/qwaylandxdgshell.h
+++ b/src/compositor/extensions/qwaylandxdgshell.h
@@ -177,6 +177,8 @@ Q_SIGNALS:
     void showWindowMenu(QWaylandInputDevice *inputDevice, const QPoint &localSurfacePosition);
     void startMove(QWaylandInputDevice *inputDevice);
     void startResize(QWaylandInputDevice *inputDevice, ResizeEdge edges);
+    void setTopLevel();
+    void setTransient();
     void setMaximized();
     void unsetMaximized();
     void setFullscreen(QWaylandOutput *output);
diff --git a/src/compositor/extensions/qwaylandxdgshell_p.h b/src/compositor/extensions/qwaylandxdgshell_p.h
index 23c95bdeb..0b2d22e6f 100644
--- a/src/compositor/extensions/qwaylandxdgshell_p.h
+++ b/src/compositor/extensions/qwaylandxdgshell_p.h
@@ -99,6 +99,12 @@ public:
     QWaylandXdgSurfacePrivate();
     static QWaylandXdgSurfacePrivate *get(QWaylandXdgSurface *xdgSurface) { return xdgSurface->d_func(); }
 
+    enum WindowType {
+        UnknownWindowType,
+        TopLevelWindowType,
+        TransientWindowType
+    };
+
     struct ConfigureEvent {
         QVector<uint> states;
         QSize size;
@@ -115,6 +121,8 @@ private:
     QWaylandSurface *m_surface;
     QWaylandXdgSurface *m_parentSurface;
 
+    WindowType m_windowType;
+
     QString m_title;
     QString m_appId;
     QRect m_windowGeometry;