Introducing QQuickItem::sceneGraphInvalidated/sceneGraphInitialized

[ChangeLog][QtQuick][QQuickItem] Added signals sceneGraphInitialized and sceneGraphInvalidated

Change-Id: Idaea88bc743f0637d093cf1ba7ac4f78acd7e6ad
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>

4 files changed, 76 insertions, 0 deletions

diff --git a/src/quick/items/qquickitem.cpp b/src/quick/items/qquickitem.cpp
index 51bec66d22..54c63c4cbf 100644
--- a/src/quick/items/qquickitem.cpp
+++ b/src/quick/items/qquickitem.cpp
@@ -2622,6 +2622,11 @@ void QQuickItemPrivate::refWindow(QQuickWindow *c)
     Q_ASSERT(window == 0);
     window = c;
 
+    if (q->flags() & QQuickItem::ItemHasContents) {
+        QObject::connect(window, SIGNAL(sceneGraphInvalidated()), q, SIGNAL(sceneGraphInvalidated()), Qt::DirectConnection);
+        QObject::connect(window, SIGNAL(sceneGraphInitialized()), q, SIGNAL(sceneGraphInitialized()), Qt::DirectConnection);
+    }
+
     if (polishScheduled)
         QQuickWindowPrivate::get(window)->itemsToPolish.insert(q);
 
@@ -2651,6 +2656,11 @@ void QQuickItemPrivate::derefWindow()
     if (--windowRefCount > 0)
         return; // There are still other references, so don't set window to null yet.
 
+    if (q->flags() & QQuickItem::ItemHasContents) {
+        QObject::disconnect(window, SIGNAL(sceneGraphInvalidated()), q, SIGNAL(sceneGraphInvalidated()));
+        QObject::disconnect(window, SIGNAL(sceneGraphInitialized()), q, SIGNAL(sceneGraphInitialized()));
+    }
+
     q->releaseResources();
     removeFromDirtyList();
     QQuickWindowPrivate *c = QQuickWindowPrivate::get(window);
@@ -5794,10 +5804,67 @@ void QQuickItem::setFlags(Flags flags)
     if (int(flags & ItemClipsChildrenToShape) != int(d->flags & ItemClipsChildrenToShape))
         d->dirty(QQuickItemPrivate::Clip);
 
+    if (window() && (flags & ItemHasContents) ^ (d->flags & ItemHasContents)) {
+        if (flags & ItemHasContents)  {
+            connect(window(), SIGNAL(sceneGraphInvalidated()), this, SIGNAL(sceneGraphInvalidated()), Qt::DirectConnection);
+            connect(window(), SIGNAL(sceneGraphInitialized()), this, SIGNAL(sceneGraphInitialized()), Qt::DirectConnection);
+        } else {
+            disconnect(window(), SIGNAL(sceneGraphInvalidated()), this, SIGNAL(sceneGraphInvalidated()));
+            disconnect(window(), SIGNAL(sceneGraphInitialized()), this, SIGNAL(sceneGraphInitialized()));
+        }
+    }
+
     d->flags = flags;
 }
 
 /*!
+    \fn void QQuickItem::sceneGraphInvalidated()
+
+    This signal is emitted when the scene graph is invalidated for
+    items that have the ItemHasContents flag set.
+
+    QSGNode instances will be cleaned up by the scene graph
+    automatically. An application will only need to react to this signal
+    to clean up resources that are stored and managed outside the
+    QSGNode structure returned from updatePaintNode().
+
+    When the scene graph is using a dedicated render thread, this
+    signal will be emitted on the scene graph's render thread. The
+    GUI thread is blocked for the duration of this call. Connections
+    should for this reason be made using Qt::DirectConnection.
+
+    The OpenGL context of this item's window will be bound when this
+    signal is emitted. The only exception is if the native OpenGL has
+    been destroyed outside Qt's control, for instance through
+    EGL_CONTEXT_LOST.
+
+    \since 5.4
+    \since QtQuick 2.4
+
+    \sa QQuickWindow::sceneGraphInvalidated()
+ */
+
+/*!
+    \fn void QQuickItem::sceneGraphInitialized()
+
+    This signal is emitted when the scene graph is is initialized for
+    items that have the ItemHasContents flag set.
+
+    When the scene graph is using a dedicated render thread, this
+    function will be called on the scene graph's render thread. The
+    GUI thread is blocked for the duration of this call. Connections
+    should for this reason be made using Qt::DirectConnection.
+
+    The OpenGL context of this item's window will be bound when
+    this signal is emitted.
+
+    \since 5.4
+    \since QtQuick 2.4
+
+    \sa QQuickWindow::sceneGraphInitialized()
+ */
+
+/*!
   \qmlproperty real QtQuick::Item::x
   \qmlproperty real QtQuick::Item::y
   \qmlproperty real QtQuick::Item::width
diff --git a/src/quick/items/qquickitem.h b/src/quick/items/qquickitem.h
index 91940c7cf0..fee04984a4 100644
--- a/src/quick/items/qquickitem.h
+++ b/src/quick/items/qquickitem.h
@@ -385,6 +385,9 @@ Q_SIGNALS:
     void implicitWidthChanged();
     void implicitHeightChanged();
 
+    Q_REVISION(2) void sceneGraphInvalidated();
+    Q_REVISION(2) void sceneGraphInitialized();
+
 protected:
     virtual bool event(QEvent *);
 
diff --git a/src/quick/items/qquickitem_p.h b/src/quick/items/qquickitem_p.h
index dbd4d51941..9ac4758182 100644
--- a/src/quick/items/qquickitem_p.h
+++ b/src/quick/items/qquickitem_p.h
@@ -297,6 +297,7 @@ public:
     static void transform_clear(QQmlListProperty<QQuickTransform> *list);
 
     void _q_resourceObjectDeleted(QObject *);
+    void _q_windowChanged(QQuickWindow *w);
 
     enum ChangeType {
         Geometry = 0x01,
diff --git a/src/quick/items/qquickwindow.cpp b/src/quick/items/qquickwindow.cpp
index 37525e6151..63e57615ba 100644
--- a/src/quick/items/qquickwindow.cpp
+++ b/src/quick/items/qquickwindow.cpp
@@ -2868,6 +2868,11 @@ QOpenGLContext *QQuickWindow::openglContext() const
     has been invalidated and all user resources tied to that context
     should be released.
 
+    The OpenGL context of this window will be bound when this function
+    is called. The only exception is if the native OpenGL has been
+    destroyed outside Qt's control, for instance through
+    EGL_CONTEXT_LOST.
+
     This signal will be emitted from the scene graph rendering thread.
  */