Add QQuickCanvas::update()

We would like to make a distinction between QQuickItem::update()
which triggers updatePaintNode() to synchronize the scene
graph and requesting the toplevel QQuickCanvas to be repainted.

If we have this distinction in place it is possible for the
scene graph to detect that the scene is unchanged and avoid
rendering unless the user has explicitely asked for the
canvas to be repainted, which is often the case when hooking
into QQuickCanvas::beforeRender().

Change-Id: Ibe77f58423593deb217ef9f8082fa12009f45daf
Reviewed-by: Samuel Rødal <samuel.rodal@nokia.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/src/quick/items/qquickcanvas.cpp b/src/quick/items/qquickcanvas.cpp
index 4fd3bf0e87..c3aecce372 100644
--- a/src/quick/items/qquickcanvas.cpp
+++ b/src/quick/items/qquickcanvas.cpp
@@ -255,6 +255,19 @@ void QQuickCanvasPrivate::setRenderWithoutShowing(bool render)
 }
 
 
+/*!
+ * Schedules the canvas to render another frame.
+ *
+ * Calling QQuickCanvas::update() differs from QQuickItem::update() in that
+ * it always triggers a repaint, regardless of changes in the underlying
+ * scene graph or not.
+ */
+void QQuickCanvas::update()
+{
+    Q_D(QQuickCanvas);
+    d->windowManager->update(this);
+}
+
 void forceUpdate(QQuickItem *item)
 {
     if (item->flags() & QQuickItem::ItemHasContents)