Renders the scene graph, described by a tree of gsk.render_node.RenderNode instances
to the renderer's surface, ensuring that the given region gets redrawn.
If the renderer has no associated surface, this function does nothing.
Renderers must ensure that changes of the contents given by the root
node as well as the area given by region are redrawn. They are however
free to not redraw any pixel outside of region if they can guarantee that
it didn't change.
The renderer will acquire a reference on the gsk.render_node.RenderNode tree while
the rendering is in progress.
Renders the scene graph, described by a tree of gsk.render_node.RenderNode instances to the renderer's surface, ensuring that the given region gets redrawn.
If the renderer has no associated surface, this function does nothing.
Renderers must ensure that changes of the contents given by the root node as well as the area given by region are redrawn. They are however free to not redraw any pixel outside of region if they can guarantee that it didn't change.
The renderer will acquire a reference on the gsk.render_node.RenderNode tree while the rendering is in progress.