rendernode example: Add support for Metal

Plus clarify QQuickWindow::begin/endExternalCommands() in combination
with QSGRenderNode in the docs. As the example demonstrates, calling
these functions is not necessary within render() of a render node.

Also fix an issue with resetting the scissor in the renderer after
calling render() of a QSGRenderNode.

Change-Id: If8c2dab38d62aa444266d37901f062a51e767f68
Reviewed-by: Christian Strømme <christian.stromme@qt.io>

1 files changed, 10 insertions, 0 deletions

diff --git a/src/quick/items/qquickwindow.cpp b/src/quick/items/qquickwindow.cpp
index 88a731b229..8b5e2a012a 100644
--- a/src/quick/items/qquickwindow.cpp
+++ b/src/quick/items/qquickwindow.cpp
@@ -4666,6 +4666,11 @@ const QQuickWindow::GraphicsStateInfo *QQuickWindow::graphicsStateInfo()
     beginExternalCommands() and endExternalCommands() together provide a
     replacement for resetOpenGLState().
 
+    Calling this function and endExternalCommands() is not necessary within the
+    \l{QSGRenderNode::render()}{render()} implementation of a QSGRenderNode
+    because the scene graph performs the necessary steps implicitly for render
+    nodes.
+
     \note This function has no effect when the scene graph is using OpenGL
     directly and the RHI graphics abstraction layer is not in use. Refer to
     resetOpenGLState() in that case.
@@ -4704,6 +4709,11 @@ void QQuickWindow::beginExternalCommands()
     beginExternalCommands() and endExternalCommands() together provide a
     replacement for resetOpenGLState().
 
+    Calling this function and beginExternalCommands() is not necessary within the
+    \l{QSGRenderNode::render()}{render()} implementation of a QSGRenderNode
+    because the scene graph performs the necessary steps implicitly for render
+    nodes.
+
     \note This function has no effect when the scene graph is using OpenGL
     directly and the RHI graphics abstraction layer is not in use. Refer to
     resetOpenGLState() in that case.