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, 6 insertions, 3 deletions

diff --git a/src/quick/scenegraph/coreapi/qsgbatchrenderer.cpp b/src/quick/scenegraph/coreapi/qsgbatchrenderer.cpp
index 293cc4cb6b..2441e14fda 100644
--- a/src/quick/scenegraph/coreapi/qsgbatchrenderer.cpp
+++ b/src/quick/scenegraph/coreapi/qsgbatchrenderer.cpp
@@ -4563,11 +4563,14 @@ void Renderer::renderRhiRenderNode(const Batch *batch) // split prepare-render (
     rd->m_matrix = nullptr;
     rd->m_clip_list = nullptr;
 
-    if (changes & QSGRenderNode::ViewportState)
+    if ((changes & QSGRenderNode::ViewportState)
+            || (changes & QSGRenderNode::ScissorState))
+    {
+        // Reset both flags if either is reported as changed, since with the rhi
+        // it could be setViewport() that will record the resetting of the scissor.
         m_pstate.viewportSet = false;
-
-    if (changes & QSGRenderNode::ScissorState)
         m_pstate.scissorSet = false;
+    }
 
     // Do not bother with RenderTargetState. Where applicable, endExternal()
     // ensures the correct target is rebound. For others (like Vulkan) it makes