Renderer: cache traversal of FrameGraph

Will be retraversed only when something in the FrameGraph has changed

Change-Id: Ibb43f8f2928b10a584f468fb13f1d4773c7fcebb
Reviewed-by: Mike Krus <mike.krus@kdab.com>

2 files changed, 20 insertions, 17 deletions

diff --git a/src/render/renderers/opengl/renderer/renderer.cpp b/src/render/renderers/opengl/renderer/renderer.cpp
index af9a6e7e6..66d404f4e 100644
--- a/src/render/renderers/opengl/renderer/renderer.cpp
+++ b/src/render/renderers/opengl/renderer/renderer.cpp
@@ -1824,26 +1824,27 @@ QVector<Qt3DCore::QAspectJobPtr> Renderer::renderBinJobs()
         // populate the RenderView with a set of RenderCommands that get
         // their details from the RenderNodes that are visible to the
         // Camera selected by the framegraph configuration
-        FrameGraphVisitor visitor(m_nodesManager->frameGraphManager());
-        const QVector<FrameGraphNode *> fgLeaves = visitor.traverse(frameGraphRoot());
-
-        // Handle single shot subtree enablers
-        const auto subtreeEnablers = visitor.takeEnablersToDisable();
-        for (auto *node : subtreeEnablers)
-            m_updatedDisables.push_back(node->peerId());
-        if (m_updatedDisables.size() > 0)
-            renderBinJobs.push_back(m_sendDisablesToFrontendJob);
-
-        // Remove leaf nodes that no longer exist from cache
-        const QList<FrameGraphNode *> keys = m_cache.leafNodeCache.keys();
-        for (FrameGraphNode *leafNode : keys) {
-            if (!fgLeaves.contains(leafNode))
-                m_cache.leafNodeCache.remove(leafNode);
+        if (frameGraphDirty) {
+            FrameGraphVisitor visitor(m_nodesManager->frameGraphManager());
+            m_frameGraphLeaves = visitor.traverse(frameGraphRoot());
+            // Remove leaf nodes that no longer exist from cache
+            const QList<FrameGraphNode *> keys = m_cache.leafNodeCache.keys();
+            for (FrameGraphNode *leafNode : keys) {
+                if (!m_frameGraphLeaves.contains(leafNode))
+                    m_cache.leafNodeCache.remove(leafNode);
+            }
+
+            // Handle single shot subtree enablers
+            const auto subtreeEnablers = visitor.takeEnablersToDisable();
+            for (auto *node : subtreeEnablers)
+                m_updatedDisables.push_back(node->peerId());
+            if (m_updatedDisables.size() > 0)
+                renderBinJobs.push_back(m_sendDisablesToFrontendJob);
         }
 
-        const int fgBranchCount = fgLeaves.size();
+        const int fgBranchCount = m_frameGraphLeaves.size();
         for (int i = 0; i < fgBranchCount; ++i) {
-            RenderViewBuilder builder(fgLeaves.at(i), i, this);
+            RenderViewBuilder builder(m_frameGraphLeaves.at(i), i, this);
             builder.setLayerCacheNeedsToBeRebuilt(layersCacheNeedsToBeRebuilt);
             builder.setRenderableCacheNeedsToBeRebuilt(renderableDirty);
             builder.setComputableCacheNeedsToBeRebuilt(computeableDirty);
diff --git a/src/render/renderers/opengl/renderer/renderer_p.h b/src/render/renderers/opengl/renderer/renderer_p.h
index 0ea27d91a..c7b4f8805 100644
--- a/src/render/renderers/opengl/renderer/renderer_p.h
+++ b/src/render/renderers/opengl/renderer/renderer_p.h
@@ -424,6 +424,8 @@ private:
     QMetaObject::Connection m_contextConnection;
     RendererCache m_cache;
     bool m_shouldSwapBuffers;
+
+    QVector<FrameGraphNode *> m_frameGraphLeaves;
 };
 
 } // namespace Render