Renderer: properly merge global stateset with per renderpass stateset

When a RenderPass stateset overriddes the global stateset set by the current
FrameGraph branch at render time, this is done by merging the global
stateset with the RenderPass defined stateset.

Change-Id: I07baca0d50b1c02cf1298b382039aedabd6084cc
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>

4 files changed, 19 insertions, 5 deletions

diff --git a/src/render/backend/renderer.cpp b/src/render/backend/renderer.cpp
index 213598b6b..f11f0e2df 100644
--- a/src/render/backend/renderer.cpp
+++ b/src/render/backend/renderer.cpp
@@ -523,6 +523,7 @@ void Renderer::enqueueRenderView(Render::RenderView *renderView, int submitOrder
 {
     //    qDebug() << Q_FUNC_INFO << QThread::currentThread();
     m_renderQueues->queueRenderView(renderView, submitOrder);
+
     if (m_renderQueues->isFrameQueueComplete()) {
         // We can increment the currentProcessingFrameIndex here
         // That index will then be used by RenderViewJobs to know which QFrameAllocator to use
@@ -765,6 +766,7 @@ void Renderer::executeCommands(const QVector<RenderCommand *> &commands)
 
         //// Draw Calls
         // Set state
+        RenderStateSet *globalState = m_graphicsContext->currentStateSet();
         if (command->m_stateSet != Q_NULLPTR)
             m_graphicsContext->setCurrentStateSet(command->m_stateSet);
 
@@ -791,6 +793,10 @@ void Renderer::executeCommands(const QVector<RenderCommand *> &commands)
                 m_graphicsContext->drawArrays(primType, 0, primCount);
             }
 
+            // Reset state if overridden by pass state
+            if (command->m_stateSet != Q_NULLPTR)
+                m_graphicsContext->setCurrentStateSet(globalState);
+
             int err = m_graphicsContext->openGLContext()->functions()->glGetError();
             if (err)
                 qCWarning(Rendering) << "GL error after drawing mesh:" << QString::number(err, 16);
diff --git a/src/render/backend/renderstate.cpp b/src/render/backend/renderstate.cpp
index 99981dcca..c92601d6e 100644
--- a/src/render/backend/renderstate.cpp
+++ b/src/render/backend/renderstate.cpp
@@ -151,6 +151,11 @@ StateMaskSet RenderStateSet::stateMask() const
     return m_stateMask;
 }
 
+void RenderStateSet::merge(RenderStateSet *other)
+{
+    m_stateMask |= other->stateMask();
+}
+
 void RenderStateSet::resetMasked(StateMaskSet maskOfStatesToReset, QGraphicsContext *gc)
 {
     // TO DO -> Call gcHelper methods instead of raw GL
diff --git a/src/render/backend/renderstate_p.h b/src/render/backend/renderstate_p.h
index b0f5d6de7..231c1b534 100644
--- a/src/render/backend/renderstate_p.h
+++ b/src/render/backend/renderstate_p.h
@@ -102,7 +102,7 @@ public:
     void apply(QGraphicsContext* gc);
 
     StateMaskSet stateMask() const;
-
+    void merge(RenderStateSet *other);
     void resetMasked(StateMaskSet maskOfStatesToReset, QGraphicsContext* gc);
 private:
     /**
diff --git a/src/render/backend/renderview.cpp b/src/render/backend/renderview.cpp
index 71108d76a..20f2f7cfa 100644
--- a/src/render/backend/renderview.cpp
+++ b/src/render/backend/renderview.cpp
@@ -418,19 +418,22 @@ void RenderView::buildRenderCommands(RenderEntity *node)
                     command->m_depth = m_data->m_eyePos.distanceToPoint(node->worldBoundingVolume()->center());
                     command->m_meshData = mesh->meshDataHandle();
                     command->m_instancesCount = 0;
-
-                    // TODO: Build the state set for a render pass only once per-pass. Not once per rendercommand and pass.
                     command->m_stateSet = Q_NULLPTR;
                     command->m_changeCost = 0;
                     // For RenderPass based states we use the globally set RenderState
                     // if no renderstates are defined as part of the pass. That means:
                     // RenderPass { renderStates: [] } will use the states defined by
                     // StateSet in the FrameGraph
-                    if (!pass->renderStates().isEmpty()) {
+                    if (!pass->renderStates().isEmpty())
                         command->m_stateSet = buildRenderStateSet(pass->renderStates(), m_allocator);
+                    if (command->m_stateSet != Q_NULLPTR) {
+                        // Merge per pass stateset with global stateset
+                        // so that the local stateset only overrides
+                        if (m_stateSet != Q_NULLPTR)
+                            command->m_stateSet->merge(m_stateSet);
                         command->m_changeCost = m_renderer->defaultRenderState()->changeCost(command->m_stateSet);
                     }
-                    setShaderAndUniforms(command, pass, globalParameter, *(node->worldTransform()));
+                    setShaderAndUniforms(command, pass, parameters, *(node->worldTransform()));
                     buildSortingKey(command);
                     m_commands.append(command);
                 }