add functionality to metal render pass to cache winding order and cull mode (#3566)

src/mbgl/mtl/context.cpp

@@ -408,7 +408,7 @@ bool Context::renderTileClippingMasks(gfx::RenderPass& renderPass,
         uboBuffer->update(tileUBOs.data(), bufferSize, /*offset=*/0);
     }
 
-    encoder->setCullMode(MTL::CullModeNone);
+    mtlRenderPass.setCullMode(MTL::CullModeNone);
 
     mtlRenderPass.bindVertex(vertexRes, /*offset=*/0, ShaderClass::attributes[0].index);
 

src/mbgl/mtl/drawable.cpp

@@ -212,8 +212,8 @@ void Drawable::draw(PaintParameters& parameters) const {
     }
 
     const auto& cullMode = getCullFaceMode();
-    encoder->setCullMode(cullMode.enabled ? mapCullMode(cullMode.side) : MTL::CullModeNone);
-    encoder->setFrontFacingWinding(mapWindingMode(cullMode.winding));
+    renderPass.setCullMode(cullMode.enabled ? mapCullMode(cullMode.side) : MTL::CullModeNone);
+    renderPass.setFrontFacingWinding(mapWindingMode(cullMode.winding));
 
     if (!impl->pipelineState) {
         impl->pipelineState = shaderMTL.getRenderPipelineState(

src/mbgl/mtl/render_pass.cpp

@@ -62,14 +62,7 @@ void RenderPass::endEncoding() {
         encoder.reset();
     }
 
-    currentDepthStencilState.reset();
-    currentStencilReferenceValue = 0;
-    for (int i = 0; i < maxBinds; ++i) {
-        vertexBinds[i].reset();
-        fragmentBinds[i].reset();
-        fragmentTextureBindings[i].reset();
-        fragmentSamplerStates[i].reset();
-    }
+    resetState();
 }
 
 void RenderPass::resetState() {
@@ -81,6 +74,9 @@ void RenderPass::resetState() {
         fragmentTextureBindings[i].reset();
         fragmentSamplerStates[i].reset();
     }
+
+    currentCullMode = MTL::CullModeNone;
+    currentWinding = MTL::WindingClockwise;
 }
 
 namespace {
@@ -197,5 +193,19 @@ void RenderPass::setFragmentSamplerState(const MTLSamplerStatePtr& state, int32_
     }
 }
 
+void RenderPass::setCullMode(const MTL::CullMode mode) {
+    if (mode != currentCullMode) {
+        encoder->setCullMode(mode);
+        currentCullMode = mode;
+    }
+}
+
+void RenderPass::setFrontFacingWinding(const MTL::Winding winding) {
+    if (winding != currentWinding) {
+        encoder->setFrontFacingWinding(winding);
+        currentWinding = winding;
+    }
+}
+
 } // namespace mtl
 } // namespace mbgl