Metal: Implement Culling and FrontFace

This is implementing the feature on a single backend and without tests
so we can get it in the hands of people trying WebGPU quickly.

BUG=dawn:43

Change-Id: I4d0611efd21dd1af053288957f137febc78a74e8
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/6721
Reviewed-by: Austin Eng <enga@chromium.org>
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>

src/dawn_native/RenderPipeline.cpp

@@ -435,6 +435,16 @@ namespace dawn_native {
         return mPrimitiveTopology;
     }
 
+    dawn::CullMode RenderPipelineBase::GetCullMode() const {
+        ASSERT(!IsError());
+        return mRasterizationState.cullMode;
+    }
+
+    dawn::FrontFace RenderPipelineBase::GetFrontFace() const {
+        ASSERT(!IsError());
+        return mRasterizationState.frontFace;
+    }
+
     std::bitset<kMaxColorAttachments> RenderPipelineBase::GetColorAttachmentsMask() const {
         ASSERT(!IsError());
         return mColorAttachmentsSet;

src/dawn_native/RenderPipeline.h

@@ -53,6 +53,8 @@ namespace dawn_native {
         const ColorStateDescriptor* GetColorStateDescriptor(uint32_t attachmentSlot);
         const DepthStencilStateDescriptor* GetDepthStencilStateDescriptor();
         dawn::PrimitiveTopology GetPrimitiveTopology() const;
+        dawn::CullMode GetCullMode() const;
+        dawn::FrontFace GetFrontFace() const;
 
         std::bitset<kMaxColorAttachments> GetColorAttachmentsMask() const;
         bool HasDepthStencilAttachment() const;

src/dawn_native/metal/CommandBufferMTL.mm

@@ -684,6 +684,8 @@ namespace dawn_native { namespace metal {
                     lastPipeline = ToBackend(cmd->pipeline).Get();
 
                     [encoder setDepthStencilState:lastPipeline->GetMTLDepthStencilState()];
+                    [encoder setFrontFacingWinding:lastPipeline->GetMTLFrontFace()];
+                    [encoder setCullMode:lastPipeline->GetMTLCullMode()];
                     lastPipeline->Encode(encoder);
                 } break;
 

src/dawn_native/metal/RenderPipelineMTL.h

@@ -30,6 +30,8 @@ namespace dawn_native { namespace metal {
 
         MTLIndexType GetMTLIndexType() const;
         MTLPrimitiveType GetMTLPrimitiveTopology() const;
+        MTLWinding GetMTLFrontFace() const;
+        MTLCullMode GetMTLCullMode() const;
 
         void Encode(id<MTLRenderCommandEncoder> encoder);
 
@@ -40,6 +42,8 @@ namespace dawn_native { namespace metal {
 
         MTLIndexType mMtlIndexType;
         MTLPrimitiveType mMtlPrimitiveTopology;
+        MTLWinding mMtlFrontFace;
+        MTLCullMode mMtlCullMode;
         id<MTLRenderPipelineState> mMtlRenderPipelineState = nil;
         id<MTLDepthStencilState> mMtlDepthStencilState = nil;
     };

src/dawn_native/metal/RenderPipelineMTL.mm

@@ -282,12 +282,34 @@ namespace dawn_native { namespace metal {
             return mtlDepthStencilDescriptor;
         }
 
+        MTLWinding MTLFrontFace(dawn::FrontFace face) {
+            switch (face) {
+                case dawn::FrontFace::CCW:
+                    return MTLWindingCounterClockwise;
+                case dawn::FrontFace::CW:
+                    return MTLWindingClockwise;
+            }
+        }
+
+        MTLCullMode ToMTLCullMode(dawn::CullMode mode) {
+            switch (mode) {
+                case dawn::CullMode::None:
+                    return MTLCullModeNone;
+                case dawn::CullMode::Front:
+                    return MTLCullModeFront;
+                case dawn::CullMode::Back:
+                    return MTLCullModeBack;
+            }
+        }
+
     }  // anonymous namespace
 
     RenderPipeline::RenderPipeline(Device* device, const RenderPipelineDescriptor* descriptor)
         : RenderPipelineBase(device, descriptor),
           mMtlIndexType(MTLIndexFormat(GetInputStateDescriptor()->indexFormat)),
-          mMtlPrimitiveTopology(MTLPrimitiveTopology(GetPrimitiveTopology())) {
+          mMtlPrimitiveTopology(MTLPrimitiveTopology(GetPrimitiveTopology())),
+          mMtlFrontFace(MTLFrontFace(GetFrontFace())),
+          mMtlCullMode(ToMTLCullMode(GetCullMode())) {
         auto mtlDevice = device->GetMTLDevice();
 
         MTLRenderPipelineDescriptor* descriptorMTL = [MTLRenderPipelineDescriptor new];
@@ -362,6 +384,14 @@ namespace dawn_native { namespace metal {
         return mMtlPrimitiveTopology;
     }
 
+    MTLWinding RenderPipeline::GetMTLFrontFace() const {
+        return mMtlFrontFace;
+    }
+
+    MTLCullMode RenderPipeline::GetMTLCullMode() const {
+        return mMtlCullMode;
+    }
+
     void RenderPipeline::Encode(id<MTLRenderCommandEncoder> encoder) {
         [encoder setRenderPipelineState:mMtlRenderPipelineState];
     }