From 4220ef3727b9d2a14c0776c49726177bc55f49b3 Mon Sep 17 00:00:00 2001
From: Brandon DeRosier <bdero@google.com>
Date: Thu, 17 Feb 2022 10:46:55 -0800
Subject: [PATCH] Add cull mode to command (#13)

---
 impeller/renderer/backend/metal/formats_mtl.h      | 12 ++++++++++++
 impeller/renderer/backend/metal/render_pass_mtl.mm |  2 +-
 impeller/renderer/command.h                        |  1 +
 impeller/renderer/formats.h                        |  8 +++++++-
 4 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/impeller/renderer/backend/metal/formats_mtl.h b/impeller/renderer/backend/metal/formats_mtl.h
index 6d1b47e69dae1..9cdb319f1bfca 100644
--- a/impeller/renderer/backend/metal/formats_mtl.h
+++ b/impeller/renderer/backend/metal/formats_mtl.h
@@ -116,6 +116,18 @@ constexpr MTLIndexType ToMTLIndexType(IndexType type) {
   }
 }
 
+constexpr MTLCullMode ToMTLCullMode(CullMode mode) {
+  switch (mode) {
+    case CullMode::kNone:
+      return MTLCullModeNone;
+    case CullMode::kBackFace:
+      return MTLCullModeBack;
+    case CullMode::kFrontFace:
+      return MTLCullModeFront;
+  }
+  return MTLCullModeNone;
+}
+
 constexpr MTLBlendOperation ToMTLBlendOperation(BlendOperation type) {
   switch (type) {
     case BlendOperation::kAdd:
diff --git a/impeller/renderer/backend/metal/render_pass_mtl.mm b/impeller/renderer/backend/metal/render_pass_mtl.mm
index 9279d16f2671d..9d7a9e24ffe50 100644
--- a/impeller/renderer/backend/metal/render_pass_mtl.mm
+++ b/impeller/renderer/backend/metal/render_pass_mtl.mm
@@ -426,7 +426,7 @@ static bool Bind(PassBindingsCache& pass,
     [encoder setFrontFacingWinding:command.winding == WindingOrder::kClockwise
                                        ? MTLWindingClockwise
                                        : MTLWindingCounterClockwise];
-    [encoder setCullMode:MTLCullModeNone];
+    [encoder setCullMode:ToMTLCullMode(command.cull_mode)];
     [encoder setStencilReferenceValue:command.stencil_reference];
     if (command.viewport.has_value()) {
       auto v = command.viewport.value();
diff --git a/impeller/renderer/command.h b/impeller/renderer/command.h
index 30c2d4cfe662c..fb73d1b16da63 100644
--- a/impeller/renderer/command.h
+++ b/impeller/renderer/command.h
@@ -70,6 +70,7 @@ struct Command {
   std::string label;
   PrimitiveType primitive_type = PrimitiveType::kTriangle;
   WindingOrder winding = WindingOrder::kClockwise;
+  CullMode cull_mode = CullMode::kNone;
   uint32_t stencil_reference = 0u;
   //----------------------------------------------------------------------------
   /// The viewport coordinates that the rasterizer linearly maps normalized
diff --git a/impeller/renderer/formats.h b/impeller/renderer/formats.h
index 94e7d94012287..092d86283fc53 100644
--- a/impeller/renderer/formats.h
+++ b/impeller/renderer/formats.h
@@ -11,9 +11,9 @@
 
 #include "flutter/fml/hash_combine.h"
 #include "flutter/fml/macros.h"
+#include "impeller/geometry/color.h"
 #include "impeller/geometry/rect.h"
 #include "impeller/geometry/scalar.h"
-#include "impeller/geometry/color.h"
 
 namespace impeller {
 
@@ -135,6 +135,12 @@ enum class WindingOrder {
   kCounterClockwise,
 };
 
+enum class CullMode {
+  kNone,
+  kFrontFace,
+  kBackFace,
+};
+
 enum class IndexType {
   kUnknown,
   k16bit,