Enabled metal on ios simulator

shell/gpu/gpu_surface_metal.h

@@ -12,12 +12,13 @@
 #include "flutter/shell/common/surface.h"
 #include "flutter/shell/gpu/gpu_surface_delegate.h"
 #include "third_party/skia/include/gpu/GrContext.h"
+#include "third_party/skia/include/gpu/mtl/GrMtlTypes.h"
 
 @class CAMetalLayer;
 
 namespace flutter {
 
-class GPUSurfaceMetal : public Surface {
+class SK_API_AVAILABLE_CA_METAL_LAYER GPUSurfaceMetal : public Surface {
  public:
   GPUSurfaceMetal(GPUSurfaceDelegate* delegate,
                   fml::scoped_nsobject<CAMetalLayer> layer,

shell/platform/darwin/ios/ios_surface.mm

@@ -7,6 +7,8 @@
 #include "flutter/shell/platform/darwin/ios/ios_surface_gl.h"
 #include "flutter/shell/platform/darwin/ios/ios_surface_software.h"
 
+#include "flutter/shell/platform/darwin/ios/rendering_api_selection.h"
+
 #if FLUTTER_SHELL_ENABLE_METAL
 #include "flutter/shell/platform/darwin/ios/ios_surface_metal.h"
 #endif  // FLUTTER_SHELL_ENABLE_METAL
@@ -39,13 +41,15 @@ bool IsIosEmbeddedViewsPreviewEnabled() {
   }
 
 #if FLUTTER_SHELL_ENABLE_METAL
-  if ([layer.get() isKindOfClass:[CAMetalLayer class]]) {
-    return std::make_unique<IOSSurfaceMetal>(
-        fml::scoped_nsobject<CAMetalLayer>(
-            reinterpret_cast<CAMetalLayer*>([layer.get() retain])),  // Metal layer
-        std::move(context),                                          // context
-        platform_views_controller                                    // platform views controller
-    );
+  if (@available(iOS kMetalOSVersionBaseline, *)) {
+    if ([layer.get() isKindOfClass:[CAMetalLayer class]]) {
+      return std::make_unique<IOSSurfaceMetal>(
+          fml::scoped_nsobject<CAMetalLayer>(
+              reinterpret_cast<CAMetalLayer*>([layer.get() retain])),  // Metal layer
+          std::move(context),                                          // context
+          platform_views_controller                                    // platform views controller
+      );
+    }
   }
 #endif  // FLUTTER_SHELL_ENABLE_METAL
 

shell/platform/darwin/ios/ios_surface_metal.h

@@ -8,12 +8,14 @@
 #include "flutter/fml/macros.h"
 #include "flutter/shell/gpu/gpu_surface_delegate.h"
 #include "flutter/shell/platform/darwin/ios/ios_surface.h"
+#include "third_party/skia/include/gpu/mtl/GrMtlTypes.h"
 
 @class CAMetalLayer;
 
 namespace flutter {
 
-class IOSSurfaceMetal final : public IOSSurface, public GPUSurfaceDelegate {
+class SK_API_AVAILABLE_CA_METAL_LAYER IOSSurfaceMetal final : public IOSSurface,
+                                                              public GPUSurfaceDelegate {
  public:
   IOSSurfaceMetal(fml::scoped_nsobject<CAMetalLayer> layer,
                   std::shared_ptr<IOSContext> context,

shell/platform/darwin/ios/rendering_api_selection.h

@@ -24,4 +24,10 @@ Class GetCoreAnimationLayerClassForRenderingAPI(
 
 }  // namespace flutter
 
+#if TARGET_OS_SIMULATOR
+#define kMetalOSVersionBaseline 13.0
+#else
+#define kMetalOSVersionBaseline 10.0
+#endif  // TARGET_OS_SIMULATOR
+
 #endif  // FLUTTER_SHELL_PLATFORM_DARWIN_IOS_RENDERING_API_SELECTION_H_

shell/platform/darwin/ios/rendering_api_selection.mm

@@ -21,7 +21,7 @@ bool ShouldUseMetalRenderer() {
   // past iOS 10.0. The processor was selected as it is the first version at which Metal was
   // supported. The iOS version floor was selected due to the availability of features used by Skia.
   bool ios_version_supports_metal = false;
-  if (@available(iOS 10.0, *)) {
+  if (@available(iOS kMetalOSVersionBaseline, *)) {
     auto device = MTLCreateSystemDefaultDevice();
     ios_version_supports_metal = [device supportsFeatureSet:MTLFeatureSet_iOS_GPUFamily1_v3];
   }
@@ -30,17 +30,20 @@ bool ShouldUseMetalRenderer() {
 #endif  // FLUTTER_SHELL_ENABLE_METAL
 
 IOSRenderingAPI GetRenderingAPIForProcess() {
-#if TARGET_IPHONE_SIMULATOR
-  return IOSRenderingAPI::kSoftware;
-#endif  // TARGET_IPHONE_SIMULATOR
-
 #if FLUTTER_SHELL_ENABLE_METAL
   static bool should_use_metal = ShouldUseMetalRenderer();
   if (should_use_metal) {
     return IOSRenderingAPI::kMetal;
   }
 #endif  // FLUTTER_SHELL_ENABLE_METAL
+
+  // OpenGL will be emulated using software rendering by Apple on the simulator, so we use the
+  // Skia software rendering since it performs a little better than the emulated OpenGL.
+#if TARGET_IPHONE_SIMULATOR
+  return IOSRenderingAPI::kSoftware;
+#else
   return IOSRenderingAPI::kOpenGLES;
+#endif  // TARGET_IPHONE_SIMULATOR
 }
 
 Class GetCoreAnimationLayerClassForRenderingAPI(IOSRenderingAPI rendering_api) {
@@ -49,10 +52,12 @@ Class GetCoreAnimationLayerClassForRenderingAPI(IOSRenderingAPI rendering_api) {
       return [CALayer class];
     case IOSRenderingAPI::kOpenGLES:
       return [CAEAGLLayer class];
-#if !TARGET_IPHONE_SIMULATOR
     case IOSRenderingAPI::kMetal:
-      return [CAMetalLayer class];
-#endif  // !TARGET_IPHONE_SIMULATOR
+      if (@available(iOS kMetalOSVersionBaseline, *)) {
+        return [CAMetalLayer class];
+      }
+      FML_CHECK(false) << "Metal availability should already have been checked";
+      break;
     default:
       break;
   }

tools/gn

@@ -216,8 +216,8 @@ def to_gn_args(args):
       gn_args['use_goma'] = False
       gn_args['goma_dir'] = None
 
-    # Enable Metal on non-simulator iOS builds.
-    if args.target_os == 'ios' and not args.simulator:
+    # Enable Metal on iOS builds.
+    if args.target_os == 'ios':
       gn_args['skia_use_metal'] = True
       gn_args['shell_enable_metal'] = True
       # Bitcode enabled builds using the current version of the toolchain leak