Add Metal to the FlutterCompositor struct in the Embedder API (flutter#25612)

Author: George Wright

shell/gpu/gpu_surface_metal.h

@@ -16,7 +16,8 @@ namespace flutter {
 class SK_API_AVAILABLE_CA_METAL_LAYER GPUSurfaceMetal : public Surface {
  public:
   GPUSurfaceMetal(GPUSurfaceMetalDelegate* delegate,
-                  sk_sp<GrDirectContext> context);
+                  sk_sp<GrDirectContext> context,
+                  bool render_to_surface = true);
 
   // |Surface|
   ~GPUSurfaceMetal();
@@ -30,6 +31,11 @@ class SK_API_AVAILABLE_CA_METAL_LAYER GPUSurfaceMetal : public Surface {
   GrMTLHandle next_drawable_ = nullptr;
   sk_sp<GrDirectContext> context_;
   GrDirectContext* precompiled_sksl_context_ = nullptr;
+  // TODO(38466): Refactor GPU surface APIs take into account the fact that an
+  // external view embedder may want to render to the root surface. This is a
+  // hack to make avoid allocating resources for the root surface when an
+  // external view embedder is present.
+  bool render_to_surface_;
 
   // |Surface|
   std::unique_ptr<SurfaceFrame> AcquireFrame(const SkISize& size) override;

shell/gpu/gpu_surface_metal.mm

@@ -19,10 +19,13 @@
 
 namespace flutter {
 
-GPUSurfaceMetal::GPUSurfaceMetal(GPUSurfaceMetalDelegate* delegate, sk_sp<GrDirectContext> context)
+GPUSurfaceMetal::GPUSurfaceMetal(GPUSurfaceMetalDelegate* delegate,
+                                 sk_sp<GrDirectContext> context,
+                                 bool render_to_surface)
     : delegate_(delegate),
       render_target_type_(delegate->GetRenderTargetType()),
-      context_(std::move(context)) {}
+      context_(std::move(context)),
+      render_to_surface_(render_to_surface) {}
 
 GPUSurfaceMetal::~GPUSurfaceMetal() {
   ReleaseUnusedDrawableIfNecessary();
@@ -55,6 +58,11 @@
     return nullptr;
   }
 
+  if (!render_to_surface_) {
+    return std::make_unique<SurfaceFrame>(
+        nullptr, true, [](const SurfaceFrame& surface_frame, SkCanvas* canvas) { return true; });
+  }
+
   PrecompileKnownSkSLsIfNecessary();
 
   switch (render_target_type_) {

shell/platform/embedder/BUILD.gn

@@ -230,6 +230,8 @@ if (enable_unittests) {
 
     if (test_enable_metal) {
       sources += [
+        "tests/embedder_test_compositor_metal.cc",
+        "tests/embedder_test_compositor_metal.h",
         "tests/embedder_test_context_metal.cc",
         "tests/embedder_test_context_metal.h",
         "tests/embedder_unittests_metal.mm",

shell/platform/embedder/embedder.cc

@@ -565,6 +565,51 @@ static sk_sp<SkSurface> MakeSkSurfaceFromBackingStore(
   return surface;
 }
 
+static sk_sp<SkSurface> MakeSkSurfaceFromBackingStore(
+    GrDirectContext* context,
+    const FlutterBackingStoreConfig& config,
+    const FlutterMetalBackingStore* metal) {
+#ifdef SHELL_ENABLE_METAL
+  GrMtlTextureInfo texture_info;
+  if (!metal->texture.texture) {
+    FML_LOG(ERROR) << "Embedder supplied null Metal texture.";
+    return nullptr;
+  }
+  sk_cf_obj<FlutterMetalTextureHandle> mtl_texture;
+  mtl_texture.retain(metal->texture.texture);
+  texture_info.fTexture = mtl_texture;
+  GrBackendTexture backend_texture(config.size.width,   //
+                                   config.size.height,  //
+                                   GrMipMapped::kNo,    //
+                                   texture_info         //
+  );
+
+  SkSurfaceProps surface_properties(0, kUnknown_SkPixelGeometry);
+
+  auto surface = SkSurface::MakeFromBackendTexture(
+      context,                   // context
+      backend_texture,           // back-end texture
+      kTopLeft_GrSurfaceOrigin,  // surface origin
+      1,                         // sample count
+      kBGRA_8888_SkColorType,    // color type
+      nullptr,                   // color space
+      &surface_properties,       // surface properties
+      static_cast<SkSurface::TextureReleaseProc>(
+          metal->texture.destruction_callback),  // release proc
+      metal->texture.user_data                   // release context
+  );
+
+  if (!surface) {
+    FML_LOG(ERROR) << "Could not wrap embedder supplied Metal render texture.";
+    return nullptr;
+  }
+
+  return surface;
+#else
+  return nullptr;
+#endif
+}
+
 static std::unique_ptr<flutter::EmbedderRenderTarget>
 CreateEmbedderRenderTarget(const FlutterCompositor* compositor,
                            const FlutterBackingStoreConfig& config,
@@ -622,6 +667,10 @@ CreateEmbedderRenderTarget(const FlutterCompositor* compositor,
       render_surface = MakeSkSurfaceFromBackingStore(context, config,
                                                      &backing_store.software);
       break;
+    case kFlutterBackingStoreTypeMetal:
+      render_surface =
+          MakeSkSurfaceFromBackingStore(context, config, &backing_store.metal);
+      break;
   };
 
   if (!render_surface) {

shell/platform/embedder/embedder.h

@@ -495,6 +495,13 @@ typedef struct {
   /// Handle to the MTLTexture that is owned by the embedder. Engine will render
   /// the frame into this texture.
   FlutterMetalTextureHandle texture;
+  /// A baton that is not interpreted by the engine in any way. It will be given
+  /// back to the embedder in the destruction callback below. Embedder resources
+  /// may be associated with this baton.
+  void* user_data;
+  /// The callback invoked by the engine when it no longer needs this backing
+  /// store.
+  VoidCallback destruction_callback;
 } FlutterMetalTexture;
 
 /// Callback for when a metal texture is requested.
@@ -944,6 +951,17 @@ typedef struct {
   VoidCallback destruction_callback;
 } FlutterSoftwareBackingStore;
 
+typedef struct {
+  /// The size of this struct. Must be sizeof(FlutterMetalBackingStore).
+  size_t struct_size;
+  union {
+    // A Metal texture for Flutter to render into. Ownership is not transferred
+    // to Flutter; the texture is CFRetained on successfully being passed in and
+    // CFReleased when no longer used.
+    FlutterMetalTexture texture;
+  };
+} FlutterMetalBackingStore;
+
 typedef enum {
   /// Indicates that the Flutter application requested that an opacity be
   /// applied to the platform view.
@@ -1001,6 +1019,8 @@ typedef enum {
   kFlutterBackingStoreTypeOpenGL,
   /// Specified an software allocation for Flutter to render into using the CPU.
   kFlutterBackingStoreTypeSoftware,
+  /// Specifies a Metal backing store. This is backed by a Metal texture.
+  kFlutterBackingStoreTypeMetal,
 } FlutterBackingStoreType;
 
 typedef struct {
@@ -1020,6 +1040,8 @@ typedef struct {
     FlutterOpenGLBackingStore open_gl;
     /// The description of the software backing store.
     FlutterSoftwareBackingStore software;
+    // The description of the Metal backing store.
+    FlutterMetalBackingStore metal;
   };
 } FlutterBackingStore;
 

shell/platform/embedder/embedder_surface_metal.mm

@@ -39,7 +39,8 @@
     return nullptr;
   }
 
-  auto surface = std::make_unique<GPUSurfaceMetal>(this, main_context_);
+  const bool render_to_surface = !external_view_embedder_;
+  auto surface = std::make_unique<GPUSurfaceMetal>(this, main_context_, render_to_surface);
 
   if (!surface->IsValid()) {
     return nullptr;

shell/platform/embedder/tests/embedder_assertions.h

@@ -65,6 +65,16 @@ inline bool operator==(const FlutterOpenGLFramebuffer& a,
          a.destruction_callback == b.destruction_callback;
 }
 
+inline bool operator==(const FlutterMetalTexture& a,
+                       const FlutterMetalTexture& b) {
+  return a.texture_id == b.texture_id && a.texture == b.texture;
+}
+
+inline bool operator==(const FlutterMetalBackingStore& a,
+                       const FlutterMetalBackingStore& b) {
+  return a.texture == b.texture;
+}
+
 inline bool operator==(const FlutterOpenGLBackingStore& a,
                        const FlutterOpenGLBackingStore& b) {
   if (!(a.type == b.type)) {
@@ -100,6 +110,8 @@ inline bool operator==(const FlutterBackingStore& a,
       return a.open_gl == b.open_gl;
     case kFlutterBackingStoreTypeSoftware:
       return a.software == b.software;
+    case kFlutterBackingStoreTypeMetal:
+      return a.metal == b.metal;
   }
 
   return false;
@@ -216,6 +228,8 @@ inline std::string FlutterBackingStoreTypeToString(
       return "kFlutterBackingStoreTypeOpenGL";
     case kFlutterBackingStoreTypeSoftware:
       return "kFlutterBackingStoreTypeSoftware";
+    case kFlutterBackingStoreTypeMetal:
+      return "kFlutterBackingStoreTypeMetal";
   }
   return "Unknown";
 }
@@ -236,6 +250,12 @@ inline std::ostream& operator<<(std::ostream& out,
              << reinterpret_cast<void*>(item.destruction_callback);
 }
 
+inline std::ostream& operator<<(std::ostream& out,
+                                const FlutterMetalTexture& item) {
+  return out << "(FlutterMetalTexture) Texture ID: " << std::hex
+             << item.texture_id << std::dec << " Handle: 0x" << std::hex
+             << item.texture;
+}
 inline std::string FlutterPlatformViewMutationTypeToString(
     FlutterPlatformViewMutationType type) {
   switch (type) {
@@ -322,6 +342,11 @@ inline std::ostream& operator<<(std::ostream& out,
              << reinterpret_cast<void*>(item.destruction_callback);
 }
 
+inline std::ostream& operator<<(std::ostream& out,
+                                const FlutterMetalBackingStore& item) {
+  return out << "(FlutterMetalBackingStore) Texture: " << item.texture;
+}
+
 inline std::ostream& operator<<(std::ostream& out,
                                 const FlutterBackingStore& backing_store) {
   out << "(FlutterBackingStore) Struct size: " << backing_store.struct_size
@@ -337,6 +362,10 @@ inline std::ostream& operator<<(std::ostream& out,
     case kFlutterBackingStoreTypeSoftware:
       out << backing_store.software;
       break;
+
+    case kFlutterBackingStoreTypeMetal:
+      out << backing_store.metal;
+      break;
   }
 
   return out;

shell/platform/embedder/tests/embedder_config_builder.cc

@@ -400,19 +400,8 @@ void EmbedderConfigBuilder::InitializeMetalRendererConfig() {
       metal_context.GetTestMetalContext()->GetMetalCommandQueue();
   metal_renderer_config_.get_next_drawable_callback =
       [](void* user_data, const FlutterFrameInfo* frame_info) {
-        EmbedderTestContextMetal* metal_context =
-            reinterpret_cast<EmbedderTestContextMetal*>(user_data);
-        SkISize surface_size =
-            SkISize::Make(frame_info->size.width, frame_info->size.height);
-        TestMetalContext::TextureInfo texture_info =
-            metal_context->GetTestMetalContext()->CreateMetalTexture(
-                surface_size);
-        FlutterMetalTexture texture;
-        texture.struct_size = sizeof(FlutterMetalTexture);
-        texture.texture_id = texture_info.texture_id;
-        texture.texture =
-            reinterpret_cast<FlutterMetalTextureHandle>(texture_info.texture);
-        return texture;
+        return reinterpret_cast<EmbedderTestContextMetal*>(user_data)
+            ->GetNextDrawable(frame_info);
       };
   metal_renderer_config_.present_drawable_callback =
       [](void* user_data, const FlutterMetalTexture* texture) -> bool {

shell/platform/embedder/tests/embedder_test_backingstore_producer.cc

@@ -5,15 +5,26 @@
 #include "flutter/shell/platform/embedder/tests/embedder_test_backingstore_producer.h"
 
 #include "flutter/fml/logging.h"
+#include "include/core/SkImageInfo.h"
+#include "include/core/SkSize.h"
 #include "third_party/skia/include/core/SkSurface.h"
 
+#include <memory>
+
 namespace flutter {
 namespace testing {
 
 EmbedderTestBackingStoreProducer::EmbedderTestBackingStoreProducer(
     sk_sp<GrDirectContext> context,
     RenderTargetType type)
-    : context_(context), type_(type) {}
+    : context_(context),
+      type_(type)
+#ifdef SHELL_ENABLE_METAL
+      ,
+      test_metal_context_(std::make_unique<TestMetalContext>())
+#endif
+{
+}
 
 EmbedderTestBackingStoreProducer::~EmbedderTestBackingStoreProducer() = default;
 
@@ -28,6 +39,10 @@ bool EmbedderTestBackingStoreProducer::Create(
       return CreateTexture(config, renderer_out);
     case RenderTargetType::kOpenGLFramebuffer:
       return CreateFramebuffer(config, renderer_out);
+#endif
+#ifdef SHELL_ENABLE_METAL
+    case RenderTargetType::kMetalTexture:
+      return CreateMTLTexture(config, renderer_out);
 #endif
     default:
       return false;
@@ -174,5 +189,52 @@ bool EmbedderTestBackingStoreProducer::CreateSoftware(
   return true;
 }
 
+bool EmbedderTestBackingStoreProducer::CreateMTLTexture(
+    const FlutterBackingStoreConfig* config,
+    FlutterBackingStore* backing_store_out) {
+#ifdef SHELL_ENABLE_METAL
+  // TODO(gw280): Use SkSurface::MakeRenderTarget instead of generating our
+  // own MTLTexture and wrapping it.
+  auto surface_size = SkISize::Make(config->size.width, config->size.height);
+  auto texture_info = test_metal_context_->CreateMetalTexture(surface_size);
+  sk_cf_obj<FlutterMetalTextureHandle> texture;
+  texture.retain(texture_info.texture);
+
+  GrMtlTextureInfo skia_texture_info;
+  skia_texture_info.fTexture = texture;
+  GrBackendTexture backend_texture(surface_size.width(), surface_size.height(),
+                                   GrMipmapped::kNo, skia_texture_info);
+
+  SkSurface::TextureReleaseProc release_mtltexture = [](void* user_data) {
+    SkCFSafeRelease(user_data);
+  };
+
+  sk_sp<SkSurface> surface = SkSurface::MakeFromBackendTexture(
+      context_.get(), backend_texture, kTopLeft_GrSurfaceOrigin, 1,
+      kBGRA_8888_SkColorType, nullptr, nullptr, release_mtltexture,
+      texture_info.texture);
+
+  if (!surface) {
+    FML_LOG(ERROR) << "Could not create Skia surface from a Metal texture.";
+    return false;
+  }
+
+  backing_store_out->type = kFlutterBackingStoreTypeMetal;
+  backing_store_out->user_data = surface.get();
+  backing_store_out->metal.texture.texture = texture_info.texture;
+  // The balancing unref is in the destruction callback.
+  surface->ref();
+  backing_store_out->metal.struct_size = sizeof(FlutterMetalBackingStore);
+  backing_store_out->metal.texture.user_data = surface.get();
+  backing_store_out->metal.texture.destruction_callback = [](void* user_data) {
+    reinterpret_cast<SkSurface*>(user_data)->unref();
+  };
+
+  return true;
+#else
+  return false;
+#endif
+}
+
 }  // namespace testing
 }  // namespace flutter