Add Impeller context

Author: bdero

ci/licenses_golden/licenses_flutter

@@ -1689,6 +1689,8 @@ ORIGIN: ../../../flutter/lib/ui/experiments/setup_hooks.dart + ../../../flutter/
 ORIGIN: ../../../flutter/lib/ui/experiments/ui.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/ui/floating_point.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/ui/geometry.dart + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/lib/ui/gpu/context.cc + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/lib/ui/gpu/context.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/ui/hash_codes.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/ui/hooks.dart + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/ui/io_manager.cc + ../../../flutter/LICENSE
@@ -4311,6 +4313,8 @@ FILE: ../../../flutter/lib/ui/experiments/setup_hooks.dart
 FILE: ../../../flutter/lib/ui/experiments/ui.dart
 FILE: ../../../flutter/lib/ui/floating_point.h
 FILE: ../../../flutter/lib/ui/geometry.dart
+FILE: ../../../flutter/lib/ui/gpu/context.cc
+FILE: ../../../flutter/lib/ui/gpu/context.h
 FILE: ../../../flutter/lib/ui/hash_codes.dart
 FILE: ../../../flutter/lib/ui/hooks.dart
 FILE: ../../../flutter/lib/ui/io_manager.cc

lib/ui/BUILD.gn

@@ -216,6 +216,12 @@ source_set("ui") {
       "painting/scene/scene_shader.h",
     ]
 
+    # Experimental "Impeller Dart" API.
+    sources += [
+      "gpu/context.cc",
+      "gpu/context.h",
+    ]
+
     deps += [ "//flutter/impeller/scene" ]
   }
 }

lib/ui/dart_ui.cc

@@ -12,6 +12,7 @@
 #include "flutter/lib/ui/compositing/scene.h"
 #include "flutter/lib/ui/compositing/scene_builder.h"
 #include "flutter/lib/ui/dart_runtime_hooks.h"
+#include "flutter/lib/ui/gpu/context.h"
 #include "flutter/lib/ui/isolate_name_server/isolate_name_server_natives.h"
 #include "flutter/lib/ui/painting/canvas.h"
 #include "flutter/lib/ui/painting/codec.h"
@@ -315,8 +316,7 @@ typedef CanvasPath Path;
   V(SceneShader, SetCameraTransform, 2) \
   V(SceneShader, Dispose, 1)
 
-#define FFI_FUNCTION_LIST_GPU(V) \
-  V(GpuContext::InitializeDefault, 1)
+#define FFI_FUNCTION_LIST_GPU(V) V(GpuContext::InitializeDefault, 1)
 
 #define FFI_METHOD_LIST_GPU(V)
 
@@ -348,9 +348,13 @@ void* ResolveFfiNativeFunction(const char* name, uintptr_t args) {
 void InitDispatcherMap() {
   FFI_FUNCTION_LIST(FFI_FUNCTION_INSERT)
   FFI_METHOD_LIST(FFI_METHOD_INSERT)
+
 #ifdef IMPELLER_ENABLE_3D
   FFI_FUNCTION_LIST_3D(FFI_FUNCTION_INSERT)
   FFI_METHOD_LIST_3D(FFI_METHOD_INSERT)
+
+  FFI_FUNCTION_LIST_GPU(FFI_FUNCTION_INSERT)
+  FFI_METHOD_LIST_GPU(FFI_METHOD_INSERT)
 #endif  // IMPELLER_ENABLE_3D
 }
 

lib/ui/experiments/gpu.dart

@@ -6,6 +6,16 @@
 
 part of dart.ui;
 
+class GpuContextException implements Exception {
+  GpuContextException(this.message);
+  String message;
+
+  @override
+  String toString() {
+    return 'GpuContextException: $message';
+  }
+}
+
 enum BlendOperation { add, subtract, reverseSubtract }
 
 enum BlendFactor {
@@ -141,7 +151,10 @@ class GpuContext extends NativeFieldWrapperClass1 {
   /// Creates a new graphics context that corresponds to the default Impeller
   /// context.
   GpuContext._createDefault() {
-    _initializeDefault();
+    final String error = _initializeDefault();
+    if (error.isNotEmpty) {
+      throw GpuContextException(error);
+    }
   }
 
   //registerShaderLibrary() async
@@ -157,9 +170,9 @@ class GpuContext extends NativeFieldWrapperClass1 {
     return RasterPipeline();
   }
 
-  /// Links this GpuContext to the default Impeller context.
-  @Native<Void Function(Handle)>(symbol: 'GpuContext::InitializeDefault')
-  external void _initializeDefault();
+  /// Associates the default Impeller context with this GpuContext.
+  @Native<Handle Function(Handle)>(symbol: 'GpuContext::InitializeDefault')
+  external String _initializeDefault();
 }
 
 GpuContext? _defaultGpuContext;

lib/ui/gpu/context.cc

@@ -7,16 +7,47 @@
 #include <memory>
 #include <sstream>
 
+#include "flutter/fml/log_level.h"
+#include "flutter/fml/logging.h"
+#include "flutter/fml/make_copyable.h"
+#include "flutter/fml/memory/ref_ptr.h"
+#include "flutter/lib/ui/ui_dart_state.h"
+#include "third_party/tonic/dart_wrappable.h"
+
 namespace flutter {
 
 IMPLEMENT_WRAPPERTYPEINFO(ui, GpuContext);
 
-void GpuContext::InitializeDefault(Dart_Handle wrapper) {
-  auto res = fml::MakeRefCounted<SceneNode>();
+std::string GpuContext::InitializeDefault(Dart_Handle wrapper) {
+  auto dart_state = UIDartState::Current();
+  if (!dart_state->IsImpellerEnabled()) {
+    return "The GpuContext API requires the Impeller rendering backend to be "
+           "enabled.";
+  }
+
+  // Grab the Impeller context from the IO manager.
+
+  std::promise<std::shared_ptr<impeller::Context>> context_promise;
+  auto impeller_context_future = context_promise.get_future();
+  dart_state->GetTaskRunners().GetIOTaskRunner()->PostTask(
+      fml::MakeCopyable([promise = std::move(context_promise),
+                         io_manager = dart_state->GetIOManager()]() mutable {
+        promise.set_value(io_manager ? io_manager->GetImpellerContext()
+                                     : nullptr);
+      }));
+
+  auto impeller_context = impeller_context_future.get();
+  if (!impeller_context) {
+    return "Unable to retrieve the Impeller context.";
+  }
+  auto res = fml::MakeRefCounted<GpuContext>(impeller_context);
   res->AssociateWithDartWrapper(wrapper);
+
+  return "";
 }
 
-GpuContext::GpuContext() = default;
+GpuContext::GpuContext(std::shared_ptr<impeller::Context> context)
+    : context_(std::move(context)) {}
 
 GpuContext::~GpuContext() = default;
 

lib/ui/gpu/context.h

@@ -7,29 +7,23 @@
 
 #include <memory>
 
-#include "impeller/context.h"
-
+#include "flutter/fml/memory/ref_counted.h"
+#include "flutter/lib/ui/dart_wrapper.h"
+#include "impeller/renderer/context.h"
 #include "third_party/tonic/dart_library_natives.h"
+#include "third_party/tonic/dart_wrappable.h"
 
 namespace flutter {
 
-/// @brief  A scene node, which may be a deserialized ipscene asset. This node
-///         can be safely added as a child to multiple scene nodes, whether
-///         they're in the same scene or a different scene. The deserialized
-///         node itself is treated as immutable on the IO thread.
-///
-///         Internally, nodes may have an animation player, which is controlled
-///         via the mutation log in the `DlSceneColorSource`, which is built by
-///         `SceneShader`.
 class GpuContext : public RefCountedDartWrappable<GpuContext> {
   DEFINE_WRAPPERTYPEINFO();
   FML_FRIEND_MAKE_REF_COUNTED(GpuContext);
 
  public:
-  GpuContext(std::shared_ptr<impeller::Context> context);
+  explicit GpuContext(std::shared_ptr<impeller::Context> context);
   ~GpuContext() override;
 
-  static void InitializeDefault(Dart_Handle wrapper);
+  static std::string InitializeDefault(Dart_Handle wrapper);
 
  private:
   std::shared_ptr<impeller::Context> context_;