[Impeller] Flutter GPU: Add GpuContext. (flutter#44359)

Move the GpuContext to its new home. I added a `flutter_tester` test that just verifies an exception is gracefully thrown when Impeller isn't available.

In a later patch, I'll land a way to eagerly supply the Impeller context on the cpp side to enable testing through the playground (as mentioned in flutter/flutter#127712).

ci/licenses_golden/excluded_files

@@ -174,6 +174,8 @@
 ../../../flutter/impeller/tools/malioc_diff.py
 ../../../flutter/impeller/tools/xxd.py
 ../../../flutter/impeller/typographer/typographer_unittests.cc
+../../../flutter/lib/gpu/analysis_options.yaml
+../../../flutter/lib/gpu/pubspec.yaml
 ../../../flutter/lib/snapshot/libraries.json
 ../../../flutter/lib/snapshot/libraries.yaml
 ../../../flutter/lib/snapshot/pubspec.yaml

ci/licenses_golden/licenses_flutter

@@ -1725,9 +1725,15 @@ ORIGIN: ../../../flutter/impeller/typographer/text_run.cc + ../../../flutter/LIC
 ORIGIN: ../../../flutter/impeller/typographer/text_run.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/typographer/typeface.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/impeller/typographer/typeface.h + ../../../flutter/LICENSE
-ORIGIN: ../../../flutter/lib/gpu/gpu.cc + ../../../flutter/LICENSE
-ORIGIN: ../../../flutter/lib/gpu/gpu.dart + ../../../flutter/LICENSE
-ORIGIN: ../../../flutter/lib/gpu/gpu.h + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/lib/gpu/context.cc + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/lib/gpu/context.h + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/lib/gpu/export.cc + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/lib/gpu/export.h + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/lib/gpu/lib/gpu.dart + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/lib/gpu/lib/src/context.dart + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/lib/gpu/lib/src/smoketest.dart + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/lib/gpu/smoketest.cc + ../../../flutter/LICENSE
+ORIGIN: ../../../flutter/lib/gpu/smoketest.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/io/dart_io.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/io/dart_io.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/lib/snapshot/snapshot.h + ../../../flutter/LICENSE
@@ -1749,8 +1755,6 @@ 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
@@ -4445,9 +4449,15 @@ FILE: ../../../flutter/impeller/typographer/text_run.cc
 FILE: ../../../flutter/impeller/typographer/text_run.h
 FILE: ../../../flutter/impeller/typographer/typeface.cc
 FILE: ../../../flutter/impeller/typographer/typeface.h
-FILE: ../../../flutter/lib/gpu/gpu.cc
-FILE: ../../../flutter/lib/gpu/gpu.dart
-FILE: ../../../flutter/lib/gpu/gpu.h
+FILE: ../../../flutter/lib/gpu/context.cc
+FILE: ../../../flutter/lib/gpu/context.h
+FILE: ../../../flutter/lib/gpu/export.cc
+FILE: ../../../flutter/lib/gpu/export.h
+FILE: ../../../flutter/lib/gpu/lib/gpu.dart
+FILE: ../../../flutter/lib/gpu/lib/src/context.dart
+FILE: ../../../flutter/lib/gpu/lib/src/smoketest.dart
+FILE: ../../../flutter/lib/gpu/smoketest.cc
+FILE: ../../../flutter/lib/gpu/smoketest.h
 FILE: ../../../flutter/lib/io/dart_io.cc
 FILE: ../../../flutter/lib/io/dart_io.h
 FILE: ../../../flutter/lib/snapshot/libraries_experimental.json
@@ -4470,8 +4480,6 @@ 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/gpu/BUILD.gn

@@ -30,10 +30,16 @@ source_set("gpu") {
     defines = []
   }
 
-  sources = [
-    "gpu.cc",
-    "gpu.h",
-  ]
+  if (!is_fuchsia) {
+    sources = [
+      "context.cc",
+      "context.h",
+      "export.cc",
+      "export.h",
+      "smoketest.cc",
+      "smoketest.h",
+    ]
+  }
   deps = [
     "//flutter/impeller",
     "//flutter/impeller/display_list:skia_conversions",

lib/gpu/analysis_options.yaml

@@ -0,0 +1,7 @@
+# Copyright 2013 The Flutter Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+linter:
+  rules:
+    - public_member_api_docs

lib/ui/gpu/context.cc → lib/gpu/context.cc

@@ -2,27 +2,35 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "flutter/lib/ui/gpu/context.h"
+#include "flutter/lib/gpu/context.h"
 
-#include <memory>
-#include <sstream>
+#include <future>
 
-#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 "dart_api.h"
 #include "flutter/lib/ui/ui_dart_state.h"
-#include "third_party/tonic/dart_wrappable.h"
+#include "fml/make_copyable.h"
+#include "tonic/converter/dart_converter.h"
 
 namespace flutter {
 
-IMPLEMENT_WRAPPERTYPEINFO(ui, GpuContext);
+IMPLEMENT_WRAPPERTYPEINFO(gpu, Context);
 
-std::string GpuContext::InitializeDefault(Dart_Handle wrapper) {
-  auto dart_state = UIDartState::Current();
+Context::Context(std::shared_ptr<impeller::Context> context)
+    : context_(std::move(context)) {}
+
+Context::~Context() = default;
+
+}  // namespace flutter
+
+//----------------------------------------------------------------------------
+/// Exports
+///
+
+Dart_Handle InternalFlutterGpu_Context_InitializeDefault(Dart_Handle wrapper) {
+  auto dart_state = flutter::UIDartState::Current();
   if (!dart_state->IsImpellerEnabled()) {
-    return "The GpuContext API requires the Impeller rendering backend to be "
-           "enabled.";
+    return tonic::ToDart(
+        "Flutter GPU requires the Impeller rendering backend to be enabled.");
   }
 
   // Grab the Impeller context from the IO manager.
@@ -38,17 +46,10 @@ std::string GpuContext::InitializeDefault(Dart_Handle wrapper) {
 
   auto impeller_context = impeller_context_future.get();
   if (!impeller_context) {
-    return "Unable to retrieve the Impeller context.";
+    return tonic::ToDart("Unable to retrieve the Impeller context.");
   }
-  auto res = fml::MakeRefCounted<GpuContext>(impeller_context);
+  auto res = fml::MakeRefCounted<flutter::Context>(impeller_context);
   res->AssociateWithDartWrapper(wrapper);
 
-  return "";
+  return Dart_Null();
 }
-
-GpuContext::GpuContext(std::shared_ptr<impeller::Context> context)
-    : context_(std::move(context)) {}
-
-GpuContext::~GpuContext() = default;
-
-}  // namespace flutter

lib/gpu/context.h

@@ -0,0 +1,40 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#pragma once
+
+#include "dart_api.h"
+#include "flutter/lib/gpu/export.h"
+#include "flutter/lib/ui/dart_wrapper.h"
+#include "impeller/renderer/context.h"
+
+namespace flutter {
+
+class Context : public RefCountedDartWrappable<Context> {
+  DEFINE_WRAPPERTYPEINFO();
+  FML_FRIEND_MAKE_REF_COUNTED(Context);
+
+ public:
+  explicit Context(std::shared_ptr<impeller::Context> context);
+  ~Context() override;
+
+ private:
+  std::shared_ptr<impeller::Context> context_;
+
+  FML_DISALLOW_COPY_AND_ASSIGN(Context);
+};
+
+}  // namespace flutter
+
+//----------------------------------------------------------------------------
+/// Exports
+///
+
+extern "C" {
+
+FLUTTER_GPU_EXPORT
+extern Dart_Handle InternalFlutterGpu_Context_InitializeDefault(
+    Dart_Handle wrapper);
+
+}  // extern "C"

lib/gpu/export.cc

@@ -0,0 +1,11 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "flutter/lib/gpu/export.h"
+
+namespace flutter {
+
+//
+
+}  // namespace flutter

lib/gpu/export.h

@@ -0,0 +1,11 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#pragma once
+
+#if FML_OS_WIN
+#define FLUTTER_GPU_EXPORT __declspec(dllexport)
+#else  // FML_OS_WIN
+#define FLUTTER_GPU_EXPORT __attribute__((visibility("default")))
+#endif  // FML_OS_WIN

lib/gpu/lib/gpu.dart

@@ -0,0 +1,15 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+/// The Flutter GPU library.
+///
+/// To use, import `package:flutter_gpu/gpu.dart`.
+///
+/// See also:
+///
+///  * [Flutter GPU Wiki page](https://github.com/flutter/flutter/wiki/Flutter-GPU).
+library flutter_gpu;
+
+export 'src/context.dart';
+export 'src/smoketest.dart';

lib/gpu/lib/src/context.dart

@@ -0,0 +1,28 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:ffi';
+import 'dart:nativewrappers';
+
+/// A handle to a graphics context. Used to create and manage GPU resources.
+///
+/// To obtain the default graphics context, use [getContext].
+class GpuContext extends NativeFieldWrapperClass1 {
+  /// Creates a new graphics context that corresponds to the default Impeller
+  /// context.
+  GpuContext._createDefault() {
+    final String? error = _initializeDefault();
+    if (error != null) {
+      throw Exception(error);
+    }
+  }
+
+  /// Associates the default Impeller context with this Context.
+  @Native<Handle Function(Handle)>(
+      symbol: 'InternalFlutterGpu_Context_InitializeDefault')
+  external String? _initializeDefault();
+}
+
+/// The default graphics context.
+final GpuContext gpuContext = GpuContext._createDefault();

lib/gpu/gpu.dart → lib/gpu/lib/src/smoketest.dart

@@ -2,26 +2,27 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// ignore_for_file: public_member_api_docs
-
 import 'dart:ffi';
 import 'dart:nativewrappers';
 
 /// This is a simple test fuction.
 @Native<Int32 Function()>(symbol: 'InternalFlutterGpuTestProc')
 external int testProc();
 
+/// A single parameter callback.
+typedef Callback<T> = void Function(T result);
+
 /// This is a test callback that follows the same pattern as much of dart:ui --
 /// immediately returning an error string and supplying an asynchronous result
 /// via callback later.
-typedef Callback<T> = void Function(T result);
 @Native<Handle Function(Handle)>(
     symbol: 'InternalFlutterGpuTestProcWithCallback')
 external String? testProcWithCallback(Callback<int> callback);
 
 /// This is a test of NativeFieldWrapperClass1, which is commonly used in
 /// dart:ui to enable Dart to dictate the lifetime of a C counterpart.
 base class FlutterGpuTestClass extends NativeFieldWrapperClass1 {
+  /// Default constructor for the test class
   FlutterGpuTestClass() {
     _constructor();
   }

lib/gpu/pubspec.yaml

@@ -0,0 +1,14 @@
+# Copyright 2013 The Flutter Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+name: flutter_gpu
+description: A framework for writing Flutter applications
+homepage: https://flutter.dev
+
+environment:
+  sdk: '>=3.0.0-0 <4.0.0'
+
+dependencies:
+  sky_engine:
+    sdk: flutter

lib/gpu/gpu.cc → lib/gpu/smoketest.cc

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "flutter/lib/gpu/gpu.h"
+#include "flutter/lib/gpu/smoketest.h"
 #include "flutter/fml/memory/ref_ptr.h"
 #include "flutter/lib/ui/dart_wrapper.h"
 #include "flutter/lib/ui/ui_dart_state.h"
@@ -23,6 +23,10 @@ FlutterGpuTestClass::~FlutterGpuTestClass() = default;
 
 }  // namespace flutter
 
+//----------------------------------------------------------------------------
+/// Exports
+///
+
 // TODO(131346): Remove this once we migrate the Dart GPU API into this space.
 uint32_t InternalFlutterGpuTestProc() {
   return 1;
@@ -52,9 +56,3 @@ void InternalFlutterGpuTestClass_Method(flutter::FlutterGpuTestClass* self,
                                         int something) {
   FML_LOG(INFO) << "Something: " << something;
 }
-
-// TODO(131346): Remove this once we migrate the Dart GPU API into this space.
-void FlutterGpuTestClass_Dispose(flutter::FlutterGpuTestClass* self,
-                                 int something) {
-  self->ClearDartWrapper();
-}