Worklet: Lazily create PaintWorkletGlobalScopes

third_party/WebKit/Source/modules/csspaint/PaintWorklet.cpp

 // Copyright 2016 The Chromium 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 "modules/csspaint/PaintWorklet.h"
 
 #include "bindings/core/v8/V8BindingForCore.h"
 #include "core/dom/Document.h"
 #include "core/frame/LocalFrame.h"
 #include "modules/csspaint/PaintWorkletGlobalScope.h"
 
 namespace blink {
 
 // static
 PaintWorklet* PaintWorklet::Create(LocalFrame* frame) {
   return new PaintWorklet(frame);
 }
 
 PaintWorklet::PaintWorklet(LocalFrame* frame)
     : MainThreadWorklet(frame),
-      global_scope_proxy_(
-          WTF::MakeUnique<PaintWorkletGlobalScopeProxy>(frame)) {}
+      pending_generator_registry_(new PaintWorkletPendingGeneratorRegistry) {}
 
 PaintWorklet::~PaintWorklet() = default;
 
-WorkletGlobalScopeProxy* PaintWorklet::GetWorkletGlobalScopeProxy() const {
-  return global_scope_proxy_.get();
-}
+CSSPaintDefinition* PaintWorklet::FindDefinition(const String& name) {
+  if (GetProxies().IsEmpty())
+    return nullptr;
 
-CSSPaintDefinition* PaintWorklet::FindDefinition(const String& name) {
-  return global_scope_proxy_->FindDefinition(name);
+  // TODO(nhiroki): Support the case where there are multiple global scopes.
+  DCHECK_EQ(1u, GetProxies().size());
+  PaintWorkletGlobalScopeProxy* proxy =
+      PaintWorkletGlobalScopeProxy::From(GetProxies().begin()->get());
+  return proxy->FindDefinition(name);
 }
 
 void PaintWorklet::AddPendingGenerator(const String& name,
                                        CSSPaintImageGeneratorImpl* generator) {
-  return global_scope_proxy_->AddPendingGenerator(name, generator);
+  if (GetProxies().IsEmpty()) {
+    pending_generator_registry_->AddPendingGenerator(name, generator);
+    return;
+  }
+
+  // TODO(nhiroki): Support the case where there are multiple global scopes.
+  DCHECK_EQ(1u, GetProxies().size());
+  PaintWorkletGlobalScopeProxy* proxy =
+      PaintWorkletGlobalScopeProxy::From(GetProxies().begin()->get());
+  return proxy->AddPendingGenerator(name, generator);
 }
 
 DEFINE_TRACE(PaintWorklet) {
+  visitor->Trace(pending_generator_registry_);
   MainThreadWorklet::Trace(visitor);
 }
 
+bool PaintWorklet::NeedsToCreateGlobalScope() {
+  // "The user agent must have, and select from at least two
+  // PaintWorkletGlobalScopes in the worklet's WorkletGlobalScopes list, unless
+  // the user agent is under memory constraints."
+  // https://drafts.css-houdini.org/css-paint-api-1/#drawing-an-image
+  // TODO(nhiroki): In the current impl, we create only one global scope. We
+  // should create at least two global scopes as the spec.
+  return GetProxies().IsEmpty();
+}
+
+std::unique_ptr<WorkletGlobalScopeProxy> PaintWorklet::CreateGlobalScope() {
+  LocalFrame* frame = ToDocument(GetExecutionContext())->GetFrame();
+  auto proxy = WTF::MakeUnique<PaintWorkletGlobalScopeProxy>(frame);
+  if (GetProxies().IsEmpty()) {
+    proxy->global_scope()->SetPendingGeneratorRegistry(
+        pending_generator_registry_);
+    pending_generator_registry_ = nullptr;
+  }
+  return std::move(proxy);
+}
+
 }  // namespace blink