Expose scroll customization for touch to JS (behind REF).

Source/bindings/core/v8/ScrollStateCallbackToScriptValue.cpp

+// Copyright 2015 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 "config.h"
+#include "core/page/scrolling/ScrollStateCallback.h"
+
+#include "bindings/core/v8/V8Element.h"
+#include "bindings/core/v8/V8ScrollState.h"
+
+namespace blink {
+
+namespace {
+
+static const char applyScrollRequiresScrollStateObject[] = "applyScroll takes a ScrollState object.";
+static const char distributeScrollRequiresScrollStateObject[] = "distributeScroll takes a ScrollState object.";
+
+// Key in |data| passed to scrollStateFunctionCallback.
+const char* kHandlerFunction = "handler_function";
+
+} // namespace
+
+static void scrollStateFunctionCallback(const v8::FunctionCallbackInfo<v8::Value>& info)
+{
+    v8::Isolate* isolate = info.GetIsolate();
+
+    v8::Local<v8::Object> data = info.Data().As<v8::Object>();
+
+    v8::Local<v8::Value> localScrollStateCallback;
+    v8::MaybeLocal<v8::Value> maybeLocalScrollStateCallback
+        = data->Get(v8::String::NewFromUtf8(info.GetIsolate(), kHandlerFunction));
+    if (!maybeLocalScrollStateCallback.ToLocal(&localScrollStateCallback))

[haraken, 2015/06/30 07:08:30]

  if (data->Get(...).ToLocal())

Nit: We want to avoid writing MaybeLocal in the binding layer as much as
possible.

+        return;
+
+    ASSERT(!localScrollStateCallback->IsUndefined());
+    ASSERT(localScrollStateCallback->IsExternal());
+    ScrollStateCallback* scrollStateCallback
+        = static_cast<ScrollStateCallback*>(localScrollStateCallback.As<v8::External>()->Value());
+
+    ASSERT(scrollStateCallback->callbackType() != ScrollStateCallback::CallbackType::UNSET);
+    bool isDistributeScroll
+        = scrollStateCallback->callbackType() == ScrollStateCallback::CallbackType::DISTRIBUTE_SCROLL;
+    const char* errorMessage
+        = isDistributeScroll ? distributeScrollRequiresScrollStateObject : applyScrollRequiresScrollStateObject;
+    if (!info[0]->IsObject()) {
+        info.GetIsolate()->ThrowException(v8::Exception::TypeError(v8::String::NewFromUtf8(isolate, errorMessage)));
+        return;
+    }
+    v8::Local<v8::Object> scrollStateObject = info[0]->ToObject();
+
+    if (!V8ScrollState::wrapperTypeInfo.domTemplateFunction(isolate)->HasInstance(scrollStateObject)) {
+        info.GetIsolate()->ThrowException(v8::Exception::TypeError(v8::String::NewFromUtf8(isolate, errorMessage)));
+        return;
+    }
+
+    ScrollState* scrollState = toScriptWrappable(scrollStateObject)->toImpl<ScrollState>();
+    ASSERT(scrollState);
+
+    Element* targetElement = toScriptWrappable(info.Holder())->toImpl<Element>();
+    ASSERT(targetElement);
+    scrollStateCallback->handleEventForElement(*targetElement, scrollState);
+}
+
+ScriptValue scrollStateCallbackToScriptValue(ScrollStateCallback& scrollStateCallback, ScriptState* scriptState)
+{
+    v8::Isolate* isolate = scriptState->isolate();
+    v8::Local<v8::Signature> signature
+        = v8::Signature::New(isolate, V8Element::wrapperTypeInfo.domTemplateFunction(isolate));
+
+    v8::Local<v8::Object> data = v8::Object::New(isolate);
+    data->Set(v8::String::NewFromUtf8(isolate, kHandlerFunction), v8::External::New(isolate, &scrollStateCallback));
+
+    v8::Local<v8::FunctionTemplate> functionTemplate
+        = v8::FunctionTemplate::New(scriptState->isolate(), &scrollStateFunctionCallback, data, signature);
+
+    ASSERT(scrollStateCallback.callbackType() != ScrollStateCallback::CallbackType::UNSET);
+
+    bool isDistributeScroll = scrollStateCallback.callbackType()
+        == ScrollStateCallback::CallbackType::DISTRIBUTE_SCROLL;
+    functionTemplate->SetClassName(v8AtomicString(isolate, isDistributeScroll ? "distributeScroll" : "applyScroll"));
+    v8::MaybeLocal<v8::Function> function = functionTemplate->GetFunction(scriptState->context());
+    return ScriptValue(scriptState, function);
+}
+
+} // namespace blink