blob: 959068dc7d8dd8e851e7ff038412f2688447b2ae [file] [log] [blame]
* Copyright 2013 Google Inc.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
#include <v8.h>
#include "Global.h"
#include "JsContext.h"
#include "Path2D.h"
#include "SkCanvas.h"
// Extracts a C string from a V8 Utf8Value.
// TODO(jcgregrio) Currently dup'd in two files, fix.
static const char* to_cstring(const v8::String::Utf8Value& value) {
return *value ? *value : "<string conversion failed>";
v8::Persistent<v8::ObjectTemplate> JsContext::gContextTemplate;
// Wraps 'this' in a Javascript object.
v8::Handle<v8::Object> JsContext::wrap() {
// Handle scope for temporary handles.
v8::EscapableHandleScope handleScope(fGlobal->getIsolate());
// Fetch the template for creating JavaScript JsContext wrappers.
// It only has to be created once, which we do on demand.
if (gContextTemplate.IsEmpty()) {
v8::Local<v8::ObjectTemplate> localTemplate = v8::ObjectTemplate::New();
// Add a field to store the pointer to a JsContext instance.
gContextTemplate.Reset(fGlobal->getIsolate(), localTemplate);
v8::Handle<v8::ObjectTemplate> templ =
v8::Local<v8::ObjectTemplate>::New(fGlobal->getIsolate(), gContextTemplate);
// Create an empty JsContext wrapper.
v8::Local<v8::Object> result = templ->NewInstance();
// Wrap the raw C++ pointer in an External so it can be referenced
// from within JavaScript.
v8::Handle<v8::External> contextPtr = v8::External::New(fGlobal->getIsolate(), this);
// Store the context pointer in the JavaScript wrapper.
result->SetInternalField(0, contextPtr);
// Return the result through the current handle scope. Since each
// of these handles will go away when the handle scope is deleted
// we need to call Close to let one, the result, escape into the
// outer handle scope.
return handleScope.Escape(result);
void JsContext::onDraw(SkCanvas* canvas) {
// Record canvas and window in this.
fCanvas = canvas;
// Create a handle scope to keep the temporary object references.
v8::HandleScope handleScope(fGlobal->getIsolate());
// Create a local context from our global context.
v8::Local<v8::Context> context = fGlobal->getContext();
// Enter the context so all the remaining operations take place there.
v8::Context::Scope contextScope(context);
// Wrap the C++ this pointer in a JavaScript wrapper.
v8::Handle<v8::Object> contextObj = this->wrap();
// Set up an exception handler before calling the Process function.
v8::TryCatch tryCatch;
// Invoke the process function, giving the global object as 'this'
// and one argument, this JsContext.
const int argc = 1;
v8::Handle<v8::Value> argv[argc] = { contextObj };
v8::Local<v8::Function> onDraw =
v8::Local<v8::Function>::New(fGlobal->getIsolate(), fOnDraw);
v8::Handle<v8::Value> result = onDraw->Call(context->Global(), argc, argv);
// Handle any exceptions or output.
if (result.IsEmpty()) {
// Print errors that happened during execution.
} else {
if (!result->IsUndefined()) {
// If all went well and the result wasn't undefined then print
// the returned value.
v8::String::Utf8Value str(result);
const char* cstr = to_cstring(str);
printf("%s\n", cstr);
// Fetch the onDraw function from the global context.
bool JsContext::initialize() {
// Create a stack-allocated handle scope.
v8::HandleScope handleScope(fGlobal->getIsolate());
// Create a local context from our global context.
v8::Local<v8::Context> context = fGlobal->getContext();
// Enter the scope so all operations take place in the scope.
v8::Context::Scope contextScope(context);
v8::TryCatch try_catch;
v8::Handle<v8::String> fn_name = v8::String::NewFromUtf8(
fGlobal->getIsolate(), "onDraw");
v8::Handle<v8::Value> fn_val = context->Global()->Get(fn_name);
if (!fn_val->IsFunction()) {
printf("Not a function.\n");
return false;
// It is a function; cast it to a Function.
v8::Handle<v8::Function> fn_fun = v8::Handle<v8::Function>::Cast(fn_val);
// Store the function in a Persistent handle, since we also want that to
// remain after this call returns.
fOnDraw.Reset(fGlobal->getIsolate(), fn_fun);
return true;