// Copyright (c) 2013 GitHub, Inc.
// Use of this source code is governed by the MIT license that can be
// found in the LICENSE file.
#include <string>
#include "base/task/post_task.h"
#include "base/values.h"
#include "content/public/renderer/render_frame.h"
#include "electron/shell/common/api/api.mojom.h"
#include "native_mate/arguments.h"
#include "native_mate/dictionary.h"
#include "native_mate/handle.h"
#include "native_mate/object_template_builder.h"
#include "native_mate/wrappable.h"
#include "services/service_manager/public/cpp/interface_provider.h"
#include "shell/common/native_mate_converters/value_converter.h"
#include "shell/common/node_bindings.h"
#include "shell/common/node_includes.h"
#include "shell/common/promise_util.h"
#include "third_party/blink/public/web/web_local_frame.h"
using blink::WebLocalFrame;
using content::RenderFrame;
namespace {
RenderFrame* GetCurrentRenderFrame() {
WebLocalFrame* frame = WebLocalFrame::FrameForCurrentContext();
if (!frame)
return nullptr;
return RenderFrame::FromWebFrame(frame);
}
class IPCRenderer : public mate::Wrappable<IPCRenderer> {
public:
explicit IPCRenderer(v8::Isolate* isolate)
: task_runner_(base::CreateSingleThreadTaskRunnerWithTraits({})) {
Init(isolate);
RenderFrame* render_frame = GetCurrentRenderFrame();
DCHECK(render_frame);
// Bind the interface on the background runner. All accesses will be via
// the thread-safe pointer. This is to support our "fake-sync"
// MessageSync() hack; see the comment in IPCRenderer::SendSync.
electron::mojom::ElectronBrowserPtrInfo info;
render_frame->GetRemoteInterfaces()->GetInterface(mojo::MakeRequest(&info));
electron_browser_ptr_ =
electron::mojom::ThreadSafeElectronBrowserPtr::Create(std::move(info),
task_runner_);
}
static void BuildPrototype(v8::Isolate* isolate,
v8::Local<v8::FunctionTemplate> prototype) {
prototype->SetClassName(mate::StringToV8(isolate, "IPCRenderer"));
mate::ObjectTemplateBuilder(isolate, prototype->PrototypeTemplate())
.SetMethod("send", &IPCRenderer::Send)
.SetMethod("sendSync", &IPCRenderer::SendSync)
.SetMethod("sendTo", &IPCRenderer::SendTo)
.SetMethod("sendToHost", &IPCRenderer::SendToHost)
.SetMethod("invoke", &IPCRenderer::Invoke);
}
static mate::Handle<IPCRenderer> Create(v8::Isolate* isolate) {
return mate::CreateHandle(isolate, new IPCRenderer(isolate));
}
void Send(bool internal,
const std::string& channel,
const base::ListValue& arguments) {
electron_browser_ptr_->get()->Message(internal, channel, arguments.Clone());
}
v8::Local<v8::Promise> Invoke(mate::Arguments* args,
const std::string& channel,
const base::Value& arguments) {
electron::util::Promise p(args->isolate());
auto handle = p.GetHandle();
electron_browser_ptr_->get()->Invoke(
channel, arguments.Clone(),
base::BindOnce([](electron::util::Promise p,
base::Value result) { p.Resolve(result); },
std::move(p)));
return handle;
}
void SendTo(bool internal,
bool send_to_all,
int32_t web_contents_id,
const std::string& channel,
const base::ListValue& arguments) {
electron_browser_ptr_->get()->MessageTo(
internal, send_to_all, web_contents_id, channel, arguments.Clone());
}
void SendToHost(const std::string& channel,
const base::ListValue& arguments) {
electron_browser_ptr_->get()->MessageHost(channel, arguments.Clone());
}
base::Value SendSync(bool internal,
const std::string& channel,
const base::ListValue& arguments) {
// We aren't using a true synchronous mojo call here. We're calling an
// asynchronous method and blocking on the result. The reason we're doing
// this is a little complicated, so buckle up.
//
// Mojo has a concept of synchronous calls. However, synchronous calls are
// dangerous. In particular, it's quite possible for two processes to call
// synchronous methods on each other and cause a deadlock. Mojo has a
// mechanism to avoid this kind of deadlock: if a process is waiting on the
// result of a synchronous call, and it receives an incoming call for a
// synchronous method, it will process that request immediately, even
// though it's currently blocking. However, if it receives an incoming
// request for an _asynchronous_ method, that can't cause a deadlock, so it
// stashes the request on a queue to be processed once the synchronous
// thing it's waiting on returns.
//
// This behavior is useful for preventing deadlocks, but it is inconvenient
// here because it can result in messages being reordered. If the main
// process is awaiting the result of a synchronous call (which it does only
// very rarely, since it's bad to block the main process), and we send
// first an asynchronous message to the main process, followed by a
// synchronous message, then the main process will process the synchronous
// one first.
//
// It turns out, Electron has some dependency on message ordering,
// especially during window shutdown, and getting messages out of order can
// result in, for example, remote objects disappearing unexpectedly. To
// avoid these issues and guarantee consistent message ordering, we send
// all messages to the main process as asynchronous messages. This causes
// them to always be queued and processed in the same order they were
// received, even if they were received while the main process was waiting
// on a synchronous call.
//
// However, in the calling process, we still need to block on the result,
// because the caller is expecting a result synchronously. So we do a bit
// of a trick: we pass the Mojo handle over to a worker thread, send the
// asynchronous message from that thread, and then block on the result.
// It's important that we pass the handle over to the worker thread,
// because that allows Mojo to process incoming messages (most importantly,
// the response to our request) on that thread. If we didn't pass it to a
// worker thread, and instead sent the call from the main thread, we would
// never receive a response because Mojo wouldn't be able to run its
// message handling code, because the main thread would be tied up blocking
// on the WaitableEvent.
//
// Phew. If you got this far, here's a gold star: ⭐️
base::Value result;
// A task is posted to a worker thread to execute the request so that
// this thread may block on a waitable event. It is safe to pass raw
// pointers to |result| and |response_received_event| as this stack frame
// will survive until the request is complete.
base::WaitableEvent response_received_event;
task_runner_->PostTask(
FROM_HERE, base::BindOnce(&IPCRenderer::SendMessageSyncOnWorkerThread,
base::Unretained(this),
base::Unretained(&response_received_event),
base::Unretained(&result), internal, channel,
arguments.Clone()));
response_received_event.Wait();
return result;
}
private:
void SendMessageSyncOnWorkerThread(base::WaitableEvent* event,
base::Value* result,
bool internal,
const std::string& channel,
base::Value arguments) {
electron_browser_ptr_->get()->MessageSync(
internal, channel, std::move(arguments),
base::BindOnce(&IPCRenderer::ReturnSyncResponseToMainThread,
base::Unretained(event), base::Unretained(result)));
}
static void ReturnSyncResponseToMainThread(base::WaitableEvent* event,
base::Value* result,
base::Value response) {
*result = std::move(response);
event->Signal();
}
scoped_refptr<base::SequencedTaskRunner> task_runner_;
scoped_refptr<electron::mojom::ThreadSafeElectronBrowserPtr>
electron_browser_ptr_;
};
void Initialize(v8::Local<v8::Object> exports,
v8::Local<v8::Value> unused,
v8::Local<v8::Context> context,
void* priv) {
mate::Dictionary dict(context->GetIsolate(), exports);
dict.Set("ipc", IPCRenderer::Create(context->GetIsolate()));
}
} // namespace
NODE_LINKED_MODULE_CONTEXT_AWARE(atom_renderer_ipc, Initialize)