blob: ab75d7eaeb728eacf52b2a9f5505fb1ebda11f29 [file] [log] [blame]
// Copyright (c) 2012 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 "content/renderer/gamepad_shared_memory_reader.h"
#include "base/debug/trace_event.h"
#include "base/metrics/histogram.h"
#include "content/common/gamepad_hardware_buffer.h"
#include "content/common/gamepad_user_gesture.h"
#include "content/public/renderer/render_thread.h"
#include "content/renderer/renderer_blink_platform_impl.h"
#include "ipc/ipc_sync_message_filter.h"
#include "third_party/WebKit/public/platform/WebGamepadListener.h"
#include "third_party/WebKit/public/platform/WebPlatformEventListener.h"
namespace content {
GamepadSharedMemoryReader::GamepadSharedMemoryReader(RenderThread* thread)
: RendererGamepadProvider(thread),
ever_interacted_with_(false) {
void GamepadSharedMemoryReader::SendStartMessage() {
CHECK(RenderThread::Get()->Send(new GamepadHostMsg_StartPolling(
void GamepadSharedMemoryReader::SendStopMessage() {
RenderThread::Get()->Send(new GamepadHostMsg_StopPolling());
void GamepadSharedMemoryReader::Start(
blink::WebPlatformEventListener* listener) {
// If we don't get a valid handle from the browser, don't try to Map (we're
// probably out of memory or file handles).
bool valid_handle = base::SharedMemory::IsHandleValid(
UMA_HISTOGRAM_BOOLEAN("Gamepad.ValidSharedMemoryHandle", valid_handle);
if (!valid_handle)
new base::SharedMemory(renderer_shared_memory_handle_, true));
void *memory = renderer_shared_memory_->memory();
gamepad_hardware_buffer_ =
void GamepadSharedMemoryReader::SampleGamepads(blink::WebGamepads& gamepads) {
// Blink should have started observing at that point.
// ==========
// ==========
// This logic is duplicated in Pepper as well. If you change it, that also
// needs to be in sync. See ppapi/proxy/
blink::WebGamepads read_into;
TRACE_EVENT0("GAMEPAD", "SampleGamepads");
if (!base::SharedMemory::IsHandleValid(renderer_shared_memory_handle_))
// Only try to read this many times before failing to avoid waiting here
// very long in case of contention with the writer. TODO(scottmg) Tune this
// number (as low as 1?) if histogram shows distribution as mostly
// 0-and-maximum.
const int kMaximumContentionCount = 10;
int contention_count = -1;
base::subtle::Atomic32 version;
do {
version = gamepad_hardware_buffer_->sequence.ReadBegin();
memcpy(&read_into, &gamepad_hardware_buffer_->buffer, sizeof(read_into));
if (contention_count == kMaximumContentionCount)
} while (gamepad_hardware_buffer_->sequence.ReadRetry(version));
UMA_HISTOGRAM_COUNTS("Gamepad.ReadContentionCount", contention_count);
if (contention_count >= kMaximumContentionCount) {
// We failed to successfully read, presumably because the hardware
// thread was taking unusually long. Don't copy the data to the output
// buffer, and simply leave what was there before.
// New data was read successfully, copy it into the output buffer.
memcpy(&gamepads, &read_into, sizeof(gamepads));
if (!ever_interacted_with_) {
// Clear the connected flag if the user hasn't interacted with any of the
// gamepads to prevent fingerprinting. The actual data is not cleared.
// WebKit will only copy out data into the JS buffers for connected
// gamepads so this is sufficient.
for (unsigned i = 0; i < blink::WebGamepads::itemsLengthCap; i++)
gamepads.items[i].connected = false;
GamepadSharedMemoryReader::~GamepadSharedMemoryReader() {
bool GamepadSharedMemoryReader::OnControlMessageReceived(
const IPC::Message& message) {
bool handled = true;
IPC_BEGIN_MESSAGE_MAP(GamepadSharedMemoryReader, message)
IPC_MESSAGE_HANDLER(GamepadMsg_GamepadConnected, OnGamepadConnected)
IPC_MESSAGE_HANDLER(GamepadMsg_GamepadDisconnected, OnGamepadDisconnected)
IPC_MESSAGE_UNHANDLED(handled = false)
return handled;
void GamepadSharedMemoryReader::OnGamepadConnected(
int index,
const blink::WebGamepad& gamepad) {
// The browser already checks if the user actually interacted with a device.
ever_interacted_with_ = true;
if (listener())
listener()->didConnectGamepad(index, gamepad);
void GamepadSharedMemoryReader::OnGamepadDisconnected(
int index,
const blink::WebGamepad& gamepad) {
if (listener())
listener()->didDisconnectGamepad(index, gamepad);
} // namespace content