exo: Implement wayland gamepad support

components/exo/gamepads.cc

+// 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 "components/exo/gamepads.h"
+
+#include <cmath>
+
+#include "base/bind.h"
+#include "base/location.h"
+#include "base/single_thread_task_runner.h"
+#include "base/threading/thread.h"
+#include "base/threading/thread_task_runner_handle.h"
+#include "components/exo/gamepads_delegate.h"
+#include "device/gamepad/gamepad_data_fetcher.h"
+#include "device/gamepad/gamepad_platform_data_fetcher.h"
+
+namespace exo {
+
+namespace {

[reveman, 2016/06/27 17:30:35]

nit: blank line after this. blank line before is not needed.

+constexpr double kEpsilon = 0.001;
+bool almostEquals(double a, double b) {

[reveman, 2016/06/27 17:30:35]

nit: AlmostEqual but might also be good to explain what it's used for in the
name. e.g. GamepadButtonValuesAreEqual.

+  return fabs(a - b) < kEpsilon;
+}
+
+}  // anonymous namespace
+
+////////////////////////////////////////////////////////////////////////////////
+// Gamepads, public:
+
+Gamepads::Gamepads(GamepadsDelegate* delegate) : Gamepads(delegate, nullptr) {}
+
+Gamepads::Gamepads(GamepadsDelegate* delegate,
+                   std::unique_ptr<device::GamepadDataFetcher> fetcher)
+    : delegate_(delegate),
+      fetcher_(std::move(fetcher)),
+      polling_thread_(new base::Thread("Exo gamepad polling thread")),
+      origin_task_runner_(base::ThreadTaskRunnerHandle::Get()) {
+  polling_thread_->StartWithOptions(
+      base::Thread::Options(base::MessageLoop::TYPE_IO, 0));
+  polling_thread_->task_runner()->PostTask(
+      FROM_HERE,
+      base::Bind(&Gamepads::InitializePollingThread, base::Unretained(this)));
+}
+
+Gamepads::~Gamepads() {
+  delegate_->OnGamepadsDestroying(this);
+  polling_thread_->Stop();
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// Gamepads, private:
+
+void Gamepads::ScheduleOnPoll() {
+  polling_thread_->task_runner()->PostDelayedTask(
+      FROM_HERE, base::Bind(&Gamepads::OnPoll, base::Unretained(this)),
+      base::TimeDelta::FromMilliseconds(16));
+}
+
+void Gamepads::InitializePollingThread() {
+  DCHECK(base::MessageLoop::current() == polling_thread_->message_loop());
+  // The platform data fetcher has to be initialized on the polling thread.
+  if (!fetcher_)
+    fetcher_.reset(new device::GamepadPlatformDataFetcher());

[reveman, 2016/06/27 17:30:34]

Would be nice if this was always passed to the ctor as a raw pointer where the
lifetime of it is managed elsewhere. That way we don't need any special function
for testing purposes. Is that possible?

+  ScheduleOnPoll();
+}
+
+void Gamepads::OnPoll() {
+  DCHECK(base::MessageLoop::current() == polling_thread_->message_loop());
+  DCHECK(fetcher_);
+
+  // Update state with data from gamepad data fetcher
+  blink::WebGamepads new_state = state_;
+  fetcher_->GetGamepadData(&new_state, false);
+
+  // Notify delegate of all changes since the last gamepad state
+  for (size_t i = 0; i < std::max(state_.length, new_state.length); ++i) {
+    bool send_frame = false;
+    const blink::WebGamepad& new_pad = new_state.items[i];
+    blink::WebGamepad& pad = state_.items[i];
+
+    // Update connection state
+    if (new_pad.connected != pad.connected) {
+      if (new_pad.connected) {
+        origin_task_runner_->PostTask(
+            FROM_HERE, base::Bind(&GamepadsDelegate::OnConnected,
+                                  base::Unretained(delegate_), i));
+      } else {
+        origin_task_runner_->PostTask(
+            FROM_HERE, base::Bind(&GamepadsDelegate::OnDisconnected,
+                                  base::Unretained(delegate_), i));
+      }
+    }
+
+    if (!new_pad.connected || new_pad.timestamp <= pad.timestamp)
+      continue;
+
+    // Notify delegate of updated axes
+    for (size_t axis = 0; axis < std::max(pad.axesLength, new_pad.axesLength);
+         ++axis) {
+      if (!almostEquals(new_pad.axes[axis], pad.axes[axis])) {
+        send_frame = true;
+        origin_task_runner_->PostTask(
+            FROM_HERE,
+            base::Bind(&GamepadsDelegate::OnAxis, base::Unretained(delegate_),
+                       i, axis, new_pad.axes[axis]));
+      }
+    }
+
+    // Notify delegate of updated buttons
+    for (size_t button = 0;
+         button < std::max(pad.buttonsLength, new_pad.buttonsLength);
+         ++button) {
+      if (!almostEquals(new_pad.buttons[button].value,
+                        pad.buttons[button].value) ||
+          pad.buttons[button].pressed != new_pad.buttons[button].pressed) {
+        send_frame = true;
+        origin_task_runner_->PostTask(
+            FROM_HERE,
+            base::Bind(&GamepadsDelegate::OnButton, base::Unretained(delegate_),
+                       i, button, new_pad.buttons[button].pressed,
+                       new_pad.buttons[button].value));
+      }
+    }
+    if (send_frame) {
+      origin_task_runner_->PostTask(
+          FROM_HERE, base::Bind(&GamepadsDelegate::OnFrame,
+                                base::Unretained(delegate_), i));
+    }
+  }
+  state_ = new_state;
+
+  ScheduleOnPoll();
+}
+
+}  // namespace exo