exo: Implement wayland gamepad support

components/exo/gamepad.cc

+// Copyright 2016 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/gamepad.h"
+
+#include <cmath>
+
+#include "ash/shell.h"
+#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/gamepad_delegate.h"
+#include "components/exo/shell_surface.h"
+#include "components/exo/surface.h"
+#include "device/gamepad/gamepad_data_fetcher.h"
+#include "device/gamepad/gamepad_platform_data_fetcher.h"
+#include "ui/aura/client/focus_client.h"
+#include "ui/aura/window.h"
+
+namespace exo {
+namespace {
+
+constexpr double kGamepadButtonValueEpsilon = 0.001;
+bool GamepadButtonValuesAreEqual(double a, double b) {
+  return fabs(a - b) < kGamepadButtonValueEpsilon;
+}
+
+// Time between gamepad polls in milliseconds.
+constexpr unsigned kPollingTimeIntervalMs = 16;
+
+}  // namespace
+
+////////////////////////////////////////////////////////////////////////////////
+// Gamepad, public:
+
+Gamepad::Gamepad(GamepadDelegate* delegate) : Gamepad(delegate, nullptr) {}
+
+Gamepad::Gamepad(GamepadDelegate* delegate, device::GamepadDataFetcher* fetcher)
+    : delegate_(delegate),
+      origin_task_runner_(base::ThreadTaskRunnerHandle::Get()),
+      polling_thread_(new base::Thread("Exo gamepad polling thread")),
+      external_fetcher_(fetcher),
+      weak_factory_(this) {
+  polling_thread_checker_.DetachFromThread();
+  post_gamepad_changes_callback_ =
+      base::Bind(&Gamepad::PostGamepadChanges, weak_factory_.GetWeakPtr());
+
+  polling_thread_->StartWithOptions(
+      base::Thread::Options(base::MessageLoop::TYPE_IO, 0));
+
+  aura::client::FocusClient* focus_client =
+      aura::client::GetFocusClient(ash::Shell::GetPrimaryRootWindow());
+  focus_client->AddObserver(this);
+  OnWindowFocused(focus_client->GetFocusedWindow(), nullptr);
+}
+
+Gamepad::~Gamepad() {
+  polling_thread_->Stop();
+  delegate_->OnGamepadDestroying(this);
+  aura::client::GetFocusClient(ash::Shell::GetPrimaryRootWindow())
+      ->RemoveObserver(this);
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// aura::client::FocusChangeObserver overrides:
+
+void Gamepad::OnWindowFocused(aura::Window* gained_focus,
+                              aura::Window* lost_focus) {
+  DCHECK(origin_thread_checker_.CalledOnValidThread());
+  Surface* target = nullptr;
+  if (gained_focus) {
+    target = Surface::AsSurface(gained_focus);
+    if (!target) {
+      aura::Window* top_level_window = gained_focus->GetToplevelWindow();
+      if (top_level_window)
+        target = ShellSurface::GetMainSurface(top_level_window);
+    }
+  }
+
+  bool focused = target && delegate_->CanAcceptGamepadEventsForSurface(target);
+  if (focused) {
+    polling_thread_->task_runner()->PostTask(
+        FROM_HERE, base::Bind(&Gamepad::ResumePolling, base::Unretained(this)));
+  } else {
+    polling_thread_->task_runner()->PostTask(
+        FROM_HERE, base::Bind(&Gamepad::PausePolling, base::Unretained(this)));
+  }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// Gamepad, private:
+
+void Gamepad::PausePolling() {
+  DCHECK(polling_thread_checker_.CalledOnValidThread());
+  is_paused_ = true;
+}
+
+void Gamepad::ResumePolling() {
+  DCHECK(polling_thread_checker_.CalledOnValidThread());
+  if (!is_paused_)
+    return;
+
+  is_paused_ = false;
+  ScheduleOnPoll();
+}
+
+void Gamepad::ScheduleOnPoll() {
+  DCHECK(polling_thread_checker_.CalledOnValidThread());
+  if (is_paused_) {
+    internal_fetcher_.reset();
+    return;
+  }
+
+  if (has_poll_scheduled_)
+    return;
+
+  has_poll_scheduled_ = true;
+  polling_thread_->task_runner()->PostDelayedTask(
+      FROM_HERE, base::Bind(&Gamepad::OnPoll, base::Unretained(this)),
+      base::TimeDelta::FromMilliseconds(kPollingTimeIntervalMs));
+}
+
+void Gamepad::OnPoll() {
+  DCHECK(polling_thread_checker_.CalledOnValidThread());
+  blink::WebGamepads new_state = state_;
+
+  if (external_fetcher_) {

[reveman, 2016/07/07 22:14:02]

hm, when I suggested a refactor to avoid confusing ownership in tests I was
expecting a refactor that wouldn't result it different logic for testing and
real usage. I'd like to avoid any unnecessary complexity because of tests and
make sure we're not entering a different code path during tests compared to real
usage.

Is there a better way to instrument this class for tests? Maybe add a virtual
GetDataFetcher() with a comment that it is virtual for testing purposes and then
subclass Gamepad as TestGamepad for unit testing.

[denniskempin, 2016/07/08 23:49:40]

Done.

+    external_fetcher_->GetGamepadData(&new_state, false);
+  } else {
+    if (!internal_fetcher_)
+      internal_fetcher_.reset(new device::GamepadPlatformDataFetcher());
+    internal_fetcher_->GetGamepadData(&new_state, false);
+  }
+
+  if (std::max(new_state.length, state_.length) > 0) {
+    if (new_state.items[0].connected != state_.items[0].connected ||
+        new_state.items[0].timestamp > state_.items[0].timestamp) {
+      origin_task_runner_->PostTask(
+          FROM_HERE,
+          base::Bind(post_gamepad_changes_callback_, new_state.items[0]));
+    }
+  }
+
+  state_ = new_state;
+  has_poll_scheduled_ = false;
+  ScheduleOnPoll();
+}
+
+void Gamepad::PostGamepadChanges(const blink::WebGamepad new_pad) {
+  DCHECK(origin_thread_checker_.CalledOnValidThread());
+  bool send_frame = false;
+
+  // Update connection state.
+  if (new_pad.connected != pad_state_.connected) {
+    delegate_->OnStateChange(new_pad.connected);
+  }
+
+  if (!new_pad.connected || new_pad.timestamp <= pad_state_.timestamp) {
+    pad_state_ = new_pad;
+    return;
+  }
+
+  // Notify delegate of updated axes.
+  for (size_t axis = 0;
+       axis < std::max(pad_state_.axesLength, new_pad.axesLength); ++axis) {
+    if (!GamepadButtonValuesAreEqual(new_pad.axes[axis],
+                                     pad_state_.axes[axis])) {
+      send_frame = true;
+      delegate_->OnAxis(axis, new_pad.axes[axis]);
+    }
+  }
+
+  // Notify delegate of updated buttons.
+  for (size_t button_id = 0;
+       button_id < std::max(pad_state_.buttonsLength, new_pad.buttonsLength);
+       ++button_id) {
+    auto button = pad_state_.buttons[button_id];
+    auto new_button = new_pad.buttons[button_id];
+    if (button.pressed != new_button.pressed ||
+        !GamepadButtonValuesAreEqual(button.value, new_button.value)) {
+      send_frame = true;
+      delegate_->OnButton(button_id, new_button.pressed, new_button.value);
+    }
+  }
+  if (send_frame)
+    delegate_->OnFrame();
+
+  pad_state_ = new_pad;
+}
+
+}  // namespace exo