Refactoring gamepad polling to support dynamically added sources

content/browser/gamepad/gamepad_provider.cc

 // 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/browser/gamepad/gamepad_provider.h"
 
 #include <stddef.h>
 #include <string.h>
 #include <cmath>
-#include <set>
 #include <utility>
 #include <vector>
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/single_thread_task_runner.h"
 #include "base/third_party/dynamic_annotations/dynamic_annotations.h"
 #include "base/thread_task_runner_handle.h"
 #include "base/threading/thread.h"
 #include "base/threading/thread_restrictions.h"
 #include "build/build_config.h"
 #include "content/browser/gamepad/gamepad_data_fetcher.h"
 #include "content/browser/gamepad/gamepad_platform_data_fetcher.h"
 #include "content/browser/gamepad/gamepad_service.h"
 #include "content/common/gamepad_hardware_buffer.h"
 #include "content/common/gamepad_messages.h"
 #include "content/common/gamepad_user_gesture.h"
 #include "content/public/browser/browser_thread.h"
 
 using blink::WebGamepad;
 using blink::WebGamepads;
 
+namespace {
+
+const float kMinAxisResetValue = 0.1f;
+
+} // namespace
+
 namespace content {
 
 GamepadProvider::ClosureAndThread::ClosureAndThread(
     const base::Closure& c,
     const scoped_refptr<base::SingleThreadTaskRunner>& m)
     : closure(c), task_runner(m) {
 }
 
 GamepadProvider::ClosureAndThread::~ClosureAndThread() {
 }
 
 GamepadProvider::GamepadProvider()
     : is_paused_(true),
       have_scheduled_do_poll_(false),
       devices_changed_(true),
-      ever_had_user_gesture_(false) {
+      ever_had_user_gesture_(false),
+      sanitize_(true) {
   Initialize(scoped_ptr<GamepadDataFetcher>());
 }
 
 GamepadProvider::GamepadProvider(scoped_ptr<GamepadDataFetcher> fetcher)
     : is_paused_(true),
       have_scheduled_do_poll_(false),
       devices_changed_(true),
       ever_had_user_gesture_(false) {
   Initialize(std::move(fetcher));
 }
 
 GamepadProvider::~GamepadProvider() {
   base::SystemMonitor* monitor = base::SystemMonitor::Get();
   if (monitor)
     monitor->RemoveDevicesChangedObserver(this);
 
   // Use Stop() to join the polling thread, as there may be pending callbacks
   // which dereference |polling_thread_|.
   polling_thread_->Stop();
-  data_fetcher_.reset();
 }
 
 base::SharedMemoryHandle GamepadProvider::GetSharedMemoryHandleForProcess(
     base::ProcessHandle process) {
   base::SharedMemoryHandle renderer_handle;
   gamepad_shared_memory_.ShareToProcess(process, &renderer_handle);
   return renderer_handle;
 }
 
 void GamepadProvider::GetCurrentGamepadData(WebGamepads* data) {
@@ skipping 45 matching lines @@
   size_t data_size = sizeof(GamepadHardwareBuffer);
   base::SystemMonitor* monitor = base::SystemMonitor::Get();
   if (monitor)
     monitor->AddDevicesChangedObserver(this);
   bool res = gamepad_shared_memory_.CreateAndMapAnonymous(data_size);
   CHECK(res);
   GamepadHardwareBuffer* hwbuf = SharedMemoryAsHardwareBuffer();
   memset(hwbuf, 0, sizeof(GamepadHardwareBuffer));
   pad_states_.reset(new PadState[WebGamepads::itemsLengthCap]);
 
+  for (unsigned i = 0; i < WebGamepads::itemsLengthCap; ++i)
+    ClearPadState(pad_states_.get()[i]);
+
   polling_thread_.reset(new base::Thread("Gamepad polling thread"));
 #if defined(OS_LINUX)
   // On Linux, the data fetcher needs to watch file descriptors, so the message
   // loop needs to be a libevent loop.
   const base::MessageLoop::Type kMessageLoopType = base::MessageLoop::TYPE_IO;
 #elif defined(OS_ANDROID)
   // On Android, keeping a message loop of default type.
   const base::MessageLoop::Type kMessageLoopType =
       base::MessageLoop::TYPE_DEFAULT;
 #else
   // On Mac, the data fetcher uses IOKit which depends on CFRunLoop, so the
   // message loop needs to be a UI-type loop. On Windows it must be a UI loop
   // to properly pump the MessageWindow that captures device state.
   const base::MessageLoop::Type kMessageLoopType = base::MessageLoop::TYPE_UI;
 #endif
   polling_thread_->StartWithOptions(base::Thread::Options(kMessageLoopType, 0));
 
+  if (fetcher) {
+    AddGamepadDataFetcher(std::move(fetcher));
+  } else {
+    AddGamepadPlatformDataFetchers(this);
+  }
+}
+
+void GamepadProvider::AddGamepadDataFetcher(
+    scoped_ptr<GamepadDataFetcher> fetcher) {
   polling_thread_->task_runner()->PostTask(
-      FROM_HERE, base::Bind(&GamepadProvider::DoInitializePollingThread,
+      FROM_HERE, base::Bind(&GamepadProvider::DoAddGamepadDataFetcher,
                             base::Unretained(this), base::Passed(&fetcher)));
 }
 
-void GamepadProvider::DoInitializePollingThread(
+void GamepadProvider::DoAddGamepadDataFetcher(
     scoped_ptr<GamepadDataFetcher> fetcher) {
   DCHECK(base::MessageLoop::current() == polling_thread_->message_loop());
-  DCHECK(!data_fetcher_.get());  // Should only initialize once.
 
-  if (!fetcher)
-    fetcher.reset(new GamepadPlatformDataFetcher);
-  data_fetcher_ = std::move(fetcher);
+  fetcher->InitializeProvider(this);
+
+  data_fetchers_.push_back(std::move(fetcher));
 }
 
 void GamepadProvider::SendPauseHint(bool paused) {
   DCHECK(base::MessageLoop::current() == polling_thread_->message_loop());
-  if (data_fetcher_)
-    data_fetcher_->PauseHint(paused);
-}
-
-bool GamepadProvider::PadState::Match(const WebGamepad& pad) const {
-  return connected_ == pad.connected &&
-         axes_length_ == pad.axesLength &&
-         buttons_length_ == pad.buttonsLength &&
-         memcmp(id_, pad.id, sizeof(id_)) == 0 &&
-         memcmp(mapping_, pad.mapping, sizeof(mapping_)) == 0;
-}
-
-void GamepadProvider::PadState::SetPad(const WebGamepad& pad) {
-  connected_ = pad.connected;
-  axes_length_ = pad.axesLength;
-  buttons_length_ = pad.buttonsLength;
-  memcpy(id_, pad.id, sizeof(id_));
-  memcpy(mapping_, pad.mapping, sizeof(mapping_));
-}
-
-void GamepadProvider::PadState::SetDisconnected() {
-  connected_ = false;
-  axes_length_ = 0;
-  buttons_length_ = 0;
-  memset(id_, 0, sizeof(id_));
-  memset(mapping_, 0, sizeof(mapping_));
-}
-
-void GamepadProvider::PadState::AsWebGamepad(WebGamepad* pad) {
-  pad->connected = connected_;
-  pad->axesLength = axes_length_;
-  pad->buttonsLength = buttons_length_;
-  memcpy(pad->id, id_, sizeof(id_));
-  memcpy(pad->mapping, mapping_, sizeof(mapping_));
-  memset(pad->axes, 0, sizeof(pad->axes));
-  memset(pad->buttons, 0, sizeof(pad->buttons));
+  for (const auto& it : data_fetchers_) {
+    it->PauseHint(paused);
+  }
 }
 
 void GamepadProvider::DoPoll() {
   DCHECK(base::MessageLoop::current() == polling_thread_->message_loop());
   DCHECK(have_scheduled_do_poll_);
   have_scheduled_do_poll_ = false;
 
   bool changed;
   GamepadHardwareBuffer* hwbuf = SharedMemoryAsHardwareBuffer();
 
   ANNOTATE_BENIGN_RACE_SIZED(
       &hwbuf->buffer,
       sizeof(WebGamepads),
       "Racey reads are discarded");
 
   {
     base::AutoLock lock(devices_changed_lock_);
     changed = devices_changed_;
     devices_changed_ = false;
   }
 
+  // Loop through each registered data fetcher and poll its gamepad data.
+  // It's expected that GetGamepadData will mark each gamepad as active (via
+  // GetPadState). If a gamepad is not marked as active during the calls to
+  // GetGamepadData then it's assumed to be disconnected.
+  for (const auto& it : data_fetchers_) {
+    it->GetGamepadData(changed);
+  }
+
+  // Send out disconnect events using the last polled data before we wipe it out
+  // in the mapping step.
+  if (ever_had_user_gesture_) {
+    for (unsigned i = 0; i < WebGamepads::itemsLengthCap; ++i) {
+      PadState& state = pad_states_.get()[i];
+
+      if (!state.active_state && state.source != GAMEPAD_SOURCE_NONE) {
+        OnGamepadConnectionChange(false, i, hwbuf->buffer.items[i]);
+        ClearPadState(state);
+      }
+    }
+  }
+
   {
     base::AutoLock lock(shared_memory_lock_);
 
     // Acquire the SeqLock. There is only ever one writer to this data.
     // See gamepad_hardware_buffer.h.
     hwbuf->sequence.WriteBegin();
-    data_fetcher_->GetGamepadData(&hwbuf->buffer, changed);
+    hwbuf->buffer.length = 0;
+    for (unsigned i = 0; i < WebGamepads::itemsLengthCap; ++i) {
+      PadState& state = pad_states_.get()[i];
+      // Must run through the map+sanitize here or CheckForUserGesture may fail.
+      MapAndSanitizeGamepadData(&state, &hwbuf->buffer.items[i]);
+      if (state.active_state)
+        hwbuf->buffer.length++;
+    }
     hwbuf->sequence.WriteEnd();
   }
 
   if (ever_had_user_gesture_) {
     for (unsigned i = 0; i < WebGamepads::itemsLengthCap; ++i) {
-      WebGamepad& pad = hwbuf->buffer.items[i];
       PadState& state = pad_states_.get()[i];
-      if (pad.connected && !state.connected()) {
-        OnGamepadConnectionChange(true, i, pad);
-      } else if (!pad.connected && state.connected()) {
-        OnGamepadConnectionChange(false, i, pad);
-      } else if (pad.connected && state.connected() && !state.Match(pad)) {
-        WebGamepad old_pad;
-        state.AsWebGamepad(&old_pad);
-        OnGamepadConnectionChange(false, i, old_pad);
-        OnGamepadConnectionChange(true, i, pad);
+
+      if (state.active_state) {
+        if (state.active_state == GAMEPAD_NEWLY_ACTIVE)
+          OnGamepadConnectionChange(true, i, hwbuf->buffer.items[i]);
+        state.active_state = GAMEPAD_INACTIVE;
       }
     }
   }
 
   CheckForUserGesture();
 
   // Schedule our next interval of polling.
   ScheduleDoPoll();
 }
 
 void GamepadProvider::ScheduleDoPoll() {
   DCHECK(base::MessageLoop::current() == polling_thread_->message_loop());
   if (have_scheduled_do_poll_)
     return;
 
   {
     base::AutoLock lock(is_paused_lock_);
     if (is_paused_)
       return;
   }
 
   base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
       FROM_HERE, base::Bind(&GamepadProvider::DoPoll, Unretained(this)),
       base::TimeDelta::FromMilliseconds(kDesiredSamplingIntervalMs));
   have_scheduled_do_poll_ = true;
 }
 
 void GamepadProvider::OnGamepadConnectionChange(
     bool connected, int index, const WebGamepad& pad) {
-  PadState& state = pad_states_.get()[index];
-  if (connected)
-    state.SetPad(pad);
-  else
-    state.SetDisconnected();
-
   BrowserThread::PostTask(
       BrowserThread::IO,
       FROM_HERE,
       base::Bind(&GamepadProvider::DispatchGamepadConnectionChange,
                  base::Unretained(this),
                  connected,
                  index,
                  pad));
 }
 
 void GamepadProvider::DispatchGamepadConnectionChange(
     bool connected, int index, const WebGamepad& pad) {
   if (connected)
     GamepadService::GetInstance()->OnGamepadConnected(index, pad);
   else
     GamepadService::GetInstance()->OnGamepadDisconnected(index, pad);
 }
 
 GamepadHardwareBuffer* GamepadProvider::SharedMemoryAsHardwareBuffer() {
   void* mem = gamepad_shared_memory_.memory();
   CHECK(mem);
   return static_cast<GamepadHardwareBuffer*>(mem);
 }
 
 void GamepadProvider::CheckForUserGesture() {
   base::AutoLock lock(user_gesture_lock_);
   if (user_gesture_observers_.empty() && ever_had_user_gesture_)
     return;
 
-  bool had_gesture_before = ever_had_user_gesture_;
   const WebGamepads& pads = SharedMemoryAsHardwareBuffer()->buffer;
   if (GamepadsHaveUserGesture(pads)) {
     ever_had_user_gesture_ = true;
     for (size_t i = 0; i < user_gesture_observers_.size(); i++) {
       user_gesture_observers_[i].task_runner->PostTask(
           FROM_HERE, user_gesture_observers_[i].closure);
     }
     user_gesture_observers_.clear();
   }
-  if (!had_gesture_before && ever_had_user_gesture_) {
-    // Initialize pad_states_ for the first time.
-    for (size_t i = 0; i < WebGamepads::itemsLengthCap; ++i) {
-      pad_states_.get()[i].SetPad(pads.items[i]);
+}
+
+void GamepadProvider::ClearPadState(PadState& state) {
+  memset(&state, 0, sizeof(PadState));
+}
+
+PadState* GamepadProvider::GetPadState(GamepadSource source, int source_id) {
+  // Check to see if the device already has a reserved slot
+  PadState* empty_slot = nullptr;
+  for (size_t i = 0; i < WebGamepads::itemsLengthCap; ++i) {
+    PadState& state = pad_states_.get()[i];
+    if (state.source == source &&
+        state.source_id == source_id) {
+      // Retrieving the pad state marks this gamepad as active.
+      state.active_state = GAMEPAD_ACTIVE;
+      return &state;
+    }
+    if (!empty_slot && state.source == GAMEPAD_SOURCE_NONE)
+      empty_slot = &state;
+  }
+  if (empty_slot) {
+    empty_slot->source = source;
+    empty_slot->source_id = source_id;
+    empty_slot->active_state = GAMEPAD_NEWLY_ACTIVE;
+  }
+  return empty_slot;
+}
+
+void GamepadProvider::MapAndSanitizeGamepadData(
+    PadState* pad_state, WebGamepad* pad) {
+  DCHECK(pad_state);
+  DCHECK(pad);
+
+  if (!pad_state->active_state) {
+    memset(pad, 0, sizeof(WebGamepad));
+    return;
+  }
+
+  // Copy the current state to the output buffer, using the mapping
+  // function, if there is one available.
+  if (pad_state->mapper)
+    pad_state->mapper(pad_state->data, pad);
+  else
+    *pad = pad_state->data;
+
+  pad->connected = true;
+
+  if (!sanitize_)
+    return;
+
+  // About sanitization: Gamepads may report input event if the user is not
+  // interacting with it, due to hardware problems or environmental ones (pad
+  // has something heavy leaning against an axis.) This may cause user gestures
+  // to be detected erroniously, exposing gamepad information when the user had
+  // no intention of doing so. To avoid this we require that each button or axis
+  // report being at rest (zero) at least once before exposing its value to the
+  // Gamepad API. This state is tracked by the axis_mask and button_mask
+  // bitfields. If the bit for an axis or button is 0 it means the axis has
+  // never reported being at rest, and the value will be forced to zero.
+
+  // We can skip axis sanitation if all available axes have been masked.
+  uint32_t full_axis_mask = (1 << pad->axesLength) - 1;
+  if (pad_state->axis_mask != full_axis_mask) {
+    for (size_t axis = 0; axis < pad->axesLength; ++axis) {
+      if (!(pad_state->axis_mask & 1 << axis)) {
+        if (fabs(pad->axes[axis]) < kMinAxisResetValue) {
+          pad_state->axis_mask |= 1 << axis;
+        } else {
+          pad->axes[axis] = 0.0f;
+        }
+      }
+    }
+  }
+
+  // We can skip button sanitation if all available buttons have been masked.
+  uint32_t full_button_mask = (1 << pad->buttonsLength) - 1;
+  if (pad_state->button_mask != full_button_mask) {
+    for (size_t button = 0; button < pad->buttonsLength; ++button) {
+      if (!(pad_state->button_mask & 1 << button)) {
+        if (!pad->buttons[button].pressed) {
+          pad_state->button_mask |= 1 << button;
+        } else {
+          pad->buttons[button].pressed = false;
+          pad->buttons[button].value = 0.0f;
+        }
+      }
     }
   }
 }
 
 }  // namespace content