Gamepad API support for chrome on android

content/browser/renderer_host/gamepad_browser_message_filter.cc

 // Copyright (c) 2011 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 "base/time/time.h"

[scottmg, 2014/02/06 21:17:07]

This should go below the include of gamepad_browser_message_filter.h with the
others after a blank line.

 #include "content/browser/renderer_host/gamepad_browser_message_filter.h"
-
 #include "content/browser/gamepad/gamepad_service.h"
 #include "content/common/gamepad_messages.h"
 
 namespace content {
 
 GamepadBrowserMessageFilter::GamepadBrowserMessageFilter()
     : is_started_(false) {
 }
 
 GamepadBrowserMessageFilter::~GamepadBrowserMessageFilter() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
   if (is_started_)
     GamepadService::GetInstance()->RemoveConsumer();
 }
 
 bool GamepadBrowserMessageFilter::OnMessageReceived(
     const IPC::Message& message,
     bool* message_was_ok) {
   bool handled = true;
   IPC_BEGIN_MESSAGE_MAP_EX(GamepadBrowserMessageFilter,
                            message,
                            *message_was_ok)
     IPC_MESSAGE_HANDLER(GamepadHostMsg_StartPolling, OnGamepadStartPolling)
     IPC_MESSAGE_HANDLER(GamepadHostMsg_StopPolling, OnGamepadStopPolling)
+    IPC_MESSAGE_HANDLER(GamepadHostMsg_ResumePolling, OnGamepadResumePolling)
+    IPC_MESSAGE_HANDLER(GamepadHostMsg_PausePolling, OnGamepadPausePolling)
+    IPC_MESSAGE_HANDLER(GamepadHostMsg_UpdateTimestamp,
+                                                    OnGamepadUpdateTimestamp)

[scottmg, 2014/02/06 21:17:07]

nit; align at (.

     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP_EX()
   return handled;
 }
 
 void GamepadBrowserMessageFilter::OnGamepadStartPolling(
     base::SharedMemoryHandle* renderer_handle) {
   GamepadService* service = GamepadService::GetInstance();
   if (!is_started_) {
     is_started_ = true;
     service->AddConsumer();
     *renderer_handle = service->GetSharedMemoryHandleForProcess(PeerHandle());
   } else {
     // Currently we only expect the renderer to tell us once to start.
     NOTREACHED();
   }
 }
 
 void GamepadBrowserMessageFilter::OnGamepadStopPolling() {
   // TODO(scottmg): Probably get rid of this message. We can't trust it will
   // arrive anyway if the renderer crashes, etc.
   if (is_started_) {
     is_started_ = false;
     GamepadService::GetInstance()->RemoveConsumer();
   } else {
     NOTREACHED();
   }
 }
 
+void GamepadBrowserMessageFilter::OnGamepadResumePolling() {
+  // The renderer will put the background polling thread to resume state.
+  if (is_started_ && GamepadService::GetInstance()->GetPollState()) {
+    GamepadService::GetInstance()->Resume();
+  } else {
+    NOTREACHED();
+  }
+}
+
+void GamepadBrowserMessageFilter::OnGamepadPausePolling() {
+  // The renderer will put the background polling thread to pause state.
+  if (is_started_ && !GamepadService::GetInstance()->GetPollState()) {
+    GamepadService::GetInstance()->Pause();
+  } else {
+    NOTREACHED();
+  }
+}
+
+void GamepadBrowserMessageFilter::OnGamepadUpdateTimestamp() {
+  // The renderer will set the timestamp for last gamepad data access. This way
+  // the polling thread can be put to pause state when webpage stops accessing
+  // data i.e browser minimize or tab change.
+  // TODO(SaurabhK): Currently this approach is expensive. We need to get rid
+  // of this message and set the polling thread to pause state everytime
+  // gamepad data access stops. One possible way is tracking the focus change
+  // on the webpage.
+  GamepadService::GetInstance()->SetGamepadAccessTimestamp(
+                                            base::Time::NowFromSystemTime());

[scottmg, 2014/02/06 21:17:07]

Ah, I see. Why can't we detect the situations above, and call
OnGamepadStopPolling instead then of Pause and Resume?

[SaurabhK, 2014/02/10 12:50:47]

On 2014/02/06 21:17:07, scottmg wrote:

Regarding the Pause/Resume and the timer, we have used it on our android browser
because we have two implementation that should work alternately.
1. Gamepad API
2. Browser controller support
Whenever any webpage accesses gamepad data we have to make sure that KeyEvent
and MotionEvent from the gamepad device should not get consumed and are
transfered to JS of the webpage.
And whenever webpage releases gamepad data, the device controller should be used
for scroll and navigational purposes.

Therefore we want to make sure that GamepadList java object is notified of
gamepad data access/release.
I can try to use StopPoll and StartPoll for the same purpose instead of
Pause/Resume. As currently start and stop is related with the lifetime of
SharedMemoryReader object, so for the usecase of tab switch i have implemented
Timer.
I think that i can start with its implementation as a seperate patch.
And in this patch, it will be better to go ahead with just the android platform
specific fetcher implementation.

+  OnGamepadResumePolling();
+}
+
 }  // namespace content