Gamepad API support for chrome on android

content/public/android/java/src/org/chromium/content/browser/input/GamepadList.java

+// Copyright 2014 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.
+
+package org.chromium.content.browser.input;
+
+import android.content.Context;
+import android.hardware.input.InputManager;
+import android.hardware.input.InputManager.InputDeviceListener;
+import android.view.InputDevice;
+import android.view.InputEvent;
+import android.view.KeyEvent;
+import android.view.MotionEvent;
+
+import org.chromium.base.CalledByNative;
+import org.chromium.base.JNINamespace;
+import org.chromium.base.ThreadUtils;
+
+/**
+ * Class to manage connected gamepad devices list.
+ *
+ * It is a Java counterpart of GamepadPlatformDataFetcherAndroid and feeds Gamepad API with input
+ * data.
+ */
+@JNINamespace("content")
+public class GamepadList implements InputDeviceListener {
+    private static final int MAX_GAMEPADS = 4;
+
+    private static GamepadList sGamepadList = null;

[jdduke (slow), 2014/05/12 15:25:35]

It looks like we're initializing this variable on one thread and reading it on
another, neither of which operations are guarded by a lock.  Do we have any
guarantees that the calls from native by the polling thread will always be made
after the first call to |onAttachedToWindow|? Ted, would a volatile be
appropriate here (at the very least) to at least make sure the assert in the
native static calls gets a sensible value?

+
+    private final Object mLock = new Object();
+
+    private final GamepadDevice[] mGamepadDevices = new GamepadDevice[MAX_GAMEPADS];
+    private InputManager mInputManager;
+    private int mAttachedToWindowCounter;
+    private boolean mIsGamepadAccessed;
+
+    private GamepadList() {}
+
+    private void initializeDevices() {
+        // Get list of all the attached input devices.
+        int[] deviceIds = mInputManager.getInputDeviceIds();
+        for (int i = 0; i < deviceIds.length; i++) {
+            InputDevice inputDevice = InputDevice.getDevice(deviceIds[i]);
+            // Check for gamepad device
+            if (isGamepadDevice(inputDevice)) {
+                // Register a new gamepad device.
+                registerGamepad(inputDevice);
+            }
+        }
+    }
+
+    /**
+     * Notifies the GamepadList that a {@link ContentView} is attached to a window and it should
+     * prepare itself for gamepad input. It must be called before {@link onGenericMotionEvent} and
+     * {@link dispatchKeyEvent}.
+     */
+    public static void onAttachedToWindow(Context context) {
+        assert ThreadUtils.runningOnUiThread();
+        createInstance();
+        sGamepadList.attachedToWindow(context);
+    }
+
+    private void attachedToWindow(Context context) {
+        if (mAttachedToWindowCounter++ == 0) {
+            mInputManager = (InputManager) context.getSystemService(Context.INPUT_SERVICE);
+            synchronized (mLock) {
+                initializeDevices();
+            }
+            // Register an input device listener.
+            mInputManager.registerInputDeviceListener(this, null);
+        }
+    }
+
+    /**
+     * Notifies the GamepadList that a {@link ContentView} is detached from it's window.
+     */
+    public static void onDetachedFromWindow() {
+        assert ThreadUtils.runningOnUiThread();
+        sGamepadList.detachedFromWindow();
+    }
+
+    private void detachedFromWindow() {
+        if (--mAttachedToWindowCounter == 0) {
+            synchronized (mLock) {
+                for (int i = 0; i < MAX_GAMEPADS; ++i) {
+                    mGamepadDevices[i] = null;
+                }
+            }
+            mInputManager.unregisterInputDeviceListener(this);
+            mInputManager = null;
+        }
+    }
+
+    // ------------------------------------------------------------
+
+    // Override InputDeviceListener methods
+    @Override
+    public void onInputDeviceChanged(int deviceId) {
+    }
+
+    @Override
+    public void onInputDeviceRemoved(int deviceId) {
+        synchronized (mLock) {
+            unregisterGamepad(deviceId);
+        }
+    }
+
+    @Override
+    public void onInputDeviceAdded(int deviceId) {
+        InputDevice inputDevice = InputDevice.getDevice(deviceId);
+        if (!isGamepadDevice(inputDevice)) return;
+        synchronized (mLock) {
+            registerGamepad(inputDevice);
+        }
+    }
+
+    // ------------------------------------------------------------
+
+    private static void createInstance() {
+        if (sGamepadList == null) {
+            sGamepadList = new GamepadList();
+        }
+    }
+
+    private int getDeviceCount() {
+        int count = 0;
+        for (int i = 0; i < MAX_GAMEPADS; i++) {
+            if (getDevice(i) != null) {
+                count++;
+            }
+        }
+        return count;
+    }
+
+    private boolean isDeviceConnected(int index) {
+        if (index < MAX_GAMEPADS && getDevice(index) != null) {
+            return true;
+        }
+        return false;
+    }
+
+    private GamepadDevice getDeviceById(int deviceId) {
+        for (int i = 0; i < MAX_GAMEPADS; i++) {
+            GamepadDevice gamepad = mGamepadDevices[i];
+            if (gamepad != null && gamepad.getId() == deviceId) {
+                return gamepad;
+            }
+        }
+        return null;
+    }
+
+    private GamepadDevice getDevice(int index) {
+        // Maximum 4 Gamepads can be connected at a time starting at index zero.
+        assert index >= 0 && index < MAX_GAMEPADS;
+        return mGamepadDevices[index];
+    }
+
+    /**
+     * Handles key events from the gamepad devices.
+     * @return True if the event has been consumed.
+     */
+    public static boolean dispatchKeyEvent(KeyEvent event) {
+        if (!isGamepadEvent(event)) return false;
+        return sGamepadList.handleKeyEvent(event);
+    }
+
+    private boolean handleKeyEvent(KeyEvent event) {
+        synchronized (mLock) {
+            if (!mIsGamepadAccessed) return false;
+            GamepadDevice gamepad = getGamepadForEvent(event);
+            if (gamepad == null) return false;
+            return gamepad.handleKeyEvent(event);
+        }
+    }
+
+    /**
+     * Handles motion events from the gamepad devices.
+     * @return True if the event has been consumed.
+     */
+    public static boolean onGenericMotionEvent(MotionEvent event) {
+        if (!isGamepadEvent(event)) return false;
+        return sGamepadList.handleMotionEvent(event);
+    }
+
+    private boolean handleMotionEvent(MotionEvent event) {
+        synchronized (mLock) {
+            if (!mIsGamepadAccessed) return false;
+            GamepadDevice gamepad = getGamepadForEvent(event);
+            if (gamepad == null) return false;
+            return gamepad.handleMotionEvent(event);
+        }
+    }
+
+    private int getNextAvailableIndex() {
+        // When multiple gamepads are connected to a user agent, indices must be assigned on a
+        // first-come first-serve basis, starting at zero. If a gamepad is disconnected, previously
+        // assigned indices must not be reassigned to gamepads that continue to be connected.
+        // However, if a gamepad is disconnected, and subsequently the same or a different
+        // gamepad is then connected, index entries must be reused.
+
+        for (int i = 0; i < MAX_GAMEPADS; ++i) {
+            if (getDevice(i) == null) {
+                return i;
+            }
+        }
+        // Reached maximum gamepads limit.
+        return -1;
+    }
+
+    private boolean registerGamepad(InputDevice inputDevice) {
+        int index = getNextAvailableIndex();
+        if (index == -1) return false; // invalid index
+
+        GamepadDevice gamepad = new GamepadDevice(index, inputDevice);
+        mGamepadDevices[index] = gamepad;
+        return true;
+    }
+
+    private void unregisterGamepad(int deviceId) {
+        GamepadDevice gamepadDevice = getDeviceById(deviceId);
+        if (gamepadDevice == null) return; // Not a registered device.
+        int index = gamepadDevice.getIndex();
+        mGamepadDevices[index] = null;
+    }
+
+    private static boolean isGamepadDevice(InputDevice inputDevice) {
+        return ((inputDevice.getSources() & InputDevice.SOURCE_JOYSTICK) ==
+                InputDevice.SOURCE_JOYSTICK);
+    }
+
+    private GamepadDevice getGamepadForEvent(InputEvent event) {
+        return getDeviceById(event.getDeviceId());
+    }
+
+    /**
+     * @return True if the motion event corresponds to a gamepad event.
+     */
+    public static boolean isGamepadEvent(MotionEvent event) {
+        return ((event.getSource() & InputDevice.SOURCE_JOYSTICK) == InputDevice.SOURCE_JOYSTICK);
+    }
+
+    /**
+     * @return True if event's keycode corresponds to a gamepad key.
+     */
+    public static boolean isGamepadEvent(KeyEvent event) {
+        int keyCode = event.getKeyCode();
+        switch (keyCode) {
+        // Specific handling for dpad keys is required because
+        // KeyEvent.isGamepadButton doesn't consider dpad keys.
+            case KeyEvent.KEYCODE_DPAD_UP:
+            case KeyEvent.KEYCODE_DPAD_DOWN:
+            case KeyEvent.KEYCODE_DPAD_LEFT:
+            case KeyEvent.KEYCODE_DPAD_RIGHT:
+                return true;
+            default:
+                return KeyEvent.isGamepadButton(keyCode);
+        }
+    }
+
+    @CalledByNative
+    static void updateGamepadData(long webGamepadsPtr) {
+        assert sGamepadList != null;
+        sGamepadList.grabGamepadData(webGamepadsPtr);
+    }
+
+    private void grabGamepadData(long webGamepadsPtr) {
+        synchronized (mLock) {
+            for (int i = 0; i < MAX_GAMEPADS; i++) {
+                final GamepadDevice device = getDevice(i);
+                if (device != null) {
+                    device.updateButtonsAndAxesMapping();
+                    nativeSetGamepadData(webGamepadsPtr, i, device.isStandardGamepad(), true,
+                            device.getName(), device.getTimestamp(), device.getAxes(),
+                            device.getButtons());
+                } else {
+                    nativeSetGamepadData(webGamepadsPtr, i, false, false, null, 0, null, null);
+                }
+            }
+        }
+    }
+
+    @CalledByNative
+    static void notifyForGamepadsAccess(boolean isAccessPaused) {
+        assert sGamepadList != null;
+        sGamepadList.setIsGamepadAccessed(!isAccessPaused);
+    }
+
+    private void setIsGamepadAccessed(boolean isGamepadAccessed) {
+        synchronized (mLock) {
+            mIsGamepadAccessed = isGamepadAccessed;
+            if (isGamepadAccessed) {
+                for (int i = 0; i < MAX_GAMEPADS; i++) {
+                    GamepadDevice gamepadDevice = getDevice(i);
+                    if (gamepadDevice == null) continue;
+                    gamepadDevice.clearData();
+                }
+            }
+        }
+    }
+
+    private native void nativeSetGamepadData(long webGamepadsPtr, int index, boolean mapping,
+            boolean connected, String devicename, long timestamp, float[] axes, float[] buttons);
+
+}