Gamepad API support for chrome on android

content/public/android/java/src/org/chromium/content/browser/GamepadDevice.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;
+
+import android.os.SystemClock;
+import android.view.InputDevice;
+import android.view.InputDevice.MotionRange;
+import android.view.KeyEvent;
+import android.view.MotionEvent;
+
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.LinkedHashMap;
+
+import org.chromium.content.browser.input.gamepad_mapping.CanonicalAxisIndex;
+import org.chromium.content.browser.input.gamepad_mapping.CanonicalButtonIndex;
+
+/*
+ * Class to manage information related to each connected gamepad device.
+ */
+
+class GamepadDevice {
+    // An id for the gamepad.
+    protected int mDeviceId;

[jdduke (slow), 2014/03/24 17:38:15]

Do you plan on subclassing this? If not, these members really ought to be
private.

[SaurabhK, 2014/03/26 16:10:07]

On 2014/03/24 17:38:15, jdduke wrote:

Done.

+    // The index of the gamepad in the Navigator.
+    protected int mDeviceIndex;
+    // Last time the data for this gamepad was updated.
+    protected long mTimestamp;
+    // If this gamepad is mapped to standard gamepad?
+    protected String mMapping;
+
+    // Array of values for all axes of the gamepad.
+    // All axis values must be linearly normalized to the range [-1.0 .. 1.0].
+    // As appropriate, -1.0 should correspond to "up" or "left", and 1.0
+    // should correspond to "down" or "right".
+    protected float[] mAxisValues;
+
+    protected float[] mButtonsValues;
+
+    // When the user agent recognizes the attached inputDevice, it is recommended
+    // that it be remapped to a canonical ordering when possible. Devices that are
+    // not recognized should still be exposed in their raw form. Therefore we must
+    // pass the raw Button and raw Axis values.
+    protected float[] mRawButtons;
+    protected float[] mRawAxes;
+
+    // An identification string for the gamepad.
+    protected String mDeviceName;
+
+    // Array of axes ids.
+    private int[] mAxes;
+
+    // List of keycodes that can be sent by a standard gamepad. Standard gamepad can have
+    // buttons as per the spec:
+    // https://dvcs.w3.org/hg/gamepad/raw-file/default/gamepad.html#remapping
+    // Need to maintain this list to get input device capabilities. We query
+    // input devices with this list and device returns list mentioning which
+    // Keycodes out of these can be sent by a gamepad device.
+    private static final int[] standardGamepadKeyCodes = {
+        KeyEvent.KEYCODE_BUTTON_A, // Button 0
+        KeyEvent.KEYCODE_BUTTON_B, // Button 1
+        KeyEvent.KEYCODE_BUTTON_X, // Button 2
+        KeyEvent.KEYCODE_BUTTON_Y, // Button 3
+        KeyEvent.KEYCODE_BUTTON_L1, // Button 4
+        KeyEvent.KEYCODE_BUTTON_R1, // Button 5
+        KeyEvent.KEYCODE_BUTTON_L2, // Button 6
+        KeyEvent.KEYCODE_BUTTON_R2, // Button 7
+        KeyEvent.KEYCODE_BUTTON_SELECT, // Button 8
+        KeyEvent.KEYCODE_BUTTON_START, // Button 9
+        KeyEvent.KEYCODE_BUTTON_THUMBL, // Button 10
+        KeyEvent.KEYCODE_BUTTON_THUMBR, // Button 11
+        KeyEvent.KEYCODE_DPAD_UP, // Button 12
+        KeyEvent.KEYCODE_DPAD_DOWN, // Button 13
+        KeyEvent.KEYCODE_DPAD_LEFT, // Button 14
+        KeyEvent.KEYCODE_DPAD_RIGHT, // Button 15
+        KeyEvent.KEYCODE_BUTTON_MODE, // Button 16??
+    };
+
+    // Hash map of supported keycodes and their current value linearly
+    // normalized to the range [0.0 .. 1.0].
+    // 0.0 must mean fully unpressed, and 1.0 must mean fully pressed.
+    protected LinkedHashMap<Integer, Float> mKeyCodeValueMap = new LinkedHashMap<Integer, Float>();
+
+    GamepadDevice(int index, InputDevice inputDevice) {
+        mDeviceIndex = index;
+        mDeviceId = inputDevice.getId();
+        mDeviceName = inputDevice.getName();
+        mTimestamp = SystemClock.uptimeMillis();
+        mMapping = " ";
+        mButtonsValues = new float[CanonicalButtonIndex.NUM_CANONICAL_BUTTONS];
+        mAxisValues = new float[CanonicalAxisIndex.NUM_CANONICAL_AXES];
+        // Get the total number of axes supported by gamepad.
+        int totalAxes = 0;
+        for (MotionRange range : inputDevice.getMotionRanges()) {
+            if ((range.getSource() & InputDevice.SOURCE_CLASS_JOYSTICK) != 0) {
+                totalAxes++;
+            }
+        }
+        // Get axis ids and initialize axes values.
+        mAxes = new int[totalAxes];
+        mRawAxes = new float[totalAxes];
+        int i = 0;
+        for (MotionRange range : inputDevice.getMotionRanges()) {
+            if ((range.getSource() & InputDevice.SOURCE_CLASS_JOYSTICK) != 0) {
+                mAxes[i] = range.getAxis();
+                mRawAxes[i] = 0.0f;
+                i++;
+            }
+        }
+        // Update supported buttons list.
+        boolean[] deviceKeys = inputDevice.hasKeys(standardGamepadKeyCodes);
+        for (int j = 0; j < standardGamepadKeyCodes.length; ++j) {
+            if (deviceKeys[j]) {
+                mKeyCodeValueMap.put(standardGamepadKeyCodes[j], 0.0f);
+            }
+        }
+        mRawButtons = new float[mKeyCodeValueMap.size()];
+    }
+
+    GamepadDevice() {}
+
+    public void mapButtonsAndAxes() {
+        int i = 0;
+        Iterator itr = mKeyCodeValueMap.values().iterator();
+        while (itr.hasNext()) {
+            mRawButtons[i++] = (Float)itr.next();
+        }
+        mMapping = GamepadMappings.mapToStandardGamepad(mAxisValues, mButtonsValues, mRawAxes,

[jdduke (slow), 2014/03/24 17:38:15]

GamepadMappings.mapToStandardGamepad returns a Boolean, so I don't really
understand this assignment.

[SaurabhK, 2014/03/26 16:10:07]

On 2014/03/24 17:38:15, jdduke wrote:

I am setting the mMapping to string "standard" if the device type is known
otherwise i should set it to  an empty string.
Doing it using ternary operator.

+                                                        mRawButtons,
+                                                        mDeviceName) ? "standard" : " ";
+    }
+
+    public int getId() { return mDeviceId; }
+
+    public String getMapping() { return mMapping; }
+
+    public String getName() { return mDeviceName; }
+
+    public int getIndex() { return mDeviceIndex; }
+
+    public long getTimestamp() { return mTimestamp; }
+
+    public float[] getAxes() {
+        if (mMapping.equals("standard"))
+            return mAxisValues;
+        else
+            return mRawAxes;
+    }
+
+    public float[] getButtons() {
+        if (mMapping.equals("standard"))
+            return mButtonsValues;
+        else
+            return mRawButtons;
+    }
+
+    public void clearData() {

[jdduke (slow), 2014/03/24 17:38:15]

I'm going to led tedchoc@ or another Java specialist chime in on these files,
but in general, particularly for non-trivial getters, you'll want to (Javadoc)
document these public methods.

[SaurabhK, 2014/03/26 16:10:07]

On 2014/03/24 17:38:15, jdduke wrote:

SO, shall i be appending "@SuppressWarnings("javadoc")" before the method
|clearData| ?

[jdduke (slow), 2014/03/26 16:37:58]

No, you should definitely comment this and all other public methods. 

[SaurabhK, 2014/03/27 13:32:31]

On 2014/03/26 16:37:58, jdduke wrote:

Done.

+        Arrays.fill(mAxisValues, 0);
+        Arrays.fill(mRawAxes, 0);
+        Arrays.fill(mButtonsValues, 0);
+        Arrays.fill(mRawButtons, 0);
+    }
+
+    public boolean updateForEvent(KeyEvent event) {
+        mTimestamp = SystemClock.uptimeMillis();

[jdduke (slow), 2014/03/24 17:38:15]

Do you want really want to update mTimestamp if it's not a gamepad key?

[SaurabhK, 2014/03/26 16:10:07]

On 2014/03/24 17:38:15, jdduke wrote:
Changeing it now.

+        // Ignore event if it is not for standard gamepad key.
+        int keyCode = event.getKeyCode();
+        if (mKeyCodeValueMap.get(keyCode) == null) {
+            return false;
+        }
+        // Button value 0.0 must mean fully unpressed, and 1.0 must mean fully pressed.
+        if (event.getAction() == KeyEvent.ACTION_DOWN) {
+            mKeyCodeValueMap.put(keyCode, 1.0f);
+        } else if (event.getAction() == KeyEvent.ACTION_UP) {
+            mKeyCodeValueMap.put(keyCode, 0.0f);
+        }
+
+        return true;
+    }
+
+    public boolean updateForEvent(MotionEvent event) {
+        mTimestamp = SystemClock.uptimeMillis();
+        // Update axes values.
+        for (int i = 0; i < mAxes.length; ++i) {
+            mRawAxes[i] = event.getAxisValue(mAxes[i]);
+        }
+        return true;
+    }
+}