Gamepad API support for chrome on android

content/public/android/java/src/org/chromium/content/browser/GamepadMappings.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;
+
+/*
+ * Class to manage mapping information related to each supported gamepad controller device.
+ */
+
+class GamepadMappings {
+
+    // Standard gamepad buttons.
+    private static class StandardButtons {
+        public static final int BUTTON_A = 0;
+        public static final int BUTTON_B = 1;
+        public static final int BUTTON_X = 2;
+        public static final int BUTTON_Y = 3;
+        public static final int LEFT_TRIGGER = 4;
+        public static final int RIGHT_TRIGGER = 5;
+        public static final int BOTTOM_LEFT_TRIGGER = 6;
+        public static final int BOTTOM_RIGHT_TRIGGER = 7;
+        public static final int SELECT = 8;
+        public static final int START = 9;
+        public static final int LEFT_THUMB = 10;
+        public static final int RIGHT_THUMB = 11;
+        public static final int DPAD_UP = 12;
+        public static final int DPAD_DOWN = 13;
+        public static final int DPAD_LEFT = 14;
+        public static final int DPAD_RIGHT = 15;
+        public static final int MODE = 16;
+        public static final int MAX_BUTTONS = 17;
+    }
+
+    // Standard gamepad axes.
+    private static class StandardAxes {
+        public static final int AXIS_0 = 0;
+        public static final int AXIS_1 = 1;
+        public static final int AXIS_2 = 2;
+        public static final int AXIS_3 = 3;
+        public static final int MAX_AXES = 4;
+    }
+
+    // We guess the gamepad inputDevice type from its name and then map it to the
+    // standard gamepad if it is one of the known gamepads.
+    protected static enum GamepadType {
+        Shield,
+        XBox360,
+        Unknown
+    }
+
+    // Following values should be changed if the gamepad layout changes
+    // or frameworks exposes different axes / buttons for a particular gamepad.
+    // mRawShieldAxes is the total raw axes on known shield gamepad.
+    protected static final int mRawShieldAxes = 10;
+    // mRawShieldButtons is the total raw buttons on known shield gamepad.
+    protected static final int mRawShieldButtons = 10;
+    // mRawXBoxAxes is the total raw axes on known XBox gamepad.
+    protected static final int mRawXBoxAxes = 10;
+    // mRawXBoxButtons is the total raw buttons on known XBox gamepad.
+    protected static final int mRawXBoxButtons = 9;
+
+    public static float[] mapToStandardGamepadAxes(float[] rawAxes, GamepadType gamepadType) {
+        switch (gamepadType) {
+            case Shield:
+                return mapShieldAxes(rawAxes);
+            case XBox360:
+                return mapXBox360Axes(rawAxes);
+        }
+        return rawAxes;
+    }
+
+    public static float[] mapToStandardGamepadButtons(float[] rawButtons, float[] rawAxes,
+                                                      GamepadType gamepadType) {
+        switch (gamepadType) {
+            case Shield:
+                return mapShieldButtons(rawButtons, rawAxes);
+            case XBox360:
+                return mapXBox360Buttons(rawButtons, rawAxes);
+        }
+        return rawAxes;
+    }
+
+    private static float negativeAxisValueAsButton(float input) {
+        return (input < -0.5f) ? 1.f : 0.f;
+    }
+
+    private static float positiveAxisValueAsButton(float input) {
+        return (input > 0.5f) ? 1.f : 0.f;
+    }
+
+    /**
+     * Method for mapping Nvidia gamepad axis values to
+     * standard gamepad axis values.
+     */
+    private static float[] mapShieldAxes(float[] rawAxes) {
+        float[] values = new float[StandardAxes.MAX_AXES];
+        // Standard gamepad can have only four axes.
+        values[StandardAxes.AXIS_0] = rawAxes[0];

[kbalazs, 2014/02/20 00:48:24]

Like I said before I think it would be probably better to use the constants
defined by KeyEvent and MotionEvent here. I did that by pushing the values to a
map (SparseArray) that use keycodes and axis id's as keys and I pass the 2 maps
to the mapper. With this we could also write a fallback mapper if we don't have
the device specific code for the actual device. The Android API is generic
enough that this could probably work in most cases.

+        values[StandardAxes.AXIS_1] = rawAxes[1];
+        values[StandardAxes.AXIS_2] = rawAxes[4];
+        values[StandardAxes.AXIS_3] = rawAxes[5];
+        return values;
+    }
+
+    /**
+     * Method for mapping Nvidia gamepad axis and button values
+     * to standard gamepad button values.
+     */
+    private static float[] mapShieldButtons(float[] rawButtons, float[] rawAxes) {
+        float[] values = new float[StandardButtons.MAX_BUTTONS];
+        // First four buttons on Nvidia gamepad appear in correct order so no mapping is required.
+        values[StandardButtons.BUTTON_A] = rawButtons[0];
+        values[StandardButtons.BUTTON_B] = rawButtons[1];
+        values[StandardButtons.BUTTON_X] = rawButtons[2];
+        values[StandardButtons.BUTTON_Y] = rawButtons[3];
+        // Third axis on Nvidia gamepad acts as a bottom left trigger button.
+        values[StandardButtons.BOTTOM_LEFT_TRIGGER] = rawAxes[2];
+        values[StandardButtons.LEFT_TRIGGER] = rawButtons[4];
+        values[StandardButtons.RIGHT_TRIGGER] = rawButtons[5];
+        values[StandardButtons.SELECT] = rawButtons[6];
+        values[StandardButtons.START] = rawButtons[7];
+        values[StandardButtons.LEFT_THUMB] = rawButtons[8];
+        values[StandardButtons.RIGHT_THUMB] = rawButtons[9];
+        // Seventh axis on Nvidia gamepad acts as a bottom right trigger button.
+        values[StandardButtons.BOTTOM_RIGHT_TRIGGER] = rawAxes[6];
+        // Ninth axis on Nvidia gamepad acts as directional pad right and left button.
+        // Positive axis value indicates dpad right.
+        // Negative value indicates dpad left.
+        values[StandardButtons.DPAD_RIGHT] = positiveAxisValueAsButton(rawAxes[8]);
+        values[StandardButtons.DPAD_LEFT] = negativeAxisValueAsButton(rawAxes[8]);
+        // Tenth axis on Nvidia gamepad acts as directional pad up and down button.
+        // Positive axis value indicates dpad down.
+        // Negative value indicates dpad up.
+        values[StandardButtons.DPAD_DOWN] = positiveAxisValueAsButton(rawAxes[9]);
+        values[StandardButtons.DPAD_UP] = negativeAxisValueAsButton(rawAxes[9]);
+        // Other standard buttons are either not present on the gamepad or not exposed to an
+        // application.
+        values[StandardButtons.MODE] = 0.0f;
+        return values;
+    }
+
+    /**
+     * Method for mapping Microsoft XBox 360 gamepad axis values to
+     * standard gamepad axis values.
+     */
+    private static float[] mapXBox360Axes(float[] rawAxes) {
+        float[] values = new float[StandardAxes.MAX_AXES];
+        // Standard gamepad can have only four axes.
+        values[StandardAxes.AXIS_0] = rawAxes[0];
+        values[StandardAxes.AXIS_1] = rawAxes[1];
+        values[StandardAxes.AXIS_2] = rawAxes[4];
+        values[StandardAxes.AXIS_3] = rawAxes[5];
+        return values;
+    }
+
+    /**
+     * Method for mapping Microsoft XBox 360 gamepad axis and button values
+     * to standard gamepad button values.
+     */
+    private static float[] mapXBox360Buttons(float[] rawButtons, float[] rawAxes) {
+        float[] values = new float[StandardButtons.MAX_BUTTONS];
+        // First four buttons on Microsoft XBox 360 gamepad appear in correct order so no mapping
+        // is required.
+        values[StandardButtons.BUTTON_A] = rawButtons[0];
+        values[StandardButtons.BUTTON_B] = rawButtons[1];
+        values[StandardButtons.BUTTON_X] = rawButtons[2];
+        values[StandardButtons.BUTTON_Y] = rawButtons[3];
+        // Third axis on Microsoft XBox 360 gamepad acts as a left bottom shoulder button.
+        values[StandardButtons.BOTTOM_LEFT_TRIGGER] = rawAxes[2];
+        values[StandardButtons.LEFT_TRIGGER] = rawButtons[4];
+        values[StandardButtons.RIGHT_TRIGGER] = rawButtons[5];
+        values[StandardButtons.START] = rawButtons[6];
+        values[StandardButtons.LEFT_THUMB] = rawButtons[7];
+        values[StandardButtons.RIGHT_THUMB] = rawButtons[8];
+        // Seventh axis on Microsoft XBox 360 gamepad acts as a right bottom shoulder button.
+        values[StandardButtons.BOTTOM_RIGHT_TRIGGER] = rawAxes[6];
+        // Ninth axis on Microsoft XBox 360 gamepad acts as directional pad right and left button.
+        // Positive axis value indicates dpad right.
+        // Negative value indicates dpad left.
+        values[StandardButtons.DPAD_RIGHT] = positiveAxisValueAsButton(rawAxes[8]);
+        values[StandardButtons.DPAD_LEFT] = negativeAxisValueAsButton(rawAxes[8]);
+        // Tenth axis on Microsoft XBox 360 gamepad acts as directional pad up and down button.
+        // Positive axis value indicates dpad down.
+        // Negative value indicates dpad up.
+        values[StandardButtons.DPAD_DOWN] = positiveAxisValueAsButton(rawAxes[9]);
+        values[StandardButtons.DPAD_UP] = negativeAxisValueAsButton(rawAxes[9]);
+        // Other standard buttons are either not present on the gamepad or not exposed to an
+        // application.
+        values[StandardButtons.SELECT] = 0.0f;
+        values[StandardButtons.MODE] = 0.0f;
+        return values;
+    }
+
+}