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) {

[bajones, 2014/02/28 23:56:11]

The way this is set up now feels like it will be awkward to maintain going
forward. I'd prefer to see it work similarly to the desktop mapping code (see
gamepad_standard_mappings_linux.cc as an example.) We should be able to retrieve
a mapping interface on device connection by passing a device identifier (name or
vendor/product id) to a factory method. Then the mapper interface can be called
abstractly from GamepadDevice without bouncing through multiple switch
statements.    

[SaurabhK, 2014/03/11 17:39:27]

On 2014/02/28 23:56:11, bajones wrote:

The new patchset now retrieves by passing device name. For more accuracy there
is additional comparision for raw buttons and raw axes on the gamepad device.

+        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];
+        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;
+    }
+
+}