src/ext/gamepad.js

   1 (function () {
   2     "use strict";
   3     /** DOM Event shim for Web Gamepad API
   4         https://dvcs.w3.org/hg/gamepad/raw-file/default/gamepad.html
   5
   6         This adds three new custom events to the window object:
   7
   8         yuugamepadbuttondown, yuugamepadbuttonup
   9             Dispatched when a button on a gamepad is pressed
  10             or released.
  11
  12             .detail.gamepad - the Gamepad instance with the button
  13             .detail.button - the numeric index of the button
  14             .detail.mapped - true if the button is known to fit the
  15                              "standard" mapping, even if gamepad.mapping
  16                              says otherwise
  17
  18         yuugamepadaxismove
  19             Dispatched when an axis on a gamepad changes.
  20
  21             .detail.gamepad - the Gamepad instance with the axis
  22             .detail.axis - the numeric index of the axis
  23             .detail.value - the value of the axis
  24             .detail.mapped - true if the axis is known to fit the
  25                              "standard" mapping, even if gamepad.mapping
  26                              says otherwise
  27
  28         It also polyfills navigator.getGamepads.
  29
  30         Including this file (e.g. in a <script> tag) is all that's
  31         necessary to enable these.
  32
  33         Because the underlying API is poll-based, events will be
  34         dispatched at most at the animation refresh rate. Inputs that
  35         exist for less than this time may be dropped.
  36      */
  37
  38     function empty () { return []; }
  39
  40     if (!navigator.getGamepads)
  41         navigator.getGamepads = (
  42             navigator.webkitGetGamepads
  43             || navigator.mozGetGamepads
  44             || empty);
  45     if (navigator.getGamepads === empty)
  46         return;
  47
  48     var requestFrame = window.requestAnimationFrame
  49         || window.mozRequestAnimationFrame
  50         || window.webkitRequestAnimationFrame;
  51
  52     var PLATFORM = (navigator.platform || "Unknown") + ".";
  53
  54     var MAPPINGS = {
  55         // Maps the logical controller button/axis (the index) to the
  56         // equivalent standard controller button/axis (the value),
  57         // based on ID.
  58         //
  59         // This needs to be keyed to the underlying platform as well
  60         // because mapping varies based on the USB stack in question.
  61         // In theory this can go as far as multiple drivers for one OS
  62         // with different mappings, but most platforms / devices have
  63         // one canonical driver.
  64         'MacIntel.54c-268-PLAYSTATION(R)3 Controller': {
  65             buttons: [8, 10, 11, 9, 12, 15, 13, 14, 6, 7,
  66                       4, 5, 3, 1, 0, 2, 16],
  67             axes: [0, 1, 2, 3]
  68         }
  69     };
  70
  71     var states = {};
  72
  73     function isPressed (button) {
  74         return isFinite(button) ? button > 0.1 : button.pressed;
  75     }
  76
  77     function isAppropriateState (state, gamepad) {
  78         return state
  79             && state.id === gamepad.id
  80             && state.buttons.length === gamepad.buttons.length
  81             && state.axes.length === gamepad.axes.length;
  82     }
  83
  84     function makeState (gamepad) {
  85         var buttons = [];
  86         for (var i = 0; i < gamepad.buttons.length; ++i)
  87             buttons.push(isPressed(gamepad.buttons[i]));
  88         return {
  89             buttons: buttons,
  90             axes: gamepad.axes.slice(),
  91             id: gamepad.id
  92         };
  93     }
  94
  95     function getState (gamepad) {
  96         var state = states[gamepad.index];
  97         // Browsers that do not support the connected/disconnected
  98         // events will silently swap in a new gamepad. Try to detect
  99         // that and reset the state.
 100         if (!isAppropriateState(state, gamepad))
 101             state = states[gamepad.index] = makeState(gamepad);
 102         return state;
 103     }
 104
 105     function connected (event) {
 106         states[event.gamepad.index] = makeState(event.gamepad);
 107     }
 108
 109     function disconnected (event) {
 110         delete states[event.gamepad.index];
 111     }
 112
 113     function buttonEvent (gamepad, button, pressed) {
 114         var mapping = MAPPINGS[PLATFORM + gamepad.id];
 115         var mapped = gamepad.mapping === "standard" || !!mapping;
 116         if (gamepad.mapping !== "standard" && mapping)
 117             button = mapping.buttons[button];
 118
 119         return new CustomEvent(
 120             pressed ? 'yuugamepadbuttondown' : 'yuugamepadbuttonup',
 121             { detail: { gamepad: gamepad, mapped: mapped, button: button } });
 122     }
 123
 124     function axisEvent (gamepad, axis, value) {
 125         var mapping = MAPPINGS[PLATFORM + gamepad.id];
 126         var mapped = gamepad.mapping === "standard" || !!mapping;
 127         if (gamepad.mapping !== "standard" && mapping)
 128             axis = mapping.axes[axis];
 129
 130         return new CustomEvent(
 131             'yuugamepadaxismove',
 132             { detail: { gamepad: gamepad, mapped: mapped,
 133                         axis: axis, value: value } });
 134     }
 135
 136     function pumpGamepad (gamepad) {
 137         var state = getState(gamepad);
 138         for (var b = 0; b < gamepad.buttons.length; ++b) {
 139             var wasPressed = isPressed(state.buttons[b]);
 140             var nowPressed = isPressed(gamepad.buttons[b]);
 141             if (wasPressed !== nowPressed) {
 142                 state.buttons[b] = nowPressed;
 143                 window.dispatchEvent(buttonEvent(gamepad, b, nowPressed));
 144             }
 145         }
 146         for (var a = 0; a < gamepad.axes.length; ++a) {
 147             if (gamepad.axes[a] !== state.axes[a]) {
 148                 var value = state.axes[a] = gamepad.axes[a];
 149                 window.dispatchEvent(axisEvent(gamepad, a, value));
 150             }
 151         }
 152     }
 153
 154     function pump () {
 155         var gamepads = navigator.getGamepads();
 156         for (var i = 0; i < gamepads.length; ++i) {
 157             var gamepad = gamepads[i];
 158             if (!gamepad)
 159                 continue;
 160             pumpGamepad(gamepad);
 161         }
 162     }
 163
 164     requestFrame.call(window, function _ () {
 165         pump();
 166         requestFrame.call(window, _);
 167     });
 168
 169     window.addEventListener('gamepadconnected', connected);
 170     window.addEventListener('gamepaddisconnected', disconnected);
 171
 172 })();