core/input/util.js

   1 /* [module]
   2  * import KeyTable from "./keysym";
   3  * import keysyms from "./keysymdef";
   4  */
   5
   6 var KeyboardUtil = {};
   7
   8 (function() {
   9     "use strict";
  10
  11     function substituteCodepoint(cp) {
  12         // Any Unicode code points which do not have corresponding keysym entries
  13         // can be swapped out for another code point by adding them to this table
  14         var substitutions = {
  15             // {S,s} with comma below -> {S,s} with cedilla
  16             0x218 : 0x15e,
  17             0x219 : 0x15f,
  18             // {T,t} with comma below -> {T,t} with cedilla
  19             0x21a : 0x162,
  20             0x21b : 0x163
  21         };
  22
  23         var sub = substitutions[cp];
  24         return sub ? sub : cp;
  25     }
  26
  27     function isMac() {
  28         return navigator && !!(/mac/i).exec(navigator.platform);
  29     }
  30     function isWindows() {
  31         return navigator && !!(/win/i).exec(navigator.platform);
  32     }
  33     function isLinux() {
  34         return navigator && !!(/linux/i).exec(navigator.platform);
  35     }
  36
  37     // Return true if a modifier which is not the specified char modifier (and is not shift) is down
  38     function hasShortcutModifier(charModifier, currentModifiers) {
  39         var mods = {};
  40         for (var key in currentModifiers) {
  41             if (parseInt(key) !== KeyTable.XK_Shift_L) {
  42                 mods[key] = currentModifiers[key];
  43             }
  44         }
  45
  46         var sum = 0;
  47         for (var k in currentModifiers) {
  48             if (mods[k]) {
  49                 ++sum;
  50             }
  51         }
  52         if (hasCharModifier(charModifier, mods)) {
  53             return sum > charModifier.length;
  54         }
  55         else {
  56             return sum > 0;
  57         }
  58     }
  59
  60     // Return true if the specified char modifier is currently down
  61     function hasCharModifier(charModifier, currentModifiers) {
  62         if (charModifier.length === 0) { return false; }
  63
  64         for (var i = 0; i < charModifier.length; ++i) {
  65             if (!currentModifiers[charModifier[i]]) {
  66                 return false;
  67             }
  68         }
  69         return true;
  70     }
  71
  72     // Helper object tracking modifier key state
  73     // and generates fake key events to compensate if it gets out of sync
  74     function ModifierSync(charModifier) {
  75         if (!charModifier) {
  76             if (isMac()) {
  77                 // on Mac, Option (AKA Alt) is used as a char modifier
  78                 charModifier = [KeyTable.XK_Alt_L];
  79             }
  80             else if (isWindows()) {
  81                 // on Windows, Ctrl+Alt is used as a char modifier
  82                 charModifier = [KeyTable.XK_Alt_L, KeyTable.XK_Control_L];
  83             }
  84             else if (isLinux()) {
  85                 // on Linux, ISO Level 3 Shift (AltGr) is used as a char modifier
  86                 charModifier = [KeyTable.XK_ISO_Level3_Shift];
  87             }
  88             else {
  89                 charModifier = [];
  90             }
  91         }
  92
  93         var state = {};
  94         state[KeyTable.XK_Control_L] = false;
  95         state[KeyTable.XK_Alt_L] = false;
  96         state[KeyTable.XK_ISO_Level3_Shift] = false;
  97         state[KeyTable.XK_Shift_L] = false;
  98         state[KeyTable.XK_Meta_L] = false;
  99
 100         function sync(evt, keysym) {
 101             var result = [];
 102             function syncKey(keysym) {
 103                 return {keysym: keysyms.lookup(keysym), type: state[keysym] ? 'keydown' : 'keyup'};
 104             }
 105
 106             if (evt.ctrlKey !== undefined &&
 107                 evt.ctrlKey !== state[KeyTable.XK_Control_L] && keysym !== KeyTable.XK_Control_L) {
 108                 state[KeyTable.XK_Control_L] = evt.ctrlKey;
 109                 result.push(syncKey(KeyTable.XK_Control_L));
 110             }
 111             if (evt.altKey !== undefined &&
 112                 evt.altKey !== state[KeyTable.XK_Alt_L] && keysym !== KeyTable.XK_Alt_L) {
 113                 state[KeyTable.XK_Alt_L] = evt.altKey;
 114                 result.push(syncKey(KeyTable.XK_Alt_L));
 115             }
 116             if (evt.altGraphKey !== undefined &&
 117                 evt.altGraphKey !== state[KeyTable.XK_ISO_Level3_Shift] && keysym !== KeyTable.XK_ISO_Level3_Shift) {
 118                 state[KeyTable.XK_ISO_Level3_Shift] = evt.altGraphKey;
 119                 result.push(syncKey(KeyTable.XK_ISO_Level3_Shift));
 120             }
 121             if (evt.shiftKey !== undefined &&
 122                 evt.shiftKey !== state[KeyTable.XK_Shift_L] && keysym !== KeyTable.XK_Shift_L) {
 123                 state[KeyTable.XK_Shift_L] = evt.shiftKey;
 124                 result.push(syncKey(KeyTable.XK_Shift_L));
 125             }
 126             if (evt.metaKey !== undefined &&
 127                 evt.metaKey !== state[KeyTable.XK_Meta_L] && keysym !== KeyTable.XK_Meta_L) {
 128                 state[KeyTable.XK_Meta_L] = evt.metaKey;
 129                 result.push(syncKey(KeyTable.XK_Meta_L));
 130             }
 131             return result;
 132         }
 133         function syncKeyEvent(evt, down) {
 134             var obj = getKeysym(evt);
 135             var keysym = obj ? obj.keysym : null;
 136
 137             // first, apply the event itself, if relevant
 138             if (keysym !== null && state[keysym] !== undefined) {
 139                 state[keysym] = down;
 140             }
 141             return sync(evt, keysym);
 142         }
 143
 144         return {
 145             // sync on the appropriate keyboard event
 146             keydown: function(evt) { return syncKeyEvent(evt, true);},
 147             keyup: function(evt) { return syncKeyEvent(evt, false);},
 148             // Call this with a non-keyboard event (such as mouse events) to use its modifier state to synchronize anyway
 149             syncAny: function(evt) { return sync(evt);},
 150
 151             // is a shortcut modifier down?
 152             hasShortcutModifier: function() { return hasShortcutModifier(charModifier, state); },
 153             // if a char modifier is down, return the keys it consists of, otherwise return null
 154             activeCharModifier: function() { return hasCharModifier(charModifier, state) ? charModifier : null; }
 155         };
 156     }
 157
 158     // Get a key ID from a keyboard event
 159     // May be a string or an integer depending on the available properties
 160     function getKey(evt){
 161         if ('keyCode' in evt && 'key' in evt) {
 162             return evt.key + ':' + evt.keyCode;
 163         }
 164         else if ('keyCode' in evt) {
 165             return evt.keyCode;
 166         }
 167         else {
 168             return evt.key;
 169         }
 170     }
 171
 172     // Get the most reliable keysym value we can get from a key event
 173     // if char/charCode is available, prefer those, otherwise fall back to key/keyCode/which
 174     function getKeysym(evt){
 175         var codepoint;
 176         if (evt.char && evt.char.length === 1) {
 177             codepoint = evt.char.charCodeAt();
 178         }
 179         else if (evt.charCode) {
 180             codepoint = evt.charCode;
 181         }
 182         else if (evt.keyCode && evt.type === 'keypress') {
 183             // IE10 stores the char code as keyCode, and has no other useful properties
 184             codepoint = evt.keyCode;
 185         }
 186         if (codepoint) {
 187             return keysyms.fromUnicode(substituteCodepoint(codepoint));
 188         }
 189         // we could check evt.key here.
 190         // Legal values are defined in http://www.w3.org/TR/DOM-Level-3-Events/#key-values-list,
 191         // so we "just" need to map them to keysym, but AFAIK this is only available in IE10, which also provides evt.key
 192         // so we don't *need* it yet
 193         if (evt.keyCode) {
 194             return keysyms.lookup(keysymFromKeyCode(evt.keyCode, evt.shiftKey));
 195         }
 196         if (evt.which) {
 197             return keysyms.lookup(keysymFromKeyCode(evt.which, evt.shiftKey));
 198         }
 199         return null;
 200     }
 201
 202     // Given a keycode, try to predict which keysym it might be.
 203     // If the keycode is unknown, null is returned.
 204     function keysymFromKeyCode(keycode, shiftPressed) {
 205         if (typeof(keycode) !== 'number') {
 206             return null;
 207         }
 208         // won't be accurate for azerty
 209         if (keycode >= 0x30 && keycode <= 0x39) {
 210             return keycode; // digit
 211         }
 212         if (keycode >= 0x41 && keycode <= 0x5a) {
 213             // remap to lowercase unless shift is down
 214             return shiftPressed ? keycode : keycode + 32; // A-Z
 215         }
 216         if (keycode >= 0x60 && keycode <= 0x69) {
 217             return KeyTable.XK_KP_0 + (keycode - 0x60); // numpad 0-9
 218         }
 219
 220         switch(keycode) {
 221             case 0x20: return KeyTable.XK_space;
 222             case 0x6a: return KeyTable.XK_KP_Multiply;
 223             case 0x6b: return KeyTable.XK_KP_Add;
 224             case 0x6c: return KeyTable.XK_KP_Separator;
 225             case 0x6d: return KeyTable.XK_KP_Subtract;
 226             case 0x6e: return KeyTable.XK_KP_Decimal;
 227             case 0x6f: return KeyTable.XK_KP_Divide;
 228             case 0xbb: return KeyTable.XK_plus;
 229             case 0xbc: return KeyTable.XK_comma;
 230             case 0xbd: return KeyTable.XK_minus;
 231             case 0xbe: return KeyTable.XK_period;
 232         }
 233
 234         return nonCharacterKey({keyCode: keycode});
 235     }
 236
 237     // if the key is a known non-character key (any key which doesn't generate character data)
 238     // return its keysym value. Otherwise return null
 239     function nonCharacterKey(evt) {
 240         // evt.key not implemented yet
 241         if (!evt.keyCode) { return null; }
 242         var keycode = evt.keyCode;
 243
 244         if (keycode >= 0x70 && keycode <= 0x87) {
 245             return KeyTable.XK_F1 + keycode - 0x70; // F1-F24
 246         }
 247         switch (keycode) {
 248
 249             case 8 : return KeyTable.XK_BackSpace;
 250             case 13 : return KeyTable.XK_Return;
 251
 252             case 9 : return KeyTable.XK_Tab;
 253
 254             case 27 : return KeyTable.XK_Escape;
 255             case 46 : return KeyTable.XK_Delete;
 256
 257             case 36 : return KeyTable.XK_Home;
 258             case 35 : return KeyTable.XK_End;
 259             case 33 : return KeyTable.XK_Page_Up;
 260             case 34 : return KeyTable.XK_Page_Down;
 261             case 45 : return KeyTable.XK_Insert;
 262
 263             case 37 : return KeyTable.XK_Left;
 264             case 38 : return KeyTable.XK_Up;
 265             case 39 : return KeyTable.XK_Right;
 266             case 40 : return KeyTable.XK_Down;
 267
 268             case 16 : return KeyTable.XK_Shift_L;
 269             case 17 : return KeyTable.XK_Control_L;
 270             case 18 : return KeyTable.XK_Alt_L; // also: Option-key on Mac
 271
 272             case 224 : return KeyTable.XK_Meta_L;
 273             case 225 : return KeyTable.XK_ISO_Level3_Shift; // AltGr
 274             case 91 : return KeyTable.XK_Super_L; // also: Windows-key
 275             case 92 : return KeyTable.XK_Super_R; // also: Windows-key
 276             case 93 : return KeyTable.XK_Menu; // also: Windows-Menu, Command on Mac
 277             default: return null;
 278         }
 279     }
 280
 281     KeyboardUtil.hasShortcutModifier = hasShortcutModifier;
 282     KeyboardUtil.hasCharModifier = hasCharModifier;
 283     KeyboardUtil.ModifierSync = ModifierSync;
 284     KeyboardUtil.getKey = getKey;
 285     KeyboardUtil.getKeysym = getKeysym;
 286     KeyboardUtil.keysymFromKeyCode = keysymFromKeyCode;
 287     KeyboardUtil.nonCharacterKey = nonCharacterKey;
 288     KeyboardUtil.substituteCodepoint = substituteCodepoint;
 289 })();
 290
 291 KeyboardUtil.QEMUKeyEventDecoder = function(modifierState, next) {
 292     "use strict";
 293
 294     function sendAll(evts) {
 295         for (var i = 0; i < evts.length; ++i) {
 296             next(evts[i]);
 297         }
 298     }
 299
 300     var numPadCodes = ["Numpad0", "Numpad1", "Numpad2",
 301         "Numpad3", "Numpad4", "Numpad5", "Numpad6",
 302         "Numpad7", "Numpad8", "Numpad9", "NumpadDecimal"];
 303
 304     var numLockOnKeySyms = {
 305         "Numpad0": 0xffb0, "Numpad1": 0xffb1, "Numpad2": 0xffb2,
 306         "Numpad3": 0xffb3, "Numpad4": 0xffb4, "Numpad5": 0xffb5,
 307         "Numpad6": 0xffb6, "Numpad7": 0xffb7, "Numpad8": 0xffb8,
 308         "Numpad9": 0xffb9, "NumpadDecimal": 0xffac
 309     };
 310
 311     var numLockOnKeyCodes = [96, 97, 98, 99, 100, 101, 102,
 312         103, 104, 105, 108, 110];
 313
 314     function isNumPadMultiKey(evt) {
 315         return (numPadCodes.indexOf(evt.code) !== -1);
 316     }
 317
 318     function getNumPadKeySym(evt) {
 319         if (numLockOnKeyCodes.indexOf(evt.keyCode) !== -1) {
 320             return numLockOnKeySyms[evt.code];
 321         }
 322         return 0;
 323     }
 324
 325     function process(evt, type) {
 326         var result = {type: type};
 327         result.code = evt.code;
 328         result.keysym = 0;
 329
 330         if (isNumPadMultiKey(evt)) {
 331             result.keysym = getNumPadKeySym(evt);
 332         }
 333
 334         var hasModifier = modifierState.hasShortcutModifier() || !!modifierState.activeCharModifier();
 335         var isShift = evt.keyCode === 0x10 || evt.key === 'Shift';
 336
 337         var suppress = !isShift && (type !== 'keydown' || modifierState.hasShortcutModifier() || !!KeyboardUtil.nonCharacterKey(evt));
 338
 339         next(result);
 340         return suppress;
 341     }
 342     return {
 343         keydown: function(evt) {
 344             sendAll(modifierState.keydown(evt));
 345             return process(evt, 'keydown');
 346         },
 347         keypress: function(evt) {
 348             return true;
 349         },
 350         keyup: function(evt) {
 351             sendAll(modifierState.keyup(evt));
 352             return process(evt, 'keyup');
 353         },
 354         syncModifiers: function(evt) {
 355             sendAll(modifierState.syncAny(evt));
 356         },
 357         releaseAll: function() { next({type: 'releaseall'}); }
 358     };
 359 };
 360
 361 KeyboardUtil.TrackQEMUKeyState = function(next) {
 362     "use strict";
 363     var state = [];
 364
 365     return function (evt) {
 366         var last = state.length !== 0 ? state[state.length-1] : null;
 367
 368         switch (evt.type) {
 369         case 'keydown':
 370
 371             if (!last || last.code !== evt.code) {
 372                 last = {code: evt.code};
 373
 374                 if (state.length > 0 && state[state.length-1].code == 'ControlLeft') {
 375                      if (evt.code !== 'AltRight') {
 376                          next({code: 'ControlLeft', type: 'keydown', keysym: 0});
 377                      } else {
 378                          state.pop();
 379                      }
 380                 }
 381                 state.push(last);
 382             }
 383             if (evt.code !== 'ControlLeft') {
 384                 next(evt);
 385             }
 386             break;
 387
 388         case 'keyup':
 389             if (state.length === 0) {
 390                 return;
 391             }
 392             var idx = null;
 393             // do we have a matching key tracked as being down?
 394             for (var i = 0; i !== state.length; ++i) {
 395                 if (state[i].code === evt.code) {
 396                     idx = i;
 397                     break;
 398                 }
 399             }
 400             // if we couldn't find a match (it happens), assume it was the last key pressed
 401             if (idx === null) {
 402                 if (evt.code === 'ControlLeft') {
 403                     return;
 404                 }
 405                 idx = state.length - 1;
 406             }
 407
 408             state.splice(idx, 1);
 409             next(evt);
 410             break;
 411         case 'releaseall':
 412             /* jshint shadow: true */
 413             for (var i = 0; i < state.length; ++i) {
 414                 next({code: state[i].code, keysym: 0, type: 'keyup'});
 415             }
 416             /* jshint shadow: false */
 417             state = [];
 418         }
 419     };
 420 };
 421
 422 // Takes a DOM keyboard event and:
 423 // - determines which keysym it represents
 424 // - determines a keyId  identifying the key that was pressed (corresponding to the key/keyCode properties on the DOM event)
 425 // - synthesizes events to synchronize modifier key state between which modifiers are actually down, and which we thought were down
 426 // - marks each event with an 'escape' property if a modifier was down which should be "escaped"
 427 // - generates a "stall" event in cases where it might be necessary to wait and see if a keypress event follows a keydown
 428 // This information is collected into an object which is passed to the next() function. (one call per event)
 429 KeyboardUtil.KeyEventDecoder = function(modifierState, next) {
 430     "use strict";
 431     function sendAll(evts) {
 432         for (var i = 0; i < evts.length; ++i) {
 433             next(evts[i]);
 434         }
 435     }
 436     function process(evt, type) {
 437         var result = {type: type};
 438         var keyId = KeyboardUtil.getKey(evt);
 439         if (keyId) {
 440             result.keyId = keyId;
 441         }
 442
 443         var keysym = KeyboardUtil.getKeysym(evt);
 444
 445         var hasModifier = modifierState.hasShortcutModifier() || !!modifierState.activeCharModifier();
 446         // Is this a case where we have to decide on the keysym right away, rather than waiting for the keypress?
 447         // "special" keys like enter, tab or backspace don't send keypress events,
 448         // and some browsers don't send keypresses at all if a modifier is down
 449         if (keysym && (type !== 'keydown' || KeyboardUtil.nonCharacterKey(evt) || hasModifier)) {
 450             result.keysym = keysym;
 451         }
 452
 453         var isShift = evt.keyCode === 0x10 || evt.key === 'Shift';
 454
 455         // Should we prevent the browser from handling the event?
 456         // Doing so on a keydown (in most browsers) prevents keypress from being generated
 457         // so only do that if we have to.
 458         var suppress = !isShift && (type !== 'keydown' || modifierState.hasShortcutModifier() || !!KeyboardUtil.nonCharacterKey(evt));
 459
 460         // If a char modifier is down on a keydown, we need to insert a stall,
 461         // so VerifyCharModifier knows to wait and see if a keypress is comnig
 462         var stall = type === 'keydown' && modifierState.activeCharModifier() && !KeyboardUtil.nonCharacterKey(evt);
 463
 464         // if a char modifier is pressed, get the keys it consists of (on Windows, AltGr is equivalent to Ctrl+Alt)
 465         var active = modifierState.activeCharModifier();
 466
 467         // If we have a char modifier down, and we're able to determine a keysym reliably
 468         // then (a) we know to treat the modifier as a char modifier,
 469         // and (b) we'll have to "escape" the modifier to undo the modifier when sending the char.
 470         if (active && keysym) {
 471             var isCharModifier = false;
 472             for (var i  = 0; i < active.length; ++i) {
 473                 if (active[i] === keysym.keysym) {
 474                     isCharModifier = true;
 475                 }
 476             }
 477             if (type === 'keypress' && !isCharModifier) {
 478                 result.escape = modifierState.activeCharModifier();
 479             }
 480         }
 481
 482         if (stall) {
 483             // insert a fake "stall" event
 484             next({type: 'stall'});
 485         }
 486         next(result);
 487
 488         return suppress;
 489     }
 490
 491     return {
 492         keydown: function(evt) {
 493             sendAll(modifierState.keydown(evt));
 494             return process(evt, 'keydown');
 495         },
 496         keypress: function(evt) {
 497             return process(evt, 'keypress');
 498         },
 499         keyup: function(evt) {
 500             sendAll(modifierState.keyup(evt));
 501             return process(evt, 'keyup');
 502         },
 503         syncModifiers: function(evt) {
 504             sendAll(modifierState.syncAny(evt));
 505         },
 506         releaseAll: function() { next({type: 'releaseall'}); }
 507     };
 508 };
 509
 510 // Combines keydown and keypress events where necessary to handle char modifiers.
 511 // On some OS'es, a char modifier is sometimes used as a shortcut modifier.
 512 // For example, on Windows, AltGr is synonymous with Ctrl-Alt. On a Danish keyboard layout, AltGr-2 yields a @, but Ctrl-Alt-D does nothing
 513 // so when used with the '2' key, Ctrl-Alt counts as a char modifier (and should be escaped), but when used with 'D', it does not.
 514 // The only way we can distinguish these cases is to wait and see if a keypress event arrives
 515 // When we receive a "stall" event, wait a few ms before processing the next keydown. If a keypress has also arrived, merge the two
 516 KeyboardUtil.VerifyCharModifier = function(next) {
 517     "use strict";
 518     var queue = [];
 519     var timer = null;
 520     function process() {
 521         if (timer) {
 522             return;
 523         }
 524
 525         var delayProcess = function () {
 526             clearTimeout(timer);
 527             timer = null;
 528             process();
 529         };
 530
 531         while (queue.length !== 0) {
 532             var cur = queue[0];
 533             queue = queue.splice(1);
 534             switch (cur.type) {
 535             case 'stall':
 536                 // insert a delay before processing available events.
 537                 /* jshint loopfunc: true */
 538                 timer = setTimeout(delayProcess, 5);
 539                 /* jshint loopfunc: false */
 540                 return;
 541             case 'keydown':
 542                 // is the next element a keypress? Then we should merge the two
 543                 if (queue.length !== 0 && queue[0].type === 'keypress') {
 544                     // Firefox sends keypress even when no char is generated.
 545                     // so, if keypress keysym is the same as we'd have guessed from keydown,
 546                     // the modifier didn't have any effect, and should not be escaped
 547                     if (queue[0].escape && (!cur.keysym || cur.keysym.keysym !== queue[0].keysym.keysym)) {
 548                         cur.escape = queue[0].escape;
 549                     }
 550                     cur.keysym = queue[0].keysym;
 551                     queue = queue.splice(1);
 552                 }
 553                 break;
 554             }
 555
 556             // swallow stall events, and pass all others to the next stage
 557             if (cur.type !== 'stall') {
 558                 next(cur);
 559             }
 560         }
 561     }
 562     return function(evt) {
 563         queue.push(evt);
 564         process();
 565     };
 566 };
 567
 568 // Keeps track of which keys we (and the server) believe are down
 569 // When a keyup is received, match it against this list, to determine the corresponding keysym(s)
 570 // in some cases, a single key may produce multiple keysyms, so the corresponding keyup event must release all of these chars
 571 // key repeat events should be merged into a single entry.
 572 // Because we can't always identify which entry a keydown or keyup event corresponds to, we sometimes have to guess
 573 KeyboardUtil.TrackKeyState = function(next) {
 574     "use strict";
 575     var state = [];
 576
 577     return function (evt) {
 578         var last = state.length !== 0 ? state[state.length-1] : null;
 579
 580         switch (evt.type) {
 581         case 'keydown':
 582             // insert a new entry if last seen key was different.
 583             if (!last || !evt.keyId || last.keyId !== evt.keyId) {
 584                 last = {keyId: evt.keyId, keysyms: {}};
 585                 state.push(last);
 586             }
 587             if (evt.keysym) {
 588                 // make sure last event contains this keysym (a single "logical" keyevent
 589                 // can cause multiple key events to be sent to the VNC server)
 590                 last.keysyms[evt.keysym.keysym] = evt.keysym;
 591                 last.ignoreKeyPress = true;
 592                 next(evt);
 593             }
 594             break;
 595         case 'keypress':
 596             if (!last) {
 597                 last = {keyId: evt.keyId, keysyms: {}};
 598                 state.push(last);
 599             }
 600             if (!evt.keysym) {
 601                 console.log('keypress with no keysym:', evt);
 602             }
 603
 604             // If we didn't expect a keypress, and already sent a keydown to the VNC server
 605             // based on the keydown, make sure to skip this event.
 606             if (evt.keysym && !last.ignoreKeyPress) {
 607                 last.keysyms[evt.keysym.keysym] = evt.keysym;
 608                 evt.type = 'keydown';
 609                 next(evt);
 610             }
 611             break;
 612         case 'keyup':
 613             if (state.length === 0) {
 614                 return;
 615             }
 616             var idx = null;
 617             // do we have a matching key tracked as being down?
 618             for (var i = 0; i !== state.length; ++i) {
 619                 if (state[i].keyId === evt.keyId) {
 620                     idx = i;
 621                     break;
 622                 }
 623             }
 624             // if we couldn't find a match (it happens), assume it was the last key pressed
 625             if (idx === null) {
 626                 idx = state.length - 1;
 627             }
 628
 629             var item = state.splice(idx, 1)[0];
 630             // for each keysym tracked by this key entry, clone the current event and override the keysym
 631             var clone = (function(){
 632                 function Clone(){}
 633                 return function (obj) { Clone.prototype=obj; return new Clone(); };
 634             }());
 635             for (var key in item.keysyms) {
 636                 var out = clone(evt);
 637                 out.keysym = item.keysyms[key];
 638                 next(out);
 639             }
 640             break;
 641         case 'releaseall':
 642             /* jshint shadow: true */
 643             for (var i = 0; i < state.length; ++i) {
 644                 for (var key in state[i].keysyms) {
 645                     var keysym = state[i].keysyms[key];
 646                     next({keyId: 0, keysym: keysym, type: 'keyup'});
 647                 }
 648             }
 649             /* jshint shadow: false */
 650             state = [];
 651         }
 652     };
 653 };
 654
 655 // Handles "escaping" of modifiers: if a char modifier is used to produce a keysym (such as AltGr-2 to generate an @),
 656 // then the modifier must be "undone" before sending the @, and "redone" afterwards.
 657 KeyboardUtil.EscapeModifiers = function(next) {
 658     "use strict";
 659     return function(evt) {
 660         if (evt.type !== 'keydown' || evt.escape === undefined) {
 661             next(evt);
 662             return;
 663         }
 664         // undo modifiers
 665         for (var i = 0; i < evt.escape.length; ++i) {
 666             next({type: 'keyup', keyId: 0, keysym: keysyms.lookup(evt.escape[i])});
 667         }
 668         // send the character event
 669         next(evt);
 670         // redo modifiers
 671         /* jshint shadow: true */
 672         for (var i = 0; i < evt.escape.length; ++i) {
 673             next({type: 'keydown', keyId: 0, keysym: keysyms.lookup(evt.escape[i])});
 674         }
 675         /* jshint shadow: false */
 676     };
 677 };
 678
 679 /* [module] export default KeyboardUtil; */