Keyboard Handling [2/8]: Core implementation of new keyboard handling

Add keyboard.js, containing the actual keyboard event parsing code.

include/keyboard.js

+var kbdUtil = (function() {
+    "use strict";
+
+    function isMac() {
+        return navigator && !!(/macintosh/i).exec(navigator.appVersion);
+    }
+    function isWindows() {
+        return navigator && !!(/windows/i).exec(navigator.appVersion);
+    }
+    function isLinux() {
+        return navigator && !!(/linux/i).exec(navigator.appVersion);
+    }
+
+    // Return true if a modifier which is not the specified char modifier (and is not shift) is down
+    function hasShortcutModifier(charModifier, currentModifiers) {
+        var mods = {};
+        for (var key in currentModifiers) {
+            if (key !== 0xffe1) {
+                mods[key] = currentModifiers[key];
+            }
+        }
+
+        var sum = 0;
+        for (var k in currentModifiers) {
+            if (mods[k]) {
+                ++sum;
+            }
+        }
+        if (hasCharModifier(charModifier, mods)) {
+            return sum > charModifier.length;
+        }
+        else {
+            return sum > 0;
+        }
+    }
+
+    // Return true if the specified char modifier is currently down
+    function hasCharModifier(charModifier, currentModifiers) {
+        if (charModifier.length === 0) { return false; }
+
+        for (var i = 0; i < charModifier.length; ++i) {
+            if (!currentModifiers[charModifier[i]]) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    // Helper object tracking modifier key state
+    // and generates fake key events to compensate if it gets out of sync
+    function ModifierSync(charModifier) {
+        var ctrl = 0xffe3;
+        var alt = 0xffe9;
+        var altGr = 0xfe03;
+        var shift = 0xffe1;
+        var meta = 0xffe7;
+
+        if (!charModifier) {
+            if (isMac()) {
+                // on Mac, Option (AKA Alt) is used as a char modifier
+                charModifier = [alt];
+            }
+            else if (isWindows()) {
+                // on Windows, Ctrl+Alt is used as a char modifier
+                charModifier = [alt, ctrl];
+            }
+            else if (isLinux()) {
+                // on Linux, AltGr is used as a char modifier
+                charModifier = [altGr];
+            }
+            else {
+                charModifier = [];
+            }
+        }
+
+        var state = {};
+        state[ctrl] = false;
+        state[alt] = false;
+        state[altGr] = false;
+        state[shift] = false;
+        state[meta] = false;
+
+        function sync(evt, keysym) {
+            var result = [];
+            function syncKey(keysym) {
+                return {keysym: keysyms.lookup(keysym), type: state[keysym] ? 'keydown' : 'keyup'};
+            }
+
+            if (evt.ctrlKey !== undefined && evt.ctrlKey !== state[ctrl] && keysym !== ctrl) {
+                state[ctrl] = evt.ctrlKey;
+                result.push(syncKey(ctrl));
+            }
+            if (evt.altKey !== undefined && evt.altKey !== state[alt] && keysym !== alt) {
+                state[alt] = evt.altKey;
+                result.push(syncKey(alt));
+            }
+            if (evt.altGraphKey !== undefined && evt.altGraphKey !== state[altGr] && keysym !== altGr) {
+                state[altGr] = evt.altGraphKey;
+                result.push(syncKey(altGr));
+            }
+            if (evt.shiftKey !== undefined && evt.shiftKey !== state[shift] && keysym !== shift) {
+                state[shift] = evt.shiftKey;
+                result.push(syncKey(shift));
+            }
+            if (evt.metaKey !== undefined && evt.metaKey !== state[meta] && keysym !== meta) {
+                state[meta] = evt.metaKey;
+                result.push(syncKey(meta));
+            }
+            return result;
+        }
+        function syncKeyEvent(evt, down) {
+            var obj = getKeysym(evt);
+            var keysym = obj ? obj.keysym : null;
+
+            // first, apply the event itself, if relevant
+            if (keysym !== null && state[keysym] !== undefined) {
+                state[keysym] = down;
+            }
+            return sync(evt, keysym);
+        }
+
+        return {
+            // sync on the appropriate keyboard event
+            keydown: function(evt) { return syncKeyEvent(evt, true);},
+            keyup: function(evt) { return syncKeyEvent(evt, false);},
+            // Call this with a non-keyboard event (such as mouse events) to use its modifier state to synchronize anyway
+            syncAny: function(evt) { return sync(evt);},
+
+            // is a shortcut modifier down?
+            hasShortcutModifier: function() { return hasShortcutModifier(charModifier, state); },
+            // if a char modifier is down, return the keys it consists of, otherwise return null
+            activeCharModifier: function() { return hasCharModifier(charModifier, state) ? charModifier : null; }
+        };
+    }
+
+    // Get a key ID from a keyboard event
+    // May be a string or an integer depending on the available properties
+    function getKey(evt){
+        if (evt.key) {
+            return evt.key;
+        }
+        else {
+            return evt.keyCode;
+        }
+    }
+
+    // Get the most reliable keysym value we can get from a key event
+    // if char/charCode is available, prefer those, otherwise fall back to key/keyCode/which
+    function getKeysym(evt){
+        var codepoint;
+        if (evt.char && evt.char.length === 1) {
+            codepoint = evt.char.charCodeAt();
+        }
+        else if (evt.charCode) {
+            codepoint = evt.charCode;
+        }
+
+        if (codepoint) {
+            var res = keysyms.fromUnicode(codepoint);
+            if (res) {
+                return res;
+            }
+        }
+        // we could check evt.key here.
+        // Legal values are defined in http://www.w3.org/TR/DOM-Level-3-Events/#key-values-list,
+        // so we "just" need to map them to keysym, but AFAIK this is only available in IE10, which also provides evt.key
+        // so we don't *need* it yet
+        if (evt.keyCode) {
+            return keysyms.lookup(keysymFromKeyCode(evt.keyCode, evt.shiftKey));
+        }
+        if (evt.which) {
+            return keysyms.lookup(keysymFromKeyCode(evt.which, evt.shiftKey));
+        }
+        return null;
+    }
+
+    // Given a keycode, try to predict which keysym it might be.
+    // If the keycode is unknown, null is returned.
+    function keysymFromKeyCode(keycode, shiftPressed) {
+        if (typeof(keycode) !== 'number') {
+            return null;
+        }
+        // won't be accurate for azerty
+        if (keycode >= 0x30 && keycode <= 0x39) {
+            return keycode; // digit
+        }
+        if (keycode >= 0x41 && keycode <= 0x5a) {
+            // remap to lowercase unless shift is down
+            return shiftPressed ? keycode : keycode + 32; // A-Z
+        }
+        if (keycode >= 0x60 && keycode <= 0x69) {
+            return 0xffb0 + (keycode - 0x60); // numpad 0-9
+        }
+
+        switch(keycode) {
+            case 0x20: return 0x20; // space
+            case 0x6a: return 0xffaa; // multiply
+            case 0x6b: return 0xffab; // add
+            case 0x6c: return 0xffac; // separator
+            case 0x6d: return 0xffad; // subtract
+            case 0x6e: return 0xffae; // decimal
+            case 0x6f: return 0xffaf; // divide
+            case 0xbb: return 0x2b; // +
+            case 0xbc: return 0x2c; // ,
+            case 0xbd: return 0x2d; // -
+            case 0xbe: return 0x2e; // .
+        }
+
+        return nonCharacterKey({keyCode: keycode});
+    }
+
+    // if the key is a known non-character key (any key which doesn't generate character data)
+    // return its keysym value. Otherwise return null
+    function nonCharacterKey(evt) {
+        // evt.key not implemented yet
+        if (!evt.keyCode) { return null; }
+        var keycode = evt.keyCode;
+
+        if (keycode >= 0x70 && keycode <= 0x87) {
+            return 0xffbe + keycode - 0x70; // F1-F24
+        }
+        switch (keycode) {
+
+            case 8 : return 0xFF08; // BACKSPACE
+            case 13 : return 0xFF0D; // ENTER
+
+            case 9 : return 0xFF09; // TAB
+
+            case 27 : return 0xFF1B; // ESCAPE
+            case 46 : return 0xFFFF; // DELETE
+
+            case 36 : return 0xFF50; // HOME
+            case 35 : return 0xFF57; // END
+            case 33 : return 0xFF55; // PAGE_UP
+            case 34 : return 0xFF56; // PAGE_DOWN
+            case 45 : return 0xFF63; // INSERT
+
+            case 37 : return 0xFF51; // LEFT
+            case 38 : return 0xFF52; // UP
+            case 39 : return 0xFF53; // RIGHT
+            case 40 : return 0xFF54; // DOWN
+            case 16 : return 0xFFE1; // SHIFT
+            case 17 : return 0xFFE3; // CONTROL
+            case 18 : return 0xFFE9; // Left ALT (Mac Option)
+
+            case 224 : return 0xFE07; // Meta
+            case 225 : return 0xFE03; // AltGr
+            case 91 : return 0xFFEC; // Super_L (Win Key)
+            case 92 : return 0xFFED; // Super_R (Win Key)
+            case 93 : return 0xFF67; // Menu (Win Menu), Mac Command
+            default: return null;
+        }
+    }
+    return {
+        hasShortcutModifier : hasShortcutModifier,
+        hasCharModifier :  hasCharModifier,
+        ModifierSync : ModifierSync,
+        getKey : getKey,
+        getKeysym : getKeysym,
+        keysymFromKeyCode : keysymFromKeyCode,
+        nonCharacterKey : nonCharacterKey
+    };
+})();
+
+// Takes a DOM keyboard event and:
+// - determines which keysym it represents
+// - determines a keyId  identifying the key that was pressed (corresponding to the key/keyCode properties on the DOM event)
+// - synthesizes events to synchronize modifier key state between which modifiers are actually down, and which we thought were down
+// - marks each event with an 'escape' property if a modifier was down which should be "escaped"
+// - generates a "stall" event in cases where it might be necessary to wait and see if a keypress event follows a keydown
+// This information is collected into an object which is passed to the next() function. (one call per event)
+function KeyEventDecoder(modifierState, next) {
+    "use strict";
+    function sendAll(evts) {
+        for (var i = 0; i < evts.length; ++i) {
+            next(evts[i]);
+        }
+    }
+    function process(evt, type) {
+        var result = {type: type};
+        var keyId = kbdUtil.getKey(evt);
+        if (keyId) {
+            result.keyId = keyId;
+        }
+
+        var keysym = kbdUtil.getKeysym(evt);
+
+        var hasModifier = modifierState.hasShortcutModifier() || !!modifierState.activeCharModifier();
+        // Is this a case where we have to decide on the keysym right away, rather than waiting for the keypress?
+        // "special" keys like enter, tab or backspace don't send keypress events,
+        // and some browsers don't send keypresses at all if a modifier is down
+        if (keysym && (type !== 'keydown' || kbdUtil.nonCharacterKey(evt) || hasModifier)) {
+            result.keysym = keysym;
+        }
+
+        var isShift = evt.keyCode === 0x10 || evt.key === 'Shift';
+
+        // Should we prevent the browser from handling the event?
+        // Doing so on a keydown (in most browsers) prevents keypress from being generated
+        // so only do that if we have to.
+        var suppress = !isShift && (type !== 'keydown' || modifierState.hasShortcutModifier() || !!kbdUtil.nonCharacterKey(evt));
+
+        // If a char modifier is down on a keydown, we need to insert a stall,
+        // so VerifyCharModifier knows to wait and see if a keypress is comnig
+        var stall = type === 'keydown' && modifierState.activeCharModifier() && !kbdUtil.nonCharacterKey(evt);
+
+        // if a char modifier is pressed, get the keys it consists of (on Windows, AltGr is equivalent to Ctrl+Alt)
+        var active = modifierState.activeCharModifier();
+
+        // If we have a char modifier down, and we're able to determine a keysym reliably
+        // then (a) we know to treat the modifier as a char modifier,
+        // and (b) we'll have to "escape" the modifier to undo the modifier when sending the char.
+        if (active && keysym) {
+            var isCharModifier = false;
+            for (var i  = 0; i < active.length; ++i) {
+                if (active[i] === keysym.keysym) {
+                    isCharModifier = true;
+                }
+            }
+            if (type === 'keypress' && !isCharModifier) {
+                result.escape = modifierState.activeCharModifier();
+            }
+        }
+
+        if (stall) {
+            // insert a fake "stall" event
+            next({type: 'stall'});
+        }
+        next(result);
+
+        return suppress;
+    }
+
+    return {
+        keydown: function(evt) {
+            sendAll(modifierState.keydown(evt));
+            return process(evt, 'keydown');
+        },
+        keypress: function(evt) {
+            return process(evt, 'keypress');
+        },
+        keyup: function(evt) {
+            sendAll(modifierState.keyup(evt));
+            return process(evt, 'keyup');
+        },
+        syncModifiers: function(evt) {
+            sendAll(modifierState.syncAny(evt));
+        },
+        releaseAll: function() { next({type: 'releaseall'}); }
+    };
+}
+
+// Combines keydown and keypress events where necessary to handle char modifiers.
+// On some OS'es, a char modifier is sometimes used as a shortcut modifier.
+// 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
+// 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.
+// The only way we can distinguish these cases is to wait and see if a keypress event arrives
+// When we receive a "stall" event, wait a few ms before processing the next keydown. If a keypress has also arrived, merge the two
+function VerifyCharModifier(next) {
+    "use strict";
+    var queue = [];
+    var timer = null;
+    function process() {
+        if (timer) {
+            return;
+        }
+        while (queue.length !== 0) {
+            var cur = queue[0];
+            queue = queue.splice(1);
+            switch (cur.type) {
+            case 'stall':
+                // insert a delay before processing available events.
+                timer = setTimeout(function() {
+                    clearTimeout(timer);
+                    timer = null;
+                    process();
+                }, 5);
+                return;
+            case 'keydown':
+                // is the next element a keypress? Then we should merge the two
+                if (queue.length !== 0 && queue[0].type === 'keypress') {
+                    // Firefox sends keypress even when no char is generated.
+                    // so, if keypress keysym is the same as we'd have guessed from keydown,
+                    // the modifier didn't have any effect, and should not be escaped
+                    if (queue[0].escape && (!cur.keysym || cur.keysym.keysym !== queue[0].keysym.keysym)) {
+                        cur.escape = queue[0].escape;
+                    }
+                    cur.keysym = queue[0].keysym;
+                    queue = queue.splice(1);
+                }
+                break;
+            }
+
+            // swallow stall events, and pass all others to the next stage
+            if (cur.type !== 'stall') {
+                next(cur);
+            }
+        }
+    }
+    return function(evt) {
+        queue.push(evt);
+        process();
+    };
+}
+
+// Keeps track of which keys we (and the server) believe are down
+// When a keyup is received, match it against this list, to determine the corresponding keysym(s)
+// in some cases, a single key may produce multiple keysyms, so the corresponding keyup event must release all of these chars
+// key repeat events should be merged into a single entry.
+// Because we can't always identify which entry a keydown or keyup event corresponds to, we sometimes have to guess
+function TrackKeyState(next) {
+    "use strict";
+    var state = [];
+
+    return function (evt) {
+        var last = state.length !== 0 ? state[state.length-1] : null;
+
+        switch (evt.type) {
+        case 'keydown':
+            // insert a new entry if last seen key was different.
+            if (!last || !evt.keyId || last.keyId !== evt.keyId) {
+                last = {keyId: evt.keyId, keysyms: {}};
+                state.push(last);
+            }
+            if (evt.keysym) {
+                // make sure last event contains this keysym (a single "logical" keyevent
+                // can cause multiple key events to be sent to the VNC server)
+                last.keysyms[evt.keysym.keysym] = evt.keysym;
+                last.ignoreKeyPress = true;
+                next(evt);
+            }
+            break;
+        case 'keypress':
+            if (!last) {
+                last = {keyId: evt.keyId, keysyms: {}};
+                state.push(last);
+            }
+            if (!evt.keysym) {
+                console.log('keypress with no keysym:', evt);
+            }
+
+            // If we didn't expect a keypress, and already sent a keydown to the VNC server
+            // based on the keydown, make sure to skip this event.
+            if (evt.keysym && !last.ignoreKeyPress) {
+                last.keysyms[evt.keysym.keysym] = evt.keysym;
+                evt.type = 'keydown';
+                next(evt);
+            }
+            break;
+        case 'keyup':
+            if (state.length === 0) {
+                return;
+            }
+            var idx = null;
+            // do we have a matching key tracked as being down?
+            for (var i = 0; i !== state.length; ++i) {
+                if (state[i].keyId === evt.keyId) {
+                    idx = i;
+                    break;
+                }
+            }
+            // if we couldn't find a match (it happens), assume it was the last key pressed
+            if (idx === null) {
+                idx = state.length - 1;
+            }
+
+            var item = state.splice(idx, 1)[0];
+            // for each keysym tracked by this key entry, clone the current event and override the keysym
+            for (var key in item.keysyms) {
+                var clone = (function(){
+                    function Clone(){}
+                    return function (obj) { Clone.prototype=obj; return new Clone(); };
+                }());
+                var out = clone(evt);
+                out.keysym = item.keysyms[key];
+                next(out);
+            }
+            break;
+        case 'releaseall':
+            for (var i = 0; i < state.length; ++i) {
+                for (var key in state[i].keysyms) {
+                    var keysym = state[i].keysyms[key];
+                    next({keyId: 0, keysym: keysym, type: 'keyup'});
+                }
+            }
+            state = [];
+        }
+    };
+}
+
+// Handles "escaping" of modifiers: if a char modifier is used to produce a keysym (such as AltGr-2 to generate an @),
+// then the modifier must be "undone" before sending the @, and "redone" afterwards.
+function EscapeModifiers(next) {
+    "use strict";
+    return function(evt) {
+        if (evt.type !== 'keydown' || evt.escape === undefined) {
+            next(evt);
+            return;
+        }
+        // undo modifiers
+        for (var i = 0; i < evt.escape.length; ++i) {
+            next({type: 'keyup', keyId: 0, keysym: keysyms.lookup(evt.escape[i])});
+        }
+        // send the character event
+        next(evt);
+        // redo modifiers
+        for (var i = 0; i < evt.escape.length; ++i) {
+            next({type: 'keydown', keyId: 0, keysym: keysyms.lookup(evt.escape[i])});
+        }
+    };
+}