]> git.proxmox.com Git - mirror_novnc.git/blobdiff - core/rfb.js
Use ES6 classes
[mirror_novnc.git] / core / rfb.js
index d1921a107743f65c5a3aaaedeefba77810ee5949..ed765e8784682ec6b9c0d2a6560cfbc07529eb2c 100644 (file)
@@ -1,7 +1,7 @@
 /*
  * noVNC: HTML5 VNC client
  * Copyright (C) 2012 Joel Martin
- * Copyright (C) 2017 Samuel Mannehed for Cendio AB
+ * Copyright (C) 2018 Samuel Mannehed for Cendio AB
  * Licensed under MPL 2.0 (see LICENSE.txt)
  *
  * See README.md for usage and integration instructions.
 
 import * as Log from './util/logging.js';
 import { decodeUTF8 } from './util/strings.js';
-import { browserSupportsCursorURIs, isTouchDevice } from './util/browsers.js';
 import EventTargetMixin from './util/eventtarget.js';
 import Display from "./display.js";
 import Keyboard from "./input/keyboard.js";
 import Mouse from "./input/mouse.js";
+import Cursor from "./util/cursor.js";
 import Websock from "./websock.js";
 import DES from "./des.js";
 import KeyTable from "./input/keysym.js";
@@ -25,241 +25,250 @@ import Inflator from "./inflator.js";
 import { encodings, encodingName } from "./encodings.js";
 import "./util/polyfill.js";
 
-/*jslint white: false, browser: true */
-/*global window, Util, Display, Keyboard, Mouse, Websock, Websock_native, Base64, DES, KeyTable, Inflator, XtScancode */
-
 // How many seconds to wait for a disconnect to finish
-var DISCONNECT_TIMEOUT = 3;
+const DISCONNECT_TIMEOUT = 3;
+
+export default class RFB extends EventTargetMixin {
+    constructor(target, url, options) {
+        if (!target) {
+            throw Error("Must specify target");
+        }
+        if (!url) {
+            throw Error("Must specify URL");
+        }
+
+        super();
+
+        this._target = target;
+        this._url = url;
+
+        // Connection details
+        options = options || {};
+        this._rfb_credentials = options.credentials || {};
+        this._shared = 'shared' in options ? !!options.shared : true;
+        this._repeaterID = options.repeaterID || '';
+
+        // Internal state
+        this._rfb_connection_state = '';
+        this._rfb_init_state = '';
+        this._rfb_auth_scheme = '';
+        this._rfb_clean_disconnect = true;
+
+        // Server capabilities
+        this._rfb_version = 0;
+        this._rfb_max_version = 3.8;
+        this._rfb_tightvnc = false;
+        this._rfb_xvp_ver = 0;
+
+        this._fb_width = 0;
+        this._fb_height = 0;
+
+        this._fb_name = "";
+
+        this._capabilities = { power: false };
+
+        this._supportsFence = false;
+
+        this._supportsContinuousUpdates = false;
+        this._enabledContinuousUpdates = false;
+
+        this._supportsSetDesktopSize = false;
+        this._screen_id = 0;
+        this._screen_flags = 0;
+
+        this._qemuExtKeyEventSupported = false;
+
+        // Internal objects
+        this._sock = null;              // Websock object
+        this._display = null;           // Display object
+        this._flushing = false;         // Display flushing state
+        this._keyboard = null;          // Keyboard input handler object
+        this._mouse = null;             // Mouse input handler object
+
+        // Timers
+        this._disconnTimer = null;      // disconnection timer
+        this._resizeTimeout = null;     // resize rate limiting
+
+        // Decoder states and stats
+        this._encHandlers = {};
+        this._encStats = {};
+
+        this._FBU = {
+            rects: 0,
+            subrects: 0,            // RRE and HEXTILE
+            lines: 0,               // RAW
+            tiles: 0,               // HEXTILE
+            bytes: 0,
+            x: 0,
+            y: 0,
+            width: 0,
+            height: 0,
+            encoding: 0,
+            subencoding: -1,
+            background: null,
+            zlibs: []               // TIGHT zlib streams
+        };
 
-export default function RFB(target, url, options) {
-    if (!target) {
-        throw Error("Must specify target");
-    }
-    if (!url) {
-        throw Error("Must specify URL");
-    }
+        for (let i = 0; i < 4; i++) {
+            this._FBU.zlibs[i] = new Inflator();
+        }
 
-    this._target = target;
-    this._url = url;
-
-    // Connection details
-    options = options || {};
-    this._rfb_credentials = options.credentials || {};
-    this._shared = 'shared' in options ? !!options.shared : true;
-    this._repeaterID = options.repeaterID || '';
-
-    // Internal state
-    this._rfb_connection_state = '';
-    this._rfb_init_state = '';
-    this._rfb_auth_scheme = '';
-    this._rfb_clean_disconnect = true;
-
-    // Server capabilities
-    this._rfb_version = 0;
-    this._rfb_max_version = 3.8;
-    this._rfb_tightvnc = false;
-    this._rfb_xvp_ver = 0;
-
-    this._fb_width = 0;
-    this._fb_height = 0;
-
-    this._fb_name = "";
-
-    this._capabilities = { power: false };
-
-    this._supportsFence = false;
-
-    this._supportsContinuousUpdates = false;
-    this._enabledContinuousUpdates = false;
-
-    this._supportsSetDesktopSize = false;
-    this._screen_id = 0;
-    this._screen_flags = 0;
-
-    this._qemuExtKeyEventSupported = false;
-
-    // Internal objects
-    this._sock = null;              // Websock object
-    this._display = null;           // Display object
-    this._flushing = false;         // Display flushing state
-    this._keyboard = null;          // Keyboard input handler object
-    this._mouse = null;             // Mouse input handler object
-
-    // Timers
-    this._disconnTimer = null;      // disconnection timer
-    this._resizeTimeout = null;     // resize rate limiting
-
-    // Decoder states and stats
-    this._encHandlers = {};
-    this._encStats = {};
-
-    this._FBU = {
-        rects: 0,
-        subrects: 0,            // RRE and HEXTILE
-        lines: 0,               // RAW
-        tiles: 0,               // HEXTILE
-        bytes: 0,
-        x: 0,
-        y: 0,
-        width: 0,
-        height: 0,
-        encoding: 0,
-        subencoding: -1,
-        background: null,
-        zlibs: []               // TIGHT zlib streams
-    };
-    for (var i = 0; i < 4; i++) {
-        this._FBU.zlibs[i] = new Inflator();
-    }
+        this._destBuff = null;
+        this._paletteBuff = new Uint8Array(1024);  // 256 * 4 (max palette size * max bytes-per-pixel)
 
-    this._destBuff = null;
-    this._paletteBuff = new Uint8Array(1024);  // 256 * 4 (max palette size * max bytes-per-pixel)
-
-    this._rre_chunk_sz = 100;
-
-    this._timing = {
-        last_fbu: 0,
-        fbu_total: 0,
-        fbu_total_cnt: 0,
-        full_fbu_total: 0,
-        full_fbu_cnt: 0,
-
-        fbu_rt_start: 0,
-        fbu_rt_total: 0,
-        fbu_rt_cnt: 0,
-        pixels: 0
-    };
-
-    // Mouse state
-    this._mouse_buttonMask = 0;
-    this._mouse_arr = [];
-    this._viewportDragging = false;
-    this._viewportDragPos = {};
-    this._viewportHasMoved = false;
-
-    // Bound event handlers
-    this._eventHandlers = {
-        focusCanvas: this._focusCanvas.bind(this),
-        windowResize: this._windowResize.bind(this),
-    };
-
-    // main setup
-    Log.Debug(">> RFB.constructor");
-
-    // Create DOM elements
-    this._screen = document.createElement('div');
-    this._screen.style.display = 'flex';
-    this._screen.style.width = '100%';
-    this._screen.style.height = '100%';
-    this._screen.style.overflow = 'auto';
-    this._screen.style.backgroundColor = 'rgb(40, 40, 40)';
-    this._canvas = document.createElement('canvas');
-    this._canvas.style.margin = 'auto';
-    // Some browsers add an outline on focus
-    this._canvas.style.outline = 'none';
-    // IE miscalculates width without this :(
-    this._canvas.style.flexShrink = '0';
-    this._canvas.width = 0;
-    this._canvas.height = 0;
-    this._canvas.tabIndex = -1;
-    this._screen.appendChild(this._canvas);
-
-    // populate encHandlers with bound versions
-    this._encHandlers[encodings.encodingRaw] = RFB.encodingHandlers.RAW.bind(this);
-    this._encHandlers[encodings.encodingCopyRect] = RFB.encodingHandlers.COPYRECT.bind(this);
-    this._encHandlers[encodings.encodingRRE] = RFB.encodingHandlers.RRE.bind(this);
-    this._encHandlers[encodings.encodingHextile] = RFB.encodingHandlers.HEXTILE.bind(this);
-    this._encHandlers[encodings.encodingTight] = RFB.encodingHandlers.TIGHT.bind(this);
-
-    this._encHandlers[encodings.pseudoEncodingDesktopSize] = RFB.encodingHandlers.DesktopSize.bind(this);
-    this._encHandlers[encodings.pseudoEncodingLastRect] = RFB.encodingHandlers.last_rect.bind(this);
-    this._encHandlers[encodings.pseudoEncodingCursor] = RFB.encodingHandlers.Cursor.bind(this);
-    this._encHandlers[encodings.pseudoEncodingQEMUExtendedKeyEvent] = RFB.encodingHandlers.QEMUExtendedKeyEvent.bind(this);
-    this._encHandlers[encodings.pseudoEncodingExtendedDesktopSize] = RFB.encodingHandlers.ExtendedDesktopSize.bind(this);
-
-    // NB: nothing that needs explicit teardown should be done
-    // before this point, since this can throw an exception
-    try {
-        this._display = new Display(this._canvas);
-    } catch (exc) {
-        Log.Error("Display exception: " + exc);
-        throw exc;
-    }
-    this._display.onflush = this._onFlush.bind(this);
-    this._display.clear();
-
-    this._keyboard = new Keyboard(this._canvas);
-    this._keyboard.onkeyevent = this._handleKeyEvent.bind(this);
-
-    this._mouse = new Mouse(this._canvas);
-    this._mouse.onmousebutton = this._handleMouseButton.bind(this);
-    this._mouse.onmousemove = this._handleMouseMove.bind(this);
-
-    this._sock = new Websock();
-    this._sock.on('message', this._handle_message.bind(this));
-    this._sock.on('open', function () {
-        if ((this._rfb_connection_state === 'connecting') &&
-            (this._rfb_init_state === '')) {
-            this._rfb_init_state = 'ProtocolVersion';
-            Log.Debug("Starting VNC handshake");
-        } else {
-            this._fail("Unexpected server connection while " +
-                       this._rfb_connection_state);
-        }
-    }.bind(this));
-    this._sock.on('close', function (e) {
-        Log.Debug("WebSocket on-close event");
-        var msg = "";
-        if (e.code) {
-            msg = "(code: " + e.code;
-            if (e.reason) {
-                msg += ", reason: " + e.reason;
+        this._rre_chunk_sz = 100;
+
+        this._timing = {
+            last_fbu: 0,
+            fbu_total: 0,
+            fbu_total_cnt: 0,
+            full_fbu_total: 0,
+            full_fbu_cnt: 0,
+
+            fbu_rt_start: 0,
+            fbu_rt_total: 0,
+            fbu_rt_cnt: 0,
+            pixels: 0
+        };
+
+        // Mouse state
+        this._mouse_buttonMask = 0;
+        this._mouse_arr = [];
+        this._viewportDragging = false;
+        this._viewportDragPos = {};
+        this._viewportHasMoved = false;
+
+        // Bound event handlers
+        this._eventHandlers = {
+            focusCanvas: this._focusCanvas.bind(this),
+            windowResize: this._windowResize.bind(this),
+        };
+
+        // main setup
+        Log.Debug(">> RFB.constructor");
+
+        // Create DOM elements
+        this._screen = document.createElement('div');
+        this._screen.style.display = 'flex';
+        this._screen.style.width = '100%';
+        this._screen.style.height = '100%';
+        this._screen.style.overflow = 'auto';
+        this._screen.style.backgroundColor = 'rgb(40, 40, 40)';
+        this._canvas = document.createElement('canvas');
+        this._canvas.style.margin = 'auto';
+        // Some browsers add an outline on focus
+        this._canvas.style.outline = 'none';
+        // IE miscalculates width without this :(
+        this._canvas.style.flexShrink = '0';
+        this._canvas.width = 0;
+        this._canvas.height = 0;
+        this._canvas.tabIndex = -1;
+        this._screen.appendChild(this._canvas);
+
+    this._cursor = new Cursor();
+
+        // populate encHandlers with bound versions
+        this._encHandlers[encodings.encodingRaw] = RFB.encodingHandlers.RAW.bind(this);
+        this._encHandlers[encodings.encodingCopyRect] = RFB.encodingHandlers.COPYRECT.bind(this);
+        this._encHandlers[encodings.encodingRRE] = RFB.encodingHandlers.RRE.bind(this);
+        this._encHandlers[encodings.encodingHextile] = RFB.encodingHandlers.HEXTILE.bind(this);
+        this._encHandlers[encodings.encodingTight] = RFB.encodingHandlers.TIGHT.bind(this, false);
+        this._encHandlers[encodings.encodingTightPNG] = RFB.encodingHandlers.TIGHT.bind(this, true);
+
+        this._encHandlers[encodings.pseudoEncodingDesktopSize] = RFB.encodingHandlers.DesktopSize.bind(this);
+        this._encHandlers[encodings.pseudoEncodingLastRect] = RFB.encodingHandlers.last_rect.bind(this);
+        this._encHandlers[encodings.pseudoEncodingCursor] = RFB.encodingHandlers.Cursor.bind(this);
+        this._encHandlers[encodings.pseudoEncodingQEMUExtendedKeyEvent] = RFB.encodingHandlers.QEMUExtendedKeyEvent.bind(this);
+        this._encHandlers[encodings.pseudoEncodingExtendedDesktopSize] = RFB.encodingHandlers.ExtendedDesktopSize.bind(this);
+
+        // NB: nothing that needs explicit teardown should be done
+        // before this point, since this can throw an exception
+        try {
+            this._display = new Display(this._canvas);
+        } catch (exc) {
+            Log.Error("Display exception: " + exc);
+            throw exc;
+        }
+        this._display.onflush = this._onFlush.bind(this);
+        this._display.clear();
+
+        this._keyboard = new Keyboard(this._canvas);
+        this._keyboard.onkeyevent = this._handleKeyEvent.bind(this);
+
+        this._mouse = new Mouse(this._canvas);
+        this._mouse.onmousebutton = this._handleMouseButton.bind(this);
+        this._mouse.onmousemove = this._handleMouseMove.bind(this);
+
+        this._sock = new Websock();
+        this._sock.on('message', this._handle_message.bind(this));
+        this._sock.on('open', function () {
+            if ((this._rfb_connection_state === 'connecting') &&
+                (this._rfb_init_state === '')) {
+                this._rfb_init_state = 'ProtocolVersion';
+                Log.Debug("Starting VNC handshake");
+            } else {
+                this._fail("Unexpected server connection while " +
+                        this._rfb_connection_state);
             }
-            msg += ")";
-        }
-        switch (this._rfb_connection_state) {
-            case 'connecting':
-                this._fail("Connection closed " + msg);
-                break;
-            case 'connected':
-                // Handle disconnects that were initiated server-side
-                this._updateConnectionState('disconnecting');
-                this._updateConnectionState('disconnected');
-                break;
-            case 'disconnecting':
-                // Normal disconnection path
-                this._updateConnectionState('disconnected');
-                break;
-            case 'disconnected':
-                this._fail("Unexpected server disconnect " +
-                           "when already disconnected " + msg);
-                break;
-            default:
-                this._fail("Unexpected server disconnect before connecting " +
-                           msg);
-                break;
-        }
-        this._sock.off('close');
-    }.bind(this));
-    this._sock.on('error', function (e) {
-        Log.Warn("WebSocket on-error event");
-    });
+        }.bind(this));
+        this._sock.on('close', function (e) {
+            Log.Debug("WebSocket on-close event");
+            let msg = "";
+            if (e.code) {
+                msg = "(code: " + e.code;
+                if (e.reason) {
+                    msg += ", reason: " + e.reason;
+                }
+                msg += ")";
+            }
+            switch (this._rfb_connection_state) {
+                case 'connecting':
+                    this._fail("Connection closed " + msg);
+                    break;
+                case 'connected':
+                    // Handle disconnects that were initiated server-side
+                    this._updateConnectionState('disconnecting');
+                    this._updateConnectionState('disconnected');
+                    break;
+                case 'disconnecting':
+                    // Normal disconnection path
+                    this._updateConnectionState('disconnected');
+                    break;
+                case 'disconnected':
+                    this._fail("Unexpected server disconnect " +
+                            "when already disconnected " + msg);
+                    break;
+                default:
+                    this._fail("Unexpected server disconnect before connecting " +
+                            msg);
+                    break;
+            }
+            this._sock.off('close');
+        }.bind(this));
+        this._sock.on('error', function (e) {
+            Log.Warn("WebSocket on-error event");
+        });
 
-    // Slight delay of the actual connection so that the caller has
-    // time to set up callbacks
-    setTimeout(this._updateConnectionState.bind(this, 'connecting'));
+        // Slight delay of the actual connection so that the caller has
+        // time to set up callbacks
+        setTimeout(this._updateConnectionState.bind(this, 'connecting'));
 
-    Log.Debug("<< RFB.constructor");
-};
+        Log.Debug("<< RFB.constructor");
 
-RFB.prototype = {
-    // ===== PROPERTIES =====
+        // ===== PROPERTIES =====
+
+        this.dragViewport = false;
+        this.focusOnClick = true;
+
+        this._viewOnly = false;
+        this._clipViewport = false;
+        this._scaleViewport = false;
+        this._resizeSession = false;
+    }
 
-    dragViewport: false,
-    focusOnClick: true,
+    // ===== PROPERTIES =====
 
-    _viewOnly: false,
-    get viewOnly() { return this._viewOnly; },
+    get viewOnly() { return this._viewOnly; }
     set viewOnly(viewOnly) {
         this._viewOnly = viewOnly;
 
@@ -273,22 +282,20 @@ RFB.prototype = {
                 this._mouse.grab();
             }
         }
-    },
+    }
 
-    get capabilities() { return this._capabilities; },
+    get capabilities() { return this._capabilities; }
 
-    get touchButton() { return this._mouse.touchButton; },
-    set touchButton(button) { this._mouse.touchButton = button; },
+    get touchButton() { return this._mouse.touchButton; }
+    set touchButton(button) { this._mouse.touchButton = button; }
 
-    _clipViewport: false,
-    get clipViewport() { return this._clipViewport; },
+    get clipViewport() { return this._clipViewport; }
     set clipViewport(viewport) {
         this._clipViewport = viewport;
         this._updateClip();
-    },
+    }
 
-    _scaleViewport: false,
-    get scaleViewport() { return this._scaleViewport; },
+    get scaleViewport() { return this._scaleViewport; }
     set scaleViewport(scale) {
         this._scaleViewport = scale;
         // Scaling trumps clipping, so we may need to adjust
@@ -300,32 +307,31 @@ RFB.prototype = {
         if (!scale && this._clipViewport) {
             this._updateClip();
         }
-    },
+    }
 
-    _resizeSession: false,
-    get resizeSession() { return this._resizeSession; },
+    get resizeSession() { return this._resizeSession; }
     set resizeSession(resize) {
         this._resizeSession = resize;
         if (resize) {
             this._requestRemoteResize();
         }
-    },
+    }
 
     // ===== PUBLIC METHODS =====
 
-    disconnect: function () {
+    disconnect() {
         this._updateConnectionState('disconnecting');
         this._sock.off('error');
         this._sock.off('message');
         this._sock.off('open');
-    },
+    }
 
-    sendCredentials: function (creds) {
+    sendCredentials(creds) {
         this._rfb_credentials = creds;
         setTimeout(this._init_msg.bind(this), 0);
-    },
+    }
 
-    sendCtrlAltDel: function () {
+    sendCtrlAltDel() {
         if (this._rfb_connection_state !== 'connected' || this._viewOnly) { return; }
         Log.Info("Sending Ctrl-Alt-Del");
 
@@ -335,23 +341,23 @@ RFB.prototype = {
         this.sendKey(KeyTable.XK_Delete, "Delete", false);
         this.sendKey(KeyTable.XK_Alt_L, "AltLeft", false);
         this.sendKey(KeyTable.XK_Control_L, "ControlLeft", false);
-    },
+    }
 
-    machineShutdown: function () {
+    machineShutdown() {
         this._xvpOp(1, 2);
-    },
+    }
 
-    machineReboot: function () {
+    machineReboot() {
         this._xvpOp(1, 3);
-    },
+    }
 
-    machineReset: function () {
+    machineReset() {
         this._xvpOp(1, 4);
-    },
+    }
 
     // Send a key press. If 'down' is not specified then send a down key
     // followed by an up key.
-    sendKey: function (keysym, code, down) {
+    sendKey(keysym, code, down) {
         if (this._rfb_connection_state !== 'connected' || this._viewOnly) { return; }
 
         if (down === undefined) {
@@ -360,7 +366,7 @@ RFB.prototype = {
             return;
         }
 
-        var scancode = XtScancode[code];
+        const scancode = XtScancode[code];
 
         if (this._qemuExtKeyEventSupported && scancode) {
             // 0 is NoSymbol
@@ -376,24 +382,24 @@ RFB.prototype = {
             Log.Info("Sending keysym (" + (down ? "down" : "up") + "): " + keysym);
             RFB.messages.keyEvent(this._sock, keysym, down ? 1 : 0);
         }
-    },
+    }
 
-    focus: function () {
+    focus() {
         this._canvas.focus();
-    },
+    }
 
-    blur: function () {
+    blur() {
         this._canvas.blur();
-    },
+    }
 
-    clipboardPasteFrom: function (text) {
+    clipboardPasteFrom(text) {
         if (this._rfb_connection_state !== 'connected' || this._viewOnly) { return; }
         RFB.messages.clientCutText(this._sock, text);
-    },
+    }
 
     // ===== PRIVATE METHODS =====
 
-    _connect: function () {
+    _connect() {
         Log.Debug(">> RFB.connect");
 
         Log.Info("connecting to " + this._url);
@@ -412,6 +418,8 @@ RFB.prototype = {
         // Make our elements part of the page
         this._target.appendChild(this._screen);
 
+        this._cursor.attach(this._canvas);
+
         // Monitor size changes of the screen
         // FIXME: Use ResizeObserver, or hidden overflow
         window.addEventListener('resize', this._eventHandlers.windowResize);
@@ -421,10 +429,11 @@ RFB.prototype = {
         this._canvas.addEventListener("touchstart", this._eventHandlers.focusCanvas);
 
         Log.Debug("<< RFB.connect");
-    },
+    }
 
-    _disconnect: function () {
+    _disconnect() {
         Log.Debug(">> RFB.disconnect");
+        this._cursor.detach();
         this._canvas.removeEventListener("mousedown", this._eventHandlers.focusCanvas);
         this._canvas.removeEventListener("touchstart", this._eventHandlers.focusCanvas);
         window.removeEventListener('resize', this._eventHandlers.windowResize);
@@ -444,14 +453,14 @@ RFB.prototype = {
         }
         clearTimeout(this._resizeTimeout);
         Log.Debug("<< RFB.disconnect");
-    },
+    }
 
-    _print_stats: function () {
-        var stats = this._encStats;
+    _print_stats() {
+        const stats = this._encStats;
 
         Log.Info("Encoding stats for this connection:");
         Object.keys(stats).forEach(function (key) {
-            var s = stats[key];
+            const s = stats[key];
             if (s[0] + s[1] > 0) {
                 Log.Info("    " + encodingName(key) + ": " + s[0] + " rects");
             }
@@ -459,12 +468,12 @@ RFB.prototype = {
 
         Log.Info("Encoding stats since page load:");
         Object.keys(stats).forEach(function (key) {
-            var s = stats[key];
+            const s = stats[key];
             Log.Info("    " + encodingName(key) + ": " + s[1] + " rects");
         });
-    },
+    }
 
-    _focusCanvas: function(event) {
+    _focusCanvas(event) {
         // Respect earlier handlers' request to not do side-effects
         if (event.defaultPrevented) {
             return;
@@ -475,9 +484,9 @@ RFB.prototype = {
         }
 
         this.focus();
-    },
+    }
 
-    _windowResize: function (event) {
+    _windowResize(event) {
         // If the window resized then our screen element might have
         // as well. Update the viewport dimensions.
         window.requestAnimationFrame(function () {
@@ -494,13 +503,13 @@ RFB.prototype = {
             clearTimeout(this._resizeTimeout);
             this._resizeTimeout = setTimeout(this._requestRemoteResize.bind(this), 500);
         }
-    },
+    }
 
     // Update state of clipping in Display object, and make sure the
     // configured viewport matches the current screen size
-    _updateClip: function () {
-        var cur_clip = this._display.clipViewport;
-        var new_clip = this._clipViewport;
+    _updateClip() {
+        const cur_clip = this._display.clipViewport;
+        let new_clip = this._clipViewport;
 
         if (this._scaleViewport) {
             // Disable viewport clipping if we are scaling
@@ -514,25 +523,25 @@ RFB.prototype = {
         if (new_clip) {
             // When clipping is enabled, the screen is limited to
             // the size of the container.
-            let size = this._screenSize();
+            const size = this._screenSize();
             this._display.viewportChangeSize(size.w, size.h);
             this._fixScrollbars();
         }
-    },
+    }
 
-    _updateScale: function () {
+    _updateScale() {
         if (!this._scaleViewport) {
             this._display.scale = 1.0;
         } else {
-            let size = this._screenSize();
+            const size = this._screenSize();
             this._display.autoscale(size.w, size.h);
         }
         this._fixScrollbars();
-    },
+    }
 
     // Requests a change of remote desktop size. This message is an extension
     // and may only be sent if we have received an ExtendedDesktopSize message
-    _requestRemoteResize: function () {
+    _requestRemoteResize() {
         clearTimeout(this._resizeTimeout);
         this._resizeTimeout = null;
 
@@ -541,31 +550,31 @@ RFB.prototype = {
             return;
         }
 
-        let size = this._screenSize();
+        const size = this._screenSize();
         RFB.messages.setDesktopSize(this._sock, size.w, size.h,
                                     this._screen_id, this._screen_flags);
 
         Log.Debug('Requested new desktop size: ' +
                    size.w + 'x' + size.h);
-    },
+    }
 
     // Gets the the size of the available screen
-    _screenSize: function () {
+    _screenSize() {
         return { w: this._screen.offsetWidth,
                  h: this._screen.offsetHeight };
-    },
+    }
 
-    _fixScrollbars: function () {
+    _fixScrollbars() {
         // This is a hack because Chrome screws up the calculation
         // for when scrollbars are needed. So to fix it we temporarily
         // toggle them off and on.
-        var orig = this._screen.style.overflow;
+        const orig = this._screen.style.overflow;
         this._screen.style.overflow = 'hidden';
         // Force Chrome to recalculate the layout by asking for
         // an element's dimensions
         this._screen.getBoundingClientRect();
         this._screen.style.overflow = orig;
-    },
+    }
 
     /*
      * Connection states:
@@ -574,8 +583,8 @@ RFB.prototype = {
      *   disconnecting
      *   disconnected - permanent state
      */
-    _updateConnectionState: function (state) {
-        var oldstate = this._rfb_connection_state;
+    _updateConnectionState(state) {
+        const oldstate = this._rfb_connection_state;
 
         if (state === oldstate) {
             Log.Debug("Already in state '" + state + "', ignoring");
@@ -631,7 +640,7 @@ RFB.prototype = {
 
         this._rfb_connection_state = state;
 
-        var smsg = "New state '" + state + "', was '" + oldstate + "'.";
+        const smsg = "New state '" + state + "', was '" + oldstate + "'.";
         Log.Debug(smsg);
 
         if (this._disconnTimer && state !== 'disconnecting') {
@@ -649,8 +658,7 @@ RFB.prototype = {
                 break;
 
             case 'connected':
-                var event = new CustomEvent("connect", { detail: {} });
-                this.dispatchEvent(event);
+                this.dispatchEvent(new CustomEvent("connect", { detail: {} }));
                 break;
 
             case 'disconnecting':
@@ -663,20 +671,19 @@ RFB.prototype = {
                 break;
 
             case 'disconnected':
-                event = new CustomEvent(
+                this.dispatchEvent(new CustomEvent(
                     "disconnect", { detail:
-                                    { clean: this._rfb_clean_disconnect } });
-                this.dispatchEvent(event);
+                                    { clean: this._rfb_clean_disconnect } }));
                 break;
         }
-    },
+    }
 
     /* Print errors and disconnect
      *
      * The parameter 'details' is used for information that
      * should be logged but not sent to the user interface.
      */
-    _fail: function (details) {
+    _fail(details) {
         switch (this._rfb_connection_state) {
             case 'disconnecting':
                 Log.Error("Failed when disconnecting: " + details);
@@ -698,16 +705,15 @@ RFB.prototype = {
         this._updateConnectionState('disconnected');
 
         return false;
-    },
+    }
 
-    _setCapability: function (cap, val) {
+    _setCapability(cap, val) {
         this._capabilities[cap] = val;
-        var event = new CustomEvent("capabilities",
-                                    { detail: { capabilities: this._capabilities } });
-        this.dispatchEvent(event);
-    },
+        this.dispatchEvent(new CustomEvent("capabilities",
+                                           { detail: { capabilities: this._capabilities } }));
+    }
 
-    _handle_message: function () {
+    _handle_message() {
         if (this._sock.rQlen() === 0) {
             Log.Warn("handle_message called on an empty receive queue");
             return;
@@ -734,13 +740,13 @@ RFB.prototype = {
                 this._init_msg();
                 break;
         }
-    },
+    }
 
-    _handleKeyEvent: function (keysym, code, down) {
+    _handleKeyEvent(keysym, code, down) {
         this.sendKey(keysym, code, down);
-    },
+    }
 
-    _handleMouseButton: function (x, y, down, bmask) {
+    _handleMouseButton(x, y, down, bmask) {
         if (down) {
             this._mouse_buttonMask |= bmask;
         } else {
@@ -778,16 +784,16 @@ RFB.prototype = {
 
         if (this._rfb_connection_state !== 'connected') { return; }
         RFB.messages.pointerEvent(this._sock, this._display.absX(x), this._display.absY(y), this._mouse_buttonMask);
-    },
+    }
 
-    _handleMouseMove: function (x, y) {
+    _handleMouseMove(x, y) {
         if (this._viewportDragging) {
-            var deltaX = this._viewportDragPos.x - x;
-            var deltaY = this._viewportDragPos.y - y;
+            const deltaX = this._viewportDragPos.x - x;
+            const deltaY = this._viewportDragPos.y - y;
 
             // The goal is to trigger on a certain physical width, the
             // devicePixelRatio brings us a bit closer but is not optimal.
-            var dragThreshold = 10 * (window.devicePixelRatio || 1);
+            const dragThreshold = 10 * (window.devicePixelRatio || 1);
 
             if (this._viewportHasMoved || (Math.abs(deltaX) > dragThreshold ||
                                            Math.abs(deltaY) > dragThreshold)) {
@@ -805,18 +811,18 @@ RFB.prototype = {
 
         if (this._rfb_connection_state !== 'connected') { return; }
         RFB.messages.pointerEvent(this._sock, this._display.absX(x), this._display.absY(y), this._mouse_buttonMask);
-    },
+    }
 
     // Message Handlers
 
-    _negotiate_protocol_version: function () {
+    _negotiate_protocol_version() {
         if (this._sock.rQlen() < 12) {
             return this._fail("Received incomplete protocol version.");
         }
 
-        var sversion = this._sock.rQshiftStr(12).substr(4, 7);
+        const sversion = this._sock.rQshiftStr(12).substr(4, 7);
         Log.Info("Server ProtocolVersion: " + sversion);
-        var is_repeater = 0;
+        let is_repeater = 0;
         switch (sversion) {
             case "000.000":  // UltraVNC repeater
                 is_repeater = 1;
@@ -840,7 +846,7 @@ RFB.prototype = {
         }
 
         if (is_repeater) {
-            var repeaterID = "ID:" + this._repeaterID;
+            let repeaterID = "ID:" + this._repeaterID;
             while (repeaterID.length < 250) {
                 repeaterID += "\0";
             }
@@ -852,19 +858,19 @@ RFB.prototype = {
             this._rfb_version = this._rfb_max_version;
         }
 
-        var cversion = "00" + parseInt(this._rfb_version, 10) +
+        const cversion = "00" + parseInt(this._rfb_version, 10) +
                        ".00" + ((this._rfb_version * 10) % 10);
         this._sock.send_string("RFB " + cversion + "\n");
         Log.Debug('Sent ProtocolVersion: ' + cversion);
 
         this._rfb_init_state = 'Security';
-    },
+    }
 
-    _negotiate_security: function () {
+    _negotiate_security() {
         // Polyfill since IE and PhantomJS doesn't have
         // TypedArray.includes()
         function includes(item, array) {
-            for (var i = 0; i < array.length; i++) {
+            for (let i = 0; i < array.length; i++) {
                 if (array[i] === item) {
                     return true;
                 }
@@ -874,14 +880,14 @@ RFB.prototype = {
 
         if (this._rfb_version >= 3.7) {
             // Server sends supported list, client decides
-            var num_types = this._sock.rQshift8();
+            const num_types = this._sock.rQshift8();
             if (this._sock.rQwait("security type", num_types, 1)) { return false; }
 
             if (num_types === 0) {
                 return this._handle_security_failure("no security types");
             }
 
-            var types = this._sock.rQshiftBytes(num_types);
+            const types = this._sock.rQshiftBytes(num_types);
             Log.Debug("Server security types: " + types);
 
             // Look for each auth in preferred order
@@ -909,7 +915,7 @@ RFB.prototype = {
         Log.Debug('Authenticating using scheme: ' + this._rfb_auth_scheme);
 
         return this._init_msg(); // jump to authentication
-    },
+    }
 
     /*
      * Get the security failure reason if sent from the server and
@@ -921,7 +927,7 @@ RFB.prototype = {
      * - The optional parameter security_result_status can be used to
      *   add a custom status code to the event.
      */
-    _handle_security_failure: function (context, security_result_status) {
+    _handle_security_failure(context, security_result_status) {
 
         if (typeof context === 'undefined') {
             context = "";
@@ -936,7 +942,7 @@ RFB.prototype = {
         if (this._sock.rQwait("reason length", 4)) {
             return false;
         }
-        let strlen = this._sock.rQshift32();
+        const strlen = this._sock.rQshift32();
         let reason = "";
 
         if (strlen > 0) {
@@ -945,76 +951,84 @@ RFB.prototype = {
         }
 
         if (reason !== "") {
-
-            let event = new CustomEvent(
+            this.dispatchEvent(new CustomEvent(
                 "securityfailure",
-                { detail: { status: security_result_status, reason: reason } });
-            this.dispatchEvent(event);
+                { detail: { status: security_result_status, reason: reason } }));
 
             return this._fail("Security negotiation failed" + context +
                               " (reason: " + reason + ")");
         } else {
-
-            let event = new CustomEvent(
+            this.dispatchEvent(new CustomEvent(
                 "securityfailure",
-                { detail: { status: security_result_status } });
-            this.dispatchEvent(event);
+                { detail: { status: security_result_status } }));
 
             return this._fail("Security negotiation failed" + context);
         }
-    },
+    }
 
     // authentication
-    _negotiate_xvp_auth: function () {
+    _negotiate_xvp_auth() {
         if (!this._rfb_credentials.username ||
             !this._rfb_credentials.password ||
             !this._rfb_credentials.target) {
-            var event = new CustomEvent("credentialsrequired",
-                                        { detail: { types: ["username", "password", "target"] } });
-            this.dispatchEvent(event);
-            return false;
+            this.dispatchEvent(new CustomEvent(
+                "credentialsrequired",
+                { detail: { types: ["username", "password", "target"] } }));
+             return false;
         }
 
-        var xvp_auth_str = String.fromCharCode(this._rfb_credentials.username.length) +
+        const xvp_auth_str = String.fromCharCode(this._rfb_credentials.username.length) +
                            String.fromCharCode(this._rfb_credentials.target.length) +
                            this._rfb_credentials.username +
                            this._rfb_credentials.target;
         this._sock.send_string(xvp_auth_str);
         this._rfb_auth_scheme = 2;
         return this._negotiate_authentication();
-    },
+    }
 
-    _negotiate_std_vnc_auth: function () {
+    _negotiate_std_vnc_auth() {
         if (this._sock.rQwait("auth challenge", 16)) { return false; }
 
         if (!this._rfb_credentials.password) {
-            var event = new CustomEvent("credentialsrequired",
-                                        { detail: { types: ["password"] } });
-            this.dispatchEvent(event);
+            this.dispatchEvent(new CustomEvent(
+                "credentialsrequired",
+                { detail: { types: ["password"] } }));
             return false;
         }
 
         // TODO(directxman12): make genDES not require an Array
-        var challenge = Array.prototype.slice.call(this._sock.rQshiftBytes(16));
-        var response = RFB.genDES(this._rfb_credentials.password, challenge);
+        const challenge = Array.prototype.slice.call(this._sock.rQshiftBytes(16));
+        const response = RFB.genDES(this._rfb_credentials.password, challenge);
         this._sock.send(response);
         this._rfb_init_state = "SecurityResult";
         return true;
-    },
+    }
 
-    _negotiate_tight_tunnels: function (numTunnels) {
-        var clientSupportedTunnelTypes = {
+    _negotiate_tight_tunnels(numTunnels) {
+        const clientSupportedTunnelTypes = {
             0: { vendor: 'TGHT', signature: 'NOTUNNEL' }
         };
-        var serverSupportedTunnelTypes = {};
+        const serverSupportedTunnelTypes = {};
         // receive tunnel capabilities
-        for (var i = 0; i < numTunnels; i++) {
-            var cap_code = this._sock.rQshift32();
-            var cap_vendor = this._sock.rQshiftStr(4);
-            var cap_signature = this._sock.rQshiftStr(8);
+        for (let i = 0; i < numTunnels; i++) {
+            const cap_code = this._sock.rQshift32();
+            const cap_vendor = this._sock.rQshiftStr(4);
+            const cap_signature = this._sock.rQshiftStr(8);
             serverSupportedTunnelTypes[cap_code] = { vendor: cap_vendor, signature: cap_signature };
         }
 
+        Log.Debug("Server Tight tunnel types: " + serverSupportedTunnelTypes);
+
+        // Siemens touch panels have a VNC server that supports NOTUNNEL,
+        // but forgets to advertise it. Try to detect such servers by
+        // looking for their custom tunnel type.
+        if (serverSupportedTunnelTypes[1] &&
+            (serverSupportedTunnelTypes[1].vendor === "SICR") &&
+            (serverSupportedTunnelTypes[1].signature === "SCHANNEL")) {
+            Log.Debug("Detected Siemens server. Assuming NOTUNNEL support.");
+            serverSupportedTunnelTypes[0] = { vendor: 'TGHT', signature: 'NOTUNNEL' };
+        }
+
         // choose the notunnel type
         if (serverSupportedTunnelTypes[0]) {
             if (serverSupportedTunnelTypes[0].vendor != clientSupportedTunnelTypes[0].vendor ||
@@ -1022,18 +1036,19 @@ RFB.prototype = {
                 return this._fail("Client's tunnel type had the incorrect " +
                                   "vendor or signature");
             }
+            Log.Debug("Selected tunnel type: " + clientSupportedTunnelTypes[0]);
             this._sock.send([0, 0, 0, 0]);  // use NOTUNNEL
             return false; // wait until we receive the sub auth count to continue
         } else {
             return this._fail("Server wanted tunnels, but doesn't support " +
                               "the notunnel type");
         }
-    },
+    }
 
-    _negotiate_tight_auth: function () {
+    _negotiate_tight_auth() {
         if (!this._rfb_tightvnc) {  // first pass, do the tunnel negotiation
             if (this._sock.rQwait("num tunnels", 4)) { return false; }
-            var numTunnels = this._sock.rQshift32();
+            const numTunnels = this._sock.rQshift32();
             if (numTunnels > 0 && this._sock.rQwait("tunnel capabilities", 16 * numTunnels, 4)) { return false; }
 
             this._rfb_tightvnc = true;
@@ -1046,7 +1061,7 @@ RFB.prototype = {
 
         // second pass, do the sub-auth negotiation
         if (this._sock.rQwait("sub auth count", 4)) { return false; }
-        var subAuthCount = this._sock.rQshift32();
+        const subAuthCount = this._sock.rQshift32();
         if (subAuthCount === 0) {  // empty sub-auth list received means 'no auth' subtype selected
             this._rfb_init_state = 'SecurityResult';
             return true;
@@ -1054,22 +1069,25 @@ RFB.prototype = {
 
         if (this._sock.rQwait("sub auth capabilities", 16 * subAuthCount, 4)) { return false; }
 
-        var clientSupportedTypes = {
+        const clientSupportedTypes = {
             'STDVNOAUTH__': 1,
             'STDVVNCAUTH_': 2
         };
 
-        var serverSupportedTypes = [];
+        const serverSupportedTypes = [];
 
-        for (var i = 0; i < subAuthCount; i++) {
-            var capNum = this._sock.rQshift32();
-            var capabilities = this._sock.rQshiftStr(12);
+        for (let i = 0; i < subAuthCount; i++) {
+            this._sock.rQshift32(); // capNum
+            const capabilities = this._sock.rQshiftStr(12);
             serverSupportedTypes.push(capabilities);
         }
 
-        for (var authType in clientSupportedTypes) {
+        Log.Debug("Server Tight authentication types: " + serverSupportedTypes);
+
+        for (let authType in clientSupportedTypes) {
             if (serverSupportedTypes.indexOf(authType) != -1) {
                 this._sock.send([0, 0, 0, clientSupportedTypes[authType]]);
+                Log.Debug("Selected authentication type: " + authType);
 
                 switch (authType) {
                     case 'STDVNOAUTH__':  // no auth
@@ -1086,9 +1104,9 @@ RFB.prototype = {
         }
 
         return this._fail("No supported sub-auth types!");
-    },
+    }
 
-    _negotiate_authentication: function () {
+    _negotiate_authentication() {
         switch (this._rfb_auth_scheme) {
             case 0:  // connection failed
                 return this._handle_security_failure("authentication scheme");
@@ -1114,12 +1132,12 @@ RFB.prototype = {
                 return this._fail("Unsupported auth scheme (scheme: " +
                                   this._rfb_auth_scheme + ")");
         }
-    },
+    }
 
-    _handle_security_result: function () {
+    _handle_security_result() {
         if (this._sock.rQwait('VNC auth response ', 4)) { return false; }
 
-        let status = this._sock.rQshift32();
+        const status = this._sock.rQshift32();
 
         if (status === 0) { // OK
             this._rfb_init_state = 'ClientInitialisation';
@@ -1129,53 +1147,53 @@ RFB.prototype = {
             if (this._rfb_version >= 3.8) {
                 return this._handle_security_failure("security result", status);
             } else {
-                let event = new CustomEvent("securityfailure",
-                                            { detail: { status: status } });
-                this.dispatchEvent(event);
+                this.dispatchEvent(new CustomEvent(
+                    "securityfailure",
+                    { detail: { status: status } }));
 
                 return this._fail("Security handshake failed");
             }
         }
-    },
+    }
 
-    _negotiate_server_init: function () {
+    _negotiate_server_init() {
         if (this._sock.rQwait("server initialization", 24)) { return false; }
 
         /* Screen size */
-        var width = this._sock.rQshift16();
-        var height = this._sock.rQshift16();
+        const width = this._sock.rQshift16();
+        const height = this._sock.rQshift16();
 
         /* PIXEL_FORMAT */
-        var bpp         = this._sock.rQshift8();
-        var depth       = this._sock.rQshift8();
-        var big_endian  = this._sock.rQshift8();
-        var true_color  = this._sock.rQshift8();
-
-        var red_max     = this._sock.rQshift16();
-        var green_max   = this._sock.rQshift16();
-        var blue_max    = this._sock.rQshift16();
-        var red_shift   = this._sock.rQshift8();
-        var green_shift = this._sock.rQshift8();
-        var blue_shift  = this._sock.rQshift8();
+        const bpp         = this._sock.rQshift8();
+        const depth       = this._sock.rQshift8();
+        const big_endian  = this._sock.rQshift8();
+        const true_color  = this._sock.rQshift8();
+
+        const red_max     = this._sock.rQshift16();
+        const green_max   = this._sock.rQshift16();
+        const blue_max    = this._sock.rQshift16();
+        const red_shift   = this._sock.rQshift8();
+        const green_shift = this._sock.rQshift8();
+        const blue_shift  = this._sock.rQshift8();
         this._sock.rQskipBytes(3);  // padding
 
         // NB(directxman12): we don't want to call any callbacks or print messages until
         //                   *after* we're past the point where we could backtrack
 
         /* Connection name/title */
-        var name_length = this._sock.rQshift32();
+        const name_length = this._sock.rQshift32();
         if (this._sock.rQwait('server init name', name_length, 24)) { return false; }
         this._fb_name = decodeUTF8(this._sock.rQshiftStr(name_length));
 
         if (this._rfb_tightvnc) {
             if (this._sock.rQwait('TightVNC extended server init header', 8, 24 + name_length)) { return false; }
             // In TightVNC mode, ServerInit message is extended
-            var numServerMessages = this._sock.rQshift16();
-            var numClientMessages = this._sock.rQshift16();
-            var numEncodings = this._sock.rQshift16();
+            const numServerMessages = this._sock.rQshift16();
+            const numClientMessages = this._sock.rQshift16();
+            const numEncodings = this._sock.rQshift16();
             this._sock.rQskipBytes(2);  // padding
 
-            var totalMessagesLength = (numServerMessages + numClientMessages + numEncodings) * 16;
+            const totalMessagesLength = (numServerMessages + numClientMessages + numEncodings) * 16;
             if (this._sock.rQwait('TightVNC extended server init header', totalMessagesLength, 32 + name_length)) { return false; }
 
             // we don't actually do anything with the capability information that TIGHT sends,
@@ -1217,9 +1235,9 @@ RFB.prototype = {
         }
 
         // we're past the point where we could backtrack, so it's safe to call this
-        var event = new CustomEvent("desktopname",
-                                    { detail: { name: this._fb_name } });
-        this.dispatchEvent(event);
+        this.dispatchEvent(new CustomEvent(
+            "desktopname",
+            { detail: { name: this._fb_name } }));
 
         this._resize(width, height);
 
@@ -1240,29 +1258,25 @@ RFB.prototype = {
         this._timing.fbu_rt_start = (new Date()).getTime();
         this._timing.pixels = 0;
 
-        // Cursor will be server side until the server decides to honor
-        // our request and send over the cursor image
-        this._display.disableLocalCursor();
-
         this._updateConnectionState('connected');
         return true;
-    },
+    }
 
-    _sendEncodings: function () {
-        var encs = [];
+    _sendEncodings() {
+        const encs = [];
 
         // In preference order
         encs.push(encodings.encodingCopyRect);
         // Only supported with full depth support
         if (this._fb_depth == 24) {
             encs.push(encodings.encodingTight);
+            encs.push(encodings.encodingTightPNG);
             encs.push(encodings.encodingHextile);
             encs.push(encodings.encodingRRE);
         }
         encs.push(encodings.encodingRaw);
 
         // Psuedo-encoding settings
-        encs.push(encodings.pseudoEncodingTightPNG);
         encs.push(encodings.pseudoEncodingQualityLevel0 + 6);
         encs.push(encodings.pseudoEncodingCompressLevel0 + 2);
 
@@ -1274,13 +1288,12 @@ RFB.prototype = {
         encs.push(encodings.pseudoEncodingFence);
         encs.push(encodings.pseudoEncodingContinuousUpdates);
 
-        if (browserSupportsCursorURIs() &&
-            !isTouchDevice && this._fb_depth == 24) {
+        if (this._fb_depth == 24) {
             encs.push(encodings.pseudoEncodingCursor);
         }
 
         RFB.messages.clientEncodings(this._sock, encs);
-    },
+    }
 
     /* RFB protocol initialization states:
      *   ProtocolVersion
@@ -1290,7 +1303,7 @@ RFB.prototype = {
      *   ClientInitialization - not triggered by server message
      *   ServerInitialization
      */
-    _init_msg: function () {
+    _init_msg() {
         switch (this._rfb_init_state) {
             case 'ProtocolVersion':
                 return this._negotiate_protocol_version();
@@ -1316,38 +1329,38 @@ RFB.prototype = {
                 return this._fail("Unknown init state (state: " +
                                   this._rfb_init_state + ")");
         }
-    },
+    }
 
-    _handle_set_colour_map_msg: function () {
+    _handle_set_colour_map_msg() {
         Log.Debug("SetColorMapEntries");
 
         return this._fail("Unexpected SetColorMapEntries message");
-    },
+    }
 
-    _handle_server_cut_text: function () {
+    _handle_server_cut_text() {
         Log.Debug("ServerCutText");
 
         if (this._sock.rQwait("ServerCutText header", 7, 1)) { return false; }
         this._sock.rQskipBytes(3);  // Padding
-        var length = this._sock.rQshift32();
+        const length = this._sock.rQshift32();
         if (this._sock.rQwait("ServerCutText", length, 8)) { return false; }
 
-        var text = this._sock.rQshiftStr(length);
+        const text = this._sock.rQshiftStr(length);
 
         if (this._viewOnly) { return true; }
 
-        var event = new CustomEvent("clipboard",
-                                    { detail: { text: text } });
-        this.dispatchEvent(event);
+        this.dispatchEvent(new CustomEvent(
+            "clipboard",
+            { detail: { text: text } }));
 
         return true;
-    },
+    }
 
-    _handle_server_fence_msg: function() {
+    _handle_server_fence_msg() {
         if (this._sock.rQwait("ServerFence header", 8, 1)) { return false; }
         this._sock.rQskipBytes(3); // Padding
-        var flags = this._sock.rQshift32();
-        var length = this._sock.rQshift8();
+        let flags = this._sock.rQshift32();
+        let length = this._sock.rQshift8();
 
         if (this._sock.rQwait("ServerFence payload", length, 9)) { return false; }
 
@@ -1356,7 +1369,7 @@ RFB.prototype = {
             length = 64;
         }
 
-        var payload = this._sock.rQshiftStr(length);
+        const payload = this._sock.rQshiftStr(length);
 
         this._supportsFence = true;
 
@@ -1383,13 +1396,13 @@ RFB.prototype = {
         RFB.messages.clientFence(this._sock, flags, payload);
 
         return true;
-    },
+    }
 
-    _handle_xvp_msg: function () {
+    _handle_xvp_msg() {
         if (this._sock.rQwait("XVP version and message", 3, 1)) { return false; }
         this._sock.rQskip8();  // Padding
-        var xvp_ver = this._sock.rQshift8();
-        var xvp_msg = this._sock.rQshift8();
+        const xvp_ver = this._sock.rQshift8();
+        const xvp_msg = this._sock.rQshift8();
 
         switch (xvp_msg) {
             case 0:  // XVP_FAIL
@@ -1406,20 +1419,20 @@ RFB.prototype = {
         }
 
         return true;
-    },
-
-    _normal_msg: function () {
-        var msg_type;
+    }
 
+    _normal_msg() {
+        let msg_type;
         if (this._FBU.rects > 0) {
             msg_type = 0;
         } else {
             msg_type = this._sock.rQshift8();
         }
 
+        let first, ret;
         switch (msg_type) {
             case 0:  // FramebufferUpdate
-                var ret = this._framebufferUpdate();
+                ret = this._framebufferUpdate();
                 if (ret && !this._enabledContinuousUpdates) {
                     RFB.messages.fbUpdateRequest(this._sock, true, 0, 0,
                                                  this._fb_width, this._fb_height);
@@ -1431,15 +1444,16 @@ RFB.prototype = {
 
             case 2:  // Bell
                 Log.Debug("Bell");
-                var event = new CustomEvent("bell", { detail: {} });
-                this.dispatchEvent(event);
+                this.dispatchEvent(new CustomEvent(
+                    "bell", 
+                    { detail: {} }));
                 return true;
 
             case 3:  // ServerCutText
                 return this._handle_server_cut_text();
 
             case 150: // EndOfContinuousUpdates
-                var first = !(this._supportsContinuousUpdates);
+                first = !this._supportsContinuousUpdates;
                 this._supportsContinuousUpdates = true;
                 this._enabledContinuousUpdates = false;
                 if (first) {
@@ -1463,20 +1477,17 @@ RFB.prototype = {
                 Log.Debug("sock.rQslice(0, 30): " + this._sock.rQslice(0, 30));
                 return true;
         }
-    },
+    }
 
-    _onFlush: function() {
+    _onFlush() {
         this._flushing = false;
         // Resume processing
         if (this._sock.rQlen() > 0) {
             this._handle_message();
         }
-    },
-
-    _framebufferUpdate: function () {
-        var ret = true;
-        var now;
+    }
 
+    _framebufferUpdate() {
         if (this._FBU.rects === 0) {
             if (this._sock.rQwait("FBU header", 3, 1)) { return false; }
             this._sock.rQskip8();  // Padding
@@ -1484,7 +1495,7 @@ RFB.prototype = {
             this._FBU.bytes = 0;
             this._timing.cur_fbu = 0;
             if (this._timing.fbu_rt_start > 0) {
-                now = (new Date()).getTime();
+                const now = (new Date()).getTime();
                 Log.Info("First FBU latency: " + (now - this._timing.fbu_rt_start));
             }
 
@@ -1505,7 +1516,7 @@ RFB.prototype = {
                 if (this._sock.rQwait("rect header", 12)) { return false; }
                 /* New FramebufferUpdate */
 
-                var hdr = this._sock.rQshiftBytes(12);
+                const hdr = this._sock.rQshiftBytes(12);
                 this._FBU.x        = (hdr[0] << 8) + hdr[1];
                 this._FBU.y        = (hdr[2] << 8) + hdr[3];
                 this._FBU.width    = (hdr[4] << 8) + hdr[5];
@@ -1522,9 +1533,9 @@ RFB.prototype = {
 
             this._timing.last_fbu = (new Date()).getTime();
 
-            ret = this._encHandlers[this._FBU.encoding]();
+            const ret = this._encHandlers[this._FBU.encoding]();
 
-            now = (new Date()).getTime();
+            const now = (new Date()).getTime();
             this._timing.cur_fbu += (now - this._timing.last_fbu);
 
             if (ret) {
@@ -1549,7 +1560,7 @@ RFB.prototype = {
                 }
 
                 if (this._timing.fbu_rt_start > 0) {
-                    var fbu_rt_diff = now - this._timing.fbu_rt_start;
+                    const fbu_rt_diff = now - this._timing.fbu_rt_start;
                     this._timing.fbu_rt_total += fbu_rt_diff;
                     this._timing.fbu_rt_cnt++;
                     Log.Info("full FBU round-trip, cur: " +
@@ -1567,16 +1578,16 @@ RFB.prototype = {
         this._display.flip();
 
         return true;  // We finished this FBU
-    },
+    }
 
-    _updateContinuousUpdates: function() {
+    _updateContinuousUpdates() {
         if (!this._enabledContinuousUpdates) { return; }
 
         RFB.messages.enableContinuousUpdates(this._sock, true, 0, 0,
                                              this._fb_width, this._fb_height);
-    },
+    }
 
-    _resize: function(width, height) {
+    _resize(width, height) {
         this._fb_width = width;
         this._fb_height = height;
 
@@ -1590,22 +1601,28 @@ RFB.prototype = {
 
         this._timing.fbu_rt_start = (new Date()).getTime();
         this._updateContinuousUpdates();
-    },
+    }
 
-    _xvpOp: function (ver, op) {
+    _xvpOp(ver, op) {
         if (this._rfb_xvp_ver < ver) { return; }
         Log.Info("Sending XVP operation " + op + " (version " + ver + ")");
         RFB.messages.xvpOp(this._sock, ver, op);
-    },
-};
+    }
 
-Object.assign(RFB.prototype, EventTargetMixin);
+    static genDES(password, challenge) {
+        const passwd = [];
+        for (let i = 0; i < password.length; i++) {
+            passwd.push(password.charCodeAt(i));
+        }
+        return (new DES(passwd)).encrypt(challenge);
+    }
+}
 
 // Class Methods
 RFB.messages = {
-    keyEvent: function (sock, keysym, down) {
-        var buff = sock._sQ;
-        var offset = sock._sQlen;
+    keyEvent(sock, keysym, down) {
+        const buff = sock._sQ;
+        const offset = sock._sQlen;
 
         buff[offset] = 4;  // msg-type
         buff[offset + 1] = down;
@@ -1622,19 +1639,18 @@ RFB.messages = {
         sock.flush();
     },
 
-    QEMUExtendedKeyEvent: function (sock, keysym, down, keycode) {
+    QEMUExtendedKeyEvent(sock, keysym, down, keycode) {
         function getRFBkeycode(xt_scancode) {
-            var upperByte = (keycode >> 8);
-            var lowerByte = (keycode & 0x00ff);
+            const upperByte = (keycode >> 8);
+            const lowerByte = (keycode & 0x00ff);
             if (upperByte === 0xe0 && lowerByte < 0x7f) {
-                lowerByte = lowerByte | 0x80;
-                return lowerByte;
+                return lowerByte | 0x80;
             }
             return xt_scancode;
         }
 
-        var buff = sock._sQ;
-        var offset = sock._sQlen;
+        const buff = sock._sQ;
+        const offset = sock._sQlen;
 
         buff[offset] = 255; // msg-type
         buff[offset + 1] = 0; // sub msg-type
@@ -1647,7 +1663,7 @@ RFB.messages = {
         buff[offset + 6] = (keysym >> 8);
         buff[offset + 7] = keysym;
 
-        var RFBkeycode = getRFBkeycode(keycode);
+        const RFBkeycode = getRFBkeycode(keycode);
 
         buff[offset + 8] = (RFBkeycode >> 24);
         buff[offset + 9] = (RFBkeycode >> 16);
@@ -1658,9 +1674,9 @@ RFB.messages = {
         sock.flush();
     },
 
-    pointerEvent: function (sock, x, y, mask) {
-        var buff = sock._sQ;
-        var offset = sock._sQlen;
+    pointerEvent(sock, x, y, mask) {
+        const buff = sock._sQ;
+        const offset = sock._sQlen;
 
         buff[offset] = 5; // msg-type
 
@@ -1677,9 +1693,9 @@ RFB.messages = {
     },
 
     // TODO(directxman12): make this unicode compatible?
-    clientCutText: function (sock, text) {
-        var buff = sock._sQ;
-        var offset = sock._sQlen;
+    clientCutText(sock, text) {
+        const buff = sock._sQ;
+        const offset = sock._sQlen;
 
         buff[offset] = 6; // msg-type
 
@@ -1687,24 +1703,43 @@ RFB.messages = {
         buff[offset + 2] = 0; // padding
         buff[offset + 3] = 0; // padding
 
-        var n = text.length;
+        let length = text.length;
 
-        buff[offset + 4] = n >> 24;
-        buff[offset + 5] = n >> 16;
-        buff[offset + 6] = n >> 8;
-        buff[offset + 7] = n;
+        buff[offset + 4] = length >> 24;
+        buff[offset + 5] = length >> 16;
+        buff[offset + 6] = length >> 8;
+        buff[offset + 7] = length;
 
-        for (var i = 0; i < n; i++) {
-            buff[offset + 8 + i] =  text.charCodeAt(i);
-        }
+        sock._sQlen += 8;
 
-        sock._sQlen += 8 + n;
-        sock.flush();
+        // We have to keep track of from where in the text we begin creating the
+        // buffer for the flush in the next iteration.
+        let textOffset = 0;
+
+        let remaining = length;
+        while (remaining > 0) {
+
+            let flushSize = Math.min(remaining, (sock._sQbufferSize - sock._sQlen));
+            if (flushSize <= 0) {
+                this._fail("Clipboard contents could not be sent");
+                break;
+            }
+
+            for (let i = 0; i < flushSize; i++) {
+                buff[sock._sQlen + i] =  text.charCodeAt(textOffset + i);
+            }
+
+            sock._sQlen += flushSize;
+            sock.flush();
+
+            remaining -= flushSize;
+            textOffset += flushSize;
+        }
     },
 
-    setDesktopSize: function (sock, width, height, id, flags) {
-        var buff = sock._sQ;
-        var offset = sock._sQlen;
+    setDesktopSize(sock, width, height, id, flags) {
+        const buff = sock._sQ;
+        const offset = sock._sQlen;
 
         buff[offset] = 251;              // msg-type
         buff[offset + 1] = 0;            // padding
@@ -1738,9 +1773,9 @@ RFB.messages = {
         sock.flush();
     },
 
-    clientFence: function (sock, flags, payload) {
-        var buff = sock._sQ;
-        var offset = sock._sQlen;
+    clientFence(sock, flags, payload) {
+        const buff = sock._sQ;
+        const offset = sock._sQlen;
 
         buff[offset] = 248; // msg-type
 
@@ -1753,11 +1788,11 @@ RFB.messages = {
         buff[offset + 6] = flags >> 8;
         buff[offset + 7] = flags;
 
-        var n = payload.length;
+        const n = payload.length;
 
         buff[offset + 8] = n; // length
 
-        for (var i = 0; i < n; i++) {
+        for (let i = 0; i < n; i++) {
             buff[offset + 9 + i] = payload.charCodeAt(i);
         }
 
@@ -1765,9 +1800,9 @@ RFB.messages = {
         sock.flush();
     },
 
-    enableContinuousUpdates: function (sock, enable, x, y, width, height) {
-        var buff = sock._sQ;
-        var offset = sock._sQlen;
+    enableContinuousUpdates(sock, enable, x, y, width, height) {
+        const buff = sock._sQ;
+        const offset = sock._sQlen;
 
         buff[offset] = 150;             // msg-type
         buff[offset + 1] = enable;      // enable-flag
@@ -1785,11 +1820,11 @@ RFB.messages = {
         sock.flush();
     },
 
-    pixelFormat: function (sock, depth, true_color) {
-        var buff = sock._sQ;
-        var offset = sock._sQlen;
+    pixelFormat(sock, depth, true_color) {
+        const buff = sock._sQ;
+        const offset = sock._sQlen;
 
-        var bpp, bits;
+        let bpp;
 
         if (depth > 16) {
             bpp = 32;
@@ -1799,7 +1834,7 @@ RFB.messages = {
             bpp = 8;
         }
 
-        bits = Math.floor(depth/3);
+        const bits = Math.floor(depth/3);
 
         buff[offset] = 0;  // msg-type
 
@@ -1833,9 +1868,9 @@ RFB.messages = {
         sock.flush();
     },
 
-    clientEncodings: function (sock, encodings) {
-        var buff = sock._sQ;
-        var offset = sock._sQlen;
+    clientEncodings(sock, encodings) {
+        const buff = sock._sQ;
+        const offset = sock._sQlen;
 
         buff[offset] = 2; // msg-type
         buff[offset + 1] = 0; // padding
@@ -1843,9 +1878,9 @@ RFB.messages = {
         buff[offset + 2] = encodings.length >> 8;
         buff[offset + 3] = encodings.length;
 
-        var i, j = offset + 4;
-        for (i = 0; i < encodings.length; i++) {
-            var enc = encodings[i];
+        let j = offset + 4;
+        for (let i = 0; i < encodings.length; i++) {
+            const enc = encodings[i];
             buff[j] = enc >> 24;
             buff[j + 1] = enc >> 16;
             buff[j + 2] = enc >> 8;
@@ -1858,9 +1893,9 @@ RFB.messages = {
         sock.flush();
     },
 
-    fbUpdateRequest: function (sock, incremental, x, y, w, h) {
-        var buff = sock._sQ;
-        var offset = sock._sQlen;
+    fbUpdateRequest(sock, incremental, x, y, w, h) {
+        const buff = sock._sQ;
+        const offset = sock._sQlen;
 
         if (typeof(x) === "undefined") { x = 0; }
         if (typeof(y) === "undefined") { y = 0; }
@@ -1884,9 +1919,9 @@ RFB.messages = {
         sock.flush();
     },
 
-    xvpOp: function (sock, ver, op) {
-        var buff = sock._sQ;
-        var offset = sock._sQlen;
+    xvpOp(sock, ver, op) {
+        const buff = sock._sQ;
+        const offset = sock._sQlen;
 
         buff[offset] = 250; // msg-type
         buff[offset + 1] = 0; // padding
@@ -1896,36 +1931,28 @@ RFB.messages = {
 
         sock._sQlen += 4;
         sock.flush();
-    },
-};
-
-RFB.genDES = function (password, challenge) {
-    var passwd = [];
-    for (var i = 0; i < password.length; i++) {
-        passwd.push(password.charCodeAt(i));
     }
-    return (new DES(passwd)).encrypt(challenge);
 };
 
+
 RFB.encodingHandlers = {
-    RAW: function () {
+    RAW() {
         if (this._FBU.lines === 0) {
             this._FBU.lines = this._FBU.height;
         }
 
-        var pixelSize = this._fb_depth == 8 ? 1 : 4;
+        const pixelSize = this._fb_depth == 8 ? 1 : 4;
         this._FBU.bytes = this._FBU.width * pixelSize;  // at least a line
         if (this._sock.rQwait("RAW", this._FBU.bytes)) { return false; }
-        var cur_y = this._FBU.y + (this._FBU.height - this._FBU.lines);
-        var curr_height = Math.min(this._FBU.lines,
+        const cur_y = this._FBU.y + (this._FBU.height - this._FBU.lines);
+        const curr_height = Math.min(this._FBU.lines,
                                    Math.floor(this._sock.rQlen() / (this._FBU.width * pixelSize)));
-        var data = this._sock.get_rQ();
-        var index = this._sock.get_rQi();
+        let data = this._sock.get_rQ();
+        let index = this._sock.get_rQi();
         if (this._fb_depth == 8) {
-            var pixels = this._FBU.width * curr_height
-            var newdata = new Uint8Array(pixels * 4);
-            var i;
-            for (i = 0;i < pixels;i++) {
+            const pixels = this._FBU.width * curr_height
+            const newdata = new Uint8Array(pixels * 4);
+            for (let i = 0; i < pixels; i++) {
                 newdata[i * 4 + 0] = ((data[index + i] >> 0) & 0x3) * 255 / 3;
                 newdata[i * 4 + 1] = ((data[index + i] >> 2) & 0x3) * 255 / 3;
                 newdata[i * 4 + 2] = ((data[index + i] >> 4) & 0x3) * 255 / 3;
@@ -1949,7 +1976,7 @@ RFB.encodingHandlers = {
         return true;
     },
 
-    COPYRECT: function () {
+    COPYRECT() {
         this._FBU.bytes = 4;
         if (this._sock.rQwait("COPYRECT", 4)) { return false; }
         this._display.copyImage(this._sock.rQshift16(), this._sock.rQshift16(),
@@ -1961,8 +1988,8 @@ RFB.encodingHandlers = {
         return true;
     },
 
-    RRE: function () {
-        var color;
+    RRE() {
+        let color;
         if (this._FBU.subrects === 0) {
             this._FBU.bytes = 4 + 4;
             if (this._sock.rQwait("RRE", 4 + 4)) { return false; }
@@ -1973,16 +2000,16 @@ RFB.encodingHandlers = {
 
         while (this._FBU.subrects > 0 && this._sock.rQlen() >= (4 + 8)) {
             color = this._sock.rQshiftBytes(4);
-            var x = this._sock.rQshift16();
-            var y = this._sock.rQshift16();
-            var width = this._sock.rQshift16();
-            var height = this._sock.rQshift16();
+            const x = this._sock.rQshift16();
+            const y = this._sock.rQshift16();
+            const width = this._sock.rQshift16();
+            const height = this._sock.rQshift16();
             this._display.fillRect(this._FBU.x + x, this._FBU.y + y, width, height, color);
             this._FBU.subrects--;
         }
 
         if (this._FBU.subrects > 0) {
-            var chunk = Math.min(this._rre_chunk_sz, this._FBU.subrects);
+            const chunk = Math.min(this._rre_chunk_sz, this._FBU.subrects);
             this._FBU.bytes = (4 + 8) * chunk;
         } else {
             this._FBU.rects--;
@@ -1992,9 +2019,9 @@ RFB.encodingHandlers = {
         return true;
     },
 
-    HEXTILE: function () {
-        var rQ = this._sock.get_rQ();
-        var rQi = this._sock.get_rQi();
+    HEXTILE() {
+        const rQ = this._sock.get_rQ();
+        let rQi = this._sock.get_rQi();
 
         if (this._FBU.tiles === 0) {
             this._FBU.tiles_x = Math.ceil(this._FBU.width / 16);
@@ -2006,21 +2033,21 @@ RFB.encodingHandlers = {
         while (this._FBU.tiles > 0) {
             this._FBU.bytes = 1;
             if (this._sock.rQwait("HEXTILE subencoding", this._FBU.bytes)) { return false; }
-            var subencoding = rQ[rQi];  // Peek
+            const subencoding = rQ[rQi];  // Peek
             if (subencoding > 30) {  // Raw
                 this._fail("Illegal hextile subencoding (subencoding: " +
                            subencoding + ")");
                 return false;
             }
 
-            var subrects = 0;
-            var curr_tile = this._FBU.total_tiles - this._FBU.tiles;
-            var tile_x = curr_tile % this._FBU.tiles_x;
-            var tile_y = Math.floor(curr_tile / this._FBU.tiles_x);
-            var x = this._FBU.x + tile_x * 16;
-            var y = this._FBU.y + tile_y * 16;
-            var w = Math.min(16, (this._FBU.x + this._FBU.width) - x);
-            var h = Math.min(16, (this._FBU.y + this._FBU.height) - y);
+            let subrects = 0;
+            const curr_tile = this._FBU.total_tiles - this._FBU.tiles;
+            const tile_x = curr_tile % this._FBU.tiles_x;
+            const tile_y = Math.floor(curr_tile / this._FBU.tiles_x);
+            const x = this._FBU.x + tile_x * 16;
+            const y = this._FBU.y + tile_y * 16;
+            const w = Math.min(16, (this._FBU.x + this._FBU.width) - x);
+            const h = Math.min(16, (this._FBU.y + this._FBU.height) - y);
 
             // Figure out how much we are expecting
             if (subencoding & 0x01) {  // Raw
@@ -2074,23 +2101,23 @@ RFB.encodingHandlers = {
                     subrects = rQ[rQi];
                     rQi++;
 
-                    for (var s = 0; s < subrects; s++) {
-                        var color;
+                    for (let s = 0; s < subrects; s++) {
+                        let color;
                         if (this._FBU.subencoding & 0x10) {  // SubrectsColoured
                             color = [rQ[rQi], rQ[rQi + 1], rQ[rQi + 2], rQ[rQi + 3]];
                             rQi += 4;
                         } else {
                             color = this._FBU.foreground;
                         }
-                        var xy = rQ[rQi];
+                        const xy = rQ[rQi];
                         rQi++;
-                        var sx = (xy >> 4);
-                        var sy = (xy & 0x0f);
+                        const sx = (xy >> 4);
+                        const sy = (xy & 0x0f);
 
-                        var wh = rQ[rQi];
+                        const wh = rQ[rQi];
                         rQi++;
-                        var sw = (wh >> 4) + 1;
-                        var sh = (wh & 0x0f) + 1;
+                        const sw = (wh >> 4) + 1;
+                        const sh = (wh & 0x0f) + 1;
 
                         this._display.subTile(sx, sy, sw, sh, color);
                     }
@@ -2110,31 +2137,22 @@ RFB.encodingHandlers = {
         return true;
     },
 
-    TIGHT: function () {
+    TIGHT(isTightPNG) {
         this._FBU.bytes = 1;  // compression-control byte
         if (this._sock.rQwait("TIGHT compression-control", this._FBU.bytes)) { return false; }
 
-        var checksum = function (data) {
-            var sum = 0;
-            for (var i = 0; i < data.length; i++) {
-                sum += data[i];
-                if (sum > 65536) sum -= 65536;
-            }
-            return sum;
-        };
-
-        var resetStreams = 0;
-        var streamId = -1;
-        var decompress = function (data, expected) {
-            for (var i = 0; i < 4; i++) {
+        let resetStreams = 0;
+        let streamId = -1;
+        const decompress = function (data, expected) {
+            for (let i = 0; i < 4; i++) {
                 if ((resetStreams >> i) & 1) {
                     this._FBU.zlibs[i].reset();
                     Log.Info("Reset zlib stream " + i);
                 }
             }
 
-            //var uncompressed = this._FBU.zlibs[streamId].uncompress(data, 0);
-            var uncompressed = this._FBU.zlibs[streamId].inflate(data, true, expected);
+            //const uncompressed = this._FBU.zlibs[streamId].uncompress(data, 0);
+            const uncompressed = this._FBU.zlibs[streamId].inflate(data, true, expected);
             /*if (uncompressed.status !== 0) {
                 Log.Error("Invalid data in zlib stream");
             }*/
@@ -2143,18 +2161,18 @@ RFB.encodingHandlers = {
             return uncompressed;
         }.bind(this);
 
-        var indexedToRGBX2Color = function (data, palette, width, height) {
+        const indexedToRGBX2Color = function (data, palette, width, height) {
             // Convert indexed (palette based) image data to RGB
             // TODO: reduce number of calculations inside loop
-            var dest = this._destBuff;
-            var w = Math.floor((width + 7) / 8);
-            var w1 = Math.floor(width / 8);
-
-            /*for (var y = 0; y < height; y++) {
-                var b, x, dp, sp;
-                var yoffset = y * width;
-                var ybitoffset = y * w;
-                var xoffset, targetbyte;
+            const dest = this._destBuff;
+            const w = Math.floor((width + 7) / 8);
+            const w1 = Math.floor(width / 8);
+
+            /*for (let y = 0; y < height; y++) {
+                let b, x, dp, sp;
+                const yoffset = y * width;
+                const ybitoffset = y * w;
+                let xoffset, targetbyte;
                 for (x = 0; x < w1; x++) {
                     xoffset = yoffset + x * 8;
                     targetbyte = data[ybitoffset + x];
@@ -2178,10 +2196,10 @@ RFB.encodingHandlers = {
                 }
             }*/
 
-            for (var y = 0; y < height; y++) {
-                var b, x, dp, sp;
+            for (let y = 0; y < height; y++) {
+                let dp, sp, x;
                 for (x = 0; x < w1; x++) {
-                    for (b = 7; b >= 0; b--) {
+                    for (let b = 7; b >= 0; b--) {
                         dp = (y * width + x * 8 + 7 - b) * 4;
                         sp = (data[y * w + x] >> b & 1) * 3;
                         dest[dp] = palette[sp];
@@ -2191,7 +2209,7 @@ RFB.encodingHandlers = {
                     }
                 }
 
-                for (b = 7; b >= 8 - width % 8; b--) {
+                for (let b = 7; b >= 8 - width % 8; b--) {
                     dp = (y * width + x * 8 + 7 - b) * 4;
                     sp = (data[y * w + x] >> b & 1) * 3;
                     dest[dp] = palette[sp];
@@ -2204,12 +2222,12 @@ RFB.encodingHandlers = {
             return dest;
         }.bind(this);
 
-        var indexedToRGBX = function (data, palette, width, height) {
+        const indexedToRGBX = function (data, palette, width, height) {
             // Convert indexed (palette based) image data to RGB
-            var dest = this._destBuff;
-            var total = width * height * 4;
-            for (var i = 0, j = 0; i < total; i += 4, j++) {
-                var sp = data[j] * 3;
+            const dest = this._destBuff;
+            const total = width * height * 4;
+            for (let i = 0, j = 0; i < total; i += 4, j++) {
+                const sp = data[j] * 3;
                 dest[i] = palette[sp];
                 dest[i + 1] = palette[sp + 1];
                 dest[i + 2] = palette[sp + 2];
@@ -2219,20 +2237,20 @@ RFB.encodingHandlers = {
             return dest;
         }.bind(this);
 
-        var rQi = this._sock.get_rQi();
-        var rQ = this._sock.rQwhole();
-        var cmode, data;
-        var cl_header, cl_data;
+        const rQi = this._sock.get_rQi();
+        const rQ = this._sock.rQwhole();
+        let cmode, data;
+        let cl_header, cl_data;
 
-        var handlePalette = function () {
-            var numColors = rQ[rQi + 2] + 1;
-            var paletteSize = numColors * 3;
+        const handlePalette = function () {
+            const numColors = rQ[rQi + 2] + 1;
+            const paletteSize = numColors * 3;
             this._FBU.bytes += paletteSize;
             if (this._sock.rQwait("TIGHT palette " + cmode, this._FBU.bytes)) { return false; }
 
-            var bpp = (numColors <= 2) ? 1 : 8;
-            var rowSize = Math.floor((this._FBU.width * bpp + 7) / 8);
-            var raw = false;
+            const bpp = (numColors <= 2) ? 1 : 8;
+            const rowSize = Math.floor((this._FBU.width * bpp + 7) / 8);
+            let raw = false;
             if (rowSize * this._FBU.height < 12) {
                 raw = true;
                 cl_header = 0;
@@ -2240,7 +2258,7 @@ RFB.encodingHandlers = {
                 //clength = [0, rowSize * this._FBU.height];
             } else {
                 // begin inline getTightCLength (returning two-item arrays is bad for performance with GC)
-                var cl_offset = rQi + 3 + paletteSize;
+                const cl_offset = rQi + 3 + paletteSize;
                 cl_header = 1;
                 cl_data = 0;
                 cl_data += rQ[cl_offset] & 0x7f;
@@ -2260,7 +2278,7 @@ RFB.encodingHandlers = {
 
             // Shift ctl, filter id, num colors, palette entries, and clength off
             this._sock.rQskipBytes(3);
-            //var palette = this._sock.rQshiftBytes(paletteSize);
+            //const palette = this._sock.rQshiftBytes(paletteSize);
             this._sock.rQshiftTo(this._paletteBuff, paletteSize);
             this._sock.rQskipBytes(cl_header);
 
@@ -2271,29 +2289,29 @@ RFB.encodingHandlers = {
             }
 
             // Convert indexed (palette based) image data to RGB
-            var rgbx;
+            let rgbx;
             if (numColors == 2) {
                 rgbx = indexedToRGBX2Color(data, this._paletteBuff, this._FBU.width, this._FBU.height);
-                this._display.blitRgbxImage(this._FBU.x, this._FBU.y, this._FBU.width, this._FBU.height, rgbx, 0, false);
             } else {
                 rgbx = indexedToRGBX(data, this._paletteBuff, this._FBU.width, this._FBU.height);
-                this._display.blitRgbxImage(this._FBU.x, this._FBU.y, this._FBU.width, this._FBU.height, rgbx, 0, false);
             }
 
+            this._display.blitRgbxImage(this._FBU.x, this._FBU.y, this._FBU.width, this._FBU.height, rgbx, 0, false);
+
 
             return true;
         }.bind(this);
 
-        var handleCopy = function () {
-            var raw = false;
-            var uncompressedSize = this._FBU.width * this._FBU.height * 3;
+        const handleCopy = function () {
+            let raw = false;
+            const uncompressedSize = this._FBU.width * this._FBU.height * 3;
             if (uncompressedSize < 12) {
                 raw = true;
                 cl_header = 0;
                 cl_data = uncompressedSize;
             } else {
                 // begin inline getTightCLength (returning two-item arrays is for peformance with GC)
-                var cl_offset = rQi + 1;
+                const cl_offset = rQi + 1;
                 cl_header = 1;
                 cl_data = 0;
                 cl_data += rQ[cl_offset] & 0x7f;
@@ -2324,7 +2342,7 @@ RFB.encodingHandlers = {
             return true;
         }.bind(this);
 
-        var ctl = this._sock.rQpeek8();
+        let ctl = this._sock.rQpeek8();
 
         // Keep tight reset bits
         resetStreams = ctl & 0xF;
@@ -2341,6 +2359,13 @@ RFB.encodingHandlers = {
         else return this._fail("Illegal tight compression received (ctl: " +
                                ctl + ")");
 
+        if (isTightPNG && (ctl < 0x08)) {
+            return this._fail("BasicCompression received in TightPNG rect");
+        }
+        if (!isTightPNG && (ctl === 0x0A)) {
+            return this._fail("PNG received in standard Tight rect");
+        }
+
         switch (cmode) {
             // fill use depth because TPIXELs drop the padding byte
             case "fill":  // TPIXEL
@@ -2362,6 +2387,7 @@ RFB.encodingHandlers = {
         if (this._sock.rQwait("TIGHT " + cmode, this._FBU.bytes)) { return false; }
 
         // Determine FBU.bytes
+        let cl_offset, filterId;
         switch (cmode) {
             case "fill":
                 // skip ctl byte
@@ -2371,7 +2397,7 @@ RFB.encodingHandlers = {
             case "png":
             case "jpeg":
                 // begin inline getTightCLength (returning two-item arrays is for peformance with GC)
-                var cl_offset = rQi + 1;
+                cl_offset = rQi + 1;
                 cl_header = 1;
                 cl_data = 0;
                 cl_data += rQ[cl_offset] & 0x7f;
@@ -2393,7 +2419,7 @@ RFB.encodingHandlers = {
                 this._display.imageRect(this._FBU.x, this._FBU.y, "image/" + cmode, data);
                 break;
             case "filter":
-                var filterId = rQ[rQi + 1];
+                filterId = rQ[rQi + 1];
                 if (filterId === 1) {
                     if (!handlePalette()) { return false; }
                 } else {
@@ -2415,16 +2441,16 @@ RFB.encodingHandlers = {
         return true;
     },
 
-    last_rect: function () {
+    last_rect() {
         this._FBU.rects = 0;
         return true;
     },
 
-    ExtendedDesktopSize: function () {
+    ExtendedDesktopSize() {
         this._FBU.bytes = 1;
         if (this._sock.rQwait("ExtendedDesktopSize", this._FBU.bytes)) { return false; }
 
-        var firstUpdate = !this._supportsSetDesktopSize;
+        const firstUpdate = !this._supportsSetDesktopSize;
         this._supportsSetDesktopSize = true;
 
         // Normally we only apply the current resize mode after a
@@ -2435,7 +2461,7 @@ RFB.encodingHandlers = {
             this._requestRemoteResize();
         }
 
-        var number_of_screens = this._sock.rQpeek8();
+        const number_of_screens = this._sock.rQpeek8();
 
         this._FBU.bytes = 4 + (number_of_screens * 16);
         if (this._sock.rQwait("ExtendedDesktopSize", this._FBU.bytes)) { return false; }
@@ -2443,7 +2469,7 @@ RFB.encodingHandlers = {
         this._sock.rQskipBytes(1);  // number-of-screens
         this._sock.rQskipBytes(3);  // padding
 
-        for (var i = 0; i < number_of_screens; i += 1) {
+        for (let i = 0; i < number_of_screens; i += 1) {
             // Save the id and flags of the first screen
             if (i === 0) {
                 this._screen_id = this._sock.rQshiftBytes(4);    // id
@@ -2467,7 +2493,7 @@ RFB.encodingHandlers = {
 
         // We need to handle errors when we requested the resize.
         if (this._FBU.x === 1 && this._FBU.y !== 0) {
-            var msg = "";
+            let msg = "";
             // The y-position indicates the status code from the server
             switch (this._FBU.y) {
             case 1:
@@ -2494,29 +2520,29 @@ RFB.encodingHandlers = {
         return true;
     },
 
-    DesktopSize: function () {
+    DesktopSize() {
         this._resize(this._FBU.width, this._FBU.height);
         this._FBU.bytes = 0;
         this._FBU.rects -= 1;
         return true;
     },
 
-    Cursor: function () {
+    Cursor() {
         Log.Debug(">> set_cursor");
-        var x = this._FBU.x;  // hotspot-x
-        var y = this._FBU.y;  // hotspot-y
-        var w = this._FBU.width;
-        var h = this._FBU.height;
+        const x = this._FBU.x;  // hotspot-x
+        const y = this._FBU.y;  // hotspot-y
+        const w = this._FBU.width;
+        const h = this._FBU.height;
 
-        var pixelslength = w * h * 4;
-        var masklength = Math.floor((w + 7) / 8) * h;
+        const pixelslength = w * h * 4;
+        const masklength = Math.floor((w + 7) / 8) * h;
 
         this._FBU.bytes = pixelslength + masklength;
         if (this._sock.rQwait("cursor encoding", this._FBU.bytes)) { return false; }
 
-        this._display.changeCursor(this._sock.rQshiftBytes(pixelslength),
-                                   this._sock.rQshiftBytes(masklength),
-                                   x, y, w, h);
+        this._cursor.change(this._sock.rQshiftBytes(pixelslength),
+                            this._sock.rQshiftBytes(masklength),
+                            x, y, w, h);
 
         this._FBU.bytes = 0;
         this._FBU.rects--;
@@ -2525,16 +2551,17 @@ RFB.encodingHandlers = {
         return true;
     },
 
-    QEMUExtendedKeyEvent: function () {
+    QEMUExtendedKeyEvent() {
         this._FBU.rects--;
 
         // Old Safari doesn't support creating keyboard events
         try {
-            var keyboardEvent = document.createEvent("keyboardEvent");
+            const keyboardEvent = document.createEvent("keyboardEvent");
             if (keyboardEvent.code !== undefined) {
                 this._qemuExtKeyEventSupported = true;
             }
         } catch (err) {
+            // Do nothing
         }
-    },
-};
+    }
+}