Ctrl Lock and Alt Lock support:

You can prevent unnecessary interference from the client when you type keys
such as "Alt + F" or "Ctrl + Alt + Backspace". And you can also type
"AltGr + Ctrl + 9" to enter "Ctrl + ]" with a German keyboard.

include/rfb.js

@@ -600,6 +600,7 @@ checkEvents = function() {
 
 // The status of the VNC server side key modifers.
 var remote_status = {shift: false, ctrl: false, alt: false, altgr: false};
+var softKeyState = {ctrlKey: false, altKey: false};
 
 keyPress = function(keysym, down, km) {
     var arr = [];
@@ -615,13 +616,15 @@ keyPress = function(keysym, down, km) {
     // Send key events for modifiers to the vnc server when:
     //  1. the status of modifers have been changed
     //  2. this is a repeated keydown event for a modifer
-    if (remote_status.ctrl !== km.ctrlKey || keysym === 0xFFE3) {
+    var ctrlKey = km.ctrlKey || softKeyState.ctrlKey;
-        arr = arr.concat(keyEvent(0xFFE3, km.ctrlKey));		// CTRL
+    var altKey = km.altKey || softKeyState.altKey;
-        remote_status.ctrl = km.ctrlKey;
+    if (remote_status.ctrl !== ctrlKey || keysym === 0xFFE3) {
+        arr = arr.concat(keyEvent(0xFFE3, ctrlKey));		// CTRL
+        remote_status.ctrl = ctrlKey;
     }
-    if (remote_status.alt !== km.altKey || keysym === 0xFFE9) {
+    if (remote_status.alt !== altKey || keysym === 0xFFE9) {
-        arr = arr.concat(keyEvent(0xFFE9, km.altKey));		// ALT
+        arr = arr.concat(keyEvent(0xFFE9, altKey));		// ALT
-        remote_status.alt = km.altKey;
+        remote_status.alt = altKey;
     }
     if (remote_status.altgr !== km.altgrKey || keysym === 0xFE03) {
         arr = arr.concat(keyEvent(0xFE03, km.altgrKey));	// ALTGR
@@ -1916,6 +1919,10 @@ that.sendKey = function(code, down) {
     ws.send(arr);
 };
 
+that.updateSoftKeyState = function(name, value) {
+    softKeyState[name] = value;
+};
+
 that.clipboardPasteFrom = function(text) {
     if (rfb_state !== "normal") { return; }
     //Util.Debug(">> clipboardPasteFrom: " + text.substr(0,40) + "...");

include/ui.js

@@ -164,6 +164,8 @@ addMouseHandlers: function() {
     $D("connectButton").onclick = UI.toggleConnectPanel;
     $D("disconnectButton").onclick = UI.disconnect;
     $D("descriptionButton").onclick = UI.toggleConnectPanel;
+    $D("ctrlLockCheckBox").onclick = UI.updateSoftKeyState;
+    $D("altLockCheckBox").onclick = UI.updateSoftKeyState;
 
     $D("noVNC_clipboard_text").onfocus = UI.displayBlur;
     $D("noVNC_clipboard_text").onblur = UI.displayFocus;
@@ -413,6 +415,10 @@ sendCtrlAltDel: function() {
     UI.rfb.sendCtrlAltDel();
 },
 
+updateSoftKeyState: function() {
+    UI.rfb.updateSoftKeyState(this.value, this.checked);
+},
+
 setMouseButton: function(num) {
     var b, blist = [0, 1,2,4], button;
 
@@ -508,11 +514,19 @@ updateVisualState: function() {
         $D('clipboardButton').style.display = "inline";
         $D('showKeyboard').style.display = "inline";
         $D('sendCtrlAltDelButton').style.display = "inline";
+        $D('ctrlLockCheckBox').style.display = "inline";
+        $D('altLockCheckBox').style.display = "inline";
+        $D('ctrlLockLabel').style.display = "inline";
+        $D('altLockLabel').style.display = "inline";
     } else {
         UI.setMouseButton();
         $D('clipboardButton').style.display = "none";
         $D('showKeyboard').style.display = "none";
         $D('sendCtrlAltDelButton').style.display = "none";
+        $D('ctrlLockCheckBox').style.display = "none";
+        $D('altLockCheckBox').style.display = "none";
+        $D('ctrlLockLabel').style.display = "none";
+        $D('altLockLabel').style.display = "none";
     }
     // State change disables viewport dragging.
     // It is enabled (toggled) by direct click on the button

vnc.html

@@ -70,6 +70,12 @@
 
         <!--noVNC Buttons-->
         <div class="noVNC-buttons-right">
+            <input type=checkbox value="ctrlKey"
+                id="ctrlLockCheckBox">
+            <label for="ctrlLockCheckBox" id="ctrlLockLabel">CtrlLock</label>
+            <input type=checkbox value="altKey"
+                id="altLockCheckBox">
+            <label for="altLockCheckBox" id="altLockLabel" >AltLock</label>
             <input type="image" src="images/ctrlaltdel.png"
                  id="sendCtrlAltDelButton" class="noVNC_status_button"
                 title="Send Ctrl-Alt-Del" />

vnc_auto.html

@@ -25,10 +25,20 @@
             <div id="noVNC_status_bar" class="noVNC_status_bar" style="margin-top: 0px;">
                 <table border=0 width="100%"><tr>
                     <td><div id="noVNC_status">Loading</div></td>
-                    <td width="1%"><div id="noVNC_buttons">
+                    <td width="300pt"><div id="noVNC_buttons">
+                      <span style="float: right">
                         <input type=button value="Send CtrlAltDel"
                             id="sendCtrlAltDelButton">
-                            </div></td>
+                      </span>
+                      <span style="float: right">
+                        <input type=checkbox value="ctrlKey"
+                            id="ctrlLockCheckBox">
+                        <label for="ctrlLockCheckBox">CtrlLock</label>
+                        <input type=checkbox value="altKey"
+                            id="altLockCheckBox">
+                        <label for="altLockCheckBox">AltLock</label>
+                      </span>
+                    </div></td>
                 </tr></table>
             </div>
             <canvas id="noVNC_canvas" width="640px" height="20px">
@@ -47,6 +57,11 @@
                            "keymap.js"]);
 
         var rfb;
+        var buttons = [
+            {name: 'ctrlLockCheckBox', onclick: updateSoftKeyState},
+            {name: 'altLockCheckBox', onclick: updateSoftKeyState},
+            {name: 'sendCtrlAltDelButton', onclick: sendCtrlAltDel}
+        ];
 
         function passwordRequired(rfb) {
             var msg;
@@ -66,11 +81,14 @@
             rfb.sendCtrlAltDel();
             return false;
         }
+        function updateSoftKeyState() {
+            rfb.updateSoftKeyState(this.value, this.checked);
+            return true;
+        }
         function updateState(rfb, state, oldstate, msg) {
-            var s, sb, cad, level;
+            var s, sb, level;
             s = $D('noVNC_status');
             sb = $D('noVNC_status_bar');
-            cad = $D('sendCtrlAltDelButton');
             switch (state) {
                 case 'failed':       level = "error";  break;
                 case 'fatal':        level = "error";  break;
@@ -80,8 +98,15 @@
                 default:             level = "warn";   break;
             }
 
-            if (state === "normal") { cad.disabled = false; }
+            var i;
-            else                    { cad.disabled = true; }
+            for (i = 0; i < buttons.length; i++) {
+                var elem = $D(buttons[i].name);
+                if (state === "normal") {
+                    elem.disabled = false;
+                } else {
+                    elem.disabled = true;
+                }
+            }
 
             if (typeof(msg) !== 'undefined') {
                 sb.setAttribute("class", "noVNC_status_" + level);
@@ -90,10 +115,15 @@
         }
 
         window.onscriptsload = function () {
-            var host, port, password, path, token;
+            var host, port, password, path, token, i;
 
-            $D('sendCtrlAltDelButton').style.display = "inline";
+            for (i = 0; i < buttons.length; i++) {
-            $D('sendCtrlAltDelButton').onclick = sendCtrlAltDel;
+                var button = buttons[i];
+                $D(button.name).style.display = "inline";
+                if (button.onclick) {
+                    $D(button.name).onclick = button.onclick;
+                }
+            }
 
             WebUtil.init_logging(WebUtil.getQueryVar('logging', 'warn'));
             document.title = unescape(WebUtil.getQueryVar('title', 'noVNC'));