add substituteKeyboardEvents option

Allows us to spy on the sane keyboard events to decide if we want mathquill to process them or not.

README.md

@@ -309,6 +309,12 @@ keyboards just don't work in Desmos on iOS, the tradeoffs are up to you.
 [stucox]: http://www.stucox.com/blog/you-cant-detect-a-touchscreen/
 [Modernizr]: https://github.com/Modernizr/Modernizr/issues/548
 
+
+`substituteKeyboardEvents`, a function that wraps the normal saneKeyboardEvents util
+so that normalized events can be spied on. If you specify new 'cut', 'paste', 'copy',
+'typedText', or 'keystroke' handlers then it's your responsibility to make sure the
+original handler gets called.
+
 Supported handlers:
 - `moveOutOf`, `deleteOutOf`, and `selectOutOf` are called with `dir` and the
   math field API object as arguments

src/publicapi.js

@@ -77,6 +77,7 @@ function getInterface(v) {
 
   MQ.L = L;
   MQ.R = R;
+  MQ.saneKeyboardEvents = saneKeyboardEvents;
 
   function config(currentOptions, newOptions) {
     if (newOptions && newOptions.handlers) {

src/services/textarea.js

@@ -66,10 +66,11 @@ Controller.open(function(_) {
       if (text) textarea.select();
     };
   };
+  Options.p.substituteKeyboardEvents = saneKeyboardEvents;
   _.editablesTextareaEvents = function() {
     var ctrlr = this, textarea = ctrlr.textarea, textareaSpan = ctrlr.textareaSpan;
 
-    var keyboardEventsShim = saneKeyboardEvents(textarea, this);
+    var keyboardEventsShim = this.options.substituteKeyboardEvents(textarea, this);
     this.selectFn = function(text) { keyboardEventsShim.select(text); };
 
     this.container.prepend(textareaSpan)

test/unit/publicapi.test.js

@@ -794,6 +794,27 @@ suite('Public API', function() {
     });
   });
 
+  suite('substituteKeyboardEvents', function() {
+    test('can intercept key events', function() {
+      var mq = MQ.MathField($('<span>').appendTo('#mock')[0], {
+        substituteKeyboardEvents: function(textarea, handlers) {
+          return MQ.saneKeyboardEvents(textarea, jQuery.extend({}, handlers, {
+            keystroke: function(_key, evt) {
+              key = _key;
+              return handlers.keystroke.apply(handlers, arguments);
+            }
+          }));
+        }
+      });
+      var key;
+
+      $(mq.el()).find('textarea').trigger({ type: 'keydown', which: '37' });
+      assert.equal(key, 'Left');
+
+      $(mq.el()).remove();
+    });
+  });
+
   suite('clickAt', function() {
     test('inserts at coordinates', function() {
       // Insert filler so that the page is taller than the window so this test is deterministic

test/visual.html

@@ -277,6 +277,12 @@ <h3>substituteTextarea</h3>
 
 <p>In Safari on iOS, this should be focusable but not bring up the on-screen keyboard; to test, try focusing anything else and confirm this blurs: <span id="no-kbd-math"></span> (confirmed working on iOS 6.1.3)</p>
 
+<h3>substituteKeyboardEvents</h3>
+
+<p>Should be able to prevent cut, typing, and pasting in this field. Should get a log of the event instead: <span id="disable-typing">1+2+3</span></p>
+
+<p>Should wrap anything you type in '<>'  <span id="wrap-typing">1+2+3</span></p>
+
 </div>
 <script type="text/javascript">
 window.onerror = function() {
@@ -446,6 +452,29 @@ <h3>substituteTextarea</h3>
     return $('<span tabindex=0 style="display:inline-block;width:1px;height:1px" />')[0];
   }
 });
+
+MQ.MathField($('#disable-typing')[0], {
+  substituteKeyboardEvents: function(textarea, handlers) {
+    return MQ.saneKeyboardEvents(textarea, $.extend({}, handlers, {
+      cut: $.noop,
+      paste: $.noop,
+      keystroke: $.noop,
+      typedText: $.noop
+    }));
+  }
+});
+
+MQ.MathField($('#wrap-typing')[0], {
+  substituteKeyboardEvents: function(textarea, handlers) {
+    return MQ.saneKeyboardEvents(textarea, $.extend({}, handlers, {
+      typedText: function (text) {
+        handlers.typedText('<');
+        handlers.typedText(text);
+        handlers.typedText('>');
+      }
+    }));
+  }
+});
 </script>
 </body>
 </html>