Add defineExtension API function

Author: marijnh

lib/codemirror.js

@@ -1441,6 +1441,10 @@ var CodeMirror = (function() {
       to: function() {if (this.atOccurrence) return copyPos(this.pos.to);}
     };
 
+    for (var ext in extensions)
+      if (extensions.propertyIsEnumerable(ext) &&
+          !instance.propertyIsEnumerable(ext))
+        instance[ext] = extensions[ext];
     return instance;
   } // (end of function CodeMirror)
 
@@ -1507,6 +1511,11 @@ var CodeMirror = (function() {
     return list;
   };
 
+  var extensions = {};
+  CodeMirror.defineExtension = function(name, func) {
+    extensions[name] = func;
+  };
+
   CodeMirror.fromTextArea = function(textarea, options) {
     if (!options) options = {};
     options.value = textarea.value;

manual.html

@@ -581,6 +581,12 @@ <h2 id="api">Programming API</h2>
       the editor's current content).</dd>
     </dl>
 
+    <p id="defineExtension">If you want define extra methods in terms
+    of the CodeMirror API, is it possible to
+    use <code>CodeMirror.defineExtension(name, value)</code>. This
+    will cause the given value (usually a method) to be added to all
+    CodeMirror instances created from then on.</p>
+
     <h2 id="modeapi">Writing CodeMirror Modes</h2>
 
     <p>Modes typically consist of a JavaScript file and a CSS file.