Add defineInitHook functionality

Author: marijnh

doc/manual.html

@@ -838,6 +838,13 @@ <h2 id="api">Programming API</h2>
     will cause the given value (usually a method) to be added to all
     CodeMirror instances created from then on.</p>
 
+    <p id="defineInitHook">If your extention just needs to run some
+    code whenever a CodeMirror instance is initialized,
+    use <code>CodeMirror.defineInitHook</code>. Give it a function as
+    its only argument, and from then on, that function will be called
+    (with the instance as argument) whenever a new CodeMirror instance
+    is initialized.</p>
+
     <h2 id="addons">Add-ons</h2>
 
     <p>The <code>lib/util</code> directory in the distribution

lib/codemirror.js

@@ -1986,6 +1986,7 @@ window.CodeMirror = (function() {
       if (extensions.propertyIsEnumerable(ext) &&
           !instance.propertyIsEnumerable(ext))
         instance[ext] = extensions[ext];
+    for (var i = 0; i < initHooks.length; ++i) initHooks[i](instance);
     return instance;
   } // (end of function CodeMirror)
 
@@ -2083,6 +2084,9 @@ window.CodeMirror = (function() {
     extensions[name] = func;
   };
 
+  var initHooks = [];
+  CodeMirror.defineInitHook = function(f) {initHooks.push(f);};
+
   var modeExtensions = CodeMirror.modeExtensions = {};
   CodeMirror.extendMode = function(mode, properties) {
     var exts = modeExtensions.hasOwnProperty(mode) ? modeExtensions[mode] : (modeExtensions[mode] = {});