Emit a transact event on the ve.dm.Document when a transaction occurs

We'll need this to let a MetaList observe a Document and adjust to changes.
We should probably also have SurfaceFragment listen to this event instead.

Change-Id: I9e811e242969eb44afe0b4fa8153d0fb1b0071cd

modules/ve/dm/ve.dm.Document.js

@@ -147,6 +147,14 @@ ve.dm.Document = function VeDmDocument( data, parentDocument ) {
 
 ve.inheritClass( ve.dm.Document, ve.Document );
 
+/* Events */
+
+/**
+ * @event transact
+ * @param {ve.dm.Transaction} tx Transaction that was just processed
+ * @param {boolean} reversed Whether the transaction was processed in reverse
+ */
+
 /* Static methods */
 
 /**

modules/ve/dm/ve.dm.TransactionProcessor.js

@@ -144,6 +144,8 @@ ve.dm.TransactionProcessor.prototype.process = function () {
 	}
 	// Mark the transaction as committed or rolled back, as appropriate
 	this.transaction.toggleApplied();
+	// Emit an event on the document
+	this.document.emit( 'transact', this.transaction, this.reversed );
 };
 
 /**

modules/ve/ve.Document.js

@@ -9,14 +9,21 @@
  * Generic document.
  *
  * @class
+ * @extends ve.EventEmitter
  * @constructor
  * @param {ve.Node} model Model to observe
  */
 ve.Document = function VeDocument( documentNode ) {
+	// Parent constructor
+	ve.EventEmitter.call( this );
 	// Properties
 	this.documentNode = documentNode;
 };
 
+/* Inheritance */
+
+ve.inheritClass( ve.Document, ve.EventEmitter );
+
 /* Methods */
 
 /**