Add support for action widgets

This is part of the groundwork for fixing #336

core/modules/widgets/action-sendmessage.js

@@ -0,0 +1,82 @@
+/*\
+title: $:/core/modules/widgets/action-sendmessage.js
+type: application/javascript
+module-type: widget
+
+Action widget to send a message
+
+\*/
+(function(){
+
+/*jslint node: true, browser: true */
+/*global $tw: false */
+"use strict";
+
+var Widget = require("$:/core/modules/widgets/widget.js").widget;
+
+var SendMessageWidget = function(parseTreeNode,options) {
+	this.initialise(parseTreeNode,options);
+};
+
+/*
+Inherit from the base widget class
+*/
+SendMessageWidget.prototype = new Widget();
+
+/*
+Render this widget into the DOM
+*/
+SendMessageWidget.prototype.render = function(parent,nextSibling) {
+	this.computeAttributes();
+	this.execute();
+};
+
+/*
+Compute the internal state of the widget
+*/
+SendMessageWidget.prototype.execute = function() {
+	this.actionMessage = this.getAttribute("$message");
+	this.actionParam = this.getAttribute("$param");
+};
+
+/*
+Refresh the widget by ensuring our attributes are up to date
+*/
+SendMessageWidget.prototype.refresh = function(changedTiddlers) {
+	var changedAttributes = this.computeAttributes();
+	if(changedAttributes["$message"] || changedAttributes["$param"]) {
+		this.refreshSelf();
+		return true;
+	}
+	return this.refreshChildren(changedTiddlers);
+};
+
+/*
+Invoke the action associated with this widget
+*/
+SendMessageWidget.prototype.invokeAction = function(triggeringWidget,event) {
+	// Get the parameter
+	var param = this.actionParam;
+	// If the parameter is missing then we'll assemble the attributes as a hashmap
+	if(!param) {
+		param = Object.create(null);
+		var count = 0;
+		$tw.utils.each(this.attributes,function(attribute,name) {
+			if(name.charAt(0) !== "$") {
+				param[name] = attribute;
+				count++;
+			}
+		});
+		// Revert to an empty parameter if no values were found
+		if(!count) {
+			param = undefined;
+		}
+	}
+	// Dispatch the message
+	this.dispatchEvent({type: this.actionMessage, param: param, tiddlerTitle: this.getVariable("currentTiddler")});
+	return true; // Action was invoked
+};
+
+exports["action-sendmessage"] = SendMessageWidget;
+
+})();