Add a count widget

core/modules/widgets/count.js

@@ -0,0 +1,59 @@
+/*\
+title: $:/core/modules/widgets/count.js
+type: application/javascript
+module-type: widget
+
+Implements the count widget that displays the number of tiddlers that match a filter
+
+\*/
+(function(){
+
+/*jslint node: true, browser: true */
+/*global $tw: false */
+"use strict";
+
+var CountWidget = function(renderer) {
+	// Save state
+	this.renderer = renderer;
+	// Execute the filter to get the initial count
+	this.executeFilter();
+	// Generate child nodes
+	this.generate();
+};
+
+CountWidget.prototype.executeFilter = function() {
+	// Get attributes
+	this.filter = this.renderer.getAttribute("filter");
+	// Execute the filter
+	if(this.filter) {
+		this.currentCount = this.renderer.renderTree.wiki.filterTiddlers(this.filter,this.renderer.tiddlerTitle).length;
+	} else {
+		this.currentCount = undefined;
+	}
+};
+
+CountWidget.prototype.generate = function() {
+	// Set the element
+	this.tag = "span";
+	this.attributes = {};
+	this.children = this.renderer.renderTree.createRenderers(this.renderer,[
+		{type: "text", text: this.currentCount !== undefined ? this.currentCount.toString() : ""}
+	]);
+};
+
+CountWidget.prototype.refreshInDom = function(changedAttributes,changedTiddlers) {
+	// Re-execute the filter to get the count
+	var oldCount = this.currentCount;
+	this.executeFilter();
+	if(this.currentCount !== oldCount) {
+		// Regenerate and rerender the widget and replace the existing DOM node
+		this.generate();
+		var oldDomNode = this.renderer.domNode,
+			newDomNode = this.renderer.renderInDom();
+		oldDomNode.parentNode.replaceChild(newDomNode,oldDomNode);
+	}
+};
+
+exports.count = CountWidget;
+
+})();