Extend list widget with "index" attribute (#5611)

* Extend list widget with "index" attribute

* Fix refreshing bug

* Clarify performance note

core/modules/widgets/list.js

@@ -61,6 +61,7 @@ ListWidget.prototype.execute = function() {
 	this.template = this.getAttribute("template");
 	this.editTemplate = this.getAttribute("editTemplate");
 	this.variableName = this.getAttribute("variable","currentTiddler");
+	this.indexName = this.getAttribute("index");
 	this.storyViewName = this.getAttribute("storyview");
 	this.historyTitle = this.getAttribute("history");
 	// Compose the list elements
@@ -72,7 +73,7 @@ ListWidget.prototype.execute = function() {
 		members = this.getEmptyMessage();
 	} else {
 		$tw.utils.each(this.list,function(title,index) {
-			members.push(self.makeItemTemplate(title));
+			members.push(self.makeItemTemplate(title,index));
 		});
 	}
 	// Construct the child widgets
@@ -105,7 +106,7 @@ ListWidget.prototype.getEmptyMessage = function() {
 /*
 Compose the template for a list item
 */
-ListWidget.prototype.makeItemTemplate = function(title) {
+ListWidget.prototype.makeItemTemplate = function(title,index) {
 	// Check if the tiddler is a draft
 	var tiddler = this.wiki.getTiddler(title),
 		isDraft = tiddler && tiddler.hasField("draft.of"),
@@ -128,7 +129,14 @@ ListWidget.prototype.makeItemTemplate = function(title) {
 		}
 	}
 	// Return the list item
-	return {type: "listitem", itemTitle: title, variableName: this.variableName, children: templateTree};
+	var parseTreeNode = {type: "listitem", itemTitle: title, variableName: this.variableName, children: templateTree};
+	if(this.indexName) {
+		parseTreeNode.index = index.toString();
+		parseTreeNode.indexName = this.indexName;
+		parseTreeNode.isFirst = index === 0;
+		parseTreeNode.isLast = index === this.list.length - 1;
+	}
+	return parseTreeNode;
 };
 
 /*
@@ -142,7 +150,7 @@ ListWidget.prototype.refresh = function(changedTiddlers) {
 		this.storyview.refreshStart(changedTiddlers,changedAttributes);
 	}
 	// Completely refresh if any of our attributes have changed
-	if(changedAttributes.filter || changedAttributes.template || changedAttributes.editTemplate || changedAttributes.emptyMessage || changedAttributes.storyview || changedAttributes.history) {
+	if(changedAttributes.filter || changedAttributes.variable || changedAttributes.index || changedAttributes.template || changedAttributes.editTemplate || changedAttributes.emptyMessage || changedAttributes.storyview || changedAttributes.history) {
 		this.refreshSelf();
 		result = true;
 	} else {
@@ -211,23 +219,41 @@ ListWidget.prototype.handleListChanges = function(changedTiddlers) {
 			this.removeChildDomNodes();
 			this.children = [];
 		}
-		// Cycle through the list, inserting and removing list items as needed
-		var hasRefreshed = false;
-		for(var t=0; t<this.list.length; t++) {
-			var index = this.findListItem(t,this.list[t]);
-			if(index === undefined) {
-				// The list item must be inserted
-				this.insertListItem(t,this.list[t]);
-				hasRefreshed = true;
-			} else {
-				// There are intervening list items that must be removed
-				for(var n=index-1; n>=t; n--) {
-					this.removeListItem(n);
+		// If we are providing an index variable then we must refresh the items, otherwise we can rearrange them
+		var hasRefreshed = false,t;
+		if(this.indexName) {
+			// Cycle through the list and remove and re-insert the first item that has changed, and all the remaining items
+			for(t=0; t<this.list.length; t++) {
+				if(hasRefreshed || !this.children[t] || this.children[t].parseTreeNode.itemTitle !== this.list[t]) {
+					if(this.children[t]) {
+						this.removeListItem(t);
+					}
+					this.insertListItem(t,this.list[t]);
 					hasRefreshed = true;
+				} else {
+					// Refresh the item we're reusing
+					var refreshed = this.children[t].refresh(changedTiddlers);
+					hasRefreshed = hasRefreshed || refreshed;
+				}
+			}
+		} else {
+			// Cycle through the list, inserting and removing list items as needed
+			for(t=0; t<this.list.length; t++) {
+				var index = this.findListItem(t,this.list[t]);
+				if(index === undefined) {
+					// The list item must be inserted
+					this.insertListItem(t,this.list[t]);
+					hasRefreshed = true;
+				} else {
+					// There are intervening list items that must be removed
+					for(var n=index-1; n>=t; n--) {
+						this.removeListItem(n);
+						hasRefreshed = true;
+					}
+					// Refresh the item we're reusing
+					var refreshed = this.children[t].refresh(changedTiddlers);
+					hasRefreshed = hasRefreshed || refreshed;
 				}
-				// Refresh the item we're reusing
-				var refreshed = this.children[t].refresh(changedTiddlers);
-				hasRefreshed = hasRefreshed || refreshed;
 			}
 		}
 		// Remove any left over items
@@ -257,7 +283,7 @@ Insert a new list item at the specified index
 */
 ListWidget.prototype.insertListItem = function(index,title) {
 	// Create, insert and render the new child widgets
-	var widget = this.makeChildWidget(this.makeItemTemplate(title));
+	var widget = this.makeChildWidget(this.makeItemTemplate(title,index));
 	widget.parentDomNode = this.parentDomNode; // Hack to enable findNextSiblingDomNode() to work
 	this.children.splice(index,0,widget);
 	var nextSibling = widget.findNextSiblingDomNode();
@@ -311,6 +337,11 @@ Compute the internal state of the widget
 ListItemWidget.prototype.execute = function() {
 	// Set the current list item title
 	this.setVariable(this.parseTreeNode.variableName,this.parseTreeNode.itemTitle);
+	if(this.parseTreeNode.indexName) {
+		this.setVariable(this.parseTreeNode.indexName,this.parseTreeNode.index);
+		this.setVariable(this.parseTreeNode.indexName + "-first",this.parseTreeNode.isFirst ? "yes" : "no");
+		this.setVariable(this.parseTreeNode.indexName + "-last",this.parseTreeNode.isLast ? "yes" : "no");
+	}
 	// Construct the child widgets
 	this.makeChildWidgets();
 };

editions/test/tiddlers/tests/test-widget.js

@@ -350,6 +350,123 @@ describe("Widget module", function() {
 		expect(wrapper.children[0].children[4].sequenceNumber).toBe(5);
 	});
 
+
+	it("should deal with the list widget using an index variable", function() {
+		var wiki = new $tw.Wiki();
+		// Add some tiddlers
+		wiki.addTiddlers([
+			{title: "TiddlerOne", text: "Jolly Old World"},
+			{title: "TiddlerTwo", text: "Worldly Old Jelly"},
+			{title: "TiddlerThree", text: "Golly Gosh"},
+			{title: "TiddlerFour", text: "Lemon Squash"}
+		]);
+		// Construct the widget node
+		var text = "<$list index='index'><$view field='text'/><$text text=<<index>>/><$text text=<<index-first>>/><$text text=<<index-last>>/></$list>";
+		var widgetNode = createWidgetNode(parseText(text,wiki),wiki);
+		// Render the widget node to the DOM
+		var wrapper = renderWidgetNode(widgetNode);
+		// Test the rendering
+		expect(wrapper.innerHTML).toBe("<p>Lemon Squash0yesnoJolly Old World1nonoGolly Gosh2nonoWorldly Old Jelly3noyes</p>");
+		// Test the sequence numbers in the DOM
+		expect(wrapper.sequenceNumber).toBe(0);
+		expect(wrapper.children[0].sequenceNumber).toBe(1);
+		expect(wrapper.children[0].children[0].sequenceNumber).toBe(2);
+		expect(wrapper.children[0].children[1].sequenceNumber).toBe(3);
+		expect(wrapper.children[0].children[2].sequenceNumber).toBe(4);
+		expect(wrapper.children[0].children[3].sequenceNumber).toBe(5);
+		expect(wrapper.children[0].children[4].sequenceNumber).toBe(6);
+		expect(wrapper.children[0].children[5].sequenceNumber).toBe(7);
+		expect(wrapper.children[0].children[6].sequenceNumber).toBe(8);
+		expect(wrapper.children[0].children[7].sequenceNumber).toBe(9);
+		expect(wrapper.children[0].children[8].sequenceNumber).toBe(10);
+		expect(wrapper.children[0].children[9].sequenceNumber).toBe(11);
+		expect(wrapper.children[0].children[10].sequenceNumber).toBe(12);
+		expect(wrapper.children[0].children[11].sequenceNumber).toBe(13);
+		expect(wrapper.children[0].children[12].sequenceNumber).toBe(14);
+		expect(wrapper.children[0].children[13].sequenceNumber).toBe(15);
+		expect(wrapper.children[0].children[14].sequenceNumber).toBe(16);
+		expect(wrapper.children[0].children[15].sequenceNumber).toBe(17);
+		// Add another tiddler
+		wiki.addTiddler({title: "TiddlerFive", text: "Jalapeno Peppers"});
+		// Refresh
+		refreshWidgetNode(widgetNode,wrapper,["TiddlerFive"]);
+		// Test the refreshing
+		expect(wrapper.innerHTML).toBe("<p>Jalapeno Peppers0yesnoLemon Squash1nonoJolly Old World2nonoGolly Gosh3nonoWorldly Old Jelly4noyes</p>");
+		// Test the sequence numbers in the DOM
+		expect(wrapper.sequenceNumber).toBe(0);
+		expect(wrapper.children[0].sequenceNumber).toBe(1);
+		expect(wrapper.children[0].children[0].sequenceNumber).toBe(18);
+		expect(wrapper.children[0].children[1].sequenceNumber).toBe(19);
+		expect(wrapper.children[0].children[2].sequenceNumber).toBe(20);
+		expect(wrapper.children[0].children[3].sequenceNumber).toBe(21);
+		expect(wrapper.children[0].children[4].sequenceNumber).toBe(22);
+		expect(wrapper.children[0].children[5].sequenceNumber).toBe(23);
+		expect(wrapper.children[0].children[6].sequenceNumber).toBe(24);
+		expect(wrapper.children[0].children[7].sequenceNumber).toBe(25);
+		expect(wrapper.children[0].children[8].sequenceNumber).toBe(26);
+		expect(wrapper.children[0].children[9].sequenceNumber).toBe(27);
+		expect(wrapper.children[0].children[10].sequenceNumber).toBe(28);
+		expect(wrapper.children[0].children[11].sequenceNumber).toBe(29);
+		expect(wrapper.children[0].children[12].sequenceNumber).toBe(30);
+		expect(wrapper.children[0].children[13].sequenceNumber).toBe(31);
+		expect(wrapper.children[0].children[14].sequenceNumber).toBe(32);
+		expect(wrapper.children[0].children[15].sequenceNumber).toBe(33);
+		expect(wrapper.children[0].children[16].sequenceNumber).toBe(34);
+		expect(wrapper.children[0].children[17].sequenceNumber).toBe(35);
+		expect(wrapper.children[0].children[18].sequenceNumber).toBe(36);
+		expect(wrapper.children[0].children[19].sequenceNumber).toBe(37);
+		// Remove a tiddler
+		wiki.deleteTiddler("TiddlerThree");
+		// Refresh
+		refreshWidgetNode(widgetNode,wrapper,["TiddlerThree"]);
+		// Test the refreshing
+		expect(wrapper.innerHTML).toBe("<p>Jalapeno Peppers0yesnoLemon Squash1nonoJolly Old World2nonoWorldly Old Jelly3noyes</p>");
+		// Test the sequence numbers in the DOM
+		expect(wrapper.sequenceNumber).toBe(0);
+		expect(wrapper.children[0].sequenceNumber).toBe(1);
+		expect(wrapper.children[0].children[0].sequenceNumber).toBe(18);
+		expect(wrapper.children[0].children[1].sequenceNumber).toBe(19);
+		expect(wrapper.children[0].children[2].sequenceNumber).toBe(20);
+		expect(wrapper.children[0].children[3].sequenceNumber).toBe(21);
+		expect(wrapper.children[0].children[4].sequenceNumber).toBe(22);
+		expect(wrapper.children[0].children[5].sequenceNumber).toBe(23);
+		expect(wrapper.children[0].children[6].sequenceNumber).toBe(24);
+		expect(wrapper.children[0].children[7].sequenceNumber).toBe(25);
+		expect(wrapper.children[0].children[8].sequenceNumber).toBe(26);
+		expect(wrapper.children[0].children[9].sequenceNumber).toBe(27);
+		expect(wrapper.children[0].children[10].sequenceNumber).toBe(28);
+		expect(wrapper.children[0].children[11].sequenceNumber).toBe(29);
+		expect(wrapper.children[0].children[12].sequenceNumber).toBe(38);
+		expect(wrapper.children[0].children[13].sequenceNumber).toBe(39);
+		expect(wrapper.children[0].children[14].sequenceNumber).toBe(40);
+		expect(wrapper.children[0].children[15].sequenceNumber).toBe(41);
+		// Add it back a tiddler
+		wiki.addTiddler({title: "TiddlerThree", text: "Something"});
+		// Refresh
+		refreshWidgetNode(widgetNode,wrapper,["TiddlerThree"]);
+		// Test the refreshing
+		expect(wrapper.innerHTML).toBe("<p>Jalapeno Peppers0yesnoLemon Squash1nonoJolly Old World2nonoSomething3nonoWorldly Old Jelly4noyes</p>");
+		// Test the sequence numbers in the DOM
+		expect(wrapper.sequenceNumber).toBe(0);
+		expect(wrapper.children[0].sequenceNumber).toBe(1);
+		expect(wrapper.children[0].children[0].sequenceNumber).toBe(18);
+		expect(wrapper.children[0].children[1].sequenceNumber).toBe(19);
+		expect(wrapper.children[0].children[2].sequenceNumber).toBe(20);
+		expect(wrapper.children[0].children[3].sequenceNumber).toBe(21);
+		expect(wrapper.children[0].children[4].sequenceNumber).toBe(22);
+		expect(wrapper.children[0].children[5].sequenceNumber).toBe(23);
+		expect(wrapper.children[0].children[6].sequenceNumber).toBe(24);
+		expect(wrapper.children[0].children[7].sequenceNumber).toBe(25);
+		expect(wrapper.children[0].children[8].sequenceNumber).toBe(26);
+		expect(wrapper.children[0].children[9].sequenceNumber).toBe(27);
+		expect(wrapper.children[0].children[10].sequenceNumber).toBe(28);
+		expect(wrapper.children[0].children[11].sequenceNumber).toBe(29);
+		expect(wrapper.children[0].children[12].sequenceNumber).toBe(42);
+		expect(wrapper.children[0].children[13].sequenceNumber).toBe(43);
+		expect(wrapper.children[0].children[14].sequenceNumber).toBe(44);
+		expect(wrapper.children[0].children[15].sequenceNumber).toBe(45);
+	});
+
 	it("should deal with the list widget followed by other widgets", function() {
 		var wiki = new $tw.Wiki();
 		// Add some tiddlers

editions/tw5.com/tiddlers/widgets/ListWidget.tid

@@ -1,6 +1,6 @@
 caption: list
 created: 20131024141900000
-modified: 20190608162410684
+modified: 20210416175333981
 tags: Widgets Lists
 title: ListWidget
 type: text/vnd.tiddlywiki
@@ -82,10 +82,43 @@ The action of the list widget depends on the results of the filter combined with
 |template |The title of a template tiddler for transcluding each tiddler in the list. When no template is specified, the body of the ListWidget serves as the item template. With no body, a simple link to the tiddler is returned. |
 |editTemplate |An alternative template to use for [[DraftTiddlers|DraftMechanism]] in edit mode |
 |variable |The name for a [[variable|Variables]] in which the title of each listed tiddler is stored. Defaults to ''currentTiddler'' |
+|index |<<.from-version "5.1.24">> Optional name for a [[variable|Variables]] in which the numeric index of each listed tiddler is stored (see below) |
 |emptyMessage |Message to be displayed when the list is empty |
 |storyview |Optional name of module responsible for animating/processing the list |
 |history |The title of the tiddler containing the navigation history |
 
+!! `index` attribute
+
+The optional `index` attribute specifies the name of a variable to hold the numeric index of the current item in the list.
+
+Two additional variables are also set to indicate the first and last items in the list:
+
+* `<index-variable-name>-first` is set to `yes` for the first entry in the list, `no` for the others
+* `<index-variable-name>-last` is set to `yes` for the last entry in the list, `no` for the others
+
+For example:
+
+
+```
+<$list filter="[tag[About]sort[title]]" index="index">
+<div>
+<<index>>: ''<$text text=<<currentTiddler>>/>'' (is first: <<index-first>>, is last: <<index-last>>)
+</div>
+</$list>
+```
+
+Displays as:
+
+<<<
+<$list filter="[tag[About]sort[title]]" index="index">
+<div>
+<<index>>: ''<$text text=<<currentTiddler>>/>'' (is first: <<index-first>>, is last: <<index-last>>)
+</div>
+</$list>
+<<<
+
+Note that using the `index` attribute degrades the performance of the list widget because it prevents the optimisation of refreshes by moving list items around instead of rerendering them.
+
 !! Edit mode
 
 The `<$list>` widget can optionally render draft tiddlers through a different template to handle editing, see DraftMechanism.