YUI Library Examples: Menu Family: Adding A Context Menu To A TreeView

When adding context menus to large data structures like a <table> or large list (<ol> or <ul>), it is recommended to bind a single YAHOO.widget.ContextMenu instance to the structure's root element, than to a set of its child nodes (<tr>s or <li>s). Doing so significantly improves the performance of a web page or application by reducing the number of "contextmenu" event handlers as well as the number of YAHOO.widget.ContextMenu instances in memory.

Begin by creating a TreeView instance. Next, create an object that maps HTML ids to their corresponding TextNode instances. As each TextNode instance is added to the TreeView, store a reference to it in the map.

/*
     Initialize the TreeView instance when the "mytreeview" <div>
     is ready to be scripted.
*/

YAHOO.util.Event.onAvailable("mytreeview", function () {

/*
         Map of YAHOO.widget.TextNode instances in the 
         TreeView instance.
    */

var oTextNodeMap = {};

// Creates a TextNode instance and appends it to the TreeView

function buildRandomTextBranch(p_oNode) {

var oTextNode,
            i;

if (p_oNode.depth < 6) {

for (i = 0; i < Math.floor(Math.random() * 4); i++) {

oTextNode = new YAHOO.widget.TextNode(p_oNode.label + "-" + i, p_oNode, false);

oTextNodeMap[oTextNode.labelElId] = oTextNode;
                
                buildRandomTextBranch(oTextNode);

}

// Create a TreeView instance

var oTreeView = new YAHOO.widget.TreeView("mytreeview");

var n, oTextNode;

for (n = 0; n < Math.floor((Math.random()*4) + 3); n++) {

oTextNode = new YAHOO.widget.TextNode("label-" + n, oTreeView.getRoot(), false);
        
        /*
             Add the TextNode instance to the map, using its
             HTML id as the key.
        */
        
        oTextNodeMap[oTextNode.labelElId] = oTextNode;
        
        buildRandomTextBranch(oTextNode);

}

oTreeView.draw();

});

Once the TreeView is created, instantiate a ContextMenu specifying the TreeView instance's root element as its trigger. Lastly, add a "triggerContextMenu" event handler for the ContextMenu instance that uses the "contextEventTarget" property to retrieve the TextNode instance that triggered its display. A reference to the TextNode is stored in a variable (oCurrentTextNode), so that it can be manipulated by the addNode, editNodeLabel, and deleteNode functions.

/*
     The YAHOO.widget.TextNode instance whose "contextmenu" 
     DOM event triggered the display of the 
     ContextMenu instance.
*/

var oCurrentTextNode = null;

/*
     Adds a new TextNode as a child of the TextNode instance 
     that was the target of the "contextmenu" event that 
     triggered the display of the ContextMenu instance.
*/

function addNode() {

var sLabel = window.prompt("Enter a label for the new node: ", ""),
        oChildNode;

if (sLabel && sLabel.length > 0) {
        
        oChildNode = new YAHOO.widget.TextNode(sLabel, oCurrentTextNode, false);

oCurrentTextNode.refresh();
        oCurrentTextNode.expand();

oTextNodeMap[oChildNode.labelElId] = oChildNode;

}

/*
     Edits the label of the TextNode that was the target of the
     "contextmenu" event that triggered the display of the 
     ContextMenu instance.
*/

function editNodeLabel() {

var sLabel = window.prompt("Enter a new label for this node: ", oCurrentTextNode.getLabelEl().innerHTML);

if (sLabel && sLabel.length > 0) {
        
        oCurrentTextNode.getLabelEl().innerHTML = sLabel;

}

/*
    Deletes the TextNode that was the target of the "contextmenu"
    event that triggered the display of the ContextMenu instance.
*/

function deleteNode() {

delete oTextNodeMap[oCurrentTextNode.labelElId];

oTreeView.removeNode(oCurrentTextNode);
    oTreeView.draw();

}

/*
    "contextmenu" event handler for the element(s) that 
    triggered the display of the ContextMenu instance - used
    to set a reference to the TextNode instance that triggered
    the display of the ContextMenu instance.
*/

function onTriggerContextMenu(p_oEvent) {

/*
         Returns a TextNode instance that corresponds to the DOM
         element whose "contextmenu" event triggered the display
         of the ContextMenu instance.
    */

function getTextNodeFromEventTarget(p_oTarget) {

if (p_oTarget.tagName.toUpperCase() == "A" && 
                p_oTarget.className == "ygtvlabel") {

return oTextNodeMap[p_oTarget.id];

}
        else {

if (p_oTarget.parentNode && 
                    p_oTarget.parentNode.nodeType == 1) {

return getTextNodeFromEventTarget(p_oTarget.parentNode);
            
            }
        
        }
    
    }

/*
         Get the TextNode instance that that triggered the 
         display of the ContextMenu instance.
    */

var oTextNode = getTextNodeFromEventTarget(this.contextEventTarget);

if (oTextNode) {

oCurrentTextNode = oTextNode;

}
    else {
    
        // Cancel the display of the ContextMenu instance.
    
        this.cancel();
        
    }

}

/*
     Instantiate a ContextMenu:  The first argument passed to 
     the constructor is the id of the element to be created; the 
     second is an object literal of configuration properties.
*/

var oContextMenu = new YAHOO.widget.ContextMenu("mytreecontextmenu", {
                                                trigger: "mytreeview",
                                                lazyload: true, 
                                                itemdata: [
                                                    { text: "Add Child Node", onclick: { fn: addNode } },
                                                    { text: "Edit Node Label", onclick: { fn: editNodeLabel } },
                                                    { text: "Delete Node", onclick: { fn: deleteNode } }
                                                ] });

/*
     Subscribe to the "contextmenu" event for the element(s)
     specified as the "trigger" for the ContextMenu instance.
*/

oContextMenu.subscribe("triggerContextMenu", onTriggerContextMenu);

YUI Library Examples: Menu Family: Adding A Context Menu To A TreeView

Menu Family Examples:

More Menu Family Resources: