Since “only top-level components in the application can have context menus“, how would one make a different ContextMenu for every type of item in a tree? In particular, I want tree leaves to have different menu items enabled than the branches; e.g., the leaves should have “Properties” menu enabled, and the “Create new” menu disabled, and vice versa for the branches. Mac Martine mentions using
rollovers, which is cute, but it looks like a more robust way is to use
MOUSE_OVER (yeah, I tried both).

To do this, use the following TreeItemRenderer in the tree in question (obviously, you can choose to add/remove things
from the ContextMenu.customItems rather than enabling/disabling them…):

 public class ServerTreeRenderer extends TreeItemRenderer {
 
 override protected function updateDisplayList(unscaledWidth:Number, unscaledHeight:Number):void {
 super.updateDisplayList(unscaledWidth, unscaledHeight);
 if(super.data) {
 if (TreeListData(super.listData)) {
 leaf:Boolean = !TreeListData(super.listData).hasChildren ;
 super.label.addEventListener(
 MouseEvent.MOUSE_OVER, 
 function(evt:MouseEvent):void {
 // This will disable all items in my context menu (it's declared somewhere 
 // else, this is not a TreeItemRenderer method, duh...
 disableAll();
 if (leaf) {
 // propertiesItem is a ContextMenuItem...
 propertiesItem.enabled = true;
 } else {
 contextMenuContainer.createNewItem.enabled = true;
 }
 [...]
 

All of this is in anticipation of a promised exegesis on how a
custom ContextMenu works anyway (I have no time for this
at the moment), but works for now…

P.S. I just like the word “exegesis”. The more exegeses, the merrier…