Tilelist buffering / caching / setting up next tile not on stage?

Question

I've created a tilelist and attached a listener to the Event.ADDED and Event.REMOVED to it, so that I can be notified when a row within it gets added and removed, for visual effect.  The problem is that the tilelist seems to buffer rows / columns in view + 1.  This breaks the entire system.  I've a sample fla file which has the following code in,
import example.testrow;
function setup():void {
     for(var i:uint = 0; i < 6; i++) {
          var row:testrow = new testrow();
          setColour(row, colours[i % 3]);
          row.listIndex = i;
          myList.addEventListener(Event.ADDED, onAddRemove);
          myList.addEventListener(Event.REMOVED, onAddRemove);
          myList.addItem({source: row});
function onAddRemove(event:Event):void {
     if(event.target is testrow) {
          trace(event.target.listIndex + ' ' + event.type);
function setColour(row:MovieClip, colour:uint):void {
     var tempCT:ColorTransform = row.transform.colorTransform;
     tempCT.color = colour;
     row.transform.colorTransform = tempCT;
myList.setStyle('skin', new Shape());
myList.setRendererStyle('imagePadding', 0);
var colours:Array = [0xFF0000, 0x00FF00, 0x0000FF];
setup();
This adds 6 new 'testrows' (simple movieclip containing a rectangle shape), then sets up the listeners as I've described, while also adding a 'listIndex' property to each row and changing their colour,  and also clearing all style from the TileList, so you can see clearly what's in it.  The TileList is set up very simply, with a rowCount of 3 and is vertical.
Below can be seen by using the thumb scroller of the scrollbar, but is much clearer when using the up & down buttons.
The problem can be seen straight away, because while only 3 should be shown, I get a trace statement from 0 to 3, ie 4 rows.  If at any stage you scroll down, it'll always be one step ahead of you, no matter how hard you try!
I can't imagine this is the proper way it is supposed to work, with this sort of ambiguous, inconsistent lookahead.  I mean, the way it works differs completely from being at the start of the list to being at the end.  If you scroll from 0 position, to position 1, you'll get the notification '0 removed' and '4 added', 0 should have been removed, but again 4 shouldn't be added yet, it's not displayed.  If you go to the end of the list and go from position 5, to position 4, you'll see that the behaviour is totally different, No notifications at all.  This shows that flash is keeping the next item cached, or whatever, as if it's on stage, without being on stage any time it can do.
This is very frustrating as I have been wanting a nice way to track what gets is on and off a tilelist and every other way has been just as frustrating, whereas I thought this would do it.  I initially thought it was just oddities with the sizing of the tilelist and the rows, but that's clearly not the case.  Is there *any* way to stop, or change this behaviour and have the tilelist add *only* the rows that are shown in the tilelist, rather than those rows, plus the next one?  It really doesn't seem like the best of behaviours.
http://seadersforums.appspot.com/static/tilelist_buffer.fla

Answer 1

1024x768 is 4x3.  2048x1536 is 4x3.  Both of these are current display dimensions for iPads 1-3.
HD video (1920x1080 or 1280x720) is a 16x9 aspect ratio.
Try putting a rectangle in a square. Unless you scale the retangle up and lose image on the sides you will not be able to properly fill the entire 4x3 display area. The easy compromise is letterboxing to ensure all of the rectangle is display in the square. The iPad is doing this with very little effort on your part.
In FC you can create a new sequence and go into the settings and customize it to 1024x768, 2048x1536 or
just about any other dimension. Even If you create a custom sequence at 1024 or 2048 in FC you will see the same results that the iPad is giving you with much less effort, render and conversion time (presuming your keynote workspace cannot change in dimensions or aspect ratio and you are unwilling to crop your 16x9 aspect ratio video to fill the space.)