Sort "flickers" on Flash target

Mike Evmm

Hello! :wave:

I'm trying to implement a Z variable system to allow for easy sprite sorting. My current code works fine on Windows, but the sprites flicker on Flash, regardless of whether I call sortSpriteByZ() before or after super.update(elapsed)!

Code:

function sortSpritesByZ() {
	sort(function(Order:Int, entityA:FlxBasic, entityB:FlxBasic):Int {
		var zA:Int = 0;
		var zB:Int = 0;
		
		if (Std.is(entityA, IZSortable)) zA = cast(entityA, IZSortable).Z;
		if (Std.is(entityB, IZSortable)) zB = cast(entityB, IZSortable).Z;
		
		return FlxSort.byValues(Order, zA, zB);
	}, FlxSort.ASCENDING);
}

And my IZSortableInterface:

interface IZSortable 
{
	public var Z:Int;
}

Result on Flash:

Imgur

starry-abyss

You should re-sort only when in group object added or changed its Z. Also make sure that overlapping objects have different Z.

Mike Evmm

Moving my sortSpritesByZ()to add(Object:FlxBasic) just doesn't work.

~~Why should overlapping objects have different Zs?~~ Just found out that's precisely why the sprites flicker; I guess HaxeFlixel isn't deterministic on how it decides which sprite should be on top, if they have the same Z value.

Still wanting to know where I should put sortSpritesByZ() instead of update() to prevent my FPS from plummeting.

starry-abyss

What do you mean by "moving my sortSpritesByZ() to add(Object:FlxBasic)"? Just call sortSpritesByZ() at the point where you add objects to FlxGroup (after both setting Z and adding to be precise).

Mike Evmm

@starry-abyss I mean

override public function add(Object:FlxBasic):FlxBasic 
{
	super.add(Object);
	sortSpritesByZ();
	return Object;
}

Which is meant to be cleaner than having to remember to call sort every time I call add. This is working now (I was calling sortSpritesByZ() before super.add(Object) and not after ), but there's still the issue of this not updating if I change a sprite's Z. Since the property comes from an Interface, I can't really have a set behaviour. Anyone have any ideas?

(By the way; flicker can be solved using

function sortSpritesByZ() {
		sort(function(Order:Int, entityA:FlxBasic, entityB:FlxBasic):Int {
			var zA:Int = 0;
			var zB:Int = 0;
			
			if (Std.is(entityA, IZSortable)) zA = cast(entityA, IZSortable).Z;
			if (Std.is(entityB, IZSortable)) zB = cast(entityB, IZSortable).Z;
			
			if (zA == zB)
				zB++;
			
			return FlxSort.byValues(Order, zA, zB);
		}, FlxSort.ASCENDING);
	}

)

starry-abyss

Can't you create similar convenience function, but for setting Z?

Mike Evmm

@starry-abyss From within the sprite itself, only if I have the sprite extend a SortableFlxSpriteor something, but I was trying to avoid that, since I can't then have the sprite extend anything else...

starry-abyss

I mean just have a method in PlayState or wherever which changes Z and calls sort.