Fix negative animation frame number

[T1mL3arn]

I got in the situation when animations play backwards despite in aseprite editor they are clearly normal. The reason was that I used format for exported frames like this bla-bla-{frame} and prefix to add the anim like bla-bla. With this combination the frames are treated as negative integers, which results with reversed frame order.

I think there is no such thing as "negative frame numbers" in spritesheet animations, so here is the fix.

[Geokureli]

Can you include a test case that reproduces the issue? At a glance it should like your prefix is "bla-bla-" but you're saying it's "bla-bla" without the final dash

[T1mL3arn]

but you're saying it's "bla-bla" without the final dash

Yes, the prefix is "bla-bla". That's why "-4" number substring is extracted from a frame name like "bla-bla-4".

[T1mL3arn]

Example

var sprite = new FlxSprite();

// plain frame data from atlas json
var framesSource = {
	"frames": [
		{
			"filename": "top-right-walk-1",
			"frame": {
				"x": 71,
				"y": 0,
				"w": 71,
				"h": 156
			},
			"rotated": false,
			"trimmed": true,
			"spriteSourceSize": {
				"x": 29,
				"y": 20,
				"w": 71,
				"h": 156
			},
			"sourceSize": {
				"w": 128,
				"h": 192
			},
			"duration": 200
		},
		{
			"filename": "top-right-walk-2",
			"frame": {
				"x": 142,
				"y": 0,
				"w": 71,
				"h": 156
			},
			"rotated": false,
			"trimmed": true,
			"spriteSourceSize": {
				"x": 29,
				"y": 20,
				"w": 71,
				"h": 156
			},
			"sourceSize": {"w": 128, "h": 192},
			"duration": 200
		},
	]
};

// just building frames, skipping loading assets steps
var atlasFrames = new FlxAtlasFrames(FlxG.bitmap.add(new BitmapData(100, 100), false));
for (frame in framesSource.frames)
{
	@:privateAccess
	FlxAtlasFrames.texturePackerHelper(frame.filename, cast frame, atlasFrames, true);
}
sprite.frames = atlasFrames;

// add two animations from the same frames, using different prefixes
sprite.animation.addByPrefix('walk-incorrect', 'top-right-walk');
sprite.animation.addByPrefix('walk-correct', 'top-right-walk-');

var incorrect = sprite.animation.getByName('walk-incorrect');
var correct = sprite.animation.getByName('walk-correct');

trace('anim frames indicies  BAD: ${incorrect.frames}');
trace('anim frames indicies GOOD: ${correct.frames}');

// anim frames indicies  BAD: [1,0]
// anim frames indicies GOOD: [0,1]

[Geokureli]

In this case I would say the fix is to put the dash in the prefix since the prefix is "top-right-walk-" but I doubt people will try to use negative frame numbers. On the off-chance that someone does I've added warning logs. I've also fixed some existing things that have been bugging me, like wtf is a "postFix", lol

[Geokureli]

Thanks!