FlxTilemap one-way collision bug

[Gama11]

Originally reported here.

Code to reproduce:

package;

import flixel.FlxG;
import flixel.FlxSprite;
import flixel.FlxState;
import flixel.graphics.FlxGraphic;
import flixel.tile.FlxTilemap;
import flixel.util.FlxColor;

class PlayState extends FlxState
{
    public var sprite:FlxSprite;
    public var tiles:FlxTilemap;

    override public function create():Void
    {
        super.create();

        sprite = new FlxSprite(0, 8);
        sprite.makeGraphic(8, 8);
        add(sprite);

        tiles = new FlxTilemap();
        tiles.loadMapFrom2DArray([[1],[0]], FlxGraphic.fromClass(GraphicAuto));
        tiles.x += 20;

        add(sprite);
        add(tiles);
    }

    override public function update(_):Void
    {
        super.update(_);
        readInput();
        FlxG.collide(sprite, tiles);
    }   

    public function readInput()
    {
        var speed = 50;
        sprite.velocity.y =
            if (FlxG.keys.anyPressed([UP, W])) -speed;
            else if (FlxG.keys.anyPressed([DOWN, S])) speed;
            else 0;

        sprite.velocity.x =
            if (FlxG.keys.anyPressed([LEFT, A])) -speed;
            else if (FlxG.keys.anyPressed([RIGHT, D])) speed;
            else 0;
    }
}

Moving from left to right works fine - right to left doesn't though, the sprite gets stuck at the edeg of the tilemap. Doesn't seem to be a target-specific issue.

Supposedly, this doesn't happen in AS3 Flixel (haven't tested myself), so comparing some of the collision code might be helpful.
Originally reported here.

Happens in both dev and 3.3.8, so not a recent regression.

[SeiferTim]

If you add another column, this stops happening.
I'm not sure what the issue is, yet.

[Gama11]

Depends on what the column looks like... The original csv from the thread looked like this:

1,1,1,1,1,1,1,1,1,1
1,0,4,0,0,0,0,4,0,1
1,1,1,0,0,0,0,1,1,1
0,0,0,0,0,0,0,0,0,0
0,0,0,0,0,0,0,0,0,0
0,0,0,0,0,0,0,0,0,0
1,1,1,0,0,0,0,1,1,1
1,0,4,0,0,0,0,4,0,1
1,1,1,0,0,0,0,1,1,1
1,0,4,0,0,0,0,4,0,1
1,1,1,0,0,0,0,1,1,1
2,0,0,0,0,0,0,0,0,3
2,0,0,0,0,0,0,0,0,3
2,0,0,0,0,0,0,0,0,3
1,1,1,0,0,0,0,1,1,1
1,0,4,0,0,0,0,4,0,1
1,1,1,1,1,1,1,1,1,1

I just reduced it as much as possible.

[chiguire]

I assume this code compiles on Dev, it doesn't on 3.3.8. Tim, how did you add the other column? I'm using a CSV in a string "1,1\n0,0" and I'm still getting the collision.

[SeiferTim]

tiles.loadMapFrom2DArray([[1, 0],[0, 0]], FlxGraphic.fromClass(GraphicAuto));

[chiguire]

In AS3 Flixel, in FlxTilemap.overlapsWithCallback selectionX and selectionY are respectively set to 0 if they're less than 0. I added this in Haxe and the collision was correct.

[SeiferTim]

It looks like the issue with with FlxTilemap.overlapsWithCallback not bounding the selectionX and selectionY variables. I'll add the change to dev.

[chiguire]

It also seems to solve the problem in the original case :-) when debugging before, it seems that the collision function was looking in a negative column (-2), maybe it was accessing an invalid tile.

[chiguire]

Cheers, thanks for all the help.