Tiled layer order should help decide zIndex

[luttje]

Right now the plugin needs us to specify a zindex property for individual inserted objects (and colliders). Tiled already provides it's own sorting system for layers. These layers are saved in order to a .tmx or .json file.

Steps to Reproduce

1. Create a map in tiled with at least 2 tile layers and one or more object layers. (at least 2, because tile layers start at z index -1)
2. Sort the layers so the objects are above the tile layers
3. Create an inserted object (or collider) in one of the top object layers.
   For demonstration purposes I've positioned a fire (child of AnimatedFire layer) on top of the fireplace (child of Overlay1 layer):
   
4. Load the map in the way described in the README

Expected Result

I would expect the Tiled layer sorting to help this plugin decide the z index for the actors. Currently for tiles a z index is automatically decided, but this is not the actual order as the layer occurs in the map file. For actors and colliders an absolute zindex (specified in the property of the object) is needed.

Actual Result

The z index of the actor is unchanged (therefor 0) because no property is set. This causes the tiles to overlap the actor. (The tiles have their z index automatically decided starting from -1)

Current Workaround

Manually set a zindex property on each object and tile layers (this is how the examples in ./examples avoid this problem)

Proposed fix

Sadly I'm not motivated enough to create a PR, though I hope I can still aid you with a (hopefully) clear bug report and proposed fix:

• The .tmx file contains all tile and object layers in order
• This code would require a substantial change
• The map file would have to be parsed preserving the order of the nodes
• The layer's default zIndex would be it's offset from the first layer node

Should this be fixed?

In my opinion: eventually yes. Because:

• The sorting is respected by the Tiled map editor.
• The behavior intuitive.
• When I didn't see my objects in-game it took me a good couple minutes to realize that it was not something I was doing wrong.
• With more objects comes more manual management of z indexes, which can be tedious

However looking at the amount of work that is required to fix this, the workaround seems a viable alternative for now.

I really hope this helps you all.

Thanks for your time and effort!

[eonarheim]

100% agree, I would expect consistent z-index/sorting behavior between Tiled and the plugin.

I think you're on track with the proposed fix 👍

[eonarheim]

I think I might also be able to squeeze this one into the next release as well 🤞

[luttje]

Whether it makes the release or not: thanks a lot for your efforts!