Allow opening of polygon editor without texture

[aXu-AP]

Gets rid of a nonsensical limitation. There's no reason to deny access to polygon editor when there's no texture set. While uv editor might not be very useful without texture (unless for custom shaders), the other editors are fully usable and useful regardless.

[RadiantUwU]

Static analysis looking great.

[akien-mga]

I suppose this makes sense, but I wonder how user-friendly it is.

While uv editor might not be very useful without texture (unless for custom shaders)

How does the UV editor look in this case?

And it's a bit confusing IMO that one needs to click a "uv" button to open the "Polygon 2D UV Editor" to edit anything but UVs.

[aXu-AP]

And it's a bit confusing IMO that one needs to click a "uv" button to open the "Polygon 2D UV Editor" to edit anything but UVs.

See godotengine/godot-proposals#8209, which aims to solve this issue and more UX problems.

How does the UV editor look in this case?

If there's a polygon, the outline (uv positions) are shown, just as with texture, but on a blank background:

If there's no polygon, then it's just blank canvas and essentially useless as there's no points to modify (the same applies to polygons and bones tabs). But this problem isn't exclusive to this pr, in current state it's the same. The proposal I linked solves this by putting "Points" tab as a first option.

[KoBeWi]

Maybe we could put a warning label that no texture is assigned? Probably more friendly than displaying empty editor window.

[KoBeWi]

The code looks fine.

Usability improvements can be done later as well, empty editor is not the only problem tbh.

[akien-mga]

Thanks!

[aXu-AP]

For solving the "blank canvas" issue, here's 2 enhancements:

• Open uv editor in point editing mode if no points #97081 Open more useful mode if there's no polygon yet
• Add pivot editing to UV editor #83612 If there's no texture, pivot point is good reference as to where one should draw the shape