Align 2D origin (0, 0) to screen viewport center instead of top-left corner

[geekley]

Having the 2D (0, 0) origin align to the viewport/screen center would be much better for game development than the current way that aligns at the top left, specially for 2D games, but also in general.

Please add at least a project setting letting us make all scenes use this logic. I'd even go as far as making it default in new projects (but obviously keeping the option if you need the current behavior).
You cut put it at display/window/world/2d_origin_alignment = center | top_left.

Reasoning

The screen center is always special in both Node2D and Control, all designs will consider it in one way or another.
But screen top-left is NOT particularly special in most usages of Node2D, and in Control you can easily use anchors to deal with the screen corners as you should: independently of resolution and aspect ratio.

Thus an option for screen center origin alignment would greatly facilitate working independently of screen factor. It would specially help in 2D scenes with only central (or no) screen movement, but also in cases like top-down games where you start at (0, 0). I'd go as far as saying even 2D aspects of 3D games would benefit from this.

It also makes much more sense in the editor for "prefab" scenes, i.e. a 2D object to be instantiated. If (0, 0) is at center, the "show viewport" feature is useful to have a size comparison between the object and the screen, as the object will be at the center.

It would be easier to work with Control and Node2D interchangeably.
Most designs are based around the center of the screen (or of parent node), with corners treated specially.
It would also help a lot with any designs that deal with any sort of symmetry.

Lastly there's also the minor reason of floating-point values being more accurate near the origin, so favoring designs that put world's center around (0, 0) should have this additional little stability benefit.

[Sauermann]

When using Camera2D, have you had a look at Camera2D.anchor_mode?

[geekley]

Yes, I'm already taking that in consideration. It only affects Node2D stuff.
The issue is stuff you do with Control (like UI, maybe a background) being misaligned with the origin (and your game world) is bad for design. Having this alignment fundamentally in the screen would improve it at lot, specially for those use cases mentioned.
This would align the "show viewport" outline in editor, and also the actual values in-game of "screen px" units, all around (0, 0).

So, basically, you would properly design your UI aligned with the initial game world position.

[Calinou]

• Related to Optional centered Scene on "Play Scene" #1313.

This would be handy for some of the official demos (so they don't need a dummy Camera2D node), but this needs to be done in a way that doesn't break compatibility. This means we can't change how the 2D coordinate system works.

[geekley]

I suggested it being a project-wide setting exactly for this reason. So that it's used mostly only in new projects, to avoid breaking stuff in scripts that rely on the assumption that the 2D coordinate system has (0, 0) at top left of the screen.
I believe custom scripts can also benefit from using the logic of: (0, 0) is screen center, everything else varies responsively according to window/screen dimensions.

[Calinou]

With the project setting, I wouldn't change the coordinate system. Instead, I'd only change where the fallback Camera2D spawns (when there is no active Camera2D in the current scene).

[geekley]

@Calinou Ah but like I said, just having a centered Camera2D on the scene alone would not solve the issue, because that affects just Node2D, not Control. It's not the core of the problem.

What I'm asking for is compatibility between Node2D and Control, so the "show viewport" outline needs to be affected too, centered at (0, 0). Just adding a centered Camera2D to the scene doesn't fix that.

For example, if you need to implement touchscreen controls for moving, you may need to use TouchScreenButton (e.g. because of passby_press) and that's a Node2D. But you may need to position it like a Control, so you would naturally make it a child of a Control so that you can be properly responsive to any screen dimensions without custom code.
But even if you can make that setup work at runtime, it won't appear right in the editor because Node2D follows the Camera2D which is centered at origin, but Control follows the viewport which is offset as its origin is at top-left.

So whichever solution is used, it needs to fix the viewport alignment too.

[geekley]

Is there a similar "default" CanvasLayer, technically speaking?
I suspect one thing that might help solving it is adding anchor_mode to CanvasLayer, like how it works in Camera2D, and making the proposed project setting also apply to the default CanvasLayer, if that makes sense?

[hsandt]

For "prefab" / scene objects to instantiate in other scenes, there is this discussion:

Related to Add ability to center editor camera on scenes when running current scene
#8970

Suggestion solutions are more editor-focused than release-focused, though.

[ryanbeard82]

Would love to see a solution for this as well. Having my canvas layer elements (HUD, UI, etc) misaligned in the editor is a nightmare and leads to a very inefficient trial-and-error design approach.

[timothyqiu]

This could be a per-scene metadata. And it would also help the editor generate better scene thumbnails.

[geekley]

I agree that a per-scene override option would be an improvement.
But only if I can still have a project-wide option with that I could set to center by default.