Expose CanvasItem.get_canvas_layer() to GDScript/C#

[TML233]

Describe the project you are working on

An alternate UI solution implemented with scripts based on Node2D.

Describe the problem or limitation you are having in your project

While handling inputs, I need to calculate the order of my custom control roots in the viewport to properly propagate input events from Viewport to my custom control roots.
Because CanvasItem.get_canvas_layer() is not exposed to GDScript/C#, It's impossible to do that like how Godot Controls do that.

Describe the feature / enhancement and how it helps to overcome the problem or limitation

Expose get_canvas_layer() to GDScript.
It's also great to have a method to get which CanvasLayer node the CanvasItem node is in, just like you can get Viewport node using CanvasItem.get_viewport().

Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams

extends Node2D
func foo():
	var layer: int = get_canvas_layer()
	var layerNode: CanvasLayer = get_canvas_layer_node()

If this enhancement will not be used often, can it be worked around with a few lines of script?

As far as I know, there's no way to get the CanvasLayer from CanvasItem via script, since it's not exposed.
The only thing you can get is canvas RIDs, but you can't pull viewport canvas stacking layer data from RenderingServer.

Is there a reason why this should be core and not an add-on in the asset library?

It's basic Viewport/CanvasLayer functions in CanvasItem nodes.

[Sauermann]

var layerNode: CanvasLayer = get_canvas_layer_node()

Unfortunately this line is not as simple.
Canvas layers come in two different variants:

• as CanvasLayer node
• as part of the Viewport: CanvasItems, that aren't children of a CanvasLayer node, are put into the viewports default canvas layer and that canvas layer is not represented by a CanvasLayer node, but implicitly generated for the viewport.

This case will need to be treated in a special way.

[TML233]

var layerNode: CanvasLayer = get_canvas_layer_node()

Unfortunately this line is not as simple. Canvas layers come in two different variants:

• as CanvasLayer node
• as part of the Viewport: CanvasItems, that aren't children of a CanvasLayer node, are put into the viewports default canvas layer and that canvas layer is not represented by a CanvasLayer node, but implicitly generated for the viewport.

This case will need to be treated in a special way.

Returning null for nodes that are directly placed under Viewport is a good option, since there's no CanvasLayer node generated by Viewport in the scene tree.

[TML233]

I've posted a PR to implement this: godotengine/godot#87095