Add the ability to blit CanvasItems to the CanvasItem behind it

[Shadowblitz16]

Describe the project you are working on

Image Editor Plugin

Describe the problem or limitation you are having in your project

I want to use ColorRects as canvas items to draw image layers
but I need to be able to merge them down

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

Add blit function to canvas item in which it draws to the canvas item's behind it with correct blending and shaders

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

Basicly it would just be as simple as blit() with no parameters.
Blitting would blit to a image if it's a TextureRect with a ImageTexture

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

It would be used for image and texture manipulation also idk

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

Its allows for easily blitting to surfaces with canvas items

[clayjohn]

I think the new CanvasGroup feature should solve this. godotengine/godot#43167

You can't blit to a canvasitem per se. You can only blit to Viewports. But I think the CanvasGroup can be used to achieve the effect you are looking for.

[Shadowblitz16]

well I need to be able to merge them down and keep the changes

[jonbonazza]

CanvasGroup will remove the need to merge them down. It solves your actual problem but in a different way than what you proposed.

[Shadowblitz16]

@jonbonazza in what way doesn't it remove the need to merge them down?
I am using them for image editing layers so I need to blit it onto the layer below and delete it

[Calinou]

Duplicate of #401 (implemented by godotengine/godot#43167).

[Shadowblitz16]

@Calinou this is more to do with images not textures