https://docs.godotengine.org/en/stable/tutorials/shaders/shader_reference/canvas_item_shader.html
CanvasItem shaders — Godot Engine (stable) documentation in English
CanvasItem shaders are used to draw all 2D elements in Godot. These include all nodes that inherit from CanvasItems, and all GUI elements. CanvasItem shaders...
canvasitem shadersgodot enginestabledocumentationenglish