Function ui_channels 

pub fn ui_channels() -> LitVertexChannels

Available on crate feature egui only.

The per-vertex channels a UI mesh is packed with.

The UI writes positions at full precision and in the plane — two components, with the shader supplying the zero third — and needs no skinning, and every vertex carries a texture coordinate and a premultiplied color. A caller packing a UI mesh builds its streams to match this.