Function ui_fragment 

pub fn ui_fragment(
    slab: &[u32],
    atlas: &Image2dArray,
    atlas_sampler: &Sampler,
    in_uv: Vec2,
    in_color: Vec4,
    in_draw_call_id: u32,
    frag_color: &mut Vec4,
)

2D UI fragment shader.

Evaluates SDF shapes, gradients, textures, and text glyphs depending on the element type.