rio-grid

Rio's shared grid-emission layer: turns a row of terminal cells plus its resolved styles into the GPU cell primitives (CellBg / CellText) that Rio's renderer draws. One pass emits backgrounds, one run-building pass emits glyphs (shaping runs, drawable sprites, underlines), with selection, search-highlight, and hint-label handling applied per row.

It sits between the terminal core (rio-vt) and the renderer, and is consumed by both the Rio terminal itself and libsugarloaf's C ABI so embedders share the exact same emission logic.