Function buildGlyphAtlas

Packs font into one RGBA8 atlas (§56 MVP tier).

const atlas = buildGlyphAtlas();                       // the built-in face
atlas.width;                                           // 128
atlas.glyphs.get("A");                                 // { u0, v0, u1, v1, … }
const texture = new Texture(atlas);                    // @fourjs/render
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The packing

A monospace font's cells are all one size, so the packer is a grid, not a bin packer: rectangle packing exists to fit differently sized boxes, and running one over 96 identical rectangles would trade an exact answer for a heuristic. Glyphs are placed left to right, bottom row of cells first, in ascending code-point order, with the fallback box last. Column count is whatever makes the atlas roughly square and then rounds the width up to a power of two, which the height gets too.

Powers of two because a §77-tier texture with LINEAR filtering and CLAMP_TO_EDGE is safest at POT sizes across the WebGL 2 / WebGL 1 boundary, and because a POT atlas can grow mipmaps later without being repacked. The unused remainder is transparent and costs one quarter of a 128² atlas — 16 kB of the built-in font's 64 kB — which is a good trade against a repack.

Determinism (§33)

Nothing here reads a clock, a random number, or the environment: the same font and the same padding produce a byte-identical buffer and an identically ordered glyph map on every machine and in every process.