---
name: schunix-text-rendering
description: "The text layer that replaces the 8x16 character-cell grid — glyph metrics, surfaces, coverage blending, UTF-8."
metadata: 
  node_type: memory
  type: project
  originSessionId: 9d8a2aef-bcf0-47a0-96c6-f706efab4a95
  modified: 2026-08-08T22:45:34.934Z
---

Built 2026-08-09. `include/gfx/text.h` + `kernel/dev/text.c`. Nexoniarz: "using ANSI
fonts in 2026 is a not funny joke."

**The font was never the problem — the grid was.** The console indexes
`font_data[256][16]` and steps the cursor eight pixels. A grid cannot do
variable-width glyphs, cannot position text off a multiple of eight, cannot
anti-alias, and cannot represent a codepoint above 255. A nicer bitmap fixes
none of that.

Three decisions that make the layer worth having:

- **Glyphs carry metrics** (`w`, `h`, `bearing_x/y`, `advance`). Variable-width
  text *is* that; everything else follows. `text_measure()` exists because you
  cannot centre or lay out anything without it.
- **Draws into a `struct surface`, not the screen.** `{pixels, stride, width,
  height}`. A compositor draws off-screen and presents; rendering that writes
  straight to the VGA aperture is useless to it. Works on the virtio-gpu back
  buffer, a window buffer, or the VGA aperture, none of which know about each
  other.
- **`struct font_ops` behind an interface, and glyphs carry 8-bit *coverage*,
  not bits.** The bitmap font fills it with 0 and 255 only, which costs nothing
  — and a TrueType rasteriser then plugs in with no caller changing, because it
  already has somewhere to put anti-aliased edges. `blend_px()` reads the
  destination for the same reason.

Pen position is on the **baseline**, as every non-terminal text API does, so
glyphs of different heights sit on a common line.

**Verified** with `echo t > /proc/sysrq` + `tools/textshot.ps1`: text at x=61
and x=63, a checkerboard background visible *around* the glyphs (no cell boxes),
`┌─┐ █▓▒░ ° ± → •` above U+00FF, and a string measured at 160 px then centred on
it. The old console renders in the same screenshot with solid cell backgrounds —
a useful side-by-side.

## Traps hit

- `include/gfx/font.h` **defines** `font_data` rather than declaring it, so
  including it from a second file duplicates the symbol under `-fno-common`.
  text.c declares `extern unsigned char font_data[256][16];` instead; the header
  is generated data and is better left alone.
- The built-in font is **CP437, not Latin-1** (known trap in this codebase).
  `to_cp437()` maps the ~25 codepoints worth having — box drawing, blocks,
  arrows, degree. **That table exists to be deleted** when a real font lands; it
  is a bridge, not a design.
- A missing glyph draws U+25A1 or `?`, never nothing. Silently shorter text
  hides the fault.
- `utf8_next()` always advances, even on malformed input — a decoder that does
  not is a hang, not a rendering artefact. Rejects surrogates and overlong
  encodings.

## The typefaces, decided 2026-08-09

- **Roboto** for the DE / WM / compositor. **Apache-2.0** -- the same licence as
  Schunix, so it needs only a NOTICE entry.
- **JetBrains Mono** for the terminal / TTY. **SIL OFL 1.1**, and it declares
  **no Reserved Font Name** (checked: the copyright line names none; the only
  "reserved font name" hit in OFL.txt is the licence defining the term). So a
  modified version may keep the name -- which matters, because pre-rasterising
  a font into bitmaps at build time *is* a modification and an RFN would have
  forbidden keeping the name on the result.

OFL keeps the font under OFL inside an Apache-2.0 system, does not reach
anything else, and only forbids selling the font on its own. Both fetched and
verified at source, not assumed. Full note in `docs/licensing.md` ("Fonts").

Neither is in the tree yet -- there is no rasteriser to use them, and shipping
a TTF nothing can read would be dead weight.

## Not done

The console still uses the old path; nothing is ported to this yet. Porting
`vga_putc` onto it is the obvious follow-up and would delete the cell grid for
good. A TTF rasteriser is a separate provider behind `font_ops` — the layer is
what was blocking it, and it no longer is.