gbos - a tiny Unix-flavored OS for the Game Boy Color (kernel, shell, coreutils in C, RAM filesystem) https://git.sl0p.foo/gbos.git/atom/src/font.asm?h=master 2026-07-16T12:53:25Z 2026-07-16T12:53:25Z user user@clank 2026-07-16T12:53:25Z urn:sha1:db022ffc366c8e81cd1120aa0190661e43d5dc32 Replace the small-caps placeholder font with a real baseline-aligned 4x8 set covering all 96 printable ASCII: distinct lowercase with true ascenders (b d f h k l t) and descenders (g j p q y), digits, and punctuation. Metrics: caps/ascenders rows 1-5, x-height rows 2-5, baseline row 5, descenders into rows 6-7. Glyphs are ~3px wide in the 4px cell -- cramped but legible; the tile mechanism itself imposes no character-set limit. genfont.py now takes per-glyph (top, rows) so glyphs sit on the baseline. Demo strings in term_test updated to show mixed case + punctuation. Verified by screenshot: descenders visibly drop below the baseline. 2026-07-16T11:54:23Z user user@clank 2026-07-16T11:54:23Z urn:sha1:4656a1003226709e9b3c804ec32b4913fca4c7f4 Add a background-tile text terminal that packs TWO 4px-wide characters into each 8x8 tile, giving a 40x18 grid instead of the 20x18 you'd get from an 8x8 font. The tilemap is static (one dedicated VRAM tile per screen position); we rebuild a tile's 16 bytes from two glyphs whenever a character changes. 360 tiles exceed the 256 a single tilemap can address, so positions 256-359 live in VRAM bank 1 via the CGB tilemap attribute bank-bit -- hence CGB-only. - Switch the ROM to CGB (rgbfix -C). Safe for the FS: every process has PROC_WRAMB=1, so SVBK stays on bank 1 and the WRAMX FS caches don't move. - CGB BG palette 0 = white bg / black text via BCPS/BCPD. - src/term.asm: term_init (palette + static tilemap + clear buffer), build_tile (combine two 4px glyphs -> one 8x8 tile, correct VRAM bank), term_redraw (rebuild all tiles), term_puts, term_show, term_test. - src/font.asm: 96-glyph 3x5-in-4x8 font, generated by tools/genfont.py. - 40x18 text buffer at $D600 (WRAMX, above the FS caches). - tools/ppmview.py: render a --shot PPM as ASCII so the LCD is inspectable from the shell during development. Verified via emulator screenshot: "GBOS TERMINAL", the alphabet, and a bank-1 row all render legibly at 40 columns. Serial shell + filesystem still work unchanged. Note: a full term_redraw builds 360 tiles and takes ~8 frames; fine for incremental single-char updates, but scrolling needs a smarter path (next milestone). Input (no keyboard) is also still TODO.