Add capsules/turtle.4th, a limited LOGO-style turtle graphics demo capsule

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First entry in the "cookbook" track: a demo capsule plus HOWTO, per the
sequencing laid out after the POST-coverage sweep. Built entirely in FORTH
on top of existing primitives -- fabric.4th's LINE (raster Bresenham) and
Q.SIN/Q.COS (Q48.16 trig), plus PLOT/FB-WIDTH/FB-HEIGHT -- no new C words.

FORWARD/BACK/LEFT/RIGHT/PENUP/PENDOWN/HOME/SETXY/SETHEADING/SETCOLOR give
the classic turtle model; POLYGON and STAR compose FORWARD+turn into simple
demo shapes; TURTLE-DEMO is a one-call visual smoke test. Not wired into
init.4th -- REPL-invoked only, matching the original idea's own scope.

Verified: mkcapsule --lint clean, hosted-build logic trace shows zero VM
errors and correct stack balance through the whole vocabulary, zero build
warnings and capsule loads cleanly on all three kernel architectures.
Visual pixel-level confirmation not yet done (needs an interactive
gtk-display session or driving past the ~25-30 min DoE-before-REPL wall),
documented as an open item in the HOWTO.

HOWTO: docs/working/architecture/TURTLE-GRAPHICS-HOWTO-20260819.md

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

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This commit is contained in:

Robert Allan James

2026-08-19 01:50:54 -04:00

co-authored by Claude Sonnet 5

parent abb858a300

commit e40134da0d

6 changed files with 13242 additions and 2 deletions

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