flan/HANDOFF-raylib-ports.md

Handoff — the last two raylib ports

Two examples, text_codepoints_loading and textures_image_processing, ported into examples/. This file is the running record: what is done, what was decided without being able to ask, and what is still open. PORTING.md has the findings that outlive the port — its last section, "Porting the raylib examples — the last two" — and this file has the state of the work.

Status — done

• examples/text-codepoints-loading.flan — builds
• examples/textures-image-processing.flan — builds
• test/programs/raylib-codepoints.flan and test/programs/raylib-image-processing.flan, both in the acceptance table, both gated on libraylib, both run plain and at -O0
• PORTING.md section for this round
• dune test --root . green

Four commits, each one a working state:

1. the plan and the open question (this file's first version)
2. PixelFormat, the one binding this round added
3. the image-processing example and its headless case
4. the codepoints example and its headless case

Open questions for the author

1. Vendor DotGothic16-Regular.ttf? text_codepoints_loading draws Japanese, and there is no CJK font in this tree. The font is SIL OFL 1.1 and therefore redistributable, but it is 2 MB of binary in a repository whose only binary asset is a 1 KB PNG, and that is a call about the repository rather than about the port. The example works either way: it looks for examples/resources/DotGothic16-Regular.ttf, and if it is not there raylib hands back the default font, the kana draw as boxes, and the program says on screen why. Drop the TTF in and the glyphs appear with nothing else to change. ~/Repositories/raylib/examples/text/resources/ has the file and its OFL notice.

2. lib/cimport.ml's agrees promises an arm it does not have. The comment at lib/cimport.ml:1291 lists, among the differences that are "expected and are not reported", "a (Ptr T) where the header says T * and the hand-written line chose something more specific". The function implements the enum-against-i32 arm and nothing else. That missing arm is the only thing standing between this round's two refused bindings and ordinary binding work — see PORTING.md §A.1 and §A.2, which have the exact declarations and the exact error. Not built: it is a compiler change and the freeze is on. It is small and it is well specified, and it is the thing to do first if these two ports are ever revisited.

3. The image-processing port keeps the C's LoadImageColors → UpdateTexture round trip even though (.data im-copy) is the same bytes and already the right type. Kept because it is what the C does and because nothing else in the corpus exercises that pair. If you would rather the example were the short version, the comment on reload-texture says exactly what to delete.

Deviations from the upstream C, all deliberate, all commented in place

• Neither asset is vendored. parrots.png has no licence at all in raylib's own LICENSE.md, so the image-processing example generates its picture. The generated image is asymmetric in both axes and has hard edges on purpose — a symmetric one makes the two flips indistinguishable and the blur invisible.
• The duplicate removal is a build-up, not a compaction. The C's shift-the-tail-down loop reads one element past the end of its allocation, which C tolerates and Flan's bounds check does not.
• The codepoint cursor clamps at both ends. The C's runs off both.
• GetCodepointPrevious is not called, because it cannot be: a Flan string reaches C as a NUL-terminated copy and that function reads backwards out of the pointer. Four lines of continuation-byte walking replace it, and the headless case pins them against LoadCodepoints.
• The UP key in image processing wraps to 7 and not to 8, which is the C's own off-by-one, left as it is so that the port and the example it claims to be do not disagree.

Things a next lane should know

• examples/ is not compiled by dune test. test/dune globs it so that imports resolve, nothing more. flan build <example> is the only proof an example compiles, and it is worth running on all of them after any change to vendor/raylib.
• The header check in vendor/raylib/headers runs on every ordinary build, not only on flan generate-c. A hand-written declare-c that disagrees with raylib-5.5.h therefore breaks every build in the tree, not just regeneration. That is what makes open question 2 a blocker rather than an inconvenience.
• (string (slice b off (len b))) is the idiom for a C char * cursor into the middle of a string, and it costs nothing. It is correct for every entry point that reads forwards and wrong for every one that reads backwards.
• slice-from-ptr is how a raylib pointer-plus-count becomes something with a length. Both new test programs lean on it.

Log

• Started from 957ba07 on dev-loop. The worktree came up on a much older commit (2c232dd, no examples/ directory at all) and was reset onto the branch tip first.