`akbasic_sink_init_tee()` wired write, writeln, readline, clear and --
conditionally -- moveto, and never `window`. The standalone AKGL frontend runs
the interpreter against a tee, so the fully implemented `sink_window()`
underneath it was unreachable: `WINDOW 0, 0, 20, 4` answered "WINDOW needs a
text device with a character grid, and this one has none" on the one build that
has a character grid. It reads as an oversight rather than a decision, because
`moveto` directly above it is forwarded with reasoning that applies unchanged.
`tee_window()` is that function, modelled on `tee_moveto()`, offered only when a
half can take it so the refusal still reads correctly through a stdio-only pair.
**Writing the test found a second one.** Both optional entry points are assigned
conditionally, and neither initializer cleared them first -- so a caller with a
sink on the stack got whatever was in that memory, and `CHAR` and `WINDOW`
decide whether they can act by testing those pointers for NULL. Both
`akbasic_sink_init_tee()` and `akbasic_sink_init_stdio()` now clear them. An
initializer that leaves a field alone is not an initializer.
tests/sink_tee.c gains a stand-in sink with a grid -- the two stdio halves have
neither entry point, which is exactly why they could not show that either is
forwarded -- and asserts both directions, the arguments arriving intact, and
that a grid-less pair still offers neither.
Verified end to end: `WINDOW 0, 0, 20, 4` then `PRINT` succeeds under
build-akgl/basic and still refuses by name under build/basic.
What this does *not* fix is that a drawing still has to be re-issued every
frame: the frontend never clears and SDL is double-buffered, so a drawing issued
once appears in one buffer only. Shrinking the text area makes the rest of the
window the program's; keeping something there is still the program's job. That
half is documented rather than fixed, and is filed as TODO.md section 9 item 5.
TODO.md section 6 item 31, struck.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
An AKGL build of `basic` was a terminal program with unused SDL linked into
it. It now opens the reference's 800x600 window, draws BASIC output in the
Commodore font, pumps events, lets you type at it, and still mirrors every
byte to stdout.
The stdout mirror is a composing sink rather than a second write inside the
interpreter, and lives in the core library where it needs no SDL. The line
editor waits for a typed line by borrowing one frame at a time from the host,
so nothing blocks and nothing owns an event loop it should not.
The whole golden corpus now runs through the SDL binary as well as the stdio
one, byte for byte.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
