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Let a program ask how big the text grid is

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`RGR(1)` and `RGR(2)` gave the window in pixels and nothing gave columns, rows
or the cell size -- so anything placing a character *and* a sprite at the same
spot had to hardcode a number measured by hand against whatever font the host
loaded. The Breakout in examples/ does exactly that, `CW# = 16`, and it is the
one thing in that listing that breaks on a different font or window.

**`RWINDOW` is BASIC 7.0's own answer and had never been implemented here.**
`RWINDOW(0)` is the current text window's rows and `RWINDOW(1)` its columns.
`RWINDOW(2)` reports a C128's 40 or 80 column screen mode, and this interpreter
has neither -- refused by name, because answering 0 would be a plausible lie,
which is worse than a refusal that says why.

The cell size in pixels is `RGR(3)` and `RGR(4)`, beside the surface's own
dimensions rather than on `RWINDOW`. Two reasons: a cell size is a fact about
the surface, and `RWINDOW` reports the *window*, so dividing `RGR(1)` by a
column count stops being right the moment a program calls `WINDOW`.

Both read a new optional `grid` entry point on `akbasic_TextSink` -- columns,
rows, cell width, cell height -- implemented by the akgl sink and forwarded by
the tee, in the shape `moveto` and `window` already had. NULL everywhere else,
so both verbs refuse by name against a sink with no grid. `akbasic_sink_init_
stdio()` clears it for the same reason it now clears the other two.

Measured on the standalone build: `RGR(3)` answers 16 and `RWINDOW` answers 50
columns by 37 rows -- the three numbers the Breakout listing had written out as
constants -- and `RWINDOW` follows a `WINDOW` call while `RGR(3)` does not.

tests/console_verbs.c drives the answers through a stand-in sink with a grid,
since the harness sink is stdio and has none; tests/graphics_verbs.c covers the
new `RGR` fields, their refusal, and the moved range bound. The `c excerpt=`
block in docs/10-embedding.md moves with the header, which is `docs_examples`
doing its job.

TODO.md section 6 item 31's second half, struck.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Co-Authored-By: Andrew Kesterson <andrew@aklabs.net>
This commit is contained in:
Tachikoma
2026-08-02 00:05:17 -04:00
parent 771485e003
commit f626d7985f
15 changed files with 361 additions and 21 deletions
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59
src/runtime_console.c
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@@ -187,6 +187,65 @@ akerr_ErrorContext *akbasic_cmd_window(akbasic_Runtime *obj, akbasic_ASTLeaf *ex
SUCCEED_RETURN(errctx);
}
/* --------------------------------------------------------------- RWINDOW -- */
/**
* @brief How big the current text window is, in characters.
*
* BASIC 7.0's own answer to the question, and it had never been implemented
* here: `RWINDOW(0)` is the number of lines and `RWINDOW(1)` the number of
* columns. Without it a program had no way to find out, so anything placing a
* character *and* a sprite at the same spot had to hardcode a cell size measured
* against whatever font the host loaded. The Breakout in `examples/` did exactly
* that, and it was the one thing in that listing that broke on a different
* window. TODO.md section 6 item 31.
*
* **`RWINDOW(2)` is refused by name.** On a C128 it answers 0 for 40-column mode
* and 1 for 80-column, and this interpreter has no such mode -- the grid is
* whatever the window divided by the font gives. Answering 0 would be a
* plausible lie, which is worse than a refusal that says why.
*
* The cell size in pixels is `RGR(3)` and `RGR(4)` rather than a field here: it
* is a question about the drawing surface, and it belongs beside the surface's
* own dimensions.
*/
akerr_ErrorContext *akbasic_fn_rwindow(akbasic_Runtime *obj, akbasic_ASTLeaf *expr, akbasic_Value *lval, akbasic_Value *rval, akbasic_Value **dest)
{
PREPARE_ERROR(errctx);
akbasic_Value *out = NULL;
double args[1];
int count = 0;
int field = 0;
int columns = 0;
int rows = 0;
int cellw = 0;
int cellh = 0;
(void)lval; (void)rval;
FAIL_ZERO_RETURN(errctx, (obj != NULL && dest != NULL), AKERR_NULLPOINTER,
"NULL argument in RWINDOW");
PASS(errctx, akbasic_args_numbers(obj, expr, "RWINDOW", args, 1, &count));
FAIL_ZERO_RETURN(errctx, (count >= 1), AKBASIC_ERR_SYNTAX, "RWINDOW expected a field number");
field = (int)args[0];
FAIL_NONZERO_RETURN(errctx, (field == 2), AKBASIC_ERR_DEVICE,
"RWINDOW(2) reports a C128's 40 or 80 column mode, and this interpreter has neither");
FAIL_ZERO_RETURN(errctx, (field == 0 || field == 1), AKBASIC_ERR_BOUNDS,
"RWINDOW: field %d is outside 0..1", field);
FAIL_ZERO_RETURN(errctx, (obj->sink != NULL), AKBASIC_ERR_DEVICE,
"RWINDOW needs a text device and this runtime has none");
FAIL_ZERO_RETURN(errctx, (obj->sink->grid != NULL), AKBASIC_ERR_DEVICE,
"RWINDOW needs a text device with a character grid, and this one has none");
PASS(errctx, obj->sink->grid(obj->sink, &columns, &rows, &cellw, &cellh));
PASS(errctx, akbasic_environment_new_value(obj->environment, &out));
PASS(errctx, akbasic_value_zero(out));
out->valuetype = AKBASIC_TYPE_INTEGER;
out->intval = (field == 0 ? (int64_t)rows : (int64_t)columns);
*dest = out;
SUCCEED_RETURN(errctx);
}
/* ---------------------------------------------------------------- service -- */
akerr_ErrorContext *akbasic_console_state_init(akbasic_ConsoleState *obj)