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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>
This commit is contained in:
Andrew Kesterson
2026-08-02 00:05:17 -04:00
parent fd1f0d7c19
commit 694b446ce4
15 changed files with 361 additions and 21 deletions
Download Patch File Download Diff File Expand all files Collapse all files

30
src/sink_akgl.c
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@@ -410,6 +410,35 @@ static akerr_ErrorContext *sink_moveto(akbasic_TextSink *self, int col, int row)
* The full-screen geometry is remembered so a later WINDOW can grow back out;
* without it each call could only ever shrink.
*/
/**
* @brief Report the character grid, for RWINDOW and RGR.
*
* The four numbers a program cannot otherwise learn. Columns and rows are the
* *current* window rather than the whole screen, which is what RWINDOW means on
* a C128 and what a program placing text actually needs; the cell size is
* unaffected by windowing, which is what keeps a windowed program's text the
* same size as an unwindowed one's.
*/
static akerr_ErrorContext *sink_grid(akbasic_TextSink *self, int *columns, int *rows, int *cellw, int *cellh)
{
PREPARE_ERROR(errctx);
akbasic_AkglSink *state = NULL;
FAIL_ZERO_RETURN(errctx, (self != NULL), AKERR_NULLPOINTER, "NULL sink in grid");
FAIL_ZERO_RETURN(errctx, (columns != NULL && rows != NULL && cellw != NULL && cellh != NULL),
AKERR_NULLPOINTER, "NULL destination in grid");
state = (akbasic_AkglSink *)self->self;
FAIL_ZERO_RETURN(errctx, (state != NULL), AKERR_NULLPOINTER, "akgl sink has no state");
FAIL_ZERO_RETURN(errctx, (state->cellw > 0 && state->cellh > 0), AKBASIC_ERR_STATE,
"The sink has no character grid to measure");
*columns = state->columns;
*rows = state->rows;
*cellw = state->cellw;
*cellh = state->cellh;
SUCCEED_RETURN(errctx);
}
static akerr_ErrorContext *sink_window(akbasic_TextSink *self, int left, int top, int right, int bottom)
{
PREPARE_ERROR(errctx);
@@ -517,6 +546,7 @@ akerr_ErrorContext *akbasic_sink_init_akgl(akbasic_TextSink *obj, akbasic_AkglSi
obj->clear = sink_clear;
obj->moveto = sink_moveto;
obj->window = sink_window;
obj->grid = sink_grid;
SUCCEED_RETURN(errctx);
}