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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

32
src/runtime_graphics.c
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@@ -291,6 +291,10 @@ akerr_ErrorContext *akbasic_fn_rgr(akbasic_Runtime *obj, akbasic_ASTLeaf *expr,
double args[1];
int count = 0;
int field = 0;
int columns = 0;
int rows = 0;
int cellw = 0;
int cellh = 0;
int64_t answer = 0;
(void)lval; (void)rval;
@@ -312,6 +316,9 @@ akerr_ErrorContext *akbasic_fn_rgr(akbasic_Runtime *obj, akbasic_ASTLeaf *expr,
* is no device -- asking how big the screen is when there is no screen is a
* program bug worth reporting -- and the refresh that makes the answer
* current rather than whatever it was at attach.
*
* Fields 3 and 4 are ours too, and come from the text sink rather than the
* graphics device; see the comment on them below.
*/
switch ( field ) {
case 0:
@@ -325,8 +332,31 @@ akerr_ErrorContext *akbasic_fn_rgr(akbasic_Runtime *obj, akbasic_ASTLeaf *expr,
PASS(errctx, require_graphics(obj, "RGR"));
answer = (int64_t)obj->gfx.devheight;
break;
/*
* Fields 3 and 4 are the character cell, in the same pixels fields 1 and 2
* are in -- so a program can place a character and a sprite at the same spot
* without hardcoding a size measured against the host's font. They come from
* the *sink*, which is where a grid lives, and the grid is a text device's
* property rather than a graphics one: hence a separate refusal, naming the
* text device rather than the graphics one.
*
* `RWINDOW` answers the other half -- how many columns and rows there are --
* and it is the C128's own function for that question. This is here rather
* than on RWINDOW because a cell size is a fact about the surface, and
* because RWINDOW reports the current *window*, which makes dividing the
* surface by the column count wrong the moment a program calls `WINDOW`.
*/
case 3:
case 4:
FAIL_ZERO_RETURN(errctx, (obj->sink != NULL), AKBASIC_ERR_DEVICE,
"RGR needs a text device and this runtime has none");
FAIL_ZERO_RETURN(errctx, (obj->sink->grid != NULL), AKBASIC_ERR_DEVICE,
"RGR needs a text device with a character grid, and this one has none");
PASS(errctx, obj->sink->grid(obj->sink, &columns, &rows, &cellw, &cellh));
answer = (field == 3 ? (int64_t)cellw : (int64_t)cellh);
break;
default:
FAIL_RETURN(errctx, AKBASIC_ERR_BOUNDS, "RGR: field %d is outside 0..2", field);
FAIL_RETURN(errctx, AKBASIC_ERR_BOUNDS, "RGR: field %d is outside 0..4", field);
}
PASS(errctx, akbasic_environment_new_value(obj->environment, &out));