`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>
ER# held numbers nothing explained. The appendix lists the four error classes
the interpreter prints, the eight codes it owns and what raises each, and the
codes that reach ER# from errno, libakerror and libakgl underneath it.
The table is not asserted. A program in the chapter trips seven of the eight and
prints what it got, and docs_examples byte-compares the result -- so the numbers
are checked rather than claimed. The eighth, 516, is not usefully trappable and
the chapter says why: entering a handler takes a scope, and the pool being empty
is what raised it.
Two things worth a reader's attention came out of writing it. Two codes register
the same ERR() text, so a program must compare the number and print the text.
And VAL reports libakerror's Value Error rather than the interpreter's 517,
which makes that number the platform's rather than ours -- filed as section 6
item 21, not fixed here, because deciding which libakstdlib failures to
translate is a boundary question and ENOENT out of DOPEN is the counter-case.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
The graphics verbs documented a coordinate transform that did not exist. With
SCALE off a coordinate went straight to akgl_draw_* as a pixel address, so an
800x600 window drew a C128 listing into its corner and left the rest unused --
while the chapter said coordinates were 320x200 and stretching to fit was the
host's business.
akbasic_GraphicsBackend gains a size entry point, require_graphics() asks it
before every verb that draws so a resized window is honoured between two
statements, and 320x200 becomes the fallback for a backend that leaves it NULL.
It is the record's one optional member, so a host written against the old header
keeps the behaviour it had.
SCALE now maps onto the device, and RGR(1)/RGR(2) report the drawing surface so
a program can use a window whose size it did not choose. RGR(0) is BASIC 7.0's
own field, the GRAPHIC mode.
SCALE also mapped xmax onto the width rather than onto the last pixel, so
SCALE 1, 319, 199 followed by DRAW 1, 319, 199 drew nothing at all -- one pixel
past the surface. Fixed in the same line, because it is what makes "SCALE gives
a C128 listing the whole window" true rather than nearly true.
The akgl test renders against a 128x128 target, deliberately smaller than the
old constants: a SCALE still dividing by them misses it entirely rather than
landing somewhere plausible.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Organised the way the C128 Programmer's Reference Guide is: the language
first, then each hardware area, then the reference sections. One markdown
file per chapter.
The verb and function references are generated from the interpreter's own
dispatch table, with an assertion that every row is described, so they cannot
drift out of step with what the program accepts. 98 verbs and 30 functions.
Every example was run before it was written down, which caught three claims
that were wrong: a whole FOR loop on one line prints nothing rather than
looping once, MID and INSTR count from zero where a C128 counts from one, and
a multi-line DEF returns a value the caller has to assign away.
Chapter 13 is the list a BASIC 7.0 programmer needs -- roughly sixty
documented differences, including the two known FOR defects and the fact that
drawing does not survive a frame.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
