slosh.git/tests/test_shadertoy.py, branch docs-new

slosh: rename the project from sl0ppty

2026-08-18T19:26:00Z

sl0p + pty was error-prone to type and the zero made it worse; slosh (slop + sh) is one syllable, impossible to typo, and slosh.foo is ours. Mechanical rename everywhere it appears: binary, env vars (SLOSH, SLOSH_SESSION, SLOSH_BIN, SLOSH_CONFIG), socket dir (/tmp/slosh-, $XDG_RUNTIME_DIR/slosh), config path (~/.config/slosh), header guards, src/sl0ppty.h -> src/slosh.h, contrib/sl0ppty-dev -> contrib/slosh-dev, the driving-slosh skill, docs and tests. The sl0ppi fork references and the sl0p theme stay: one is history, the other is the brand. The rename surfaced a latent bug in test_osc5577: the hello-reply answer always appeared on screen twice (ECHOCTL echo plus cat -v), but a seven-character implementation name happened to wrap the second copy across the 60-column boundary, so counting substrings in wrapped text found one and passed for the wrong reason. A five-character name moved the wrap and exposed it. The loop guard itself is correct -- with echo off before the request there is exactly one reply -- so the test now counts on de-wrapped text and tolerates the pane's own echo.

sl0ppty: ruff format the Python

2026-08-17T12:36:59Z

The bumpy one, again. Every `.py` outside `vendor/` plus the three `contrib/` scripts that are Python with no extension: 60 files, 6,714 lines rewritten, no behaviour changed. Nothing here is worth reading -- the next commit adds it to `.git-blame-ignore-revs` so `git blame` walks past it. It is a bigger reformat than the C was, 60% of the lines against 17%, and for a reason worth writing down rather than tuning away: ruff and black break a call that does not fit onto one argument per line, where this code aligned the continuation under the opening paren. The test suite is thousands of `check("some prose", cond, detail)` calls, so nearly every one of them changed shape and the suite grew 3,308 lines. Line length was the one lever that moved it -- 120 columns would have been a 40% reformat and no growth at all -- and it was left at 88, because picking an unusual width to dodge a one-time diff is paying forever to avoid paying once. Import sorting came with it. Two files had `import os, pty, uuid, select, struct, sys, termios, time, fcntl, signal` on one line and now have ten. Verified after, not before, because a formatter that alters behaviour would be worse than none: - `make retest`, 1801 checks green -- and this reformats the suite that does the checking, including `harness.py`, which every one of those files imports. - `make test-live`, the tty tests the fast suite skips. They matter here more than usual: `live_input.py` and `live_m0.py` are two of the files whose comma-imports were split, and nothing in the fast suite would have noticed if that broke them. - All 60 files still compile, `make fmt` twice in a row changes nothing the second time, and `ruff check --select I` has nothing left to say.

sl0ppty: PI is 180

2026-08-16T14:16:19Z

Angles here are degrees, and pi in an angle language is not a number -- it is a half turn. So `PI` is 180, `TAU` is 360, and a formula written the radian way ports across as written: sin(TAU * x / cols) one cycle over the pane's width sin(TAU * p * 3 / perim) three lobes fitted exactly to a border PI / 2 a quarter turn PI / 6 thirty degrees, exactly That last line is the argument. A numeric pi would be 3 in this language, and `3.14159 / 6` in integers is 0 -- so radians cannot express a sixth of a turn here at all, while degrees give it as a whole number. The pun is not a compromise; it is the more precise reading of the two. Which is why there is no `deg2rad` or `rad2deg` beside them, and asking for one says `unknown function`. There is one angle unit. A conversion could only lose the angle (`deg2rad(90)` is 1, and `sin(1)` is nearly nothing) or invent a second scale for the language to disagree with itself about. Spelled-out numbers rather than variables: they read no environment, carry no dependency, and fold into the program like the literals they are. The browser preview learned the same two, from the same table. Verified: 12 cases in `tests/expr_test.c`, including that `deg2rad` and `rad2deg` are refused; the cross-check agrees with the compiler on 700 evaluations, now including `sin(TAU * x / cols)` and friends. Two smaller things ride along, both from the repl. `PI`/`TAU` tab-complete, and its drift test grew a third table to check -- it already caught `sin`/`cos` missing before I did. And it now checks the script *parses* before starting a pane that runs it: I broke the indentation of one line here, and the failure arrived as `IndexError: list index out of range` from a pane that died before its prompt, which is a long way from "line 212".

sl0ppty: sin and cos

2026-08-16T13:58:11Z

128 + sin(t / 4) / 2 a breathe that is actually a sine abs(sin(x * 6 + t / 5)) a wave travelling along a frame abs(sin(dist(x, y, curx, cury) * 20 - t / 4)) / 2 ripples from the cursor Degrees in, -255..255 out. Two decisions, both for the same reason -- this is a language people type into a config file, not one they read a manual for. Degrees because that is what anybody guesses, and 255 because it is the scale every strength here already uses: `128 + sin(t / 4) / 2` is a breathe centred half way up with nothing to rescale, and `abs(sin(...))` is an amount as it stands. Every angle wraps, negative ones included. `t / 4` does not stop at 360 and an expression that died at one turn would be no use for the one thing this is for. A 91-entry table of round(255*sin) at one-degree steps, three quadrants by symmetry, no interpolation -- the argument is an integer and there is nothing between two degrees to interpolate. A table and not a polynomial because `contrib/shadertoy.html` reimplements this language in JavaScript so the preview can run in a browser, and `tests/test_shadertoy.py` compares the two on every expression: identical data with identical reduction cannot drift the way two approximations of one curve would. The JS carries the same 91 numbers. Until now the only oscillator was `abs(t / 6 % 510 - 255)`, a triangle wave written as arithmetic. It works and it looks like what it is -- a ramp with a corner in it. A sine has no corner, which is the whole difference between a pane that pulses and a pane that flickers. Verified: 19 cases in `tests/expr_test.c` (the cardinal angles, quadrant symmetry, wrapping past a turn and below zero, and the breathe idiom); the cross-check now agrees with the compiler on 660 evaluations including generated trig; the repl's completion drift test caught `sin`/`cos` missing from its list before I did, which is what it is for. Then six chains in a real pane -- breathe, travelling wave, clipped crests, plasma, rolling scanlines, cursor ripples -- each measured over eight distinct frames.

sl0ppty: bits

2026-08-16T13:49:07Z

`&` `|` `^` `~` `<<` `>>`, on the 32-bit value the VM already used. There was nothing: `x & 7` answered `unexpected trailing input at offset 2` and `(x ^ y) % 16 < 2` answered `expected ) at offset 3`, which is a fair description of a parser that had never heard of either. `^` is the reason to bother. `(x ^ y) & 1` is the cheapest interesting texture there is, and the language could express a sweep, a ramp and a comparison but not one bit of pattern without `%` gymnastics. **Bits bind tighter than comparison, which is not what C does.** `x & 7 == 0` means `x & (7 == 0)` in C -- a precedence Ritchie put on record as a mistake, kept for a decade of compatibility that a shader expression in a config file does not have. Here it asks what it looks like it asks. Among themselves the usual `&` then `^` then `|`; shifts stay where C has them, just under `+ -`. `&&` and `||` still parse as themselves: the bitwise rungs decline the first character when a second one follows it. Semantics are JavaScript's, deliberately and to the letter -- the shift count masked to five bits (`1 << 33` is 2), `>>` keeping the sign (`-8 >> 1` is -4). Not taste: `contrib/shadertoy.html` reimplements this language in JS so the preview can run in a browser, and `tests/test_shadertoy.py` compares the two on every expression it can think of. Anything C leaves implementation-defined had to be pinned to what JS would show, so the signed right shift is written out in the VM rather than left to the compiler. Verified: 22 new cases in `tests/expr_test.c` covering the operators, both precedence questions, the sign, and the masked count; the preview learned the same six operators and the same ladder, and the cross-check now agrees with the compiler on 564 evaluations, including generated ones that reach for bits. Then seven bitwise chains in a real pane -- an XOR texture, a drifting one, a stepped pulse that walks eight shades of `t >> 7 & 7` and needs no `abs`.

sl0ppty: shaders on the chrome, and two keys for the arrangement

2026-08-15T21:06:32Z

Five things, in one commit because they land in the same few files -- the action table, the shader pass, config.kdl -- and splitting them by hunk would buy a tidier log at the price of commits that do not build. Each is verified end to end; the suite is 46 files green. Chrome shaders. `where="chrome"` on any entry in `shaders` or in a `states` block runs that pass over a pane's frame -- border, padding, title, buttons -- instead of its contents. Nothing else changes: same registry, same `amount`, same expressions, same chain order, one new word, because a frame is another rect and so it is another pass. It runs over the frame's whole rect with the contents punched out as a hole, rather than four passes over four sides: an effect has to be able to travel round a border, and four passes would each count x/y from zero and restart at every corner. The hole keeps the two honest -- a skipped cell is never visited, so a full-strength chrome tint cannot reach your text. It is also the only kind of pass that can colour a pane a small window has collapsed to a single row (D6), which is the state where a colour is worth the most. `channel="fg"|"bg"|"both"` came out of looking at the first border flash: `tint` mixes both of a cell's colours, and a frame's background is the terminal's own default, so the pass materialised it to our guess at that default and mixed towards the colour -- a dark rectangle behind the glyphs, left there until the pane changed state. The mask is enforced by the pass, not the shader: the other colour is snapshotted before materialising and put back after, so an unset colour goes back to unset, it works for a built-in and a plugin alike, and no shader grows an fg-only twin of itself. A `bell` pane state and a `since` variable, because "flash the border when a pane rings" needed both and neither existed. `since` is milliseconds since the pane entered its current state, stamped in the one function that decides the state -- a transition is the one thing a frame cannot tell you, so it is remembered where it cannot disagree with the state it dates. `bell` ranks above the ambient states and below `dead`: a pane that rang while you were elsewhere is news, and a pane that rang and then exited is a pane that exited. It ends when you look at the pane, because that is what answering a bell is. Animation needed a clock and did not have one: a shader reading `t` only advanced when something else caused a frame, so a pulse froze the moment you stopped typing. `app_next_deadline_ms` now reports `anim_ms` while a chain that reads the clock ran over the last frame -- derived from what was applied, so a pulse hung off `dead` costs a clock while a pane is dead and nothing for the rest of the session. A `deadline` verb makes that observable; the server's poll loop already lived on the number. contrib/chrome has seven presets and the perimeter trick they are built on: on a frame the coordinate you want is distance along the ring, which the language can work out, and `min(d, P - d)` is what makes an effect cross the corner it started from. Hand-written, unlike contrib/shaders, because the toy previews contents and a frame has no preview to give -- so tests/test_chrome_presets.py checks each one the only way left: load it into a real session, assert the frame moves and the contents do not. `equalize` (C-a =) puts every share back to even: each split's children weighted by how many visible panes are behind them, so one pane beside a stack of three is a quarter of the width and "even" means the same thing at every depth. Exactly equal cell counts are not something a tree can always express, so the action promises the even division it can. `rotate-layout` (C-a Space) turns the whole tab a quarter turn clockwise. Every split changes axis and a row split's children reverse, because the pane on top of a stack is the pane on the right once you turn it; get that asymmetry wrong and you have a mirror image, which looks almost right until four turns fail to come back. They do come back, exactly, which is why the inverse is three more turns rather than a second mirrored routine with its own chance of being wrong -- and why a key as easy as space is the right one rather than a hazard. A turn is refused when it would not fit: a share of the height is not always a share the width can afford, and a node that cannot give its children their floor takes the whole tab down to a list. So the turn is tried, the layout is asked what it made of it, and one that flattened the tab is put back with a word. Same rule `split_fits` applies to splitting. Keys: the palette moves from `shift+p` to `p`, and cycling tabs from `n`/`p` to tab/shift+tab. `p` is pressed far more often than "the tab before this one" and was the only shifted letter in the defaults; tab is what every other tabbed thing cycles with, and `\e[Z` decodes as shift+tab on a plain terminal, so this costs nothing on a client without the kitty protocol. `n` is free again. The actions are untouched: two lines of config put the old binds back. The shader ABI goes to 3: `shade_ctx_t` gained `state_ms` and struct shader gained `channels`, both the pass's business rather than a shader's. Plugins need a rebuild, which is what the version is for.

contrib: presets worth stealing, and a test that they do anything

2026-08-14T22:02:51Z

Eleven examples, grouped, and most of them are less "effect" than *instrument*: a cursor line, a crosshair, indent guides, a right margin at three quarters, a torch that dims everything more than eight cells from where you are looking. Things that tell you where you are, inside a program that has never heard of any of them -- which is the argument for shading contents rather than chrome, made in examples instead of prose. Then the fun: phosphor and amber CRTs (grayscale, tint, scanlines, vignette as a four-pass chain), film grain, a rolling bar, an interlace flicker; sonar pings expanding from the cursor, ripples, a barber pole, plasma from two triangle waves, matrix rain with a fading tail; and every built-in written as an expression, because `vignette` being `dim` with an argument is the whole design and is better shown than argued. Two rules the presets follow, both about staying identical to the C: never multiply `t` (it is a millisecond clock and gets large -- divide it down first and the arithmetic stays in an int32 forever), and keep hash coefficients small for the same reason. `(x * 11) % 23` is fine; the usual Knuth constant is a different number in C than in JavaScript. The test now lifts the *presets* out of the page as well as the evaluator, so one added later is conformance-checked without anyone remembering to add it. And it evaluates every preset over a whole pane at four points in time and fails any that is zero everywhere -- an example that does nothing reads as a broken shader system rather than a bad example. That check caught its own first draft: sampling every other row made three `y % 2` effects look dead when they were fine. It samples every cell now, which costs six hundredths of a second for four hundred thousand evaluations, because the thing being tested is quick.

contrib: a shadertoy for shader expressions

2026-08-14T21:53:53Z

You cannot see an expression by reading it. `(y % 2) * 40` is scanlines and `(x > cols - 10) * 120` is a right margin, and neither is obvious until it is on a screen -- so here is a screen. One HTML file, no build and no server: open it and it works, offline, including from a checkout on a machine that has never run sl0ppty. It draws a fake pane with plausible contents, applies a chain of passes to every cell, and prints the config line to paste. The mouse moves the cursor, so `dist(x, y, curx, cury)` behaves the way it will in a pane rather than the way it does at coordinates you imagined. Anything reading `t` animates. The presets are every built-in written as an expression, which is the equivalence the whole design rests on: `vignette` and `spotlight` are not special, they are `dim` with an argument. It also reports what each expression *reads* and whether that makes it cacheable, because the dependency analysis is the interesting half of the implementation and is otherwise invisible. The hazard is that this is a second implementation of the language, in another language, and it would disagree with the compiler quietly -- in the third digit of a colour, on one preset, at one cursor position. So tests/test_shadertoy.py lifts the evaluator straight out of the page (not a copy of it, the page itself) and runs a few hundred expression/environment pairs through both it and src/expr.c, including the corners: division by zero, the ternary's untaken branch, `dist` counting a row double, and six expressions that both sides must refuse. build/expr_eval is the real compiler as a filter, which is what makes that comparison possible at all. It found a bug on its first run, in the page: unary `-` and `!` did not thread the environment through their closures, so `!x` threw instead of evaluating. Which is the argument for the test, made better than I could have made it. Skipped with a message when node is missing -- a checker for a contrib toy is not a reason the suite cannot run.