slosh.git/src/pty.c, branch docs-new

windows: a native port, on ConPTY and AF_UNIX

2026-08-27T22:23:19Z

slosh builds and runs on Windows 10/11, x86-64 and ARM64, as one exe with no runtime dependency beyond the OS: panes, splits, tabs, detachable sessions, the config file and its live reload, the control socket, the mouse. The port is a compatibility layer rather than a fork. compat/win holds stub , , and friends that redirect to include/compat_win.h, which is force-included ahead of every translation unit -- so the existing sources keep their POSIX includes and their POSIX call sites, and the platform differences are answered in one place. Two decisions carry most of it. Everything the event loop waits on is a socket. On POSIX a pty master, an inotify descriptor and a unix socket are all file descriptors, so one poll() covers them; Windows has no such union, and WSAPoll waits on SOCKETs and nothing else. Rather than rewrite server.c's loop around WaitForMultipleObjects -- which caps at 64 objects and cannot express POLLOUT -- each non-socket source gets a pump thread that copies it into one end of a loopback socketpair. The loop is then the POSIX one unchanged, and only what sits behind the descriptor differs. Socket descriptors are tagged rather than guessed: a wrapped SOCKET comes back as SL_SOCK_BASE + slot, so read, write, close and poll can tell a socket from a CRT descriptor with certainty instead of inferring it from the numeric range. That is why socket() and accept() are shimmed too -- an untagged descriptor escaping into the loop is the one failure mode this scheme has, and it is worth closing completely. Three things bit hard enough to be worth naming. A pseudoconsole does not stop the child inheriting your stdio. CreateProcess copies the parent's standard handles into the child when STARTF_USESTDHANDLES is absent, and those win. With slosh's own stdout redirected -- a pipe under ssh, a file under --script, a log under the daemon -- the shell wrote its banner into slosh's output instead of into the pane, and the pane had a correct title (ConPTY emits that itself) over an empty body. The three handles are cleared for the duration of the call, leaving the child nothing to inherit. A ConPTY never reports EOF. The output pipe belongs to the pseudoconsole, not to the child, so it stays open after the child exits and pane_pump()'s read() -- the entire mechanism by which a pane learns its program is gone -- never returns 0. A pane whose shell had been told `exit` sat there looking alive forever. So the exit is waited for on the process handle, and ClosePseudoConsole is what then produces the EOF. That third thread is also why the per-pty state is reference counted: a pump blocked on a dead pipe must not be waited for, or pty_close would hang the session on the one program that misbehaves, so whoever finishes last frees. cmd.exe does not use CommandLineToArgvW's quoting. A literal quote is \" to an ordinary program and a backslash-then-end-of-quoted-section to cmd, so building `cmd /c notepad "C:\...\config.kdl"` the first way handed the editor \"C:\...\config.kdl\", backslashes and all, and notepad answered "Not a valid file name" about a path that existed. cmd /c now gets the rest of the line verbatim -- the caller composed a complete command with its own quoting, exactly as it does for sh -c. Paths are mixed, and only some programs mind. slosh joins with '/' while the environment supplies '\', so the config landed at C:\Users\you/.config/slosh/config.kdl. The CRT opens that without complaint, which is why --check reported it fine, but a GUI file dialog rejects it outright. Anything handed to another program now goes through sl_path_native() first; the internal representation is left alone. The rest is small. Panes run %ComSpec%, sessions live in %LOCALAPPDATA%\slosh rather than $XDG_RUNTIME_DIR because a session socket must not follow a roaming profile to another host, there is no SIGWINCH so a resize is noticed by comparing the console size on a bounded poll, no fork so the daemon is a fresh detached process that reconstructs its arguments on the command line, and no process group on a pty so the foreground program is the youngest descendant of the pane's shell. C-a e prefers whichever console editor is actually installed -- notepad is a GUI program, so a pane running it draws nothing and looks broken -- and says so when it has to fall back. make -f Makefile.windows ARCH=x86_64 (or aarch64) cross-compiles from a mac or Linux, and builds natively on the box with zig on PATH.

pty: open the slave before the fork, so a pane's size reaches it

2026-08-27T14:31:56Z

On Darwin a pty master has no line discipline until its slave has been opened: every TIOCSWINSZ on the master until then fails with ENOTTY and the size is dropped without a word. A pane is born 1x1 and told how big it really is by the layout an instant after the fork -- and with the child doing the open(), that message raced the child and usually lost. Nothing ever sent it again, so the program in the pane spent its whole life believing it had one row and one column. `C-a e` hit it every time, because the editor's pane is always brand new: nvim drew its screen into two rows in the corner of a 94x15 pane. The old code knew half of this -- the child set the winsize on the slave it had just opened, which is what kept a fresh pane from being 0x0 -- but that only fixed the *spawn* size. Every resize after it still went to a master that might not have a slave yet. So open the slave here, before the fork, and let the child inherit it. The fork copies the fd table, so the slave is open from the child's first instruction and every resize the parent sends afterwards lands; BSD's forkpty() does the same thing for the same reason. The winsize is set on that slave before the fork, which orders it ahead of anything the parent sends later, and the child no longer sets it at all: by the time the child ran, the size it was spawned with could already be stale, and writing it back would undo the very resize this is about. test_pty_size.py asks the pane's own program what size it thinks it is -- for the first pane, for a pane from a split, and after a resize -- and compares it to the pane. It printed "1 1" against a 74x18 pane before this. live_m0.py asked `tput cols`, which needs a terminfo entry for xterm-ghostty and therefore fails on most macs for a reason that has nothing to do with resizing. `stty size` asks the tty itself, which is the thing under test.

macos: the kernel still knows, it just spells /proc differently

2026-08-26T14:11:42Z

Portability fixes contributed by our macOS developer, applied with one hardening tweak (below). Darwin has no /proc, so everything that read one gets the native answer: live_cwd via proc_pidinfo(PROC_PIDVNODEPATHINFO), the foreground command via sysctl(KERN_PROCARGS2) parsed back into the NUL-separated shape /proc//cmdline gives, and SLOSH_BIN via _NSGetExecutablePath plus realpath. The pty gets its winsize set on the slave after opening it, because Darwin attaches no line discipline to the master until then and the earlier TIOCSWINSZ was silently dropped -- a pane born 0x0. The shader repl binds tab in libedit's own words, since macOS ships Python's readline as a libedit wrapper that accepts GNU syntax in silence. Two finds are cross-platform bugs: a toast wider than the screen minus the gap computed a negative x that uint16_t made ~65533, drawing the longest messages -- the ones most worth reading -- off screen; now the middle is elided (a path's tail is the half you needed) and x clamps. And a pane label was 128 bytes, which a Homebrew interpreter's full path exceeds before its arguments even start; dump-layout wrote the truncation down and a restore ran it, so it is 1024 now. Saving a layout learned cwd_as_named: the kernel answers with the physical path, and on macOS /tmp is a symlink to /private/tmp, so a layout that said cwd="/tmp" stopped round-tripping through a save. If realpath(named) is where the pane still is, the named spelling wins. Tests follow: realpath'd tmpdirs, the scroll test reads the shell's first prompt instead of spelling out bash 5.3, and wrapped pane text is joined before matching a long path. One tweak on top of the contribution: the elision needs five columns for a head, the dots and a tail -- below that `avail - 3` goes negative, and negative as size_t is a pointer into the weeds; a terminal that narrow gets a plain clip.

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: clang-format the tree

2026-08-17T12:22:38Z

The bumpy one. `make fmt` over every `.c` and `.h` outside `vendor/`: 32 files, 1,843 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. Two thirds of it is alignment the formatter now owns: trailing comments in a struct, continuation lines under a signature. The rest is the hand-packed tables opening up to one entry per line -- `ACTIONS`, `NAMED_KEYS`, `ACTION_HELP`. That is a real loss of density and a real gain in diffs: adding an action was a reflow of the block and is now one line. Anything worth keeping packed can be fenced with `// clang-format off`; nothing was, on the grounds that a table is the thing a formatter is for. **One change is not formatting.** `src/config.h` had three trailing comments glued onto one field: uint16_t hover_delay_ms; /* how long the pointer must rest to arm a guide */ /* how long an announcement stays up */ /* rows per wheel notch */ -- `toast_ms`'s and `scroll_lines`' comments, landed on their neighbour by an earlier edit, documenting the wrong things ever since. It is in this commit because it is what caught it: clang-format could not settle on that line, wrapping it one way and then re-indenting the wrap on a second pass, so `make fmt` was not idempotent. The comments are back where they belong and it is. Verified after the reformat, not before: `make clean && make all` is warning-free, `make retest` is 1801 checks green, and `make fmt` twice in a row changes nothing the second time. A formatter that alters behaviour would be worse than none, so the gate was the whole suite rather than a reading of the diff.

sl0ppty: carry the terminal's cell size, so images can have a size

2026-08-14T21:13:56Z

"Kitty graphics pass through" was true of the tests and not of anything else. Every test transmitted and placed in one command with explicit c=/r=; real programs upload once with `a=t` and place per frame with `a=p`, saying nothing about cells, and that path was broken from end to end. A placement that does not say how many cells it covers is sized from the image's pixels and the cell size. We never had a cell size: - pty_spawn and pty_resize left ws_xpixel/ws_ypixel at zero, so a program asking its own tty how big a cell is got nothing and fell back to guessing; - ghostty_terminal_resize was called with 0, 0 for the cell size, so lib-vt computed zero cells for such a placement -- and a placement covering zero cells is skipped, which on screen is an image that simply is not there. So the size now runs the whole way through. The client reads it from TIOCGWINSZ (re-read on every resize, because a window can move to a monitor with different metrics), MSG_HELLO and MSG_RESIZE carry it -- a 4-byte payload still means "I did not say", so an older client still attaches -- the app hands it to every pane in every tab, and each pane gives it to both its pty and its terminal. Where nobody knows, the default is 8x16 rather than 0. That is the whole lesson of this bug: a plausible cell size means an image appears at roughly the right size, and a zero means it does not appear at all. `{"cmd":"resize"}` takes optional cell_w/cell_h, so a script can be a client that knows its own metrics, and so the tests can be one. The tests now use the protocol the way programs use it, including a check that a program can read real pixel dimensions out of its own pty -- the thing that was silently zero. The remaining half of the fix is one layer down, in vendor/patches/0001.

sl0ppty: let a child's exit status survive long enough to be read

2026-08-14T19:32:25Z

The server set `signal(SIGCHLD, SIG_IGN)`, which is not the same as having no handler. SIG_IGN asks the kernel to reap children itself and throw their statuses away, so `waitpid` can never answer: every pane's program exited with "no idea". Nothing read a status yet, so nothing was visibly wrong -- and the headless driver, which is what the whole test suite drives, never set it at all. A suite that is green either way is a suite that would never have caught this. SIG_DFL is what was actually wanted: SIGCHLD's default action is to be discarded, so nothing is interrupted and no handler is needed, but the child waits as a zombie until somebody asks how it went. That makes statuses readable and zombies possible, so pty_close now collects the child it just hung up rather than glancing once with WNOHANG -- bounded to a few hundred microseconds, because a process that outlives a SIGHUP is a larger problem than the process-table entry it leaves behind.

sl0ppty: rename from sl0ptty

2026-08-14T10:13:18Z

A pty is a pseudo-terminal, and that is what this multiplexes: the extra t was never standing for anything. Renaming now, while the only users are the people who typed the old name on purpose, is cheaper than renaming later. Mechanical, but not only cosmetic. The name is also the runtime contract, so this moves $SL0PTTY and $SL0PTTY_CONFIG, ~/.config/sl0ptty/config.kdl, the socket directory ($XDG_RUNTIME_DIR/sl0ptty, /tmp/sl0ptty-), and the identity string a program gets back from an OSC 5577 hello. A session left running under the old binary keeps its old socket directory and is invisible to the new one; there is no migration and it does not seem worth writing one. The sl0ppi fork keeps its name: it is a different thing, and D1 still points at it.

sl0ptty: M0 — libghostty-vt vendored, one pane, compositor, diff renderer

2026-08-13T20:00:03Z

Design contract in DESIGN.md. libghostty-vt vendored fresh from ghostty main@bedb6f2 (zig 0.16), built to a 14MB static lib. M0: pty spawn (no libutil), a lib-vt terminal per pane, a screen cell buffer, a diff emitter that repaints only what changed, raw mode, SIGWINCH, and a ~120Hz frame cap that coalesces pty reads. Also the seed of the headless harness: --headless dumps the composited screen without a tty, so composition is testable in milliseconds. tests/live_m0.py covers what headless cannot: raw mode, the diff emitter, resize propagation, and the quit path. 6/6 green.