180 lines
9.8 KiB
Markdown
180 lines
9.8 KiB
Markdown
# vterm
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Minimalist terminal for Sublime Text 4, built to run TUI coding agents
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(`pi`, `claude`) in a tab. macOS only. No panels, no images,
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no build-system integration.
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Requires Sublime Text 4 with the Python 3.8 plugin host (build 4149+, for
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`View.folded_regions`) and Package Control.
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## Install
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Symlink this folder into Sublime packages as `vterm`:
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```sh
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ln -s /Users/vaclavt/devel/vt/vterm "$HOME/Library/Application Support/Sublime Text/Packages/vterm"
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```
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Dependencies (pyte, ptyprocess, wcwidth) are Package Control libraries declared
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in `dependencies.json`. If they are not yet in `Lib/python38` (e.g. Terminus was
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never installed), run **Package Control: Satisfy Libraries** and restart Sublime.
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Package Control garbage-collects libraries no package requires, so if imports
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ever fail after uninstalling another package, re-run *Satisfy Libraries*.
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## Use
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Command palette:
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- **vterm: Open Terminal** — login shell in a tab (cwd = first project folder,
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else the active file's directory, else `~`)
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- **vterm: Open Terminal in Project Folder** — opens the external terminal from
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the settings (Apple Terminal by default) in the project folder of the active file
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- **vterm: Clear Screen** (`cmd+shift+k`) — empties the tab, its screen and all
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scrollback, then asks the app to redraw, so the tab looks freshly started
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- **vterm: Select Theme** — pick a colour palette, previewing each as you move
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through the list; Esc restores what you had
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To launch an agent directly, add your own palette entry or keybinding — `vterm_open`
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takes `cmd`, `cwd`, `env` and `title`:
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```json
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{ "caption": "vterm: pi", "command": "vterm_open", "args": {"cmd": ["pi"], "title": "pi"} }
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```
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Keys: Shift+Enter sends `ESC CR`, or `CSI 27;2;13~` while the app has xterm
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modifyOtherKeys on — pi turns it on and reads a bare `ESC CR` as Alt+Enter,
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which submits instead of breaking the line. Shift+PgUp/PgDn page
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the view over the scrollback and Shift+Up/Down move it one line, instead of
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reaching the app, as xterm and kitty do — `scroll_modifier` moves that to Ctrl,
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or turns it off. Copy/paste use the normal Sublime keys, and pastes are
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bracketed when the app asks for it. Copying re-joins soft-wrapped lines. The
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middle button pastes the current selection straight into the app, X11-style,
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without going near the clipboard; it does nothing when nothing is selected. The
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wheel scrolls the view normally; while the app tracks the mouse the wheel and
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left click go to it instead, and on the alternate screen without tracking each
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wheel tick sends arrow keys (alternate scroll, as kitty/iTerm2 do — this is
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what scrolls Claude Code's fullscreen UI before it enables mouse reporting).
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Sublime raises no wheel event at all for the trackpad (sublime_text#1838): set
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a utility such as [LinearMouse](https://linearmouse.app/) to discrete scrolling
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for Sublime Text and it arrives as wheel notches like any other. While an app owns the
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alternate screen the scrollback above it is folded away, kitty-style, and
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unfolds when the app leaves it.
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## Settings
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`vterm.sublime-settings`: `auto_close` (close the tab when the process exits;
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off leaves it open with a `[process exited with code N]` line),
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`scrollback_history_size`, `scroll_modifier` (the modifier that scrolls the
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view with PgUp/PgDn and Up/Down; `null` gives all four keys to the app),
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`min_columns` / `max_columns`, `terminal` / `parameters` (the external terminal
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for *vterm: Open Terminal in Project Folder*; `%CWD%` in `parameters` is
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replaced with the project folder, defaulting to Apple Terminal, with kitty
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commented out beside it), `debug` (verbose logging to the ST console), plus the
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colours:
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- `theme` — `"default"` (Terminal.app Basic, light), `"homebrew"`, `"pro"`,
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`"slate"`, or `null` to follow the active Sublime colour scheme. Set it with
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*vterm: Select Theme* or by hand; either way open terminals restyle in place,
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no restart needed.
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- `ansi_colors` — override individual base colours, e.g. `{"red": "#ff0000"}`,
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applied on top of the theme.
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A light theme is reported to the running agent (OSC 11, DSR 996), so `pi` and
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`claude` switch to their light UI to match. An app subscribed to mode 2031 is also
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told unprompted when you change the theme mid-session.
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## How it works
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For the full picture — class inventory, data flows, threading, and a primer on the
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terminal protocols — see `Architecture.md`.
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- `vterm/emulator.py` — pyte subclasses. The parser is rewritten because stock
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pyte swallows what these agents rely on: `>`/`<`/`=` prefixed CSI, DECRQM `$p`,
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multi-digit OSC. It answers DA1 (Claude Code's query sentinel, which has no
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timeout) and DA2, CPR, XTVERSION + DECRQM 2026 (this is what unlocks Claude
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Code's flicker-free synchronized output on a generic `TERM`), the kitty keyboard
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probe, and OSC 10/11 colour queries; OSC 52 goes to the Sublime clipboard.
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Combining characters are merged as NFC, because Sublime draws decomposed
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sequences badly.
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- `vterm/terminal.py` — pty process, reader and renderer threads at ~33 Hz.
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Rendering is held back inside a `?2026` frame, and the pty is resized from the
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view size (TIOCSWINSZ → SIGWINCH). Reads go through an incremental UTF-8
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decoder so a sequence split across chunks is not dropped. The child gets
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`TERM=xterm-256color` and `COLORTERM=truecolor`, with `TERM_PROGRAM` stripped.
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A forced repaint narrows the pty by one column for 250 ms — never ctrl+L, which
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is `/clear` in Claude Code.
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- `vterm/render.py` — scrollback and live screen are real view text: dirty rows
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are whole-line replaced, colours are `add_regions` overlays, and the Sublime
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caret doubles as the terminal cursor (DECTCEM turns it into a block, so an app
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drawing its own lands on the same cell; a view with no caret at all loses the
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space key and IME text).
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- `vterm/scheme.py` + `vterm/themes.py` — colour scheme rules generated on demand
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per (fg, bg, style) into `Packages/User/vterm/`, truecolor quantized into the
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256 palette to bound the rule table, palette from the selected theme or your
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editor scheme.
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- `vterm/keys.py` + generated `Default.sublime-keymap` — every key including the
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printable characters is bound to `vterm_keypress`, so nothing is ever inserted
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into the view: an app that does not echo (vim in normal mode) would otherwise
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leave the character behind. `on_modified` in `vterm/listeners.py` remains the
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fallback for IME and composed input.
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- `vterm/mouse.py` — SGR mouse reporting (wheel, click) when the app enables
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tracking; native selection and scrolling otherwise. The trackpad is not
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handled: it reaches no mousemap on macOS and is converted to wheel notches
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outside the plugin.
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Supported: alt screen (1049), synchronized output (2026), bracketed paste (2004),
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mouse tracking 1000/1002/1003 + SGR 1006 (wheel and left click are reported; no
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drag, no right button; the middle button pastes the selection instead of being
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reported), focus events (1004),
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xterm modifyOtherKeys (`CSI > 4 ; n m`, for the modified keys with no
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unambiguous legacy encoding: enter, tab, backspace, space), cursor styles (DECSCUSR —
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block/bar and blink/steady via the view's caret settings; underline falls back
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to bar, 0 is the default blinking block), scroll regions, autowrap,
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50 000 lines of scrollback that ED 3 does not erase (agents repaint with it;
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`honor_erase_scrollback` restores the usual meaning),
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256-colour and truecolor SGR (truecolor quantized to the 256 palette),
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wcwidth-aware wide characters, OSC 0/2 titles,
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DEC line drawing (`ESC(0`, so ncurses apps such as mutt or dialog draw real
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borders even under a non-UTF-8 locale).
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Deliberately absent: the kitty keyboard protocol (legacy encodings are sent
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instead), image protocols, Windows, panels.
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## Rough edges
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- Streaming output is expensive: every scroll marks all rows dirty and each row is
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rewritten over the plugin-host IPC boundary. A per-row cache skips rewriting rows
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whose content did not change, but a genuinely changing full screen still costs
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real CPU. Batching the colour regions across a frame is the known next fix.
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- Editing `vterm/*.py` needs a **Sublime restart**. Submodules are deliberately
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not purged on reload, because rebuilding the terminal registry silently orphans
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open tabs; an orphaned tab shows a "disconnected" status and stops accepting
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input, so close it and open a new one.
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- CJK and emoji rely on wcwidth agreeing with Sublime's font metrics; where they
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disagree the caret can drift.
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- Trackpad scrolling needs a helper on macOS: Sublime never delivers it to a
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plugin (sublime_text#1838), so set a utility such as
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[LinearMouse](https://linearmouse.app/) to discrete/linear scrolling for
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Sublime Text. It then arrives as wheel notches and scrolls the app. Without
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one, the trackpad does nothing in a full-screen app; the mouse wheel,
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`shift+pageup/pagedown` and `shift+up/down` work regardless.
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## Dev
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```sh
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python3 tests/test_emulator.py # emulator, query responder, clear — chunked and char-by-char
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python3 tests/test_imports.py # modules import, keymap parses, command/flag/theme wiring
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python3 tests/test_render.py # render layer on a fake view: trimming, selection, colouring
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python3 tests/test_commands.py # theme picker, live restyle, generated scheme
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python3 tests/harness_live.py CMD SECONDS [--send TEXT] # run a real app in the emulator, dump the screen
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python3 tools/gen_keymap.py # regenerate Default.sublime-keymap
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python3 benchmarks/bench_vs_terminus.py # render cost per frame, against Terminus on the same input
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python3 benchmarks/profiling.py # feed-path hotspots, per-char micro-benches of draw
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```
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`harness_live.py` is the useful one: it drives a real `pi` or `claude` through the
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emulator with no Sublime involved, and prints the queries answered plus the
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resulting screen. Tests import pyte/ptyprocess/wcwidth from Sublime's
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`Lib/python38` (pure Python, so any Python 3 runs them).
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Code style is in `CODE.md`, working agreements in `CLAUDE.md`.
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