wordcraft/docs/control-protocol.md

Control protocol

Start the app with a control port: wordcraft --control 7981 (or WORDCRAFT_CONTROL_PORT=7981). A missing or invalid port after --control (not 1–65535) prints an error and exits with status 2. It listens on 127.0.0.1 only. Send one JSON object per line, with the window's key (see Keys); each gets one reply line:

{"id": 1, "key": "…", "method": "engine.execute", "params": {"command": "text.insert", "params": {"text": "Hello"}}}
{"id": 1, "ok": true, "result": {"anchor": {...}, "focus": {...}}}

Errors come back as {"id": …, "ok": false, "error": "message"}. A failed command leaves the document unchanged. A line that isn't valid JSON gets one error reply, then the server closes the connection (so an HTTP request sent to the port can't run a command); reconnect to continue.

Keys

Any local program (and possibly a web page) can reach a loopback port, so every request needs the window's key. Once the port is bound, the app writes a random key (256 bits, as hex) to <settings>/control-key.<instance> and removes the file when the window closes; a new start writes a new key. WORDCRAFT_PROFILE_DIR overrides the whole profile folder for isolated runs, including recovery copies. See local recovery. <settings> is the folder that holds the preferences: on Linux $XDG_CONFIG_HOME/wordcraft (by default ~/.config/wordcraft), on macOS ~/Library/Application Support/WordCraft, on Windows %APPDATA%\WordCraft. <instance> is the Flatpak instance id inside Flatpak, and local-<port> otherwise. On Unix the file has mode 0600.

cat ~/.config/wordcraft/control-key.local-7981   # Linux, outside Flatpak, port 7981

• Send the key as top-level "key" with every request, or once per connection with {"method": "auth", "key": "…"} (reply {"ok": true, "result": {}}); later requests on that connection may leave key out. Only auth reads params.key; for other methods params.key is an ordinary parameter (ui.key {"key": "Enter"} presses Enter).
• The key is checked on every request. A missing or wrong key gets {"ok": false, "error": "unauthorized"}, and the app closes the connection.
• A line over 1 MiB gets {"ok": false, "error": "line too long"}, and the app closes the connection.
• A connection that sends no authorised request within 30 s of being accepted is closed. That is one limit: blank lines and bad JSON do not extend it. After an authorised request the connection may stay idle.

wordcraft-cli mcp --connect takes the key from WORDCRAFT_CONTROL_KEY, or else from the key file for the port it connects to, and reads it again on every new connection (the app may have restarted). It sends the key only to the app's own address, 127.0.0.1 (localhost connects there too, never to ::1): another loopback address such as ::1 or 127.0.0.2 is not where the app listens, so whoever listens there gets no key (#3699). For any other host it sends no key, says so, and the app refuses its requests: to drive an app on another machine, forward its port to 127.0.0.1 (for example ssh -L 7981:127.0.0.1:7981 host) and set WORDCRAFT_CONTROL_KEY to that app's key.

Methods

Method	Params	Result
engine.execute	command, params, doc?	the command's result (any id from engine.commands, including UI commands ui.tab, ui.dialog ({"name": dialog, "part"?: table style part}; part opens New / Modify Table Style (newTableStyle / modifyTableStyle) on that part: wholeTable, headerRow, firstColumn, bandedRows, nwCell… as table.modifyStyle names them), ui.backstage, ui.zotero.* (see docs/zotero.md), ui.language ({"value": "auto"|"en"|"zh-hans"|"zh-hant"|"ja"|"pt-br"|"es"|"uk"|"sr"|"sr-latn"|"et"|"tr"|"ru"|"pl"|"de"|"it"|"cs"|"hu"|"fr"}), ui.theme ({"value": "system"|"light"|"dark"}; system follows the OS appearance, light when it reports none), ui.interfaceSize ({"value": "auto"} or {"percent": 50–300}, clamped; no value reads it; auto keeps the system display scale, a percentage is absolute, so 100 is one screen pixel per point (#822); the result's percent is the size drawn at and auto whether it follows the system; document zoom stays view.zoom), ui.animations ({"value": "system"|"on"|"off"}; no value reads it; system follows the system's animation setting, which the desktop app reads on Windows, macOS, Linux and the BSDs and the web app from prefers-reduced-motion, and means on where the system doesn't say; the result's enabled is what the setting comes to and system what the system reports, null when it doesn't say), ui.fileBrowser (desktop: {"purpose": "document"|"picture"|"recipients"|"save"} opens WordCraft's own file browser, for when the system file dialog doesn't show up, #576), ui.saveAsTemplate (File › Save As › Save as Word Template: the Save dialog for a .dotx, starting in the user templates folder; the result's dir is that folder, null on the web, #2852), ui.caretAnimation ({"value": true|false}; no value reads it; off, the caret jumps and blinks on and off instead of gliding and fading), ui.startScreen ({"value": true|false}; no value reads it; on, the default, the desktop and web apps start on File › Home when launched with nothing to open, #766), ui.alignmentGuides ({"value": true|false}; no value reads it; on, the default, moving a picture or shape snaps it to the page, the margins and other objects, with guide lines while dragging; Alt moves freely), ui.quickAccessToolbar ({"value": true|false}; no value toggles it; false takes the Quick Access Toolbar out of the title bar, as its menu's Hide Quick Access Toolbar does, and true brings it back, #1945), ui.focusRibbon ({"value": true|false}; no value toggles it; in Focus, true drops the ribbon down over the page, as the bar's ⋯ does, and false puts it away, as a click on the page does; outside Focus it stays put away, #1678), ui.contextMenu (opens the page's context menu below the caret, as Shift+F10 does), ui.paneDock ({"pane": "navigation"|"clipboard"|"styles"|"styleInspector"|"accessibility"|"altText"|"formatShape"|"restrictEditing"|"comments"|"smartArtText", "dock"?: "left"|"right"|"float", "before"?: pane|null}; no dock reads it; docks or floats a task pane as its menu does, kept between runs; Styles is view.stylesPaneDock, #1756; before puts the pane directly before that pane in the order, outside it on their edge, as a drop over a docked pane's outer third does, and null after every pane; the order is kept between runs)…)
engine.commands	—	every command: id, label, location, shortcut, params, enabled
document.inspect	text?, doc?	blocks (text, style, runs, lists, tables), parts, sections, selection, pages
ui.inspect	—	UI state, view, dialog, window size, page rects on screen, caret, comment balloons (balloons: id + screen rect; balloon: the selected one), perf; document: the active document's id; documents: the open documents (id, title, path, dirty, active)
ui.click	x, y, button?, count?, shift?, cmd?, alt?	real pointer input at window coordinates
ui.clickText	page (0-based), x, y (points from the page's top-left), count?	click inside a page
ui.move / ui.drag	x,y / x,y,toX,toY,steps?	pointer move / drag
ui.press / ui.release	x,y, modifiers	primary button down / up there (with ui.move between: a drag you can screenshot halfway)
ui.wheel	x, y, dy, dx?, unit? (point/line/page), phase? (start/move/end), modifiers	mouse-wheel or trackpad scroll at window coordinates (dy < 0 scrolls down)
ui.key	key (B, Enter, Left…), shift?, alt?, cmd?	key press through egui (shortcuts apply)
ui.text	text	typed text through egui
ui.screenshot	path?	PNG of the window: written to path, or without one returned as base64 png in the reply
ui.render	path?, page? (1-based), scale?, doc?	PNG of a page, rendered by the engine: written to path, or without one returned as base64 png in the reply (never a fixed name in the shared temporary folder)
ui.parity	—	feature-catalog parity
ui.resize	width, height	asks for that window content size in points; sizes that aren't positive and finite are refused, the rest are clamped to the app's minimum (760 × 480) and to the largest surface the GPU can draw (at most 16384; that limit wins over the minimum), and the reply's width and height are the size asked for
ui.focus / app.quit		window control

Any other method name is treated as a command id: {"method": "format.bold"} works.

Task pane docking. ui.paneDock and view.stylesPaneDock use physical left / right (the window's left and right edges), matching Dock Left / Dock Right in the pane menu. That stays true in a right-to-left interface language: {"dock":"left"} always puts the pane on the physical left and the command reports "left". A pane that has never been docked keeps its default start-/end-edge role when mirrored: start-default panes (e.g. Navigation) open on the physical right in Arabic, end-default panes (e.g. Comments) on the physical left. Saved docks and explicit requests are never flipped.

Language packs (see MCP) are commands like any other: proof.packs, proof.installPack {"locale": "nl"} and proof.removePack {"locale": "nl"}. Through the control channel they act on the running app's packs, and install only while its downloading setting is on; they never turn it on, and neither does a ui.click or ui.key on the app's Install, Show available languages or Refresh buttons. An install or a refresh runs in the background ("started": true); proof.packs reports its progress, then the result. ui.dialog {"name": "languageData"} opens About › Language data.

Open documents

Several documents can be open at once. Each has an id, a whole number that stays the same while the document is open and is never reused by the running app. On the desktop each open document has a native window of its own; the web app shows them one at a time in its one window. One document is the active one: on the desktop, the document of the window focused last (the active window); in the browser, the one the window shows. Commands work on it unless told otherwise.

• file.new opens another document in a new window, focused, and makes it active. file.open does the same with a file; it replaces a blank document nobody has used yet in that document's window, and a file that is already open becomes active again and its window comes to the front ("alreadyOpen": true). Its result carries the document's id.
• view.switchWindows lists the open documents ({"documents": [{"id", "title", "path", "dirty", "active"}]}); with {"id": n} it makes that document active and brings its window to the front.
• file.closeDocument {"id"?, "force"?} closes a document; its window closes with it unless it is the last window.
• engine.execute, document.inspect and ui.render take doc, the id of the document to work on, next to their other params. The command runs on that document and the active window stays active. A dialog or page the command opens (Save As, Print) opens in that document's window, which comes to the front:

{"id": 2, "key": "…", "method": "engine.execute", "params": {"command": "text.insert", "params": {"text": "Hello"}, "doc": 3}}

doc left out, or null, is the active document. An id that names no open document, or a value that isn't a whole number from 0 up, is an error and nothing runs. Window commands (ui.*) work on the active window only: with the id of another document they are an error.

The active window

Input and window methods go to the active window, the one focused last: ui.click, ui.key, ui.text, ui.wheel and the other input methods (coordinates are that window's), ui.screenshot (a PNG of that window), ui.inspect (its size), ui.resize and ui.focus. To work in another window, make its document active first with view.switchWindows {"id": n}.

The CharProps and ParaProps that format.set, para.set and styles.modify take are listed in MCP server.

Positions are {"story": "body" | {"part": n}, "path": [block, row, cell, block, …], "off": byteOffset}.

Keyboard and text input

ui.key and ui.text go to this window's focused widget even when another app is in front (#2420). A focused Find field receives the text; a document receives it only while its canvas owns keyboard focus. Shortcuts, dialogs and document protection still apply. These methods do not activate the native window. ui.focus separately requests native activation.

The {"queued": true} reply acknowledges the input queue, not a completed edit. Input is applied on subsequent UI frames. Inspect the resulting document or widget state before continuing with an operation that depends on it; do not replay an edit simply because its effect is not immediate.

Closing the document

engine.execute with file.close never shows the Save / Don't Save / Cancel prompt. On a document with unsaved changes it replies with an error (the app keeps running and the edits stay); save first (file.save), or pass {"force": true} to discard the changes and close. The bare form {"method": "file.close", "force": true} (a method name that is a command id) is guarded the same way, and only a boolean true counts as force. A document without unsaved changes closes at once (#1268). Closing closes the document and its window, and the window focused before it becomes the active one. The last window stays open with no page, and file.new or file.open goes on from there (#1712); closing it doesn't quit the app. With doc naming a document in the background, file.close closes that document and its window under the same rule (unsaved changes need {"force": true}), and the active window stays active.

Native printing

engine.execute can call ui.printSettings with {} to inspect the printer list, selected printer, copies, duplex, grayscale, discovery/submission status and backend receipt/error. {"refresh":true} starts background discovery; poll the same command until discovering is false. Set printer to a discovered name, integer copies from 1 to 999, duplex to printerDefault, off, longEdge or shortEdge, and boolean grayscale. Invalid updates are rejected without changing earlier settings. ui.printSubmit explicitly submits the current print-ready PDF without opening a dialog; inspect ui.printSettings until busy becomes false and check status/detail. The browser keeps its own print hook. PDF export remains separate.

ui.printSubmit / ui.print also accept the upstream PDF page settings (range, pages, parity, copies, collate). Native printing renders the selected pages once and passes copies/collation to the spooler; the browser and file.printPdf keep copies in the PDF. Omitting native copies uses the configured ui.printSettings value. collate defaults to File › Print's setting; invalid ranges submit no job. paper (none, or a Layout › Size name such as Letter, Legal, A4) is Scale to paper size (#2108): every page is scaled onto that paper and centred, and native jobs ask the spooler for that media; the document's page size is unchanged. file.printPdf takes it too; an unknown paper submits no job.

engine.commands {"search":"print"} lists the engine print commands and the app-owned ui.printSettings, ui.printSubmit, and legacy ui.print alias, with current enablement and their parameter documentation. Search is case-insensitive across IDs, labels, locations and parameter descriptions. Listing commands never discovers printers, submits a job or opens a dialog. Settings inspection is always available; submission becomes enabled when the native printer is ready, or when the browser host provides its print flow.