control-protocol.md

GridCraft control protocol

Start the desktop app with a control port:

gridcraft --control 7979            # or GRIDCRAFT_CONTROL_PORT=7979

Then send newline-delimited JSON to 127.0.0.1:7979. Every request line gets one reply line:

{"id": 1, "method": "engine.execute", "params": {"command": "cell.set", "params": {"cell": "B2", "input": "=SUM(A1:A9)"}}}
{"id": 1, "ok": true, "result": {"cell": "B2", "value": "45"}}

Errors come back as {"id": …, "ok": false, "error": "…"}.

A line that is not a JSON object with a string method (an HTTP request, text that isn't JSON, bytes that aren't UTF-8, a line over 64 MiB) gets one error reply and the server closes the connection; nothing sent after it runs. Blank lines are skipped.

Methods

Method	Params	What it does
engine.execute	{command, params}	Runs any engine command (see engine.commands or gridcraft-cli commands). edit.goTo, edit.goToSpecial, selection.set and selection.move scroll the active cell into view, as Go To does in the window
engine.commands	{search?}	Every command: id, label, ribbon path, shortcut, params doc, enabled; search keeps those whose id, label or ribbon path contains it (case-insensitive)
engine.journal		Commands run so far (replayable). Passwords (password, …Password params) are left out, so a replayed Protect Sheet has no password. Capped at 10,000 entries and 64 MB (serialized); past either cap the oldest entries go
document.inspect		Workbook summary: sheets, used ranges, tables, charts, names, selection, undo labels
sheet.read	{range?, sheet?, formulas?, formatted?}	Values (or formulas / displayed text) of a range
cell.get	{cell?}	One cell: value, formula, displayed text, style, merge, comment, link
ui.inspect		UI state: ribbon tab, editor, open dialog, Backstage page, message, grid rect, scroll, perf
ui.click / ui.drag / ui.move	{x, y, toX?, toY?, button?, count?, shift?, cmd?, alt?}	Real pointer input in window points; refused with an error if it would leave more than 10,000 pointer events queued
ui.cell.click / ui.cell.drag	{cell} / {from, to}	Pointer input at a cell's centre (works in point mode while editing); same 10,000-event queue limit
ui.key / ui.text	{key, shift?, cmd?, alt?, ctrl?} / {text}	Keyboard input (typing in the grid starts editing)
ui.edit.begin / ui.edit.text / ui.edit.commit / ui.edit.cancel	{text?} / {move?: down|right|up|left|none}	Drive the cell editor
ui.ribbon	{tab}	Switch ribbon tab
ui.dialog / ui.dialog.set / ui.dialog.confirm / ui.dialog.cancel	{name} / {field, value}	Open, fill in and confirm dialogs; confirm runs the dialog's command with the same parameters as its OK button
ui.backstage (via engine.execute)	{page?: home|new|open|info|saveAs|print|export|options|account|close}	Open the File tab's Backstage view on a page, or close it (ui.inspect reports the open page as backstage)
ui.screenshot	{path?}	PNG of the window (base64 when no path). Animations are settled first: the picture shows the final state
ui.set	{dark?, formulaBar?, ribbonCollapsed?, animations?}	UI preferences (formulaBar runs view.formulaBar)
ui.resize / ui.focus	{width, height}	Window control
app.open / app.save / app.quit	{path, password?} / {path?}	Files and lifetime. password opens a password-protected workbook; without it, such a workbook returns an error (never a dialog)

Any other method name that is a command id (e.g. home.bold) runs that command.

Use engine.execute with {command: "view.theme", params: {mode: "system"}} to choose the display theme; mode accepts "system", "light", or "dark". System follows live OS appearance changes and falls back to Light when the platform supplies no preference. The saved choice remains System; new users still start in Light. The legacy view.darkMode command and ui.set {dark} select a fixed Light or Dark theme.

{command: "view.animations", params: {on: false}} turns motion in the UI off (the selection outline then jumps to a new selection instead of gliding there); without on it toggles. It is the View ▸ Animations checkbox, saved with the other UI preferences and on by default.

{command: "app.language.set", params: {language: "ja"}} switches the interface language (code is accepted as an alias for language); app.language.english and app.language.japanese are shortcuts. engine.commands lists every code it takes (en, es, zh, ja, ko, ru, pt, de, cs, fr, sr), as does the error for an unknown one. Only interface chrome is translated, never command ids or document text. The choice is saved in ui.json; with nothing saved the desktop app follows the system language.

{command: "file.open", params: {path: "Secret.xlsx", password: "…"}} opens a password-protected workbook (Agile or Standard encryption). Without password it returns an error containing "is password-protected. Enter its password to open it." and never opens a dialog; a wrong password returns "The password is incorrect." The password is left out of the journal and never quoted in an error. The opened workbook has no save path, so Save asks where to save it, without the password, and never replaces the encrypted original.

For a headless equivalent (no window), use gridcraft-cli mcp or gridcraft-cli run; see mcp.md and cli.md.

Native printing

Desktop engine.commands {"search":"print"} (and connected MCP list_commands) lists ui.printSettings and ui.printSubmit with their parameter and result fields.

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. GridCraft accepts the existing file.print sheet/pagination params on ui.printSubmit; the engine file.print command returns the PDF without spooling.