mkui

A config-driven, dependency-free web GUI framework with a floating-frame workspace and dockable panes inside each frame. Designed to pair with mkio — the same project's TOML-driven microservice backend — but works against any backend (or none at all).

Model

mkui-app
├── mkui-menubar
├── mkui-workspace
│   ├── mkui-frame  ← floating, movable, resizable. Clamped to workspace.
│   │   └── layout tree
│   │       └── TabGroup
│   │           ├── tab bar
│   │           └── mkui-pane  ← leaf content host
│   ├── mkui-frame
│   │   └── split (h | v)
│   │       ├── TabGroup → panes
│   │       └── TabGroup → panes
│   └── ...
└── mkui-statusbar

Top-level windows are frames — floating chrome with 8-way resize. There is no dedicated titlebar: every tab bar at the top edge doubles as a drag region, and the right-most one also carries the window controls. Frames don't dock into each other. Inside each frame lives an independent, normalized layout tree of splits, tab groups, and panes. Docking — splitting, tabbing, tearing out — happens entirely inside frames.

Design commitments (things meant to hold up indefinitely):

• Structural invariant: every pane leaf sits inside a tab group. A single-pane frame is a single-tab group. This removes a whole class of special cases from the renderer and the drop logic.
• Proportional resize by construction: frame positions are fractions of the workspace rect, and split ratios sum to 1. Resizing the browser rescales every frame, every split, and every pane with no extra code.
• Viewport clamping invariant: every frame move/resize passes through a single clampToDock helper. Frames cannot escape the workspace — shrinking the viewport drags stragglers back in.
• Stable pane identity: pane elements live in a workspace-owned pool and are re-parented via appendChild when re-docked. Content state, subscriptions, scroll position, and DOM focus all survive.
• Zero runtime dependencies. Web Components, so it drops into React / Vue / Svelte / vanilla identically. All chrome icons (window controls, tab scroll arrows, sort carets, filter hamburgers, paging controls) are inline SVG built from vendored path data — no icon font, no external fetch, and they recolor with the theme via currentColor.

Interactions

• Top tab row → drag the whitespace next to the tabs to move the frame (clamped). Double-click the same region to toggle maximize. On non-docking frames (dialogs, login) the title tab itself also drags the frame — it acts as titlebar text. Frame edges/corners → 8-way resize (clamped, min 180×80).
• Dragging a tiled or maximized frame restores it to its pre-tile size under the cursor on first motion. Resize handles or explicit maximize-toggle also clear the restore state.
• Frame close button → closes the frame; panes inside are parked in the pool (state preserved) and can be brought back by code.
• Tab click → switch active pane in that tab group. Clicking a tab or pane content also makes that group the keyboard-focus target; clicking the bar's empty area only raises the frame.
• Tab drag within the bar → reorders the tab in its group. If the cursor leaves the tab bar by more than a few pixels, the pane is torn out into a new frame at the cursor.
• Tab overflow → tabs shrink to fit the bar, down to 3em of label each. If they still don't fit, the strip clips with no scrollbar and ‹ › scroll arrows appear on either side of it; arrows dim at their end of the strip. The bar always keeps at least one tab plus the arrows visible, and the active tab is scrolled back into view whenever the bar re-renders.
• Alt+Shift+Left / Alt+Shift+Right → move the active tab left or right within its group (acts on the top-most frame).
• Ctrl/Cmd+C, Ctrl/Cmd+A, Escape → copy, select-all, and clear-selection, routed to the focused frame's active pane (tables implement all three). Either modifier works on every platform; text inputs and native text selections keep the browser behavior.
• Dragging a torn-out (or any single-pane) frame over another frame shows drop zones: edges split, center adds as a tab. Release to dock.
• Splitter drag → resize the ratio between two children of a split.
• Left button only — menus, drags, resizes, sorting, and selection respond to the primary mouse button; right and middle clicks are inert (except that any button raises a frame, matching OS convention). Modified clicks are inert where the modifier has no meaning: e.g. ctrl/cmd/alt+click on a sort header leaves the sort untouched (shift+click still builds multi-column sort).
• Any mousedown inside a frame raises it to the top of the z-order. The top frame gets an accent border; within it, the last-clicked tab group's selected tab is raised in the selected-tab color, while selected tabs of other groups (and of unfocused frames) flatten to the idle tab color — the raised tab marks the bar keyboard hotkeys act on.

Configs

mkui's runtime input is JSON. When the backend is mkio, add config_dir to your server.toml and point your HTML at /config/client.json — mkio reads client.toml from that directory and serves it as JSON. The browser never needs a TOML parser. For other backends, author or generate client.json directly.

Minimal config:

{
  "app":     { "title": "Trading desk", "theme": "dark" },
  "menubar": [{ "label": "File", "items": [{ "label": "Quit", "action": "app.quit" }] }],
  "statusbar": { "left": [{ "type": "text", "bind": "status.message" }] },

  "panes": {
    "orders":    { "title": "Orders", "type": "mkio-table", "service": "all_orders", "protocol": "query" },
    "chart":     { "title": "Chart",  "widgets": [{ "type": "text", "text": "Chart goes here" }] },
    "inspector": { "title": "Inspector", "widgets": [{ "type": "text", "text": "Properties" }] }
  },

  "frames": [
    {
      "id": "main",
      "x": 0.05, "y": 0.05, "w": 0.65, "h": 0.9,
      "layout": { "type": "tabs", "active": 0, "children": ["orders", "chart"] }
    },
    {
      "id": "aux",
      "x": 0.72, "y": 0.05, "w": 0.23, "h": 0.9,
      "layout": { "type": "tabs", "children": ["inspector"] }
    }
  ],

  "mkio": { "url": "ws://localhost:8080/ws" }
}

Frame positions (x, y, w, h) are fractions of the workspace rect.

Statusbar

statusbar is a top-level object with left and right widget arrays, plus an optional bindStyle map that binds CSS properties to state paths:

"statusbar": {
  "left":  [{ "type": "text", "bind": "status.message" }],
  "right": [{ "type": "text", "text": "v0.1" }],
  "bindStyle": { "background": "status.background", "color": "status.color" }
}

Each bindStyle entry subscribes to the given state path. When the value changes, the CSS property is set as an inline style on <mkui-statusbar>. Setting the state value to null (or empty string "") removes the inline override, reverting to the stylesheet default. Empty string is treated as null to support TOML configs, which have no null literal.

mkio connection state

When config.mkio.url is set, <mkui-app> automatically connects to the mkio server and verifies its identity. Connection is two-phase:

1. Connect — WebSocket opens, mkio.connected becomes true, and the connected state map is applied immediately.
2. Verify — an async _mkio request confirms the server is a genuine mkio server and optionally checks its name, version, and protocol against expectations declared in config.mkio.expect. On success mkio.verified becomes true; on failure the incompatible state map is applied. Verification re-runs on every reconnect.

"mkio": {
  "url": "ws://localhost:8080/ws",
  "expect": {
    "name": "order-book",
    "version": "1.0",
    "protocol": "1.0",
    "mkio": "0.1"
  },
  "connected":    { "status.message": "Connected", "status.background": null },
  "incompatible": { "status.message": "Wrong server", "status.background": "#cc0000" },
  "disconnected": { "status.message": "Disconnected", "status.background": "#858585" }
}

The expect keys are all optional. name is checked by exact match; version, protocol, and mkio use semver-compatible matching (delegated to the server's _mkio service). When expect is absent, the _mkio query still runs to confirm it is an mkio server and to populate mkio.server.* state paths (name, version, protocol, mkio).

The _mkio request has a configurable timeout (config.mkio.timeout, default 5000 ms) — non-mkio servers that don't respond are detected as incompatible.

State maps default to { "status.message": "Connected" }, { "status.message": "Disconnected" }, and { "status.message": "Incompatible server" }. Combine with statusbar.bindStyle to change the statusbar appearance on disconnect or server mismatch.

Authentication

When config.auth is present, a login dialog gates the app — no frames appear until the user authenticates. Three modes:

1. mkio built-in (method: "mkio") — calls client.auth() against mkio's _mkio_users table. Config-only, no code needed.
2. Custom (method: "custom") — register a handler with app.registerAuthHandler({ authenticate({username, password}) }).
3. Disabled — omit the auth section entirely.

"auth": {
  "method": "mkio",
  "connected":    { "status.message": "Connected", "status.background": null },
  "disconnected": { "status.message": "Disconnected", "status.background": "#858585" }
}

The login dialog is unclosable (no close button). After login, auth.authenticated, auth.user, and auth.role state paths are set. The built-in auth.logout action reloads the page.

mkio's scaffold creates default users: admin/password (admin role) and user/password (user role). Customize the dialog labels with auth.dialog: title, usernameLabel, passwordLabel, submitLabel.

Menubar

menubar is a top-level array. Each element is a dropdown menu with a label and an items array:

"menubar": [
  {
    "label": "File",
    "items": [
      { "label": "New Frame", "action": "demo.newFrame" },
      { "sep": true },
      { "label": "Open Recent", "items": [
          { "label": "foo.txt", "action": "demo.open", "args": "foo.txt" }
        ]
      },
      { "label": "Quit", "action": "app.quit" }
    ]
  },
  {
    "label": "Window",
    "items": [
      { "label": "Cascade", "action": "window.cascade" },
      { "label": "Tile", "items": [
          { "label": "Horizontal", "action": "window.tileH" },
          { "label": "Vertical",   "action": "window.tileV" },
          { "label": "Grid",       "action": "window.grid" }
        ]
      }
    ]
  }
]

Item keys:

Any item with an items array is a submenu; submenus nest arbitrarily. Leaf items (no items) fire action on click via app.fireAction().

Built-in actions: app.quit, pane.show (takes a pane ID as args — switches to that pane's tab and raises its frame, or opens a new frame if the pane is parked/closed), window.tileH, window.tileV, window.grid, window.cascade, edit.copy, edit.selectAll (the last two route to the focused frame's active pane — the same path the Ctrl/Cmd+C and Ctrl/Cmd+A shortcuts take). Register custom actions with app.registerAction(name, fn).

A typical Edit menu:

{ "label": "Edit", "items": [
  { "label": "Copy", "action": "edit.copy", "shortcut": "mod+C" },
  { "sep": true },
  { "label": "Select All", "action": "edit.selectAll", "shortcut": "mod+A" }
]}

A typical Window menu lists the arrangement commands first, then the open windows dynamically:

{ "label": "Window", "items": [
  { "label": "Cascade", "action": "window.cascade" },
  { "sep": true },
  { "windows": true }
]}

{ "windows": true } expands — every time the menu opens — into one entry per pane currently hosted in a frame, labeled with the pane's title. Selecting an entry raises the frame that contains the pane and switches to its tab (dialogs and other noDock frames are excluded). Static pane.show entries are still useful for reopening panes whose frame has been closed.

Tabs can be renamed in place: ctrl+click (or cmd+click on macOS) a tab, edit the title, and press Enter (Escape cancels). The new title is stored on the pane spec, so tab bars and the Window menu both reflect it.

Themes

dark and light are built-in. To ship additional themes, list them under app.themes — each entry is a flat object of CSS custom property overrides, applied as inline styles on <mkui-app> so every descendant inherits them:

{
  "app": {
    "theme": "solarized",
    "themes": {
      "solarized": {
        "--mkui-bg":        "#002b36",
        "--mkui-bg-alt":    "#073642",
        "--mkui-bg-hover":  "#0a4350",
        "--mkui-fg":        "#93a1a1",
        "--mkui-fg-mute":   "#586e75",
        "--mkui-border":    "#0a4350",
        "--mkui-tab-active": "#0e4d5e",
        "--mkui-accent":    "#268bd2",
        "--mkui-accent-fg": "#fdf6e3",
        "--mkui-focus":     "#eee8d5"
      }
    }
  }
}

Any variable from styles/mkui.css (--mkui-*) may be overridden. Missing keys fall back to the default (dark) values. Switch themes at runtime with appEl.setTheme("solarized").

Standalone mode

<!doctype html>
<link rel="stylesheet" href="/mkui/styles/mkui.css">
<script type="module" src="/mkui/src/index.js"></script>
<mkui-app config="/mkui/client.json"></mkui-app>

Library mode

import { registerPaneType } from "mkui";
import "mkui";   // side-effect: registers custom elements

registerPaneType("clock", (spec, app, host) => {
  const el = document.createElement("div");
  host.appendChild(el);
  setInterval(() => { el.textContent = new Date().toLocaleTimeString(); }, 1000);
});

const root = document.querySelector("mkui-app");
await customElements.whenDefined("mkui-app");
root.setConfig({
  panes:  { clock: { title: "Clock", type: "clock" } },
  frames: [{ id: "f1", x: 0.3, y: 0.3, w: 0.3, h: 0.3,
             layout: { type: "tabs", children: ["clock"] } }],
});

// Add more frames at runtime:
root.workspace.addFrame({ x: 0.5, y: 0.1, w: 0.4, h: 0.4,
                          layout: { type: "tabs", children: ["other-pane"] } });

Built-in widgets and pane types (v1)

• Widgets (lightweight content inside a pane or statusbar slot):
  • text — static or bind-ed to a state path
  • button — fires an action by name
• Pane types (whole-pane custom rendering):
  • mkio-table — subscribes to an mkio service (query, subpub, or stream) and renders a live-updating table with flash animations for inserts, deletes, and field changes. Row identity is per-protocol: query uses _mkio_row, stream uses _mkio_ref, subpub uses _mkio_topic. Column headers render immediately when columns is configured; optional labels maps column keys to display text (e.g. { "ts": "Timestamp" }). Rows are virtualized — only the slice overlapping the viewport exists in the DOM, so scrolling, window moves, and window resizes stay fast into the millions of rows. Columns are fully interactive: click a header to sort (shift+click adds secondary sort keys), the hamburger button opens a per-column filter dropdown with search and value checkboxes — when a column is sorted, that button's icon becomes the sort caret (still opening the filter dropdown, and showing the sort priority as a digit knocked out of the caret under multi-sort) — dragging a header reorders columns, and dragging the grip centered on a column divider resizes the column to its left — double-click the grip to auto-size the column to fit its content (capped at 80% of the viewport; with a selection active, all selected columns fit at once, so select-all + double-click fits the whole table). Column widths start at the header row's width and grow to fit records as they arrive (capped at 50% of the pane width, never shrinking, and never overriding a manual resize) — paging to another page never resizes them, and they don't change when the window resizes — extra pane width flows into a filler column that extends the header row to the pane's right edge, and subtle dividers separate the columns. Columns whose values are all numeric right-align with each value padded so decimal points line up down the column, in the cells and in the filter dropdown's value list alike. Subscriptions are deferred until the pane is first visible, unsubscribed immediately when the frame is closed, and dropped after 5 minutes of being hidden (e.g. inactive tab) — brief tab switches preserve the live connection. Large query snapshots render progressively in chunked batches to avoid freezing the UI. Stream tables support time-anchored paged navigation with a toolbar showing ◀ Earlier | time range | Later ▶ | ● Live | ⟳. By default, the initial fetch starts from local midnight (start: "today"); start: "" starts from the beginning of the buffer. The toolbar displays the time range of visible rows in the browser's local timezone with adaptive precision — HH:MM down to nanoseconds in 3-digit increments depending on how close the boundary timestamps are; cross-day ranges include the date. Boundary indicators ((start), (end), (all)) show when you've reached the edges of the dataset. The ⟳ button re-fetches the current page. Navigation is ref-based (each page fetches relative to the first or last row's _mkio_ref), with before: true for backward fetches, so pages stay correct even when records are added or deleted mid-session. When navigating backward yields no data, the previous page is automatically restored and the Earlier button is disabled. A toggleable "Live" button switches to real-time streaming from the current page's last ref; in live mode, clicking Earlier uses a separate subscription to fetch and prepend historical pages without interrupting the live stream (toolbar shows HH:mm – Live). Live streams follow the tail like a terminal: entering live jumps to the newest row, and while the viewport is parked at the bottom, arriving rows keep scrolling into view — scroll up to inspect history and the viewport stays put. Set live: true to start in live mode: the start page loads first and then hands off to the live stream, so start is still honored rather than the whole buffer being replayed; exiting live returns to that start page, and reopening the pane re-arms it. Exiting live mode re-fetches the saved page from the server so that rows inserted or deleted during live mode are reflected. When the WebSocket disconnects while live mode is active, the toolbar shows "Disconnected" (or HH:mm – Disconnected with earlier pages) in muted text instead of the green blinking "Live" indicator — live mode stays active for seamless reconnect. Stream tables track the last received ref and use it on re-subscribe to avoid duplicate data transfer — existing rows are preserved and only new records are fetched. Query and subpub snapshots fully replace the table on each arrival, so records deleted on the server between disconnect and reconnect are properly removed. Tables are fully selectable, Excel-style: a sticky row-number column (disable with rowColumn: false) selects rows — click, ctrl/cmd-click to toggle, shift-click for ranges, drag for a range, or click the header corner to select all — while clicking a cell places the focused cell (accent outline; its whole row gets a subtle highlight so the record stays readable, distinct from the stronger row-selection tint). Drag across cells for a rectangle, ctrl/cmd-click to add or remove individual cells, shift-click or shift+arrows to extend; arrows/Home/End/PageUp/PageDown move the cursor, Space (or Shift+Space) selects the focused row, ctrl/cmd+Space toggles it, Ctrl/Cmd+A selects all visible rows, and Escape clears the selection. Ctrl/Cmd+C copies the selection to the OS clipboard in both TSV and HTML flavors, so pasting into Excel/Sheets preserves cell and row structure — row selections include a header row of column labels; cell selections copy values only, with blanks outside the selected rectangles; the copied cells pulse and the statusbar briefly shows "Copied N rows/cells" (via the status.message state path). Selection follows the filtered view (hidden rows are never selected or copied) and tracks records rather than positions: re-sorting moves the selection with its rows (rows that sort into the middle of a selected block don't join it), rows inserted live inside a selected range stay unselected, and members hidden by a filter rejoin the selection when the filter is relaxed. Table toolbar buttons can declare a selection unit ("rows" default, "row", "cells", "cell" — singular units imply exactly-one): row-unit buttons receive the rows containing the cell selection (or the focused cell) even when no row is explicitly selected, and cell-unit buttons get a cells array of { row, column, value } in their action context. Set select = { state = "<path>" } to mirror the current row into app state as the selection moves, so a detail pane or chart can follow the table without any custom code; clearing the cursor publishes null (as do deleting that row and closing the pane), and a live update to that row republishes it. Set formatters = { col = "<name>" } to route a column through a function registered with registerFormatter — the derived value is what the table renders, sorts, filters, and copies, and a formatter may produce a virtual column that no row carries. Conditional styling colors cells and rows from their values: styles = { col = <styler> } styles a cell, rowStyle = <styler> styles the whole row, where a styler is either the name of a function registered with registerStyler or a config-only rule array evaluated first-match-wins — each rule mixes conditions (eq, ne, lt/lte/gt/gte, in, match regex; row rules condition on any columns via when) with styling (color, background, bold, italic, underline, strike, custom class, arbitrary css); styled backgrounds blend with, rather than hide, the selection tint, and styles are recomputed on every live update.
• Dialogs:
  • openDialog(spec, context, app, extra) — config-driven modal dialog with typed fields (text, number, select, checkbox, textarea, readonly, hidden), validation, conditional visibility (showWhen), async service-backed options (optionsFrom), and RPC submission with error handling. The dialog floats as a non-docking frame whose title text doubles as a drag handle; if the rendered form is taller than the initial frame, the frame grows to fit it (capped at 90% of the workspace) and re-centers. A pin button (SVG pin icon) in the titlebar keeps the dialog open after successful submission — when active, the pin rotates 45° counterclockwise with a smooth transition; the form resets to defaults only after the server confirms success; errors leave the form intact for retry.
• Custom pane types are the primary extensibility surface. Register with registerPaneType(name, factory); reference from config as type = "<name>".
• Column formatters let a declarative mkio-table show a derived value without becoming a custom pane. Register with registerFormatter(name, fn) — called as (value, row, col) — and reference it as formatters = { col = "<name>" }. The formatted value is what the table renders, sorts, filters, measures, and copies; a formatter can also produce a virtual column that no row carries (list it in columns). Button action payloads always carry raw row fields.
• Stylers do the same for looks: registerStyler(name, fn) — cell form (value, row, col) => style, row form (row) => style — referenced as styles = { col = "<name>" } or rowStyle = "<name>", or written declaratively in config as rule arrays with no code at all (see the mkio-table example).

Quick start

pip install mkui mkio
mkui init myapp
mkui serve myapp
# http://localhost:8080/

mkui init scaffolds a complete project:

myapp/
  server.toml          ← mkio server config (schema, services, routes)
  config/
    client.toml        ← mkui app config (panes, menus, layout)
  static/
    index.html         ← entry point

mkui serve starts an mkio server that handles static files, config serving (TOML→JSON), the WebSocket endpoint, and the mkio client JS — all from one process, one port.

Installation

pip install mkui mkio

CLI

mkui init [dir]               # scaffold a new project (default: .)
mkui serve [dir] [-p PORT]    # serve with mkio backend (default port from server.toml)
mkui --version

serve reads server.toml in the project directory, resolves the <mkui.static_dir> placeholder to the installed package path, and delegates to mkio.create_app(). The --port flag overrides the port in server.toml.

Library usage

For custom backends (no mkio), serve the static assets directly:

import mkui

# With FastAPI / Starlette:
from starlette.staticfiles import StaticFiles
app.mount("/mkui", StaticFiles(directory=mkui.static_dir))

Running the examples

The standalone and library examples need only a static file server:

cd mkui/static
python3 -m http.server 8000
# http://localhost:8000/examples/standalone-json/
# http://localhost:8000/examples/library-js/

The mkio-table example requires mkio:

cd mkui/static/examples/mkio-table
mkio serve          # starts on port 8080 (configured in server.toml)
python seed.py      # (optional) populates sample orders in a loop
# http://localhost:8080/

Project layout

mkui/                    Python package (pip install mkui)
  __init__.py            Exposes static_dir path and version
  __main__.py            CLI: init + serve commands
  static/
    src/
      core.js            State store, registries, App class
      index.js           Side-effect entry point
      layout/
        tree.js          Normalized tree math
        drag.js          clampToDock, snap, dropZoneFor, frac↔rect
      lib/
        expressions.js   ${path} expression resolution
        icons.js         SVG icon library (vendored Lucide paths)
      components/
        app.js           <mkui-app> — the shell
        menubar.js       <mkui-menubar>
        statusbar.js     <mkui-statusbar>
        workspace.js     <mkui-workspace> — frame list, arrangement, snap
        frame.js         <mkui-frame> + <mkui-pane>
      widgets/
        text.js  button.js  mkio-table.js  mkui-dialog.js
      auth.js            Config-driven login dialog
      mkio-bridge.js     Lazy-loads mkio's /mkio.js client
    styles/mkui.css      Default theme (CSS custom properties)
    examples/
      standalone-json/   Loaded from a static config
      library-js/        Built imperatively from JS
      mkio-table/        Live table backed by mkio query/subpub services
                         (static/app.js registers the notional formatter
                         and the order-detail follower pane)
pyproject.toml           Python build config
tests/
  layout.test.js         Layout tree unit tests (node:test)
  state.test.js          State + connection lifecycle tests (node:test)
  table.test.js          mkio-table pane tests (node:test)
  dialog.test.js         Dialog expression + submission tests (node:test)
  auth.test.js           Authentication module + state lifecycle tests (node:test)
  expressions.test.js    ${...} expression resolver tests (node:test)
  styles.test.js         mkui.css layout invariants (node:test)
  test_cli.py            CLI init/serve tests (unittest)