bond-wm/wm.ts

An X Window Manager built on web technologies.

const x11: IX11Mod = require("x11");

import * as path from "path";
import * as os from "os";
import {
  app,
  ipcMain,
  BrowserWindow,
  HandlerDetails,
  BrowserWindowConstructorOptions,
  DidCreateWindowDetails,
} from "electron";
import {
  IBounds,
  IGeometry,
  IScreen,
  IPCMessages,
  IWindowManagerServer,
  KeyRegistrationMap,
  LayoutPluginConfig,
  WindowType,
  XWMEventConsumerArgs,
  XWMEventConsumerArgsWithType,
  XWMEventConsumerKeyPressArgs,
  XWMWindowType,
  geometriesDiffer,
  getConfig,
  getConfigWithOverrides,
  getLayoutPluginName,
  selectVisibleWindowsFromCurrentTags,
  setConfig,
  setConfigAction,
  X11_EVENT_TYPE,
  IXEvent,
  IXConfigureEvent,
  IXScreen,
  IXDisplay,
  IXClient,
  IXKeyEvent,
  XCbWithErr,
  XGeometry,
  XWindowAttrs,
  IXPropertyNotifyEvent,
  XMapState,
  XCB_EVENT_MASK_NO_EVENT,
  IX11Mod,
  IX11Client,
  XFocusRevertTo,
  PointerRoot,
  IXConfigureInfo,
  CWMaskBits,
  IClientMessageEvent,
  Atom,
  IXMotionNotifyEvent,
  IXButtonReleaseEvent,
  WMSizeHints,
  WMHintsStates,
  ContextMenuKind,
  anyIntersect,
  arraysEqual,
  fitGeometryWithinAnother,
  requireXinerama,
  addWindowAction,
  configureWindowAction,
  focusWindowAction,
  removeWindowAction,
  setFrameExtentsAction,
  setWindowFullscreenAction,
  setWindowIntoScreenAction,
  setWindowMaximizedAction,
  setWindowMinimizedAction,
  setWindowTagsAction,
  setWindowTitleAction,
  setWindowVisibleAction,
  addScreenAction,
  setScreenCurrentTagsAction,
  setScreenZoomLevelAction,
  getWindowMinHeight,
  getWindowMinWidth,
  IWindow,
  windowAcceptsFocus,
  switchToNextLayout,
} from "@bond-wm/shared";
import { spawn } from "child_process";
import { AsyncReturnType, Writable } from "type-fest";
import { log, logDir, logError } from "./log";
import { configureWMStore, ServerRootState, ServerStore } from "./configureStore";
import { Action, Middleware, UnknownAction, isAction } from "redux";
import { ViteDevServer, createServer as createViteServer } from "vite";
import { ViteNodeServer } from "vite-node/server";
import { ViteNodeRunner } from "vite-node/client";
import { installSourcemapsSupport } from "vite-node/source-map";
import { createEWMHEventConsumer } from "./ewmh";
import { changeWindowEventMask, getPropertyValue, internAtomAsync } from "./xutils";
import { getScreenIndexWithCursor, queryPointer } from "./pointer";
import { createICCCMEventConsumer, getNormalHints, getWMClass, getWMHints, getWMTransientFor } from "./icccm";
import { createMotifModule, hasMotifDecorations } from "./motif";
import { showContextMenu } from "./menus";
import { setupAutocompleteListener } from "./autocomplete";
import { createDragModule } from "./drag";
import { loggingEnabled } from "./args";
import { createShortcutsModule } from "./shortcuts";
import { assert } from "./assert";
import { determineConfigPath } from "./config";
import { createTrayEventConsumer } from "./systray";
import { createDesktopEntriesModule } from "./desktopEntries";
import { readVersionInfo } from "./version";
import { fileURLToPath } from "node:url";
import { dirname } from "path";
import { setupContentSecurityPolicy } from "./csp";
import { updateWindowTagsForNextScreen } from "./window";

// Path constants
const __dirname = dirname(fileURLToPath(import.meta.url));
const PRELOAD_JS = path.resolve(path.join(__dirname, "preload.js"));

// The values here are arbitrary; we call InternAtom to get the true constants.
export const ExtraAtoms = {
  UTF8_STRING: -1,

  WM_PROTOCOLS: 10000,
  WM_DELETE_WINDOW: 10001,

  _NET_WM_NAME: 340,
};

const NO_EVENT_MASK = x11.eventMask.None;

const ROOT_WIN_EVENT_MASK =
  x11.eventMask.SubstructureRedirect |
  x11.eventMask.SubstructureNotify |
  x11.eventMask.EnterWindow |
  x11.eventMask.LeaveWindow |
  x11.eventMask.StructureNotify |
  x11.eventMask.ButtonPress |
  x11.eventMask.ButtonRelease |
  x11.eventMask.FocusChange |
  x11.eventMask.PropertyChange;

const FRAME_WIN_EVENT_MASK =
  x11.eventMask.StructureNotify |
  x11.eventMask.EnterWindow |
  x11.eventMask.LeaveWindow |
  x11.eventMask.SubstructureRedirect |
  x11.eventMask.PointerMotion |
  x11.eventMask.ButtonRelease |
  x11.eventMask.KeyPress;

const CLIENT_WIN_EVENT_MASK =
  x11.eventMask.StructureNotify |
  x11.eventMask.PropertyChange |
  x11.eventMask.FocusChange |
  x11.eventMask.PointerMotion;

export interface XWMEventConsumerSetFrameExtentsArgs extends XWMEventConsumerArgs {
  frameExtents: IBounds;
}

export interface XWMEventConsumerClientMessageArgs extends XWMEventConsumerArgsWithType {
  messageType: Atom;
  data: number[];
}

export interface XWMEventConsumerScreenCreatedArgs {
  /** Root window id. */
  root: number;
  /** Window id of the desktop window created for the screen. */
  desktopWindowId: number;
}

export interface XWMEventConsumerReduxActionArgs {
  action: Action;
  getState(): ServerRootState;
}

export interface XWMEventConsumerPointerMotionArgs extends XWMEventConsumerArgsWithType {
  rootx: number;
  rooty: number;
}

export interface IXWMEventConsumer {
  onScreenCreated?(args: XWMEventConsumerScreenCreatedArgs): void;
  onReduxAction?(args: XWMEventConsumerReduxActionArgs): void;

  onClientMessage?(args: XWMEventConsumerClientMessageArgs): void;
  onMapNotify?(args: XWMEventConsumerArgsWithType): void;
  onUnmapNotify?(args: XWMEventConsumerArgsWithType): void;
  onPointerMotion?(args: XWMEventConsumerPointerMotionArgs): void;
  onButtonRelease?(args: XWMEventConsumerArgsWithType): void;
  onKeyPress?(args: XWMEventConsumerKeyPressArgs): boolean;

  onSetFrameExtents?(args: XWMEventConsumerSetFrameExtentsArgs): void;
}

export interface XWMContext {
  X: IXClient;
  XDisplay: IXDisplay;
  store: ServerStore;
  wmServer: IWindowManagerServer;

  getWindowIdFromFrameId(wid: number): number | undefined;
  getFrameIdFromWindowId(wid: number): number | undefined;
}

export function startWindowManager(): Promise<IWindowManagerServer> {
  return createServer();
}

export async function createServer(): Promise<IWindowManagerServer> {
  let XDisplay: IXDisplay;
  let X: IXClient;

  const eventConsumers: IXWMEventConsumer[] = [];

  let desktopEntriesModule: AsyncReturnType<typeof createDesktopEntriesModule>;
  let ewmhModule: AsyncReturnType<typeof createEWMHEventConsumer>;
  let dragModule: AsyncReturnType<typeof createDragModule>;
  let motif: AsyncReturnType<typeof createMotifModule>;
  let shortcuts: AsyncReturnType<typeof createShortcutsModule>;

  const layoutsByScreen: Map<number, readonly LayoutPluginConfig[]> = new Map();

  const knownWids = new Set<number>();
  const winIdToRootId: { [wid: number]: number } = {};

  const desktopBrowsers: (BrowserWindow | null)[] = [];
  /** Desktop window handle to index into `desktopBrowsers`. */
  const desktopBrowserHandles: { [did: number]: number } = {};
  const screenIndexToDesktopId: { [screenIndex: number]: number } = {};

  const frameBrowserWindows: { [wid: number]: BrowserWindow | undefined } = {};
  const frameBrowserWinIdToFrameId: { [wid: number]: number | undefined } = {};
  const frameBrowserFrameIdToWinId: { [fid: number]: number | undefined } = {};
  let frameBrowserOnDeck: {
    win: BrowserWindow;
    fid: number;
    winLoadPromise: Promise<void>;
  } | null = null;

  const initializingWins: { [win: number]: boolean } = {};

  let childWindowCounter = 0;
  const childWindows: Map<string, { wid: number | null; alwaysOnTop: boolean }> = new Map();

  let ignoreEnterLeave = false;

  /**
   * The last frame extents used for a window.
   * Since the frame takes a little bit to render, and the extents are usually the same,
   * we track this and use these extents as default as an optimization.
   */
  let lastFrameExtents: IBounds | undefined;

  const store = __setupStore();
  await readVersionInfo(store);

  const configPath = await determineConfigPath(store);

  const [viteNodeServer, viteNodeRunner] = await __setupViteNodeServer(configPath);
  setConfig((await viteNodeRunner.executeId(configPath)).default);
  const config = getConfig();
  log("Initial config", config);
  store.dispatch(setConfigAction(config));

  const viteWebServer = await __setupViteWebServer(configPath);
  const viteLocalhost = viteWebServer.resolvedUrls?.local[0];
  log("Vite web server at " + viteLocalhost);

  const desktopLocation = viteLocalhost + "desktop/index.html";
  const frameLocation = viteLocalhost + "frame/index.html";

  setupContentSecurityPolicy();

  let context: XWMContext;

  const sendKeyToBrowser = async (args: XWMEventConsumerKeyPressArgs) => {
    const screenIndex = await getScreenIndexWithCursor(context, args.wid);
    const browser = desktopBrowsers[screenIndex];
    if (browser) {
      browser.webContents.send("x-keypress", {
        keyString: args.originalKeyString,
      });
    }
  };

  async function destroy(): Promise<void> {
    await viteNodeServer.close();
    await viteWebServer.close();
  }

  const wmServer: IWindowManagerServer = {
    restart: async () => {
      await destroy();
      app.relaunch();
      app.exit(0);
    },

    quit: async () => {
      await destroy();
      app.quit();
    },

    closeFocusedWindow,
    launchProcess,

    registerShortcuts: (registrationMap: KeyRegistrationMap) => {
      const screens = store.getState().screens;
      const registeredRootWids = new Set<number>();
      for (const screen of screens) {
        const { root } = screen;
        if (!registeredRootWids.has(root)) {
          registeredRootWids.add(root);
          shortcuts.registerShortcuts(root, registrationMap);
        }
      }
    },

    sendActiveWindowToNextScreen,
    sendActiveWindowToTag,
    setTagIndexForActiveDesktop,
    showDevtoolsForFocusedWindowFrame,
    startDragFocusedWindow,
    switchToNextLayout: switchToNextLayoutWM,
  };

  // Initialization.
  const client: IX11Client = x11.createClient(async (err: unknown, display: IXDisplay) => {
    if (err || !display) {
      logError(err ?? "No display available.");
      process.exit(1);
    }

    XDisplay = display;
    X = display.client;

    context = {
      X,
      XDisplay,
      store,
      wmServer,
      getWindowIdFromFrameId,
      getFrameIdFromWindowId,
    };

    desktopEntriesModule = await createDesktopEntriesModule(context);
    dragModule = await createDragModule(context, (screenIndex) => layoutsByScreen.get(screenIndex));
    eventConsumers.push(dragModule);
    eventConsumers.push(await createICCCMEventConsumer(context));
    ewmhModule = await createEWMHEventConsumer(context, dragModule);
    eventConsumers.push(ewmhModule);
    eventConsumers.push(await createTrayEventConsumer(context));

    motif = await createMotifModule(context);
    shortcuts = await createShortcutsModule(context);
    eventConsumers.push(shortcuts);

    await __setupAtoms();
    await __initDesktop();

    for (let s = 0; s < desktopBrowsers.length; s++) {
      const layoutPlugins = getConfigWithOverrides(s).layouts;
      layoutsByScreen.set(s, layoutPlugins ?? []);
    }

    if (typeof config.onWindowManagerReady === "function") {
      await config.onWindowManagerReady({ wm: wmServer });
    }

    // Prep one frame window to speed up rendering for the first window.
    setTimeout(() => createFrameBrowserOnDeck(), 0);
  });

  client.on("error", logError);
  client.on("event", __onXEvent);

  ipcMain.on(IPCMessages.RaiseWindow, (event, wid) => {
    raiseWindow(wid);
  });

  ipcMain.on(IPCMessages.MinimizeWindow, (event, wid) => {
    minimize(wid);
  });

  ipcMain.on(IPCMessages.MaximizeWindow, (event, wid) => {
    maximize(wid);
  });

  ipcMain.on(IPCMessages.RestoreWindow, (event, wid) => {
    restore(wid);
  });

  ipcMain.on(IPCMessages.CloseWindow, (event, wid) => {
    closeWindow(wid);
  });

  ipcMain.on(IPCMessages.FocusDesktopBrowser, (event, args: { screenIndex: number; takeVisualFocus?: boolean }) => {
    setFocusToDesktopWindow(args.screenIndex, args.takeVisualFocus);
  });

  ipcMain.on(IPCMessages.FrameWindowMouseEnter, (event, wid) => {
    // Alternative in case we don't receive PointerMotion over a window.
    if (ignoreEnterLeave) {
      widLog(wid, IPCMessages.FrameWindowMouseEnter, "clearing enterleave ignore");
      ignoreEnterLeave = false;
    }
  });

  ipcMain.on(IPCMessages.DesktopZoomIn, (event, args: { screenIndex: number }) => {
    desktopZoomIn(args.screenIndex);
  });

  ipcMain.on(IPCMessages.DesktopZoomOut, (event, args: { screenIndex: number }) => {
    desktopZoomOut(args.screenIndex);
  });

  ipcMain.on(IPCMessages.DesktopZoomReset, (event, args: { screenIndex: number }) => {
    desktopZoomReset(args.screenIndex);
  });

  ipcMain.on(IPCMessages.ExecDesktopEntry, (event, args: { entryName: string }) => {
    desktopEntriesModule.launchDesktopEntry(args.entryName);
  });

  ipcMain.on(IPCMessages.ShowContextMenu, (event, args: { menuKind: ContextMenuKind }) => {
    showContextMenu(event, args.menuKind, store.getState().config.version);
  });

  ipcMain.on(IPCMessages.ShowDesktopDevTools, (event, args: { screenIndex: number }) => {
    desktopBrowsers[args.screenIndex]?.webContents?.openDevTools();
  });

  ipcMain.on(IPCMessages.RegisterDesktopShortcut, (event, args: { keyString: string; screenIndex: number }) => {
    const screen = store.getState().screens[args.screenIndex];
    shortcuts.registerShortcut(screen.root, args.keyString, sendKeyToBrowser);
  });

  // ipcMain.on(IPCMessages.UnregisterDesktopShortcut, (event, args: { keyString: string; screenIndex: number }) => {
  //   // Not implemented yet.
  // });

  setupAutocompleteListener();

  async function __setupViteNodeServer(configPath: string): Promise<[ViteDevServer, ViteNodeRunner]> {
    const viteServer = await createViteServer({
      root: configPath,
      mode: "development",
      server: {
        port: 19108,
      },
      optimizeDeps: {
        noDiscovery: true,
        include: undefined,
      },
    });
    await viteServer.pluginContainer.buildStart({});
    const viteNodeServer = new ViteNodeServer(viteServer);
    installSourcemapsSupport({
      getSourceMap: (source) => viteNodeServer.getSourceMap(source),
    });
    const runner = new ViteNodeRunner({
      root: viteServer.config.root,
      base: viteServer.config.base,
      fetchModule(id) {
        return viteNodeServer.fetchModule(id);
      },
      resolveId(id, importer) {
        return viteNodeServer.resolveId(id, importer);
      },
    });
    await viteServer.listen();
    return [viteServer, runner];
  }

  async function __setupViteWebServer(configPath: string): Promise<ViteDevServer> {
    const viteWebServer = await createViteServer({
      root: configPath,
      mode: "development",
      server: {
        port: 19109,
      },
    });

    // Endpoint for "/icon/[desktopEntry]" to get an icon image response.
    viteWebServer.middlewares.use("/icon", async (req, res) => {
      log("Icon request: " + req.url);

      let desktopEntryName = req.url!;
      while (desktopEntryName.endsWith("/")) {
        desktopEntryName = desktopEntryName.substring(0, desktopEntryName.length - 1);
      }
      while (desktopEntryName.startsWith("/")) {
        desktopEntryName = desktopEntryName.substring(1);
      }
      const iconInfo = await desktopEntriesModule.getDesktopEntryIcon(desktopEntryName);
      if (!iconInfo) {
        res.statusCode = 404;
        res.end();
        return;
      }
      res.setHeader("Content-Type", iconInfo.mimeType);
      res.end(iconInfo.data);
    });
    viteWebServer.middlewares.stack.unshift(viteWebServer.middlewares.stack.pop()!);

    await viteWebServer.listen();
    return viteWebServer;
  }

  async function __setupAtoms(): Promise<void> {
    // TODO: Typings are a little awkward here.
    /* eslint-disable @typescript-eslint/no-explicit-any */
    const extraAtoms = ExtraAtoms as Writable<typeof ExtraAtoms>;
    extraAtoms.UTF8_STRING = (await internAtomAsync(X, "UTF8_STRING")) as any;

    extraAtoms.WM_PROTOCOLS = (await internAtomAsync(X, "WM_PROTOCOLS")) as any;
    extraAtoms.WM_DELETE_WINDOW = (await internAtomAsync(X, "WM_DELETE_WINDOW")) as any;

    extraAtoms._NET_WM_NAME = (await internAtomAsync(X, "_NET_WM_NAME")) as any;

    log("ExtraAtoms", extraAtoms);
    /* eslint-enable @typescript-eslint/no-explicit-any */
  }

  async function __initDesktop(): Promise<void> {
    for (const screen of XDisplay.screen) {
      await __initScreen(screen);
    }

    // Set focus to the initial window/desktop.
    const firstDesktopWid = getNextFocusWidForScreen(0, undefined);
    if (typeof firstDesktopWid === "number") {
      setFocus(firstDesktopWid);
    }
  }

  async function __initScreen(screen: IXScreen): Promise<void> {
    const root = screen.root;

    const debugScreen = Object.assign({}, screen);
    delete (debugScreen as any).depths; // eslint-disable-line
    log("Processing X screen", debugScreen);

    X.GrabServer();

    changeWindowEventMask(X, root, ROOT_WIN_EVENT_MASK);

    X.UngrabServer();

    const logicalScreens = await getScreenGeometries(screen);
    log("Obtained logical screens", logicalScreens);

    for (const logicalScreen of logicalScreens) {
      store.dispatch(
        addScreenAction({
          x: logicalScreen.x,
          y: logicalScreen.y,
          width: logicalScreen.width,
          height: logicalScreen.height,
          root,
          tags: config.tags,
          initialTag: config.initialTag,
          initialLayout: config.initialLayout,
        })
      );

      const did = await createDesktopBrowser({
        x: logicalScreen.x,
        y: logicalScreen.y,
        width: logicalScreen.width,
        height: logicalScreen.height,
      });

      X.ReparentWindow(did, root, logicalScreen.x, logicalScreen.y);

      X.ConfigureWindow(did, {
        borderWidth: 0,
        x: logicalScreen.x,
        y: logicalScreen.y,
        width: logicalScreen.width,
        height: logicalScreen.height,
      });
    }

    X.QueryTree(root, (err, tree) => {
      tree.children.forEach((childWid) => manageWindow(childWid, { screenIndex: 0, checkUnmappedState: true }));
    });

    X.SetInputFocus(PointerRoot, XFocusRevertTo.PointerRoot);

    eventConsumers.forEach((consumer) =>
      consumer.onScreenCreated?.({
        root,
        desktopWindowId: screenIndexToDesktopId[0],
      })
    );
  }

  function isDesktopBrowserWin(wid: number): boolean {
    return desktopBrowserHandles.hasOwnProperty(wid);
  }

  function isFrameBrowserWin(wid: number): boolean {
    return frameBrowserFrameIdToWinId.hasOwnProperty(wid) || frameBrowserOnDeck?.fid === wid;
  }

  function isTrayWin(wid: number): boolean {
    return wid in store.getState().tray.windows;
  }

  function getFrameIdFromWindowId(wid: number): number | undefined {
    return frameBrowserWinIdToFrameId[wid];
  }

  function getWindowIdFromFrameId(wid: number): number | undefined {
    return frameBrowserFrameIdToWinId[wid];
  }

  function getRootIdFromWindowId(wid: number): number | undefined {
    return winIdToRootId[wid];
  }

  async function createDesktopBrowser(props: IGeometry): Promise<number> {
    const win = new BrowserWindow({
      frame: false,
      fullscreen: true,
      width: props.width,
      height: props.height,
      x: props.x,
      y: props.y,
      type: "desktop",
      webPreferences: {
        preload: PRELOAD_JS,
      },
    });

    const index = desktopBrowsers.length;
    desktopBrowsers[index] = win;

    const handle = getNativeWindowHandleInt(win);
    if (!handle) {
      logError("Browser handle was null");
    }
    desktopBrowserHandles[handle] = index;
    screenIndexToDesktopId[index] = handle;

    log("Created browser window", handle);

    win.webContents.setWindowOpenHandler(onWindowOpen);
    win.webContents.addListener("did-create-window", onChildWindowCreated);

    if (!desktopLocation) {
      throw new Error("Missing desktop config. Desktop windows cannot be created without a desktop plugin.");
    }
    const url = desktopLocation + "?screen=" + index;
    await win.loadURL(url);

    const zoomLevel = win.webContents.getZoomLevel();
    if (zoomLevel !== 1) {
      store.dispatch(setScreenZoomLevelAction({ screenIndex: index, zoom: zoomLevel }));
    }

    // Uncomment to help debug total failures of the desktop window.
    // win.webContents.openDevTools({ mode: "right" });

    win.on("closed", function () {
      desktopBrowsers[index] = null;
    });

    return handle;
  }

  const FrameBrowserBaseProperties: Electron.BrowserWindowConstructorOptions = {
    frame: false,
    backgroundColor: "#00000000",
    transparent: true,
    hasShadow: false,
    webPreferences: {
      preload: PRELOAD_JS,
    },
  };

  function createFrameBrowserOnDeck() {
    if (frameBrowserOnDeck) {
      return;
    }

    const win = new BrowserWindow({
      ...FrameBrowserBaseProperties,
      show: false,
    });
    const winLoadPromise = win.loadURL(frameLocation);

    const fid = getNativeWindowHandleInt(win);
    if (!fid) {
      logError("Frame window handle was null");
    }

    frameBrowserOnDeck = { win, fid, winLoadPromise };
  }

  function createFrameBrowser(wid: number, screen: IScreen, geometry: IGeometry) {
    // If we have a pre-made frame window, use it. Otherwise, create one.
    let win: BrowserWindow;
    let fid: number;
    if (frameBrowserOnDeck) {
      const onDeckInfo = frameBrowserOnDeck;
      frameBrowserOnDeck = null;
      win = onDeckInfo.win;
      fid = onDeckInfo.fid;
      win.setSize(geometry.width, geometry.height, false);
      win.setPosition(geometry.x, geometry.y, false);
      onDeckInfo.winLoadPromise.then(() => {
        win.webContents.send(IPCMessages.SetFrameWid, wid);
        win.webContents.setZoomLevel(screen.zoom);
      });
      win.show();
    } else {
      win = new BrowserWindow({
        ...FrameBrowserBaseProperties,
        width: geometry.width,
        height: geometry.height,
        x: geometry.x,
        y: geometry.y,
      });
      win.webContents.on("did-finish-load", () => {
        win.webContents.setZoomLevel(screen.zoom);
      });
      win.loadURL(`${frameLocation}?wid=${wid}`);

      fid = getNativeWindowHandleInt(win);
      if (!fid) {
        logError("Frame window handle was null");
      }
    }

    frameBrowserWindows[wid] = win;

    frameBrowserWinIdToFrameId[wid] = fid;
    frameBrowserFrameIdToWinId[fid] = wid;

    log("Created frame window", fid);

    if (!frameBrowserOnDeck) {
      setTimeout(() => createFrameBrowserOnDeck(), 0);
    }

    return fid;
  }

  type WindowOpenResult =
    | { action: "deny" }
    | { action: "allow"; outlivesOpener?: boolean; overrideBrowserWindowOptions?: BrowserWindowConstructorOptions };

  function onWindowOpen(details: HandlerDetails): WindowOpenResult {
    const { url, features } = details;
    if (url === "about:blank" && features?.includes("BondWmChildWindow=true")) {
      const title = `BondWmChildWindow-${++childWindowCounter}`;
      const alwaysOnTop = features?.includes("alwaysOnTop=true") ?? false;
      const windowOpenResult: WindowOpenResult = {
        action: "allow",
        overrideBrowserWindowOptions: {
          title,
          alwaysOnTop,
          frame: false,
          fullscreenable: false,
          resizable: false,
          backgroundColor: "#00FFFFFF", // AARRGGBB
          transparent: true,
          hasShadow: false,
        },
      };
      log("onWindowOpen", windowOpenResult);
      childWindows.set(title, {
        wid: null, // Assigned when created
        alwaysOnTop,
      });
      return windowOpenResult;
    }
    return { action: "allow" };
  }

  function onChildWindowCreated(win: BrowserWindow, details: DidCreateWindowDetails) {
    log("Child window created", details);

    // win.webContents.openDevTools({ mode: "detach" });
  }

  function __onXEvent(ev: IXEvent) {
    const { type } = ev;

    switch (type) {
      case X11_EVENT_TYPE.KeyPress:
        onKeyPress(ev as IXKeyEvent);
        break;
      case X11_EVENT_TYPE.KeyRelease:
        break;
      case X11_EVENT_TYPE.ButtonPress:
        onButtonPress(ev as IXButtonReleaseEvent);
        break;
      case X11_EVENT_TYPE.ButtonRelease:
        onButtonRelease(ev as IXButtonReleaseEvent);
        break;
      case X11_EVENT_TYPE.MotionNotify:
        onPointerMotion(ev as IXMotionNotifyEvent);
        break;
      case X11_EVENT_TYPE.EnterNotify:
        onEnterNotify(ev);
        break;
      case X11_EVENT_TYPE.LeaveNotify:
        onLeaveNotify(ev);
        break;
      case X11_EVENT_TYPE.FocusIn:
        widLog(ev.wid, "onFocusIn", ev);
        break;
      case X11_EVENT_TYPE.FocusOut:
        widLog(ev.wid, "onFocusOut", ev);
        break;
      case X11_EVENT_TYPE.Expose:
        widLog(ev.wid, "onExpose", ev);
        break;
      case X11_EVENT_TYPE.CreateNotify:
        onCreateNotify(ev);
        break;
      case X11_EVENT_TYPE.DestroyNotify:
        onDestroyNotify(ev);
        break;
      case X11_EVENT_TYPE.UnmapNotify:
        onUnmapNotify(ev);
        break;
      case X11_EVENT_TYPE.MapNotify:
        onMapNotify(ev);
        break;
      case X11_EVENT_TYPE.MapRequest:
        onMapRequest(ev);
        break;
      case X11_EVENT_TYPE.ReparentNotify:
        widLog(ev.wid, "onReparentNotify", ev);
        break;
      case X11_EVENT_TYPE.ConfigureNotify:
        break;
      case X11_EVENT_TYPE.ConfigureRequest:
        onConfigureRequest(ev as IXConfigureEvent);
        break;
      case X11_EVENT_TYPE.ClientMessage:
        onClientMessage(ev as IClientMessageEvent);
        break;
      case X11_EVENT_TYPE.PropertyNotify:
        onPropertyNotify(ev as IXPropertyNotifyEvent);
        break;
      default:
        log("Unhandled event", ev);
        break;
    }
  }

  interface ManageWindowOpts {
    screenIndex: number;
    checkUnmappedState: boolean;
    focusWindow?: boolean;
  }

  async function manageWindow(wid: number, opts: ManageWindowOpts): Promise<void> {
    const { checkUnmappedState } = opts;
    let { screenIndex, focusWindow } = opts;

    widLog(wid, `Manage window on screen ${screenIndex}`);

    if (initializingWins[wid]) {
      log(`Skip manage, ${wid} is already initializing`);
      return;
    }
    if (knownWids.has(wid)) {
      log(`Skip manage, ${wid} is known`);
      return;
    }
    if (isFrameBrowserWin(wid)) {
      log(`Skip manage, ${wid} is a frame window`);
      return;
    }
    if (isTrayWin(wid)) {
      log(`Skip manage, ${wid} is a tray window`);
      return;
    }

    // Make sure we don't respond to too many messages at once.
    initializingWins[wid] = true;
    knownWids.add(wid);

    const values = await Promise.all([
      determineWindowAttributes(wid),
      determineWindowGeometry(wid),
      getWindowTitle(wid),
      getWMClass(X, wid),
      getWMHints(X, wid),
      getNormalHints(X, wid),
      motif.getMotifHints(wid),
      getWMTransientFor(X, wid),
      ewmhModule.getNetWmType(wid),
      ewmhModule.getNetWmIcons(wid),
    ]);

    const [attrs, clientGeom, title, wmClass, wmHints, normalHints, motifHints, transientFor, winType, icons] = values;
    log(`got values for ${wid}:`, values);

    const isOverrideRedirect = attrs.overrideRedirect === 1;
    if (isOverrideRedirect) {
      log(`Not managing ${wid} due to override redirect.`);
    }

    const isUnmappedState = checkUnmappedState && attrs.mapState === XMapState.IsUnmapped;
    if (isUnmappedState) {
      log(`Not managing ${wid} due to unmapped state.`);
    }

    const isChildWindow = title?.startsWith("BondWmChildWindow-");
    if (isChildWindow) {
      const childWindowInfo = childWindows.get(title!);
      if (!childWindowInfo) {
        logError("Missing child window info");
      } else {
        childWindowInfo.wid = wid;
      }
      log(`Not managing ${wid} due to it being a ChildWindow.`);
    }

    if (isOverrideRedirect || isUnmappedState || isChildWindow) {
      delete initializingWins[wid];
      X.MapWindow(wid);
      return;
    }

    ignoreEnterLeave = true;

    X.ChangeSaveSet(1, wid);

    if (shouldCreateFrame(wid, clientGeom)) {
      const initialGeometry = getInitialGeometryForWindow(clientGeom, normalHints);

      const win: Partial<IWindow> = {
        outer: {
          x: initialGeometry.x,
          y: initialGeometry.y,
          width: initialGeometry.width,
          height: initialGeometry.height,
        },
        frameExtents: lastFrameExtents,
        visible: true,
        type: winType ?? WindowType.Normal,
        transientFor,
        decorated: hasMotifDecorations(motifHints),
        title,
        wmClass,
        screenIndex,
        wmHints,
        normalHints,
        icons,
      };

      const state = store.getState();

      if (typeof config.onWindowCreated === "function") {
        config.onWindowCreated({ win: win as IWindow, state });
      }

      assert(typeof win.screenIndex === "number");
      assert(win.outer);

      // Accept any update to screenIndex (if it is valid).
      let screen = state.screens[win.screenIndex];
      if (screen) {
        screenIndex = win.screenIndex;
      } else {
        win.screenIndex = screenIndex;
        screen = state.screens[win.screenIndex];
      }

      if (!win.tags) {
        win.tags = [screen.currentTags[0]];
      }

      const [frameX, frameY] = [screen.x + win.outer.x, screen.y + win.outer.y];

      const fid = createFrameBrowser(wid, screen, { ...win.outer, x: frameX, y: frameY });
      knownWids.add(fid);

      winIdToRootId[wid] = screen.root;
      winIdToRootId[fid] = screen.root;

      X.ReparentWindow(fid, screen.root, frameX, frameY);
      X.ReparentWindow(wid, fid, lastFrameExtents?.left || 0, lastFrameExtents?.top || 0);

      X.GrabServer();

      changeWindowEventMask(X, fid, FRAME_WIN_EVENT_MASK);
      changeWindowEventMask(X, wid, CLIENT_WIN_EVENT_MASK);

      X.UngrabServer();

      X.ConfigureWindow(fid, {
        borderWidth: 0,
        x: frameX,
        y: frameY,
        width: win.outer.width,
        height: win.outer.height,
      });
      X.ConfigureWindow(wid, { borderWidth: 0 });

      if (lastFrameExtents) {
        eventConsumers.forEach((consumer) => consumer.onSetFrameExtents?.({ wid, frameExtents: lastFrameExtents! }));
      }

      store.dispatch(addWindowAction({ wid, ...win }));

      X.MapWindow(fid);

      if (focusWindow && !windowAcceptsFocus(win as IWindow)) {
        focusWindow = false;
      }
    }

    log("Initial map of wid", wid);
    X.MapWindow(wid);

    if (focusWindow) {
      setFocus(wid);
    }

    delete initializingWins[wid];
  }

  function unmanageWindow(wid: number): void {
    if (isFrameBrowserWin(wid)) {
      widLog(wid, `Unmanage frame window`);

      const innerWid = frameBrowserFrameIdToWinId[wid];
      delete frameBrowserFrameIdToWinId[wid];
      if (typeof innerWid === "number") {
        delete frameBrowserWinIdToFrameId[innerWid];
        delete frameBrowserWindows[innerWid];
      }
    } else if (isClientWin(wid)) {
      widLog(wid, `Unmanage window`);

      const focusedWid = getFocusedWindowId();
      const win = getWinFromStore(wid);
      if (!win) {
        return;
      }

      store.dispatch(removeWindowAction(wid));

      const fid = getFrameIdFromWindowId(wid);
      if (typeof fid === "number" && fid !== wid) {
        // Reparent the hosted window back to the root before destroying the BrowserWindow.
        // This prevents a browser save popup closing from taking out the entire browser process for example.
        // (Presumably destroying the BrowserWindow with a window inside it triggers mass destruction.)
        const screen = store.getState().screens[win.screenIndex];
        X.ReparentWindow(wid, screen.root, 0, 0);

        log("Destroying BrowserWindow for frame " + fid);
        frameBrowserWindows[wid]?.destroy();
      }

      if (wid === focusedWid && win) {
        tryReplaceFocusForScreen(win.screenIndex, focusedWid);
      }
    }

    knownWids.delete(wid);
    delete winIdToRootId[wid];
  }

  function shouldCreateFrame(wid: number, geometry: XGeometry): boolean {
    if (isDesktopBrowserWin(wid)) {
      return false;
    }

    // Positioned negatively outside the desktop.
    if (geometry.xPos + geometry.width < 0 || geometry.yPos + geometry.height < 0) {
      return false;
    }

    // TODO: Positioned positively outside?

    return true;
  }

  function getInitialGeometryForWindow(clientGeom: XGeometry, normalHints: WMSizeHints | undefined): IGeometry {
    const initialGeometry = {
      height: clientGeom.height,
      width: clientGeom.width,
      x: clientGeom.xPos,
      y: clientGeom.yPos,
    };
    if (normalHints) {
      if (normalHints.maxHeight && normalHints.maxHeight > 0) {
        initialGeometry.height = Math.min(initialGeometry.height, normalHints.maxHeight);
      }
      if (normalHints.minHeight && normalHints.minHeight > 0) {
        initialGeometry.height = Math.max(initialGeometry.height, normalHints.minHeight);
      }
      if (normalHints.maxWidth && normalHints.maxWidth > 0) {
        initialGeometry.width = Math.min(initialGeometry.width, normalHints.maxWidth);
      }
      if (normalHints.minWidth && normalHints.minWidth > 0) {
        initialGeometry.width = Math.max(initialGeometry.width, normalHints.minWidth);
      }
    }

    return initialGeometry;
  }

  function runXCallsWithoutEvents(wid: number, fn: VoidFunction): void {
    X.GrabServer();
    try {
      const root = getRootIdFromWindowId(wid);
      if (typeof root === "number") {
        changeWindowEventMask(X, root, NO_EVENT_MASK);
      }
      const fid = getFrameIdFromWindowId(wid);
      if (typeof fid === "number") {
        changeWindowEventMask(X, fid, NO_EVENT_MASK);
      }
      changeWindowEventMask(X, wid, NO_EVENT_MASK);

      try {
        fn();
      } finally {
        if (typeof root === "number") {
          changeWindowEventMask(X, root, ROOT_WIN_EVENT_MASK);
        }
        if (typeof fid === "number") {
          changeWindowEventMask(X, fid, FRAME_WIN_EVENT_MASK);
        }
        changeWindowEventMask(X, wid, CLIENT_WIN_EVENT_MASK);
      }
    } finally {
      X.UngrabServer();
    }
  }

  async function onCreateNotify(ev: IXEvent) {
    const { wid } = ev;
    widLog(wid, "onCreateNotify", ev);

    const wmHints = await getWMHints(X, wid);
    if (knownWids.has(wid)) {
      widLog(wid, "onCreateNotify exiting after obtaining WM_HINTS; window was already managed.");
      return;
    }

    const initialState = wmHints?.initialState;
    if (typeof initialState === "number") {
      widLog(wid, `onCreateNotify initial state: ${initialState} (${WMHintsStates[initialState]})`);
      // if (initialState === WMHintsStates.IconicState) {
      //   const screenIndex = Math.max(0, await getScreenIndexWithCursor(context, wid));
      //   manageWindow(wid, { screenIndex, focusWindow: true, checkUnmappedState: false });
      // }
    }
  }

  async function onMapRequest(ev: IXEvent) {
    const { wid } = ev;
    widLog(wid, "onMapRequest", ev);

    if (initializingWins[wid]) return;

    if (knownWids.has(wid)) {
      showWindow(wid);
    } else {
      const screenIndex = Math.max(0, await getScreenIndexWithCursor(context, wid));
      manageWindow(wid, { screenIndex, focusWindow: true, checkUnmappedState: false });
    }
  }

  function onMapNotify(ev: IXEvent) {
    const { wid } = ev;
    widLog(wid, "onMapNotify", ev);

    if (isClientWin(wid)) {
      eventConsumers.forEach((consumer) => consumer.onMapNotify?.({ wid, windowType: getWindowType(wid) }));
    }
  }

  function onUnmapNotify(ev: IXEvent) {
    const { wid } = ev;
    widLog(wid, "onUnmapNotify", ev);

    eventConsumers.forEach((consumer) => consumer.onUnmapNotify?.({ wid, windowType: getWindowType(wid) }));

    unmanageWindow(wid);
  }

  function onDestroyNotify(ev: IXEvent) {
    const { wid } = ev;
    widLog(wid, "onDestroyNotify", ev);

    childWindows.forEach((childWindowInfo, title) => {
      if (wid === childWindowInfo.wid) {
        log(`Removing child window ${wid} ${title}`);
        childWindows.delete(title);
      }
    });

    unmanageWindow(wid);
  }

  function onConfigureRequest(ev: IXConfigureEvent) {
    const { wid } = ev;

    // Until node-x11 5a1fb64 reaches npm, `mask` needs to be read from the raw data.
    const mask = (ev.mask = ev.rawData.readUInt16LE(26));

    widLog(wid, "onConfigureRequest", ev);

    // Ignore any configure requests for these; we always control their size.
    if (isFrameBrowserWin(wid)) {
      return;
    }

    if (!mask) {
      return; // There's no requested changes?
    }

    const config: Partial<IXConfigureInfo> = {};
    if (mask & CWMaskBits.CWX) {
      // ev.x is absolute, but our state is relative to the screen.
      config.x = ev.x;
    }
    if (mask & CWMaskBits.CWY) {
      config.y = ev.y;
    }
    if (mask & CWMaskBits.CWWidth) {
      config.width = ev.width;
    }
    if (mask & CWMaskBits.CWHeight) {
      config.height = ev.height;
    }
    if (mask & CWMaskBits.CWBorderWidth) {
      config.borderWidth = ev.borderWidth;
    }
    if (mask & CWMaskBits.CWSibling) {
      config.sibling = ev.sibling;
    }
    if (mask & CWMaskBits.CWStackMode) {
      // Don't allow the desktop to come to the front.
      if (!isDesktopBrowserWin(wid)) {
        config.stackMode = ev.stackMode;
      }
    }

    if (isClientWin(wid)) {
      const win = getWinFromStore(wid);
      if (!win) {
        return;
      }
      const screen = store.getState().screens[win.screenIndex];

      // ev.x|y is absolute, but our state is relative to the screen.
      if (mask & CWMaskBits.CWX) {
        config.x! -= screen.x;
      }
      if (mask & CWMaskBits.CWY) {
        config.y! -= screen.y;
      }

      if (Object.keys(config).length > 0) {
        store.dispatch(configureWindowAction({ wid, ...config }));
      }
    } else {
      // Some unmanaged window; pass the call through.
      X.ConfigureWindow(wid, config);
    }
  }

  function onEnterNotify(ev: IXEvent) {
    const { wid } = ev;
    widLog(wid, "onEnterNotify", ignoreEnterLeave ? "ignoring" : "handling");

    if (ignoreEnterLeave) {
      return;
    }

    focusWindowOnEnter(wid);
  }

  function focusWindowOnEnter(wid: number): void {
    const isFrame = isFrameBrowserWin(wid);
    const focusWid = isFrame ? getWindowIdFromFrameId(wid) : wid;
    if (typeof focusWid === "number") {
      const win = getWinFromStore(focusWid);
      if (win && windowAcceptsFocus(win)) {
        setFocus(focusWid);
      }
    }
  }

  function onLeaveNotify(ev: IXEvent) {
    const { wid } = ev;
    widLog(wid, "onLeaveNotify", ignoreEnterLeave ? "ignoring" : "handling");
  }

  function onPointerMotion(ev: IXMotionNotifyEvent): void {
    const { wid } = ev;
    // widLog(wid, "onPointerMotion", ev);

    if (ignoreEnterLeave) {
      widLog(wid, "onMotionNotify", "clearing enterleave ignore");
      ignoreEnterLeave = false;
      focusWindowOnEnter(wid); // In case we don't get onEnterNotify
    }

    eventConsumers.forEach((consumer) =>
      consumer.onPointerMotion?.({
        wid,
        windowType: getWindowType(wid),
        rootx: ev.rootx,
        rooty: ev.rooty,
      })
    );
  }

  async function onKeyPress(ev: IXKeyEvent) {
    const { wid } = ev;
    widLog(wid, "onKeyPress", ev);

    for (const consumer of eventConsumers) {
      if (
        consumer.onKeyPress?.({
          wid,
          windowType: getWindowType(wid),
          modifiers: ev.buttons,
          keycode: ev.keycode,
        })
      ) {
        break; // Handled if returned true.
      }
    }
  }

  function onButtonPress(ev: IXButtonReleaseEvent) {
    const { wid } = ev;

    // Why is this coming through ButtonPress?
    if (ev.name === "ButtonRelease") {
      onButtonRelease(ev);
      return;
    }

    raiseWindow(wid);

    widLog(wid, "onButtonPress", ev);
  }

  function onButtonRelease(ev: IXButtonReleaseEvent) {
    const { wid } = ev;
    widLog(wid, "onButtonRelease", ev);

    raiseWindow(wid);

    eventConsumers.forEach((consumer) =>
      consumer.onButtonRelease?.({
        wid,
        windowType: getWindowType(wid),
      })
    );
  }

  function onClientMessage(ev: IClientMessageEvent) {
    const { wid } = ev;

    widLog(wid, "onClientMessage", ev);
    X.GetAtomName(ev.message_type, (err, name) => log(`(Client message message_type ${ev.message_type} == ${name})`));

    eventConsumers.forEach((consumer) =>
      consumer.onClientMessage?.({
        wid,
        windowType: getWindowType(wid),
        messageType: ev.message_type,
        data: ev.data,
      })
    );
  }

  async function onPropertyNotify(ev: IXPropertyNotifyEvent): Promise<void> {
    const { wid, atom } = ev;
    widLog(wid, "onPropertyNotify", ev);

    if (isFrameBrowserWin(wid) || isDesktopBrowserWin(wid)) {
      return;
    }

    switch (atom) {
      case X.atoms.WM_NAME:
      case ExtraAtoms._NET_WM_NAME:
        {
          const title = await getWindowTitle(wid);
          store.dispatch(setWindowTitleAction({ wid, title: title || "" }));
        }
        break;

      default:
        X.GetAtomName(atom, (err, name) => log(`Atom ${atom} (${name}) for property change is unhandled.`));
        break;
    }
  }

  function launchProcess(command: string): void {
    log("launchProcess", command);

    const child = spawn(command, {
      detached: true,
      stdio: "ignore",
      shell: true,
    });
    child.unref(); // Allow electron to close before this child
  }

  function determineWindowAttributes(wid: number): Promise<XWindowAttrs> {
    return new Promise((resolve, reject) => {
      X.GetWindowAttributes(wid, function (err: unknown, attrs) {
        if (err) {
          logError("Couldn't GetWindowAttributes", wid, err);
          reject(err);
          return;
        }

        resolve(attrs);
      });
    });
  }

  function determineWindowGeometry(wid: number): Promise<XGeometry> {
    return new Promise((resolve, reject) => {
      X.GetGeometry(wid, function (err: unknown, clientGeom) {
        if (err) {
          logError("Couldn't read geometry", err);
          reject(err);
          return;
        }

        resolve(clientGeom);
      });
    });
  }

  async function getWindowTitle(wid: number): Promise<string | undefined> {
    const [name, utf8name] = await Promise.all([
      getPropertyValue<string>(X, wid, X.atoms.WM_NAME, X.atoms.STRING),
      getPropertyValue<string>(X, wid, ExtraAtoms._NET_WM_NAME, ExtraAtoms.UTF8_STRING),
    ]);

    return utf8name || name;
  }

  /**
   * By default, one screen means one screen geometry.
   * But if Xinerama is in play, we may have multiple logical screens
   * represented within a single screen.
   */
  function getScreenGeometries(screen: IXScreen): Promise<IGeometry[]> {
    return new Promise((resolve) => {
      const defaultGeometry: IGeometry = {
        x: 0,
        y: 0,
        width: screen.pixel_width,
        height: screen.pixel_height,
      };

      requireXinerama(XDisplay, (err, xinerama) => {
        if (!xinerama) {
          resolve([defaultGeometry]);
          return;
        }

        xinerama.IsActive((err, isActive) => {
          if (!isActive) {
            resolve([defaultGeometry]);
            return;
          }

          xinerama.QueryScreens((err, screenInfos) => {
            if (err || !screenInfos) {
              resolve([defaultGeometry]);
              return;
            }

            resolve(screenInfos);
          });
        });
      });
    });
  }

  function getFocusedWindowId(screenIndex?: number): number | null {
    const windows = store.getState().windows;
    for (const widStr in windows) {
      const win = windows[widStr];
      if (win.focused) {
        if (typeof screenIndex !== "number" || win.screenIndex === screenIndex) {
          return parseInt(widStr);
        }
      }
    }
    return null;
  }

  /** Returns a window id if there is only one window in existence. */
  function getOnlyWindowId(): number | null {
    const windows = store.getState().windows;
    const wids = Object.keys(windows);
    if (wids.length === 1) {
      return parseInt(wids[0], 10);
    }
    return null;
  }

  function anyWindowHasFocus(screenIndex?: number): boolean {
    return typeof getFocusedWindowId(screenIndex) === "number";
  }

  function XGetWMProtocols(wid: number, callback: XCbWithErr<[number[] | void]>) {
    X.GetProperty(0, wid, ExtraAtoms.WM_PROTOCOLS, 0, 0, 10000000, (err, prop) => {
      if (err) {
        callback(err);
        return;
      }

      const protocols = [];
      if (prop && prop.data && prop.data.length) {
        const len = prop.data.length;
        if (len % 4) {
          callback("Bad length on WM protocol buffer");
          return;
        }

        for (let i = 0; i < len; i += 4) {
          protocols.push(prop.data.readUInt32LE(i));
        }
      }

      callback(null, protocols);
    });
  }

  async function startDragFocusedWindow(): Promise<void> {
    const wid = getFocusedWindowId();
    if (typeof wid === "number" && !isDesktopBrowserWin(wid)) {
      const pointerInfo = await queryPointer(X, wid);
      if (pointerInfo) {
        dragModule.startMove(wid, [pointerInfo.rootX, pointerInfo.rootY]);
      }
    }
  }

  function showDevtoolsForFocusedWindowFrame(): void {
    const wid = getFocusedWindowId() ?? getOnlyWindowId();
    if (typeof wid === "number") {
      log(`Opening dev tools for ${wid}`);
      frameBrowserWindows[wid]?.webContents?.openDevTools({ mode: "detach" });
    }
  }

  function closeFocusedWindow(): void {
    const wid = getFocusedWindowId();
    if (typeof wid === "number" && !isDesktopBrowserWin(wid)) {
      closeWindow(wid);
    }
  }

  function closeWindow(wid: number) {
    const nextFocusWid = wid === getFocusedWindowId() ? getNextFocusWid(wid) : undefined;

    supportsGracefulDestroy(wid, (err, args) => {
      if (err) {
        log("Error in supportsGracefulDestroy", err);
      }
      if (args && args.supported) {
        const eventData = Buffer.alloc(32);
        eventData.writeUInt8(X11_EVENT_TYPE.ClientMessage, 0); // Event Type 33 = ClientMessage
        eventData.writeUInt8(32, 1); // Format
        eventData.writeUInt32LE(wid, 4); // Window ID
        eventData.writeUInt32LE(ExtraAtoms.WM_PROTOCOLS, 8); // Message Type
        eventData.writeUInt32LE(ExtraAtoms.WM_DELETE_WINDOW, 12); // data32[0]
        // Also send a timestamp in data32[1]?
        widLog(wid, "Sending graceful kill", eventData);
        X.SendEvent(wid, false, XCB_EVENT_MASK_NO_EVENT, eventData);
      } else {
        widLog(wid, "Killing window client");
        X.KillClient(wid);
      }

      if (typeof nextFocusWid == "number") {
        setFocus(nextFocusWid);
      }
    });
  }

  function supportsGracefulDestroy(wid: number, callback: XCbWithErr<[{ supported: boolean } | void]>) {
    XGetWMProtocols(wid, (err, protocols) => {
      if (err) {
        logError("XGetWMProtocols error", err);
        callback(err);
        return;
      }

      callback(null, {
        supported: !!protocols && protocols.indexOf(ExtraAtoms.WM_DELETE_WINDOW) >= 0,
      });
    });
  }

  function getNextFocusWid(widLosingFocus: number): number | undefined {
    let nextFocusWid: number | undefined;
    const win = getWinFromStore(widLosingFocus);
    if (win) {
      return getNextFocusWidForScreen(win.screenIndex, widLosingFocus);
    }
    return nextFocusWid;
  }

  function getNextFocusWidForScreen(screenIndex: number, widLosingFocus: number | undefined): number | undefined {
    let nextFocusWid: number | undefined;
    const wins = store.getState().windows;
    for (const widStr in wins) {
      const otherWin = wins[widStr];
      if (
        otherWin.id !== widLosingFocus &&
        otherWin.screenIndex === screenIndex &&
        otherWin.visible &&
        windowAcceptsFocus(otherWin)
      ) {
        nextFocusWid = otherWin.id;

        // Not breaking here, on the chance that we end up finding the "most recent"
        // window later on in the enumeration. (Probably should implement some sort
        // of true "focus history" stack.)
      }
    }

    if (typeof nextFocusWid === "undefined") {
      nextFocusWid = screenIndexToDesktopId[screenIndex];
    }
    return nextFocusWid;
  }

  function tryReplaceFocusForScreen(screenIndex: number, widLosingFocus: number | undefined) {
    const nextFocusWid = getNextFocusWidForScreen(screenIndex, widLosingFocus);
    if (typeof nextFocusWid === "number") {
      setFocus(nextFocusWid);
    }
  }

  function showWindow(wid: number) {
    let fid;
    const isFrame = isFrameBrowserWin(wid);
    if (isFrame) {
      fid = wid;
      const trueWid = getWindowIdFromFrameId(wid);
      assert(typeof trueWid === "number");
      wid = trueWid;
    } else {
      fid = getFrameIdFromWindowId(wid);
    }

    if (typeof fid === "number") {
      log("showWindow frame id", fid);
      X.MapWindow(fid);
    }

    const win = getWinFromStore(wid);
    if (win?.minimized) {
      setWindowMinimized(wid, false);
    }
    if (win?.visible === false) {
      store.dispatch(setWindowVisibleAction({ wid, visible: true }));
    }

    log("showWindow id", wid);
    X.MapWindow(wid);
  }

  /** Hides a window without destroying its frame. */
  function hideWindow(wid: number): void {
    const fid = getFrameIdFromWindowId(wid);

    runXCallsWithoutEvents(wid, () => {
      if (typeof fid === "number") {
        X.UnmapWindow(fid);
      } else if (wid) {
        X.UnmapWindow(wid);
      }
    });

    const win = getWinFromStore(wid);
    if (win?.visible === true) {
      store.dispatch(setWindowVisibleActio