Window API

English API reference for the window family.

This page is the primary owner for the namespaces listed below. Method names, parameter keys, and return fields follow the C++ RegisterApi handlers.

window

window.blur

No parameters.

Returns: {"error":"...","success":true}

const result = await fb2k.invoke('window.blur');

window.broadcast

Parameter	Type	Required	Description
`message`	`json`	Yes	JSON message body delivered to every window except the sender via `window:message`.

Returns: {"error":"...","success":true}

await fb2k.invoke('window.broadcast', { message: { type: 'themeChanged', theme: 'dark' } });

window.cancelClose

No parameters.

Returns: {"error":"...","success":true}

const result = await fb2k.invoke('window.cancelClose');

window.center

No parameters.

Returns: {"error":"...","success":true}

const result = await fb2k.invoke('window.center');

window.clearClickThroughExcludeRegions

Parameter	Type	Required	Description
`windowId`	`string`	No	Popups only; may be omitted when calling from the target popup itself.

Returns: {"error":"...","success":true,"windowId":"..."}

// popup-scoped; omit windowId only when calling from the popup itself
await fb2k.invoke('window.clearClickThroughExcludeRegions', { windowId: 'popup-1' });

window.clearDragRegions

No parameters.

Returns: {"error":"...","success":true}

const result = await fb2k.invoke('window.clearDragRegions');

window.clearNoDragRegions

No parameters.

Returns: {"error":"...","success":true}

const result = await fb2k.invoke('window.clearNoDragRegions');

window.close

No parameters.

Returns: {"success":true}

const result = await fb2k.invoke('window.close');

window.closeAllPopups

No parameters.

Returns: {"success":true}

const result = await fb2k.invoke('window.closeAllPopups');

window.closePopup

Parameter	Type	Required	Description
`windowId`	`string`	Yes	Popup id to close; no fallback to the calling window.

Returns: {"error":"...","success":true}

// windowId is required here; there is no fallback to the calling window
await fb2k.invoke('window.closePopup', { windowId: 'popup-1' });

window.confirmClose

No parameters.

Returns: {"error":"...","success":true}

const result = await fb2k.invoke('window.confirmClose');

window.createPopup

Parameter	Type	Required	Default	Description
`url`	`string`	No	—	Page loaded into the popup.
`title`	`string`	No	—
`x`	`integer`	No	system default	System placement when omitted (CW_USEDEFAULT).
`y`	`integer`	No	system default
`width`	`integer`	No	`400`
`height`	`integer`	No	`300`
`minWidth`	`integer`	No	`200`
`minHeight`	`integer`	No	`150`
`maxWidth`	`integer`	No	`0`	`0` means no upper bound.
`maxHeight`	`integer`	No	`0`	`0` means no upper bound.
`resizable`	`boolean`	No	`true`
`frame`	`boolean`	No	`true`	`false` creates a borderless popup.
`transparent`	`boolean`	No	`false`	Transparent background.
`alwaysOnTop`	`boolean`	No	`false`
`showInTaskbar`	`boolean`	No	`false`
`clickThrough`	`boolean`	No	`false`	Mouse click-through.
`beforeClose`	`boolean`	No	`false`	Emits `window:beforeClose` for close confirmation.
`profile`	`string`	No	—	Behavior preset: `standard` / `miniPlayer` / `desktopLyrics`.
`behavior`	`object`	No	—	Behavior overrides (see `setPopupBehavior`).
`backdropPolicy`	`object`	No	—	Backdrop policy (see `setBackdropPolicy`).

Returns: {"error":"...","success":true,"windowId":"..."}

const { windowId } = await fb2k.invoke('window.createPopup', {
    url: 'popup.html',
    width: 480,
    height: 320,
    title: 'Now Playing',
});

window.enterFullscreen

Parameter	Type	Required	Default	Description
`windowId`	`string`	No	caller window

Returns: {"error":"...","isFullscreen":"...","success":true}

const result = await fb2k.invoke('window.enterFullscreen');

window.exitFullscreen

Parameter	Type	Required	Default	Description
`windowId`	`string`	No	caller window

Returns: {"error":"...","isFullscreen":"...","success":true}

const result = await fb2k.invoke('window.exitFullscreen');

window.flash

Parameter	Type	Required	Default	Description
`count`	`integer`	No	`3`	Flash count.
`enabled`	`boolean`	No	`true`

Returns: {"error":"...","success":true}

// omit count and enabled to start flashing 3 times
await fb2k.invoke('window.flash');

window.flashTaskbar

Parameter	Type	Required	Default	Description
`count`	`integer`	No	`3`	Flash count.

Returns: {"success":true}

// omit count to flash 3 times
await fb2k.invoke('window.flashTaskbar');

window.focus

Parameter	Type	Required	Default	Description
`windowId`	`string`	No	caller window	`main` or a popup id.

Returns: {"error":"...","success":true}

// omit windowId to focus the calling window
await fb2k.invoke('window.focus');

window.getAllWindows

No parameters.

Returns: {"items":"...","success":true}

const result = await fb2k.invoke('window.getAllWindows');

window.getBackdropPolicy

Reads a window's DWM backdrop policy. Supports both the main window and popups.

Parameter	Type	Required	Default	Description
`windowId`	`string`	No	caller window	Target window.

Returns: { "success": true, "windowId": "...", "backdropPolicy": { ... }, "resolvedBackdropPolicy": { ... } }

resolvedBackdropPolicy is the effective policy after profile defaults are applied. A window that cannot be resolved returns { "success": false, "error": "..." }.

// omit windowId to read the calling window
const { resolvedBackdropPolicy } = await fb2k.invoke('window.getBackdropPolicy');

window.getBounds

No parameters.

Returns: {"height":"...","width":"...","x":"...","y":"..."}

const result = await fb2k.invoke('window.getBounds');

window.getCaptionButtonsWidth

Reports the geometry of the main window's custom-drawn caption buttons (minimise / maximise / close), for frontends that render their own titlebar. Main window only: it does not accept windowId and ignores the calling window. Popups have no custom-drawn caption buttons, so there is no popup-scoped value to report.

No parameters.

Returns: {"buttonWidth":"...","width":"..."}

Values are physical pixels and track the main window's DPI. When no main window exists the call returns the DIP-baseline defaults (width: 138, buttonWidth: 46) rather than an error, so callers cannot distinguish "no window" from a genuine 100%-scale measurement.

const result = await fb2k.invoke('window.getCaptionButtonsWidth');

window.getCornerPreference

Returns the main window's Windows 11 corner-rounding preference; mode and preference are the same value under two names. Main window only: it does not accept windowId and ignores the calling window. Popups do not expose this setting — they manage corner rounding internally (rounded when borderless, system default otherwise) and report supportsCornerPreference: false in their capabilities.

No parameters.

Returns: {"mode":"...","preference":"..."}

When no main window exists the call returns "default" rather than an error.

const result = await fb2k.invoke('window.getCornerPreference');

window.getCurrentWindowId

No parameters.

Returns: {"success":true,"windowId":"..."}

const result = await fb2k.invoke('window.getCurrentWindowId');

window.getDevServerConfig

No parameters.

Returns: {"devServerUrl":"...","success":true,"useDevServer":"..."}

const result = await fb2k.invoke('window.getDevServerConfig');

window.getDpiScale

No parameters.

Returns: {"dpi":"...","scale":"...","success":true}

const result = await fb2k.invoke('window.getDpiScale');

window.getMaxSize

Reads a window's requested maximum size. Resolution selects the explicit windowId or the calling window; it does not fall back to the main window, so a call from an unresolvable context fails instead of silently reporting another window's constraints. Panel (DUI/CUI) callers are rejected with panelMode: true, because a panel is not a window shell.

Parameter	Type	Required	Default	Description
`windowId`	`string`	No	caller window	Target window.

Returns: {"height":"...","success":true,"width":"...","windowId":"..."}. A window that cannot be resolved returns { "success": false, "error": "..." }.

Values are physical pixels; the host stores constraints in DIPs and converts using the target window's DPI. 0 means "no upper bound" and survives the conversion exactly.

The returned values are the requested constraints, not the currently effective window size. A physical → DIP → physical round-trip is quantized to whole DIPs, so at non-100% scaling get may differ from the value passed to set by up to 1px per axis (for example, 202px at 125% reads back as 203px). Treat the getters as reporting the constraint you set to within ±1px rather than byte-for-byte. 0 is exempt.

const result = await fb2k.invoke('window.getMaxSize');

window.getMinSize

Reads a window's requested minimum size. Resolution selects the explicit windowId or the calling window; it does not fall back to the main window, so a call from an unresolvable context fails instead of silently reporting another window's constraints. Panel (DUI/CUI) callers are rejected with panelMode: true, because a panel is not a window shell.

Parameter	Type	Required	Default	Description
`windowId`	`string`	No	caller window	Target window.

Returns: {"height":"...","success":true,"width":"...","windowId":"..."}. A window that cannot be resolved returns { "success": false, "error": "..." }.

Values are physical pixels; the host stores constraints in DIPs and converts using the target window's DPI.

const result = await fb2k.invoke('window.getMinSize');

window.getMode

No parameters.

Returns: {"mode":"...","panel":"...","panelMode":"...","windowId":"..."}

const result = await fb2k.invoke('window.getMode');

window.getPopupBehavior

Parameter	Type	Required	Default	Description
`windowId`	`string`	No	calling popup	Popups only.

Returns: {"success":true,"windowId":"..."}

const info = await fb2k.invoke('window.getPopupBehavior', { windowId: 'popup-1' });

window.getState

No parameters.

Returns: {"alwaysOnTop":"...","focused":"...","fullscreen":"...","height":"...","isAlwaysOnTop":"...","isFocused":"...","isFullscreen":"...","isMaximized":"...","isMinimized":"...","maximized":"...","minimized":"...","width":"...","x":"...","y":"..."}

const result = await fb2k.invoke('window.getState');

window.getTitle

No parameters.

Returns: {"title":"..."}

const result = await fb2k.invoke('window.getTitle');

window.getTitlebarHeight

No parameters.

Returns: {"height":"..."}

const result = await fb2k.invoke('window.getTitlebarHeight');

window.getTitlebarInfo

Bundles the main window's titlebar height with its custom-drawn caption-button geometry and maximised state. Main window only: it does not accept windowId and ignores the calling window. Three of the four fields have no popup equivalent — popups expose only a titlebar height and have no custom-drawn caption buttons — so the call stays main-scoped rather than returning zeros for the missing fields.

No parameters.

Returns: {"captionButtonWidth":"...","captionButtonsWidth":"...","height":"...","isMaximized":"..."}

Values are physical pixels and track the main window's DPI. When no main window exists the call returns the DIP-baseline defaults (height: 32, captionButtonsWidth: 138, captionButtonWidth: 46) rather than an error; those fallbacks are unscaled, so on non-100% displays they differ in unit from the normal path.

const result = await fb2k.invoke('window.getTitlebarInfo');

window.getZoom

No parameters.

Returns: {"dpi":"...","dpiScale":"...","success":true,"zoom":"..."}

const result = await fb2k.invoke('window.getZoom');

window.hasSavedBounds

No parameters.

Returns: {"description":"...","hasSavedBounds":"..."}

const result = await fb2k.invoke('window.hasSavedBounds');

window.isAlwaysOnTop

No parameters.

Returns: {"enabled":"...","isAlwaysOnTop":"..."}

const result = await fb2k.invoke('window.isAlwaysOnTop');

window.isClickThrough

Parameter	Type	Required	Default	Description
`windowId`	`string`	No	caller window	Popups only.

Returns: {"clickThrough":"...","error":"...","success":true}

const { clickThrough } = await fb2k.invoke('window.isClickThrough', { windowId: 'popup-1' });

window.isFullscreen

Parameter	Type	Required	Description
`windowId`	`string`	No	Target window id. Defaults to the calling window.

Returns: {"fullscreen":"...","isFullscreen":"..."}

// omit windowId to query the calling window
const { isFullscreen } = await fb2k.invoke('window.isFullscreen');

window.isMaximized

No parameters.

Returns: {"isMaximized":"...","maximized":"..."}

const result = await fb2k.invoke('window.isMaximized');

window.isMinimized

No parameters.

Returns: {"minimized":"..."}

const result = await fb2k.invoke('window.isMinimized');

window.isResizable

Reports a window's requested resizable state. Resolution selects the explicit windowId or the calling window; it does not fall back to the main window. Panel (DUI/CUI) callers are rejected with panelMode: true.

Parameter	Type	Required	Default	Description
`windowId`	`string`	No	caller window	Target window.

Returns: {"resizable":"...","success":true,"windowId":"..."}. A window that cannot be resolved returns { "success": false, "error": "..." }.

Every window shell — including fully borderless popups — supports changing this at runtime via window.setResizable.

const result = await fb2k.invoke('window.isResizable');

window.maximize

No parameters.

Returns: {"error":"...","success":true}

const result = await fb2k.invoke('window.maximize');

window.minimize

No parameters.

Returns: {"error":"...","success":true}

const result = await fb2k.invoke('window.minimize');

window.refreshWebView

No parameters.

Returns: {"error":"...","success":true}

const result = await fb2k.invoke('window.refreshWebView');

window.reload

No parameters.

Returns: {"error":"...","success":true}

const result = await fb2k.invoke('window.reload');

window.resetZoom

No parameters.

Returns: {"error":"...","success":true,"zoom":"..."}

const result = await fb2k.invoke('window.resetZoom');

window.restore

No parameters.

Returns: {"error":"...","success":true}

const result = await fb2k.invoke('window.restore');

window.sendMessage

Parameter	Type	Required	Description
`targetWindowId`	`string`	Yes	Target window id (`main` or a popup id).
`message`	`json`	Yes	Arbitrary JSON delivered via the `window:message` event.

Returns: {"error":"...","success":true}

await fb2k.invoke('window.sendMessage', {
    targetWindowId: 'popup-1',
    message: { type: 'seek', position: 42 },
});

window.setAcrylic

Applies or clears the acrylic backdrop. Not supported in panel mode.

Parameter	Type	Required	Default
`windowId`	`string`	No	caller window
`enabled`	`boolean`	No	`true`
`darkMode`	`boolean`	No	current mode

Returns: { "success": true, "enabled": true }, plus darkMode echoed back only when you supplied it.

success reports whether the backdrop was actually applied, so it can be false even for a valid window when the platform refuses the effect.

await fb2k.invoke('window.setAcrylic', { enabled: true, darkMode: true });

window.setAlwaysOnTop

Parameter	Type	Required	Default	Description
`enabled`	`boolean`	No	`true`

Returns: {"error":"...","success":true}

await fb2k.invoke('window.setAlwaysOnTop', { enabled: true });

window.setBackdropPolicy

Parameter	Type	Required	Default	Description
`windowId`	`string`	No	caller window
`backdropPolicy`	`object`	Yes	—	Field-level patch; a `null` field resets it to the default.

Returns: {"error":"...","success":true}

await fb2k.invoke('window.setBackdropPolicy', {
    backdropPolicy: { activeEffect: 'acrylic', darkMode: true },
});

window.setBackgroundTransparency

Parameter	Type	Required	Default	Description
`windowId`	`string`	No	caller window
`transparent`	`boolean`	No	`true`

Returns: {"description":"...","error":"...","success":true,"transparent":"..."}

await fb2k.invoke('window.setBackgroundTransparency', { transparent: true });

window.setBlur

Parameter	Type	Required	Default	Description
`windowId`	`string`	No	caller window
`enabled`	`boolean`	No	`true`

Returns: {"enabled":"...","success":true}

await fb2k.invoke('window.setBlur', { enabled: true });

window.setBounds

Parameter	Type	Required	Default
`x`	`integer`	No	current value
`y`	`integer`	No	current value
`width`	`integer`	No	current value
`height`	`integer`	No	current value

Returns: {"error":"...","success":true}

await fb2k.invoke('window.setBounds', { x: 100, y: 100, width: 480, height: 320 });

window.setClickThrough

Parameter	Type	Required	Default	Description
`windowId`	`string`	No	caller window	Popups only.
`enabled`	`boolean`	No	`true`

Returns: {"clickThrough":"...","error":"...","success":true}

await fb2k.invoke('window.setClickThrough', { enabled: true });

window.setClickThroughExcludeRegions

Parameter	Type	Required	Default	Description
`windowId`	`string`	No	calling popup	Popups only.
`regions`	`array`	No	—	CSS-pixel rectangles `{ x, y, width, height }`.

Returns: {"count":0,"dpiScale":"...","success":true,"warning":"...","windowId":"..."}

await fb2k.invoke('window.setClickThroughExcludeRegions', {
    regions: [{ x: 12, y: 12, width: 160, height: 40 }],
});

window.setCornerPreference

Sets the main window's Windows 11 corner-rounding preference. Main window only: it does not accept windowId and ignores the calling window. Popups do not accept this setting — they manage corner rounding internally and report supportsCornerPreference: false — so the call has no popup-scoped form. Panel (DUI/CUI) callers are rejected with panelMode: true.

Parameter	Type	Required	Description
`mode`	`string`	No	`"default"`, `"none"`, `"round"` or `"small"`; defaults to `"default"`.

Returns: {"error":"...","success":true}

"default" maps to rounded corners, because a borderless window has no standard non-client frame for the system default to apply to.

await fb2k.invoke('window.setCornerPreference', { mode: 'round' });

window.setDarkMode

Parameter	Type	Required	Default	Description
`windowId`	`string`	No	caller window
`enabled`	`boolean`	No	`true`

Returns: {"enabled":"...","success":true}

await fb2k.invoke('window.setDarkMode', { enabled: true });

window.setDevServerConfig

Parameter	Type	Required	Default	Description
`useDevServer`	`boolean`	No	`false`
`devServerUrl`	`string`	No	—	Dev server address, e.g. `http://localhost:5173`.

Returns: {"devServerUrl":"...","success":true,"useDevServer":"..."}

await fb2k.invoke('window.setDevServerConfig', {
    useDevServer: true,
    devServerUrl: 'http://localhost:5173',
});

window.setDragRegions

Parameter	Type	Required	Description
`regions`	`array`	No	CSS-pixel rectangles `{ x, y, width, height }`.

Returns: {"count":"...","dpiScale":"...","error":"...","success":true}

await fb2k.invoke('window.setDragRegions', {
    regions: [{ x: 0, y: 0, width: 800, height: 32 }],
});

window.setFrameless

Parameter	Type	Required	Default	Description
`windowId`	`string`	No	caller window
`frameless`	`boolean`	No	`true`

Returns: {"error":"...","frameless":"...","success":true}

await fb2k.invoke('window.setFrameless', { frameless: true });

window.setFullscreen

Parameter	Type	Required	Default	Description
`windowId`	`string`	No	caller window
`enabled`	`boolean`	No	`true`

Returns: {"error":"...","fullscreen":"...","success":true}

await fb2k.invoke('window.setFullscreen', { enabled: true });

window.setMaxSize

Sets a window's maximum size. Resolution selects the explicit windowId or the calling window; it never falls back to the main window, so a call from an unresolvable context fails rather than resizing an unintended window. Panel (DUI/CUI) callers are rejected with panelMode: true.

Parameter	Type	Required	Default	Description
`windowId`	`string`	No	caller window	Target window.
`width`	`integer`	No	`0`
`height`	`integer`	No	`0`

Returns: {"error":"...","success":true,"windowId":"..."}

Values are physical pixels, converted to the host's DIP storage using the target window's DPI; 0 (or negative) clears the bound. Applying a constraint re-validates the current window size immediately, so a window already larger than the new maximum is shrunk rather than waiting for the next user resize.

await fb2k.invoke('window.setMaxSize', { width: 1920, height: 1080 });

window.setMica

Applies or clears the Mica backdrop. Not supported in panel mode.

Parameter	Type	Required	Default	Description
`windowId`	`string`	No	caller window
`enabled`	`boolean`	No	`true`
`variant`	`string`	No	`mica`	`mica` or `mica-alt`.
`darkMode`	`boolean`	No	current mode

Returns: { "success": true, "enabled": true, "variant": "mica" }, plus darkMode echoed back only when you supplied it.

Only mica-alt selects the alternate variant; every other value — including an unrecognized one — is normalized to mica rather than rejected. The returned variant echoes that normalized request, not the effect that ended up on screen: popups do not support Mica Alt and are downgraded, so variant: "mica-alt" can come back for a window that received a different backdrop. success reports whether the backdrop was actually applied and can be false for a valid window when the platform refuses the effect.

await fb2k.invoke('window.setMica', { enabled: true, variant: 'mica-alt' });

window.setMicaEffect

Compatibility alias of window.setMica. Same parameters, same behavior, same return shape — prefer window.setMica in new code. Because both share one implementation, the panel-mode rejection names window.setMica even when you called this alias.

Parameter	Type	Required	Default	Description
`windowId`	`string`	No	caller window
`enabled`	`boolean`	No	`true`
`variant`	`string`	No	`mica`	`mica` or `mica-alt`.
`darkMode`	`boolean`	No	current mode

Returns: { "success": true, "enabled": true, "variant": "mica" }, plus darkMode echoed back only when you supplied it.

await fb2k.invoke('window.setMicaEffect', { enabled: true });

window.setMinSize

Sets a window's minimum size. Resolution selects the explicit windowId or the calling window; it never falls back to the main window, so a call from an unresolvable context fails rather than resizing an unintended window. Panel (DUI/CUI) callers are rejected with panelMode: true.

Parameter	Type	Required	Default	Description
`windowId`	`string`	No	caller window	Target window.
`width`	`integer`	No	`0`
`height`	`integer`	No	`0`

Returns: {"error":"...","success":true,"windowId":"..."}

Values are physical pixels, converted to the host's DIP storage using the target window's DPI, which keeps the constraint stable across DPI changes. Non-positive values normalise to a 1px floor. Applying a constraint re-validates the current window size immediately, so a window already smaller than the new minimum is grown rather than waiting for the next user resize.

await fb2k.invoke('window.setMinSize', { width: 480, height: 320 });

window.setNoDragRegions

Parameter	Type	Required	Description
`regions`	`array`	No	CSS-pixel rectangles `{ x, y, width, height }`.

Returns: {"count":"...","dpiScale":"...","error":"...","success":true}

await fb2k.invoke('window.setNoDragRegions', {
    regions: [{ x: 690, y: 0, width: 110, height: 32 }],
});

window.setPopupBehavior

Updates a popup's behavior policy at runtime. Popups only — the main window is not a valid target.

Parameter	Type	Required	Default	Description
`windowId`	`string`	No	calling popup	Target popup id.
`profile`	`string`	No	current profile	`standard`, `miniPlayer`, or `desktopLyrics`.
`behavior`	`object`	No	—	Field-level overrides. Applied only when supplied.

Returns: { "success": true, "windowId": "...", "profile": "...", "behavior": { ... }, "resolvedBehavior": { ... } }

resolvedBehavior is the effective policy after the profile defaults and your overrides are merged. profile and behavior are independent: supplying one does not reset the other, and a null value inside behavior erases that override rather than storing null.

Profile matching is case-insensitive and also accepts hyphen and underscore spellings, so miniPlayer, miniplayer, mini-player, and mini_player are equivalent. The returned profile is always one of the three canonical names.

Passing windowId: "main" fails with window.setPopupBehavior does not support main window. Omitting windowId requires the caller to itself be a popup, otherwise the call fails with Window not found.

// switch profile only
await fb2k.invoke('window.setPopupBehavior', { profile: 'miniPlayer' });
// field-level override, keeping the current profile
await fb2k.invoke('window.setPopupBehavior', { behavior: { closeOnFocusLoss: true } });

window.setPosition

Parameter	Type	Required	Default	Description
`x`	`integer`	No	`0`
`y`	`integer`	No	`0`

Returns: {"success":true}

await fb2k.invoke('window.setPosition', { x: 100, y: 100 });

window.setResizable

Sets whether a window can be resized by the user. Resolution selects the explicit windowId or the calling window; it never falls back to the main window. Panel (DUI/CUI) callers are rejected with panelMode: true. Setting the value a window already has succeeds — idempotent calls are not failures.

Parameter	Type	Required	Default	Description
`windowId`	`string`	No	caller window	Target window.
`resizable`	`boolean`	No	`true`

Returns: {"error":"...","success":true,"windowId":"..."}

Every window shell supports this at runtime, including fully borderless popups (frame: false plus transparent: true with no backdrop effect): those windows collapse their entire non-client area, so adding a sizing border changes hit-testing without altering appearance. success: false therefore indicates a genuine Win32 failure — the style could not be written, or the frame could not be refreshed — not an unsupported window shape; the requested state is not committed in that case.

Behavior change

This call previously always targeted the main window regardless of caller, so invoking it from a popup reconfigured the main window instead.

await fb2k.invoke('window.setResizable', { resizable: false });

window.setSize

Parameter	Type	Required	Default	Description
`width`	`integer`	No	`800`
`height`	`integer`	No	`600`

Returns: {"success":true}

await fb2k.invoke('window.setSize', { width: 1024, height: 640 });

window.setTitle

Parameter	Type	Required	Default	Description
`title`	`string`	No	`foobar2000`

Returns: {"error":"...","success":true}

await fb2k.invoke('window.setTitle', { title: 'Now Playing' });

window.setTitlebarHeight

Parameter	Type	Required	Default	Description
`height`	`integer`	No	`32`	Valid range 24–100.

Returns: {"error":"...","height":"...","success":true}

await fb2k.invoke('window.setTitlebarHeight', { height: 40 });

window.setZoom

Parameter	Type	Required	Default	Description
`zoom`	`number`	No	`1`	Zoom factor, e.g. `1.25`.

Returns: {"error":"...","success":true,"zoom":"..."}

await fb2k.invoke('window.setZoom', { zoom: 1.25 });

window.setZoomForDpi

Parameter	Type	Required	Default	Description
`dpi`	`integer`	No	`0`	Omit or `0` to derive from the calling window's current DPI.

Returns: {"dpi":"...","error":"...","success":true,"zoom":"..."}

// omit dpi to derive the zoom from the calling window's current DPI
const { zoom } = await fb2k.invoke('window.setZoomForDpi');

window.showSystemMenu

Parameter	Type	Required	Default	Description
`x`	`integer`	No	`0`	Exclusion area left; without `w`/`h`, `x`/`y` are used as the menu position.
`y`	`integer`	No	`0`	Exclusion area top.
`w`	`integer`	No	`0`	Exclusion area width.
`h`	`integer`	No	`0`	Exclusion area height.

Returns: {"error":"...","success":true}

// pass w/h to keep the menu clear of the button that opened it
await fb2k.invoke('window.showSystemMenu', { x: 8, y: 0, w: 32, h: 32 });

window.startDrag

No parameters.

Returns: {"error":"...","success":true}

const result = await fb2k.invoke('window.startDrag');

window.startResize

Parameter	Type	Required	Default	Description
`edge`	`string`	No	`bottomright`	Edge or corner to drag.

Returns: {"error":"...","success":true}

await fb2k.invoke('window.startResize', { edge: 'bottomright' });

window.toggleAlwaysOnTop

No parameters.

Returns: {"enabled":"...","success":true}

const result = await fb2k.invoke('window.toggleAlwaysOnTop');

window.toggleFullscreen

Parameter	Type	Required	Default	Description
`windowId`	`string`	No	caller window

Returns: {"error":"...","fullscreen":"...","success":true}

const result = await fb2k.invoke('window.toggleFullscreen');

window.toggleMaximize

No parameters.

Returns: {"maximized":"...","success":true}

const result = await fb2k.invoke('window.toggleMaximize');

Runtime behavior and events

All window.* calls run in the context of the calling WebView unless a method accepts windowId. A value of main identifies the main shell; popup IDs are returned by window.createPopup and window.getAllWindows. Calls that require a standalone shell report an unsupported or not-found result in panel mode instead of silently targeting an unrelated window.

window.setDragRegions, window.setNoDragRegions, and click-through exclude regions accept CSS-pixel rectangles. The native handler converts them using the target window DPI. Popup-only operations such as click-through and close confirmation reject a main-window target.

The runtime emits window:stateChanged when shell state changes and routes window:beforeClose to the popup that requested close confirmation. Popup lifecycle and coordination events include window:popupOpened, window:popupClosed, window:message, window:behaviorChanged, window:backdropStateChanged, window:hoverStateChanged, window:minimizeSuppressed, and window:alwaysOnTopChanged. Event payloads are runtime data; callers should tolerate fields added by the shell.

Window API ​

window ​

window.blur ​

window.broadcast ​

window.cancelClose ​

window.center ​

window.clearClickThroughExcludeRegions ​

window.clearDragRegions ​

window.clearNoDragRegions ​

window.close ​

window.closeAllPopups ​

window.closePopup ​

window.confirmClose ​

window.createPopup ​

window.enterFullscreen ​

window.exitFullscreen ​

window.flash ​

window.flashTaskbar ​

window.focus ​

window.getAllWindows ​

window.getBackdropPolicy ​

window.getBounds ​

window.getCaptionButtonsWidth ​

window.getCornerPreference ​

window.getCurrentWindowId ​

window.getDevServerConfig ​

window.getDpiScale ​

window.getMaxSize ​

window.getMinSize ​

window.getMode ​

window.getPopupBehavior ​

window.getState ​

window.getTitle ​

window.getTitlebarHeight ​

window.getTitlebarInfo ​

window.getZoom ​

window.hasSavedBounds ​

window.isAlwaysOnTop ​

window.isClickThrough ​

window.isFullscreen ​

window.isMaximized ​

window.isMinimized ​

window.isResizable ​

window.maximize ​

window.minimize ​

window.refreshWebView ​

window.reload ​

window.resetZoom ​

window.restore ​

window.sendMessage ​

window.setAcrylic ​

window.setAlwaysOnTop ​

window.setBackdropPolicy ​

window.setBackgroundTransparency ​

window.setBlur ​

window.setBounds ​

window.setClickThrough ​

window.setClickThroughExcludeRegions ​

window.setCornerPreference ​

window.setDarkMode ​

window.setDevServerConfig ​

window.setDragRegions ​

window.setFrameless ​

window.setFullscreen ​

window.setMaxSize ​

window.setMica ​

window.setMicaEffect ​

window.setMinSize ​

window.setNoDragRegions ​

window.setPopupBehavior ​

window.setPosition ​

window.setResizable ​

window.setSize ​

window.setTitle ​

window.setTitlebarHeight ​

window.setZoom ​

window.setZoomForDpi ​

window.showSystemMenu ​

window.startDrag ​

window.startResize ​

Window API

window

window.blur

window.broadcast

window.cancelClose

window.center

window.clearClickThroughExcludeRegions

window.clearDragRegions

window.clearNoDragRegions

window.close

window.closeAllPopups

window.closePopup

window.confirmClose

window.createPopup

window.enterFullscreen

window.exitFullscreen

window.flash

window.flashTaskbar

window.focus

window.getAllWindows

window.getBackdropPolicy

window.getBounds

window.getCaptionButtonsWidth

window.getCornerPreference

window.getCurrentWindowId

window.getDevServerConfig

window.getDpiScale

window.getMaxSize

window.getMinSize

window.getMode

window.getPopupBehavior

window.getState

window.getTitle

window.getTitlebarHeight

window.getTitlebarInfo

window.getZoom

window.hasSavedBounds

window.isAlwaysOnTop

window.isClickThrough

window.isFullscreen

window.isMaximized

window.isMinimized

window.isResizable

window.maximize

window.minimize

window.refreshWebView

window.reload

window.resetZoom

window.restore

window.sendMessage

window.setAcrylic

window.setAlwaysOnTop

window.setBackdropPolicy

window.setBackgroundTransparency

window.setBlur

window.setBounds

window.setClickThrough

window.setClickThroughExcludeRegions

window.setCornerPreference

window.setDarkMode

window.setDevServerConfig

window.setDragRegions

window.setFrameless

window.setFullscreen

window.setMaxSize

window.setMica

window.setMicaEffect

window.setMinSize

window.setNoDragRegions

window.setPopupBehavior

window.setPosition

window.setResizable

window.setSize

window.setTitle

window.setTitlebarHeight

window.setZoom

window.setZoomForDpi

window.showSystemMenu

window.startDrag

window.startResize