Kilian Valkhof 21d1849723 Update browser-window.md with alpha hex formatting (#16269 )

HEX with alpha can be #RRGGBBAA or #AARRGGBB. In Electron it's the latter. It's nice to explicitly state that, so others wont have to try twice like me :).

2019-01-04 10:33:12 -08:00

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BrowserWindow

Create and control browser windows.

Process: Main

// In the main process.
const { BrowserWindow } = require('electron')

// Or use `remote` from the renderer process.
// const { BrowserWindow } = require('electron').remote

let win = new BrowserWindow({ width: 800, height: 600 })
win.on('closed', () => {
  win = null
})

// Load a remote URL
win.loadURL('https://github.com')

// Or load a local HTML file
win.loadURL(`file://${__dirname}/app/index.html`)

Frameless window

To create a window without chrome, or a transparent window in arbitrary shape, you can use the Frameless Window API.

Showing window gracefully

When loading a page in the window directly, users may see the page load incrementally, which is not a good experience for a native app. To make the window display without visual flash, there are two solutions for different situations.

Using `ready-to-show` event

While loading the page, the ready-to-show event will be emitted when the renderer process has rendered the page for the first time if the window has not been shown yet. Showing the window after this event will have no visual flash:

const { BrowserWindow } = require('electron')
let win = new BrowserWindow({ show: false })
win.once('ready-to-show', () => {
  win.show()
})

This event is usually emitted after the did-finish-load event, but for pages with many remote resources, it may be emitted before the did-finish-load event.

Setting `backgroundColor`

For a complex app, the ready-to-show event could be emitted too late, making the app feel slow. In this case, it is recommended to show the window immediately, and use a backgroundColor close to your app's background:

const { BrowserWindow } = require('electron')

let win = new BrowserWindow({ backgroundColor: '#2e2c29' })
win.loadURL('https://github.com')

Note that even for apps that use ready-to-show event, it is still recommended to set backgroundColor to make app feel more native.

Parent and child windows

By using parent option, you can create child windows:

const { BrowserWindow } = require('electron')

let top = new BrowserWindow()
let child = new BrowserWindow({ parent: top })
child.show()
top.show()

The child window will always show on top of the top window.

A modal window is a child window that disables parent window, to create a modal window, you have to set both parent and modal options:

const { BrowserWindow } = require('electron')

let child = new BrowserWindow({ parent: top, modal: true, show: false })
child.loadURL('https://github.com')
child.once('ready-to-show', () => {
  child.show()
})

Page visibility

The Page Visibility API works as follows:

On all platforms, the visibility state tracks whether the window is hidden/minimized or not.
Additionally, on macOS, the visibility state also tracks the window occlusion state. If the window is occluded (i.e. fully covered) by another window, the visibility state will be hidden. On other platforms, the visibility state will be hidden only when the window is minimized or explicitly hidden with win.hide().
If a BrowserWindow is created with show: false, the initial visibility state will be visible despite the window actually being hidden.
If backgroundThrottling is disabled, the visibility state will remain visible even if the window is minimized, occluded, or hidden.

It is recommended that you pause expensive operations when the visibility state is hidden in order to minimize power consumption.

Platform notices

On macOS modal windows will be displayed as sheets attached to the parent window.
On macOS the child windows will keep the relative position to parent window when parent window moves, while on Windows and Linux child windows will not move.
On Linux the type of modal windows will be changed to dialog.
On Linux many desktop environments do not support hiding a modal window.

Class: BrowserWindow

Create and control browser windows.

Process: Main

BrowserWindow is an EventEmitter.

It creates a new BrowserWindow with native properties as set by the options.

`new BrowserWindow([options])`

options Object (optional)
- width Integer (optional) - Window's width in pixels. Default is 800.
- height Integer (optional) - Window's height in pixels. Default is 600.
- x Integer (optional) (required if y is used) - Window's left offset from screen. Default is to center the window.
- y Integer (optional) (required if x is used) - Window's top offset from screen. Default is to center the window.
- useContentSize Boolean (optional) - The width and height would be used as web page's size, which means the actual window's size will include window frame's size and be slightly larger. Default is false.
- center Boolean (optional) - Show window in the center of the screen.
- minWidth Integer (optional) - Window's minimum width. Default is 0.
- minHeight Integer (optional) - Window's minimum height. Default is 0.
- maxWidth Integer (optional) - Window's maximum width. Default is no limit.
- maxHeight Integer (optional) - Window's maximum height. Default is no limit.
- resizable Boolean (optional) - Whether window is resizable. Default is true.
- movable Boolean (optional) - Whether window is movable. This is not implemented on Linux. Default is true.
- minimizable Boolean (optional) - Whether window is minimizable. This is not implemented on Linux. Default is true.
- maximizable Boolean (optional) - Whether window is maximizable. This is not implemented on Linux. Default is true.
- closable Boolean (optional) - Whether window is closable. This is not implemented on Linux. Default is true.
- focusable Boolean (optional) - Whether the window can be focused. Default is true. On Windows setting focusable: false also implies setting skipTaskbar: true. On Linux setting focusable: false makes the window stop interacting with wm, so the window will always stay on top in all workspaces.
- alwaysOnTop Boolean (optional) - Whether the window should always stay on top of other windows. Default is false.
- fullscreen Boolean (optional) - Whether the window should show in fullscreen. When explicitly set to false the fullscreen button will be hidden or disabled on macOS. Default is false.
- fullscreenable Boolean (optional) - Whether the window can be put into fullscreen mode. On macOS, also whether the maximize/zoom button should toggle full screen mode or maximize window. Default is true.
- simpleFullscreen Boolean (optional) - Use pre-Lion fullscreen on macOS. Default is false.
- skipTaskbar Boolean (optional) - Whether to show the window in taskbar. Default is false.
- kiosk Boolean (optional) - The kiosk mode. Default is false.
- title String (optional) - Default window title. Default is "Electron". If the HTML tag <title> is defined in the HTML file loaded by loadURL(), this property will be ignored.
- icon (NativeImage | String) (optional) - The window icon. On Windows it is recommended to use ICO icons to get best visual effects, you can also leave it undefined so the executable's icon will be used.
- show Boolean (optional) - Whether window should be shown when created. Default is true.
- frame Boolean (optional) - Specify false to create a Frameless Window. Default is true.
- parent BrowserWindow (optional) - Specify parent window. Default is null.
- modal Boolean (optional) - Whether this is a modal window. This only works when the window is a child window. Default is false.
- acceptFirstMouse Boolean (optional) - Whether the web view accepts a single mouse-down event that simultaneously activates the window. Default is false.
- disableAutoHideCursor Boolean (optional) - Whether to hide cursor when typing. Default is false.
- autoHideMenuBar Boolean (optional) - Auto hide the menu bar unless the Alt key is pressed. Default is false.
- enableLargerThanScreen Boolean (optional) - Enable the window to be resized larger than screen. Default is false.
- backgroundColor String (optional) - Window's background color as a hexadecimal value, like #66CD00 or #FFF or #80FFFFFF (alpha in #AARRGGBB format is supported if transparent is set to true). Default is #FFF (white).
- hasShadow Boolean (optional) - Whether window should have a shadow. This is only implemented on macOS. Default is true.
- opacity Number (optional) - Set the initial opacity of the window, between 0.0 (fully transparent) and 1.0 (fully opaque). This is only implemented on Windows and macOS.
- darkTheme Boolean (optional) - Forces using dark theme for the window, only works on some GTK+3 desktop environments. Default is false.
- transparent Boolean (optional) - Makes the window transparent. Default is false.
- type String (optional) - The type of window, default is normal window. See more about this below.
- titleBarStyle String (optional) - The style of window title bar. Default is default. Possible values are:
  - default - Results in the standard gray opaque Mac title bar.
  - hidden - Results in a hidden title bar and a full size content window, yet the title bar still has the standard window controls ("traffic lights") in the top left.
  - hiddenInset - Results in a hidden title bar with an alternative look where the traffic light buttons are slightly more inset from the window edge.
  - customButtonsOnHover Boolean (optional) - Draw custom close, and minimize buttons on macOS frameless windows. These buttons will not display unless hovered over in the top left of the window. These custom buttons prevent issues with mouse events that occur with the standard window toolbar buttons. Note: This option is currently experimental.
- fullscreenWindowTitle Boolean (optional) - Shows the title in the title bar in full screen mode on macOS for all titleBarStyle options. Default is false.
- thickFrame Boolean (optional) - Use WS_THICKFRAME style for frameless windows on Windows, which adds standard window frame. Setting it to false will remove window shadow and window animations. Default is true.
- vibrancy String (optional) - Add a type of vibrancy effect to the window, only on macOS. Can be appearance-based, light, dark, titlebar, selection, menu, popover, sidebar, medium-light or ultra-dark. Please note that using frame: false in combination with a vibrancy value requires that you use a non-default titleBarStyle as well.
- zoomToPageWidth Boolean (optional) - Controls the behavior on macOS when option-clicking the green stoplight button on the toolbar or by clicking the Window > Zoom menu item. If true, the window will grow to the preferred width of the web page when zoomed, false will cause it to zoom to the width of the screen. This will also affect the behavior when calling maximize() directly. Default is false.
- tabbingIdentifier String (optional) - Tab group name, allows opening the window as a native tab on macOS 10.12+. Windows with the same tabbing identifier will be grouped together. This also adds a native new tab button to your window's tab bar and allows your app and window to receive the new-window-for-tab event.
- webPreferences Object (optional) - Settings of web page's features.
  - devTools Boolean (optional) - Whether to enable DevTools. If it is set to false, can not use BrowserWindow.webContents.openDevTools() to open DevTools. Default is true.
  - nodeIntegration Boolean (optional) - Whether node integration is enabled. Default is true.
  - nodeIntegrationInWorker Boolean (optional) - Whether node integration is enabled in web workers. Default is false. More about this can be found in Multithreading.
  - preload String (optional) - Specifies a script that will be loaded before other scripts run in the page. This script will always have access to node APIs no matter whether node integration is turned on or off. The value should be the absolute file path to the script. When node integration is turned off, the preload script can reintroduce Node global symbols back to the global scope. See example here.
  - sandbox Boolean (optional) - If set, this will sandbox the renderer associated with the window, making it compatible with the Chromium OS-level sandbox and disabling the Node.js engine. This is not the same as the nodeIntegration option and the APIs available to the preload script are more limited. Read more about the option here. Note: This option is currently experimental and may change or be removed in future Electron releases.
  - enableRemoteModule Boolean (optional) - Whether to enable the remote module. Default is true.
  - session Session (optional) - Sets the session used by the page. Instead of passing the Session object directly, you can also choose to use the partition option instead, which accepts a partition string. When both session and partition are provided, session will be preferred. Default is the default session.
  - partition String (optional) - Sets the session used by the page according to the session's partition string. If partition starts with persist:, the page will use a persistent session available to all pages in the app with the same partition. If there is no persist: prefix, the page will use an in-memory session. By assigning the same partition, multiple pages can share the same session. Default is the default session.
  - affinity String (optional) - When specified, web pages with the same affinity will run in the same renderer process. Note that due to reusing the renderer process, certain webPreferences options will also be shared between the web pages even when you specified different values for them, including but not limited to preload, sandbox and nodeIntegration. So it is suggested to use exact same webPreferences for web pages with the same affinity. This property is experimental
  - zoomFactor Number (optional) - The default zoom factor of the page, 3.0 represents 300%. Default is 1.0.
  - javascript Boolean (optional) - Enables JavaScript support. Default is true.
  - webSecurity Boolean (optional) - When false, it will disable the same-origin policy (usually using testing websites by people), and set allowRunningInsecureContent to true if this options has not been set by user. Default is true.
  - allowRunningInsecureContent Boolean (optional) - Allow an https page to run JavaScript, CSS or plugins from http URLs. Default is false.
  - images Boolean (optional) - Enables image support. Default is true.
  - textAreasAreResizable Boolean (optional) - Make TextArea elements resizable. Default is true.
  - webgl Boolean (optional) - Enables WebGL support. Default is true.
  - webaudio Boolean (optional) - Enables WebAudio support. Default is true.
  - plugins Boolean (optional) - Whether plugins should be enabled. Default is false.
  - experimentalFeatures Boolean (optional) - Enables Chromium's experimental features. Default is false.
  - scrollBounce Boolean (optional) - Enables scroll bounce (rubber banding) effect on macOS. Default is false.
  - enableBlinkFeatures String (optional) - A list of feature strings separated by ,, like CSSVariables,KeyboardEventKey to enable. The full list of supported feature strings can be found in the RuntimeEnabledFeatures.json5 file.
  - disableBlinkFeatures String (optional) - A list of feature strings separated by ,, like CSSVariables,KeyboardEventKey to disable. The full list of supported feature strings can be found in the RuntimeEnabledFeatures.json5 file.
  - defaultFontFamily Object (optional) - Sets the default font for the font-family.
    - standard String (optional) - Defaults to Times New Roman.
    - serif String (optional) - Defaults to Times New Roman.
    - sansSerif String (optional) - Defaults to Arial.
    - monospace String (optional) - Defaults to Courier New.
    - cursive String (optional) - Defaults to Script.
    - fantasy String (optional) - Defaults to Impact.
  - defaultFontSize Integer (optional) - Defaults to 16.
  - defaultMonospaceFontSize Integer (optional) - Defaults to 13.
  - minimumFontSize Integer (optional) - Defaults to 0.
  - defaultEncoding String (optional) - Defaults to ISO-8859-1.
  - backgroundThrottling Boolean (optional) - Whether to throttle animations and timers when the page becomes background. This also affects the Page Visibility API. Defaults to true.
  - offscreen Boolean (optional) - Whether to enable offscreen rendering for the browser window. Defaults to false. See the offscreen rendering tutorial for more details.
  - contextIsolation Boolean (optional) - Whether to run Electron APIs and the specified preload script in a separate JavaScript context. Defaults to false. The context that the preload script runs in will still have full access to the document and window globals but it will use its own set of JavaScript builtins (Array, Object, JSON, etc.) and will be isolated from any changes made to the global environment by the loaded page. The Electron API will only be available in the preload script and not the loaded page. This option should be used when loading potentially untrusted remote content to ensure the loaded content cannot tamper with the preload script and any Electron APIs being used. This option uses the same technique used by Chrome Content Scripts. You can access this context in the dev tools by selecting the 'Electron Isolated Context' entry in the combo box at the top of the Console tab.
  - nativeWindowOpen Boolean (optional) - Whether to use native window.open(). Defaults to false. Child windows will always have node integration disabled. Note: This option is currently experimental.
  - webviewTag Boolean (optional) - Whether to enable the <webview> tag. Defaults to the value of the nodeIntegration option. Note: The preload script configured for the <webview> will have node integration enabled when it is executed so you should ensure remote/untrusted content is not able to create a <webview> tag with a possibly malicious preload script. You can use the will-attach-webview event on webContents to strip away the preload script and to validate or alter the <webview>'s initial settings.
  - additionalArguments String[] (optional) - A list of strings that will be appended to process.argv in the renderer process of this app. Useful for passing small bits of data down to renderer process preload scripts.
  - safeDialogs Boolean (optional) - Whether to enable browser style consecutive dialog protection. Default is false.
  - safeDialogsMessage String (optional) - The message to display when consecutive dialog protection is triggered. If not defined the default message would be used, note that currently the default message is in English and not localized.
  - navigateOnDragDrop Boolean (optional) - Whether dragging and dropping a file or link onto the page causes a navigation. Default is false.

When setting minimum or maximum window size with minWidth/maxWidth/ minHeight/maxHeight, it only constrains the users. It won't prevent you from passing a size that does not follow size constraints to setBounds/setSize or to the constructor of BrowserWindow.

The possible values and behaviors of the type option are platform dependent. Possible values are:

On Linux, possible types are desktop, dock, toolbar, splash, notification.
On macOS, possible types are desktop, textured.
- The textured type adds metal gradient appearance (NSTexturedBackgroundWindowMask).
- The desktop type places the window at the desktop background window level (kCGDesktopWindowLevel - 1). Note that desktop window will not receive focus, keyboard or mouse events, but you can use globalShortcut to receive input sparingly.
On Windows, possible type is toolbar.

Instance Events

Objects created with new BrowserWindow emit the following events:

Note: Some events are only available on specific operating systems and are labeled as such.

Event: 'page-title-updated'

Returns:

event Event
title String

Emitted when the document changed its title, calling event.preventDefault() will prevent the native window's title from changing.

Event: 'close'

Returns:

event Event

Emitted when the window is going to be closed. It's emitted before the beforeunload and unload event of the DOM. Calling event.preventDefault() will cancel the close.

Usually you would want to use the beforeunload handler to decide whether the window should be closed, which will also be called when the window is reloaded. In Electron, returning any value other than undefined would cancel the close. For example:

window.onbeforeunload = (e) => {
  console.log('I do not want to be closed')

  // Unlike usual browsers that a message box will be prompted to users, returning
  // a non-void value will silently cancel the close.
  // It is recommended to use the dialog API to let the user confirm closing the
  // application.
  e.returnValue = false // equivalent to `return false` but not recommended
}

Note: There is a subtle difference between the behaviors of window.onbeforeunload = handler and window.addEventListener('beforeunload', handler). It is recommended to always set the event.returnValue explicitly, instead of only returning a value, as the former works more consistently within Electron.

Event: 'closed'

Emitted when the window is closed. After you have received this event you should remove the reference to the window and avoid using it any more.

Event: 'session-end' Windows

Emitted when window session is going to end due to force shutdown or machine restart or session log off.

Event: 'unresponsive'

Emitted when the web page becomes unresponsive.

Event: 'responsive'

Emitted when the unresponsive web page becomes responsive again.

Event: 'blur'

Emitted when the window loses focus.

Event: 'focus'

Emitted when the window gains focus.

Event: 'show'

Emitted when the window is shown.

Event: 'hide'

Emitted when the window is hidden.

Event: 'ready-to-show'

Emitted when the web page has been rendered (while not being shown) and window can be displayed without a visual flash.

Event: 'maximize'

Emitted when window is maximized.

Event: 'unmaximize'

Emitted when the window exits from a maximized state.

Event: 'minimize'

Emitted when the window is minimized.

Event: 'restore'

Emitted when the window is restored from a minimized state.

Event: 'will-resize' macOS Windows

Returns:

event Event
newBounds Rectangle - Size the window is being resized to.

Emitted before the window is resized. Calling event.preventDefault() will prevent the window from being resized.

Note that this is only emitted when the window is being resized manually. Resizing the window with setBounds/setSize will not emit this event.

Event: 'resize'

Emitted after the window has been resized.

Event: 'will-move' Windows

Returns:

event Event
newBounds Rectangle - Location the window is being moved to.

Emitted before the window is moved. Calling event.preventDefault() will prevent the window from being moved.

Note that this is only emitted when the window is being resized manually. Resizing the window with setBounds/setSize will not emit this event.

Event: 'move'

Emitted when the window is being moved to a new position.

Note: On macOS this event is an alias of moved.

Event: 'moved' macOS

Emitted once when the window is moved to a new position.

Event: 'enter-full-screen'

Emitted when the window enters a full-screen state.

Event: 'leave-full-screen'

Emitted when the window leaves a full-screen state.

Event: 'enter-html-full-screen'

Emitted when the window enters a full-screen state triggered by HTML API.

Event: 'leave-html-full-screen'

Emitted when the window leaves a full-screen state triggered by HTML API.

Event: 'always-on-top-changed' macOS

Returns:

event Event
isAlwaysOnTop Boolean

Emitted when the window is set or unset to show always on top of other windows.

Event: 'app-command' Windows Linux

Returns:

event Event
command String

Emitted when an App Command is invoked. These are typically related to keyboard media keys or browser commands, as well as the "Back" button built into some mice on Windows.

Commands are lowercased, underscores are replaced with hyphens, and the APPCOMMAND_ prefix is stripped off. e.g. APPCOMMAND_BROWSER_BACKWARD is emitted as browser-backward.

const { BrowserWindow } = require('electron')
let win = new BrowserWindow()
win.on('app-command', (e, cmd) => {
  // Navigate the window back when the user hits their mouse back button
  if (cmd === 'browser-backward' && win.webContents.canGoBack()) {
    win.webContents.goBack()
  }
})

The following app commands are explictly supported on Linux:

browser-backward
browser-forward

Event: 'scroll-touch-begin' macOS

Emitted when scroll wheel event phase has begun.

Event: 'scroll-touch-end' macOS

Emitted when scroll wheel event phase has ended.

Event: 'scroll-touch-edge' macOS

Emitted when scroll wheel event phase filed upon reaching the edge of element.

Event: 'swipe' macOS

Returns:

event Event
direction String

Emitted on 3-finger swipe. Possible directions are up, right, down, left.

Event: 'sheet-begin' macOS

Emitted when the window opens a sheet.

Event: 'sheet-end' macOS

Emitted when the window has closed a sheet.

Event: 'new-window-for-tab' macOS

Emitted when the native new tab button is clicked.

Static Methods

The BrowserWindow class has the following static methods:

`BrowserWindow.getAllWindows()`

Returns BrowserWindow[] - An array of all opened browser windows.

`BrowserWindow.getFocusedWindow()`

Returns BrowserWindow | null - The window that is focused in this application, otherwise returns null.

`BrowserWindow.fromWebContents(webContents)`

webContents WebContents

Returns BrowserWindow - The window that owns the given webContents.

`BrowserWindow.fromBrowserView(browserView)`

browserView BrowserView

Returns BrowserWindow | null - The window that owns the given browserView. If the given view is not attached to any window, returns null.

`BrowserWindow.fromId(id)`

id Integer

Returns BrowserWindow - The window with the given id.