menus.onShown
Fired when the browser has shown a menu.
An extension can use this event to update its menu items using information that's only available once the menu is shown. Typically an extension will figure out the update in its onShown
handler and then call menus.refresh()
to update the menu itself.
The handler can add, remove, or update menu items.
For example, the menu-labelled-open example extension adds a menu item that's shown when the user clicks a link, and that, when clicked, just opens the link. It uses onShown
and refresh()
to annotate the menu item with the hostname for the link, so the user can easily see where they will go before they click.
Note that an extension should not take too much time before calling refresh()
, or the update will be noticeable to the user.
The handler is passed some information about the menu and its contents, and some information from the page (such as the link and/or selection text). To get access to the information from the page, your extension must have the host permission for it.
If the onShown
handler calls any asynchronous APIs, then it's possible that the menu has been closed again before the handler resumes execution. Because of this, if a handler calls any asynchronous APIs, it should check that the menu is still being displayed before it updates the menu. For example:
js
let lastMenuInstanceId = 0;
let nextMenuInstanceId = 1;
browser.menus.onShown.addListener(async (info, tab) => {
let menuInstanceId = nextMenuInstanceId++;
lastMenuInstanceId = menuInstanceId;
// Call an async function
await /* the function to call */ ;
// After completing the async operation, check whether the menu is still shown.
if (menuInstanceId !== lastMenuInstanceId) {
return; // Menu was closed and shown again.
}
// Now use menus.create/update + menus.refresh.
});
browser.menus.onHidden.addListener(() => {
lastMenuInstanceId = 0;
});
Note that it is possible to call menus API functions synchronously, and in this case you don't have to perform this check:
js
browser.menus.onShown.addListener(async (info, tab) => {
browser.menus.update(menuId /*, …*/);
// Note: Not waiting for returned promise.
browser.menus.refresh();
});
However, if you call these APIs asynchronously, then you do have to perform the check:
js
browser.menus.onShown.addListener(async (info, tab) => {
let menuInstanceId = nextMenuInstanceId++;
lastMenuInstanceId = menuInstanceId;
await browser.menus.update(menuId /*, …*/);
// must now perform the check
if (menuInstanceId !== lastMenuInstanceId) {
return;
}
browser.menus.refresh();
});
Firefox makes this event available via the contextMenus
namespace as well as the menus
namespace.
Syntax
js
browser.menus.onShown.addListener(listener)
browser.menus.onShown.removeListener(listener)
browser.menus.onShown.hasListener(listener)
Events have three functions:
addListener(listener)
-
Adds a listener to this event.
removeListener(listener)
-
Stop listening to this event. The
listener
argument is the listener to remove. hasListener(listener)
-
Check whether
listener
is registered for this event. Returnstrue
if it is listening,false
otherwise.
addListener syntax
Parameters
listener
-
The function called when this event occurs. The function is passed these arguments:
info
-
Object
. This is just like themenus.OnClickData
object, except it contains two extra properties:contexts
: an array of all thecontexts
that are applicable to this menu.menuIds
: an array of IDs of all menu items belonging to this extension that are being shown in this menu.
Compared with
menus.OnClickData
, theinfo
object also omits themenuItemId
andmodifiers
properties, because of course these are not available until a menu item has been selected.The
contexts
,menuIds
,frameId
, andeditable
properties are always provided. All the other properties ininfo
are only provided if the extension has the host permission for the page. tab
-
tabs.Tab
. The details of the tab where the click took place. If the click did not take place in or on a tab, this parameter will be missing.
Examples
This example listens for the context menu to be shown over a link, then updates the openLabelledId
menu item with the link's hostname:
js
function updateMenuItem(linkHostname) {
browser.menus.update(openLabelledId, {
title: `Open (${linkHostname})`,
});
browser.menus.refresh();
}
browser.menus.onShown.addListener((info) => {
if (!info.linkUrl) {
return;
}
let linkElement = document.createElement("a");
linkElement.href = info.linkUrl;
updateMenuItem(linkElement.hostname);
});
Example extensions
Browser compatibility
BCD tables only load in the browser