watcher

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Watch for events on certain UI elements (including windows and applications)
You can watch the following events:
Application-level events
See hs.application.watcher for more events you can watch.
hs.uielement.watcher.applicationActivated: The current application switched to this one.
hs.uielement.watcher.applicationDeactivated: The current application is no longer this one.
hs.uielement.watcher.applicationHidden: The application was hidden.
hs.uielement.watcher.applicationShown: The application was shown.
Focus change events
These events are watched on the application level, but send the relevant child element to the handler.
hs.uielement.watcher.mainWindowChanged: The main window of the application was changed.
hs.uielement.watcher.focusedWindowChanged: The focused window of the application was changed. Note that the application may not be activated itself.
hs.uielement.watcher.focusedElementChanged: The focused UI element of the application was changed.
Window-level events
hs.uielement.watcher.windowCreated: A window was created. You should watch for this event on the application, or the parent window.
hs.uielement.watcher.windowMoved: The window was moved.
hs.uielement.watcher.windowResized: The window was resized.
hs.uielement.watcher.windowMinimized: The window was minimized.
hs.uielement.watcher.windowUnminimized: The window was unminimized.
Element-level events
These work on all UI elements, including windows.
hs.uielement.watcher.elementDestroyed: The element was destroyed.
hs.uielement.watcher.titleChanged: The element's title was changed.
API Overview
Methods - API calls which can only be made on an object returned by a constructor
​element​
​pid​
​start​
​stop​
API Documentation
Methods
​element​
Signature
hs.uielement.watcher:element() -> object
Type
Method
Description
Returns the element the watcher is watching.
Parameters
None
Returns
The element the watcher is watching.
​pid​
Signature
hs.uielement.watcher:pid() -> number
Type
Method
Description
Returns the PID of the element being watched
Parameters
None
Returns
The PID of the element being watched
​start​
Signature
hs.uielement.watcher:start(events) -> hs.uielement.watcher
Type
Method
Description
Tells the watcher to start watching for the given list of events.
Parameters
An array of events to be watched for.
Returns
hs.uielement.watcher
Notes
See hs.uielement.watcher for a list of events. You may also specify arbitrary event names as strings.
Does nothing if the watcher has already been started. To start with different events, stop it first.
​stop​
Signature
hs.uielement.watcher:stop() -> hs.uielement.watcher
Type
Method
Description
Tells the watcher to stop listening for events.
Parameters
None
Returns
hs.uielement.watcher
Notes
This is automatically called if the element is destroyed.