_Added in 1.9.0_

*<notextile>on <level>:OPEN:<?|@|=|!|*>:<matchtext>:<commands></notextile>*

Trigger for various events relating to the opening of a window of different types of windows.
Note: If you halt an on ^open event triggered by an incoming private message, no [[on TEXT]]/[[on ACTION]] events is triggered

See also [[on CLOSE]].

*Parameters*

<level> - The level for the event to trigger.
<*#?=!@> - The Matchtarget to listen to.
<matchtext> - Matchtext to listen to.
<commands> - The commands to be performed when the event listener's criteria is met.

*Example*

<pre>
; Print a message when a query window is opened.
on *:OPEN:?:*:echo -ag Opened query window for $nick
</pre>