#pragma section-numbers off
#pragma camelcase off

= SDL_AddEventWatch =
Use this function to add a callback to be triggered when an event is added to the event queue.

<<TableOfContents()>>

== Syntax ==
{{{#!highlight cpp
void SDL_AddEventWatch(SDL_EventFilter filter,
                       void*           userdata)
}}}

== Function Parameters ==
||'''filter'''||the function to call when an event happens; see [[#Remarks|Remarks]] for details||
||'''userdata'''||a pointer that is passed to '''filter'''||

== Code Examples ==
{{{#!highlight cpp
You can add your code example here
}}}

== Remarks ==
<<Include(SDL_SetEventFilter, , , from="Start Include here.", to="##End Include here")>>
 . where `YourEventFilter` is the name of your function and its parameters are:
 ||`userdata`||what was passed as '''userdata''' to [[SDL_AddEventWatch]]()||
 ||`event`||the event that triggered the callback||

 . '''filter''' will be called when an event happens, and its return value is ignored.

/!\ WARNING: Be very careful of what you do in the event filter function, as it may run in a different thread!

If the quit event is generated by a signal (e.g. SIGINT), it will bypass the internal queue and be delivered to the watch callback immediately, and arrive at the next event poll.

Note: the callback is called for events posted by the user through [[SDL_PushEvent]](), but not for disabled events, nor for events by a filter callback set with [[SDL_SetEventFilter]](), nor for events posted by the user through [[SDL_PeepEvents]]().

== Related Functions ==
 .[[SDL_DelEventWatch]]
 .[[SDL_SetEventFilter]]

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[[CategoryAPI]], [[CategoryEvents]]