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| Deletions are marked like this. | Additions are marked like this. |
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| ||'''userdata'''||a pointer that is passed to the first parameter of '''filter'''|| | ||'''userdata'''||a pointer that is passed to '''filter'''|| |
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| . where `YourEventFilter` is the name of your function, `userdata` is what was passed as '''userdata''' to [[SDL_AddEventWatch]]() and `event` is the event that triggered the callback. | . 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|| |
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| If the '''filter''' returns 0 then the event will be dropped from the queue, otherwise the event queue will be preserved. | If '''filter''' returns 0 then the event will be dropped from the queue, otherwise the event queue will be preserved. |
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SDL_AddEventWatch
Use this function to add a callback to be triggered when an event is added to the event queue.
Syntax
void SDL_AddEventWatch(SDL_EventFilter filter,
void* userdata)
Function Parameters
filter |
the function to call when an event happens; see Remarks for details |
userdata |
a pointer that is passed to filter |
Code Examples
You can add your code example here
Remarks
The function prototype for filter is:
int YourEventFilter(void* userdata,
SDL_Event* event)
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
If filter returns 0 then the event will be dropped from the queue, otherwise the event queue will be preserved.
![/!\](/moin_static198/fixedleft/img/alert.png "/!\"){kind=small}
Be very careful of what you do in the event filter function, as it may run in a different thread!
There is one caveat when dealing with the SDL_QUITEVENT event type. The event filter is only called when the window manager desires to close the application window. If the event filter returns 1, then the window will be closed, otherwise the window will remain open if possible.
If the quit event is generated by an interrupt signal, it will bypass the internal queue and be delivered to the application at the next event poll. green
