[SDL] timers and the event loop

[Bob Pendleton]

What you described is the only way I know of to do what you want to do
using SDL.

		Bob Pendleton

On Sun, 2007-07-01 at 12:23 -0400, Sean Middleditch wrote:
> Hi everyone,
> 
> I'm having trouble groking how to properly handle timers and the event
> loop at the same time in SDL.  I'm far more experienced with server
> programming, so possibly I'm just approaching things wrong.
> 
> The way I'd handle an event loop with timers normally is something like:
> 
>   while poll (event_sources, event_source_count, get_next_timer_ms())
>     handle_events()
>     process_timers()
> 
> As timers will be spaced apart by a good amount (usually around 300ms),
> I want to be able to both let the app sleep that full time (yay battery
> power) when possible.  However, I also want to process events
> immediately, as waiting up to 300ms before responding to input is pretty
> noticeable.
> 
> With SDL, the only possible way I can figure out how to do this is to
> set a timer in SDL_Timer, and then have the callback push a user event
> to the event queue, and then use SDL_WaitEvents.  Something like:
> 
>   function handle_timer
>     SDL_PushEvent (... SDL_USEREVENT1 ...)
> 
>   function main
>     init()
> 
>     SDL_SetTimer(get_next_timer_ms(), handle_timer)
>     while SDL_WaitEvents()
>       if event is SDL_USEREVENT1
>         process_timers()
>       else
>         process_input()
> 
>       SDL_SetTimer(get_next_timer_ms(), handle_timer)
>   
> That feels really clunky and heavyweight to me.  I'm guessing this might
> be because Windows or some other port doesn't let you wait on both input
> events and a timer expiration like posix poll/select does, but that
> doesn't really help me much.
> 
> Is that the only way to do this, or is there some other preferred way to
> handle this situation that I'm missing?
> 
-- 
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