SDL  2.0
SDL_timer.h File Reference
#include "SDL_stdinc.h"
#include "SDL_error.h"
#include "begin_code.h"
#include "close_code.h"
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Macros

#define SDL_TICKS_PASSED(A, B)   ((Sint32)((B) - (A)) <= 0)
 

Typedefs

typedef Uint32(* SDL_TimerCallback) (Uint32 interval, void *param)
 
typedef int SDL_TimerID
 

Functions

Uint32 SDL_GetTicks (void)
 
Uint64 SDL_GetTicks64 (void)
 
Uint64 SDL_GetPerformanceCounter (void)
 
Uint64 SDL_GetPerformanceFrequency (void)
 
void SDL_Delay (Uint32 ms)
 
SDL_TimerID SDL_AddTimer (Uint32 interval, SDL_TimerCallback callback, void *param)
 
SDL_bool SDL_RemoveTimer (SDL_TimerID id)
 

Detailed Description

Header for the SDL time management routines.

Definition in file SDL_timer.h.

Macro Definition Documentation

◆ SDL_TICKS_PASSED

#define SDL_TICKS_PASSED (   A,
 
)    ((Sint32)((B) - (A)) <= 0)

Compare 32-bit SDL ticks values, and return true if A has passed B.

This should be used with results from SDL_GetTicks(), as this macro attempts to deal with the 32-bit counter wrapping back to zero every ~49 days, but should not be used with SDL_GetTicks64(), which does not have that problem.

For example, with SDL_GetTicks(), if you want to wait 100 ms, you could do this:

const Uint32 timeout = SDL_GetTicks() + 100;
while (!SDL_TICKS_PASSED(SDL_GetTicks(), timeout)) {
// ... do work until timeout has elapsed
}
uint32_t Uint32
Definition: SDL_stdinc.h:220
Uint32 SDL_GetTicks(void)
#define SDL_TICKS_PASSED(A, B)
Definition: SDL_timer.h:106

Note that this does not handle tick differences greater than 2^31 so take care when using the above kind of code with large timeout delays (tens of days).

Definition at line 106 of file SDL_timer.h.

Typedef Documentation

◆ SDL_TimerCallback

typedef Uint32( * SDL_TimerCallback) (Uint32 interval, void *param)

Function prototype for the timer callback function.

The callback function is passed the current timer interval and returns the next timer interval. If the returned value is the same as the one passed in, the periodic alarm continues, otherwise a new alarm is scheduled. If the callback returns 0, the periodic alarm is cancelled.

Definition at line 157 of file SDL_timer.h.

◆ SDL_TimerID

typedef int SDL_TimerID

Definition of the timer ID type.

Definition at line 162 of file SDL_timer.h.

Function Documentation

◆ SDL_AddTimer()

SDL_TimerID SDL_AddTimer ( Uint32  interval,
SDL_TimerCallback  callback,
void *  param 
)

Call a callback function at a future time.

If you use this function, you must pass SDL_INIT_TIMER to SDL_Init().

The callback function is passed the current timer interval and the user supplied parameter from the SDL_AddTimer() call and should return the next timer interval. If the value returned from the callback is 0, the timer is canceled.

The callback is run on a separate thread.

Timers take into account the amount of time it took to execute the callback. For example, if the callback took 250 ms to execute and returned 1000 (ms), the timer would only wait another 750 ms before its next iteration.

Timing may be inexact due to OS scheduling. Be sure to note the current time with SDL_GetTicks() or SDL_GetPerformanceCounter() in case your callback needs to adjust for variances.

Parameters
intervalthe timer delay, in milliseconds, passed to callback
callbackthe SDL_TimerCallback function to call when the specified interval elapses
parama pointer that is passed to callback
Returns
a timer ID or 0 if an error occurs; call SDL_GetError() for more information.
Since
This function is available since SDL 2.0.0.
See also
SDL_RemoveTimer

◆ SDL_Delay()

void SDL_Delay ( Uint32  ms)

Wait a specified number of milliseconds before returning.

This function waits a specified number of milliseconds before returning. It waits at least the specified time, but possibly longer due to OS scheduling.

Parameters
msthe number of milliseconds to delay
Since
This function is available since SDL 2.0.0.

◆ SDL_GetPerformanceCounter()

Uint64 SDL_GetPerformanceCounter ( void  )

Get the current value of the high resolution counter.

This function is typically used for profiling.

The counter values are only meaningful relative to each other. Differences between values can be converted to times by using SDL_GetPerformanceFrequency().

Returns
the current counter value.
Since
This function is available since SDL 2.0.0.
See also
SDL_GetPerformanceFrequency

◆ SDL_GetPerformanceFrequency()

Uint64 SDL_GetPerformanceFrequency ( void  )

Get the count per second of the high resolution counter.

Returns
a platform-specific count per second.
Since
This function is available since SDL 2.0.0.
See also
SDL_GetPerformanceCounter

◆ SDL_GetTicks()

Uint32 SDL_GetTicks ( void  )

Get the number of milliseconds since SDL library initialization.

This value wraps if the program runs for more than ~49 days.

This function is not recommended as of SDL 2.0.18; use SDL_GetTicks64() instead, where the value doesn't wrap every ~49 days. There are places in SDL where we provide a 32-bit timestamp that can not change without breaking binary compatibility, though, so this function isn't officially deprecated.

Returns
an unsigned 32-bit value representing the number of milliseconds since the SDL library initialized.
Since
This function is available since SDL 2.0.0.
See also
SDL_TICKS_PASSED

◆ SDL_GetTicks64()

Uint64 SDL_GetTicks64 ( void  )

Get the number of milliseconds since SDL library initialization.

Note that you should not use the SDL_TICKS_PASSED macro with values returned by this function, as that macro does clever math to compensate for the 32-bit overflow every ~49 days that SDL_GetTicks() suffers from. 64-bit values from this function can be safely compared directly.

For example, if you want to wait 100 ms, you could do this:

const Uint64 timeout = SDL_GetTicks64() + 100;
while (SDL_GetTicks64() < timeout) {
// ... do work until timeout has elapsed
}
uint64_t Uint64
Definition: SDL_stdinc.h:233
Uint64 SDL_GetTicks64(void)
Returns
an unsigned 64-bit value representing the number of milliseconds since the SDL library initialized.
Since
This function is available since SDL 2.0.18.

◆ SDL_RemoveTimer()

SDL_bool SDL_RemoveTimer ( SDL_TimerID  id)

Remove a timer created with SDL_AddTimer().

Parameters
idthe ID of the timer to remove
Returns
SDL_TRUE if the timer is removed or SDL_FALSE if the timer wasn't found.
Since
This function is available since SDL 2.0.0.
See also
SDL_AddTimer