SDL
2.0
|
Go to the source code of this file.
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) |
Header for the SDL time management routines.
Definition in file SDL_timer.h.
#define SDL_TICKS_PASSED | ( | A, | |
B | |||
) | ((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:
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.
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.
typedef int SDL_TimerID |
Definition of the timer ID type.
Definition at line 162 of file SDL_timer.h.
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.
interval | the timer delay, in milliseconds, passed to callback |
callback | the SDL_TimerCallback function to call when the specified interval elapses |
param | a pointer that is passed to callback |
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.
ms | the number of milliseconds to delay |
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().
Uint64 SDL_GetPerformanceFrequency | ( | void | ) |
Get the count per second of the high resolution counter.
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.
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:
SDL_bool SDL_RemoveTimer | ( | SDL_TimerID | id | ) |
Remove a timer created with SDL_AddTimer().
id | the ID of the timer to remove |