# SDL_HINT_MAIN_CALLBACK_RATE Request [SDL_AppIterate](SDL_AppIterate)() be called at a specific rate. ## Header File Defined in [](https://github.com/libsdl-org/SDL/blob/main/include/SDL3/SDL_hints.h) ## Syntax ```c #define SDL_HINT_MAIN_CALLBACK_RATE "SDL_MAIN_CALLBACK_RATE" ``` ## Remarks If this is set to a number, it represents Hz, so "60" means try to iterate 60 times per second. "0" means to iterate as fast as possible. Negative values are illegal, but reserved, in case they are useful in a future revision of SDL. There are other strings that have special meaning. If set to "waitevent", [SDL_AppIterate](SDL_AppIterate) will not be called until new event(s) have arrived (and been processed by [SDL_AppEvent](SDL_AppEvent)). This can be useful for apps that are completely idle except in response to input. On some platforms, or if you are using [SDL_main](SDL_main) instead of [SDL_AppIterate](SDL_AppIterate), this hint is ignored. When the hint can be used, it is allowed to be changed at any time. This defaults to 0, and specifying NULL for the hint's value will restore the default. This hint can be set anytime. ## Version This hint is available since SDL 3.2.0. ---- [CategoryAPI](CategoryAPI), [CategoryAPIMacro](CategoryAPIMacro), [CategoryHints](CategoryHints)