Function projectm_set_preset_duration 

pub unsafe extern "C" fn projectm_set_preset_duration(
    instance: projectm_handle,
    seconds: f64,
)

@brief Sets the preset display duration before switching to the next using a soft cut.

This can be considered as the maximum time a preset is displayed. If this time is reached, a smooth cut will be initiated. A hard cut, if any, will always happen before this time.

@param instance The projectM instance handle. @param seconds The number of seconds a preset will be displayed before the next is shown.