This API allows you to get regular callbacks during the flight loop, the part of X-Plane where the plane's position calculates the physics of flight, etc. Use these APIs to accomplish periodic tasks like logging data and performing I/O.

WARNING: Do NOT use these callbacks to draw! You cannot draw during flight loop callbacks. Use the drawing callbacks (see XPLMDisplay for more info) for graphics.



typedef float (* XPLMFlightLoop_f)(
                                   float                inElapsedSinceLastCall,    
                                   float                inElapsedTimeSinceLastFlightLoop,    
                                   int                  inCounter,    
                                   void *               inRefcon);    
This is your flight loop callback. Each time the flight loop is iterated through, you receive this call at the end. You receive a time since you were last called and a time since the last loop, as well as a loop counter. The 'phase' parameter is deprecated and should be ignored.

Your return value controls when you will next be called. Return 0 to stop receiving callbacks. Pass a positive number to specify how many seconds until the next callback. (You will be called at or after this time, not before.) Pass a negative number to specify how many loops must go by until you are called. For example, -1.0 means call me the very next loop. Try to run your flight loop as infrequently as is practical, and suspend it (using return value 0) when you do not need it; lots of flight loop callbacks that do nothing lowers x-plane's frame rate.

Your callback will NOT be unregistered if you return 0; it will merely be inactive.

The reference constant you passed to your loop is passed back to you.


XPLM_API float                XPLMGetElapsedTime(void);
This routine returns the elapsed time since the sim started up in decimal seconds.


XPLM_API int                  XPLMGetCycleNumber(void);
This routine returns a counter starting at zero for each sim cycle computed/video frame rendered.


XPLM_API void                 XPLMRegisterFlightLoopCallback(
                                   XPLMFlightLoop_f     inFlightLoop,    
                                   float                inInterval,    
                                   void *               inRefcon);    
This routine registers your flight loop callback. Pass in a pointer to a flight loop function and a refcon. inInterval defines when you will be called. Pass in a positive number to specify seconds from registration time to the next callback. Pass in a negative number to indicate when you will be called (e.g. pass -1 to be called at the next cylcle). Pass 0 to not be called; your callback will be inactive.


XPLM_API void                 XPLMUnregisterFlightLoopCallback(
                                   XPLMFlightLoop_f     inFlightLoop,    
                                   void *               inRefcon);    
This routine unregisters your flight loop callback. Do NOT call it from your flight loop callback. Once your flight loop callback is unregistered, it will not be called again.


XPLM_API void                 XPLMSetFlightLoopCallbackInterval(
                                   XPLMFlightLoop_f     inFlightLoop,    
                                   float                inInterval,    
                                   int                  inRelativeToNow,    
                                   void *               inRefcon);    
This routine sets when a callback will be called. Do NOT call it from your callback; use the return value of the callback to change your callback interval from inside your callback.

inInterval is formatted the same way as in XPLMRegisterFlightLoopCallback; positive for seconds, negative for cycles, and 0 for deactivating the callback. If inRelativeToNow is 1, times are from the time of this call; otherwise they are from the time the callback was last called (or the time it was registered if it has never been called.

Copyright 2005 Sandy Barbour and Ben Supnik

All rights reserved. See license.txt for usage.

X-Plane SDK Version: 1.0.2