XPLMAvionicsCallback_f

XPLMAvionicsCallback_f

typedef int (* XPLMAvionicsCallback_f)(
                         XPLMDeviceID         inDeviceID,
                         int                  inIsBefore,
                         void *               inRefcon);

This is the prototype for drawing callbacks for customized built-in device. You are passed in the device you are enhancing/replacing, and (if this is used for a built-in device that you are customizing) whether it is before or after X-Plane drawing. If you are before X-Plane, return 1 to let X-Plane draw or 0 to suppress X-Plane drawing. If you are called after X-Plane, the return value is ignored.

Refcon is a unique value that you specify when registering the callback, allowing you to slip a pointer to your own data to the callback.

Upon entry the OpenGL context will be correctly set up for you and OpenGL will be in panel coordinates for 2d drawing. The OpenGL state (texturing, etc.) will be unknown.