XPLMGetAvionicsGeometry

XPLM_API void       XPLMGetAvionicsGeometry(
                         XPLMAvionicsID       inHandle,
                         int *                outLeft,    /* Can be NULL */
                         int *                outTop,    /* Can be NULL */
                         int *                outRight,    /* Can be NULL */
                         int *                outBottom);    /* Can be NULL */

Returns the bounds of a cockpit device’s popup window in the X-Plane coordinate system.