EXPERIMENTAL USE ONLY!!! -- [What?] -- Login to add public annotations [How? >>YouTube].

XPLMGetScreenSize

XPLM_API void       XPLMGetScreenSize(
                         int *                outWidth,    /* Can be NULL */
                         int *                outHeight);    /* Can be NULL */

This routine returns the size of the main X-Plane OpenGL window in pixels. This number can be used to get a rough idea of the amount of detail the user will be able to see when drawing in 3-d.