https://invisible-island.net/xterm/xtoolkit/
XtGetKeysymTable, XtKeysymToKeycodeList - query keysyms and keycodes
#include <X11/Intrinsic.h>
KeySym* XtGetKeysymTable(Display* display, KeyCode* min_keycode_return,
int *keysyms_per_keycode_return);
void XtKeysymToKeycodeList(Display* display, KeySym keysym, KeyCode**
keycodes_return, Cardinal* keycount_return);
display Specifies the display whose table is required.
min_keycode_return
Returns the minimum KeyCode valid for the display.
keysyms_per_keycode_return
Returns the number of KeySyms stored for each KeyCode.
keysym Specifies the KeySym for which to search.
keycodes_return
Returns a list of KeyCodes that have keysym associated with
them, or NULL if keycount_return is 0.
keycount_return
Returns the number of KeyCodes in the keycode list.
XtGetKeysymTable returns a pointer to the Intrinsics' copy of the
server's KeyCode-to-KeySym table. This table must not be modified.
The XtKeysymToKeycodeList procedure returns all the KeyCodes that have
keysym in their entry for the keyboard mapping table associated with
display. The caller should free the storage pointed to by keycodes_re-
turn using XtFree when it is no longer useful.
X Toolkit Intrinsics - C Language Interface
Xlib - C Language X Interface
X Version 11 libXt 1.3.1 XtGetKeysymTable(3)