XkbGetKeyModifierMap - Man Page

Status XkbGetKeyModifierMap (Display *dpy, unsigned int first, unsigned int num, XkbDescPtr xkb);

dpy

connection to X server

first

keycode of first key to get

num

number of keys for which information is desired

xkb

keyboard description to update

The modmap entry of the client map is an array, indexed by keycode, specifying the real  modifiers bound to a key. Each entry is a mask composed of a bitwise inclusive  OR of the legal real modifiers: ShiftMask, LockMask, ControlMask, Mod1Mask,  Mod2Mask, Mod3Mask, Mod4Mask, and Mod5Mask. If a bit is set in a modmap entry, the corresponding key is bound to that modifier.

Pressing or releasing the key bound to a modifier changes the modifier set and  unset state. The particular manner in which the modifier set and unset state  changes is determined by the behavior and actions assigned to the key.

XkbGetKeyModifierMap sends a request to the server for the modifier mappings for num keys starting with the key whose keycode is first. It waits for a reply and places the results in the xkb->map->modmap array. If successful, XkbGetKeyModifier returns Success.
 If the map component of the xkb parameter has not been allocated, XkbGetKeyModifierMap allocates and initializes it.

If a compatible version of Xkb is not available in the server or the Xkb  extension has not been properly initialized, XkbGetKeySyms returns BadAccess. If any allocation errors occur while obtaining the modifier  map, XkbGetKeyModifierMap returns BadAlloc.

BadAccess

The Xkb extension has not been properly initialized

BadAlloc

Unable to allocate storage

XkbGetMap(3), XkbGetUpdatedMap(3), XkbSetMap(3).