Xkb maintains a virtualmodifiermapping, which lists the virtual modifiers associated with, or bound to,
each key. The real modifiers bound to a virtual modifier always include all of the modifiers bound to any
of the keys that specify that virtual modifier in their virtual modifier mapping. The server.vmodmap
array indicates which virtual modifiers are bound to each key; each entry is a bitmask for the virtual
modifier bits. The server.vmodmap array is indexed by keycode.
The vmodmap and vmods members of the server map are the "master" virtual modifier definitions. Xkb
automatically propagates any changes to these fields to all other fields that use virtual modifier
mappings.
For example, if Mod3 is bound to the Num_Lock key by the core protocol modifier mapping, and the NumLock
virtual modifier is bound to they Num_Lock key by the virtual modifier mapping, Mod3 is added to the set
of modifiers associated with NumLock.
The virtual modifier mapping is normally updated whenever actions are automatically applied to symbols
and few applications should need to change the virtual modifier mapping explicitly.
Use XkbGetMap to get the virtual modifiers from the server or use XkbGetVirtualMods to update a local
copy of the virtual modifiers bindings from the server. To set the binding of a virtual modifier to a
real modifier, use XkbGetVirtualMods
If the keyboard description defined by xkb includes bindings for virtual modifiers, XkbVirtualModsToReal
uses those bindings to determine the set of real modifiers that correspond to the set of virtual
modifiers specified in virtual_mask. The virtual_mask parameter is a mask specifying the virtual
modifiers to translate; the i-th bit (0 relative) of the mask represents the i-th virtual modifier. If
mask_rtrn is non-NULL, XkbVirtualModsToReal backfills it with the resulting real modifier mask. If the
keyboard description in xkb does not include virtual modifier bindings, XkbVirtualModsToReal returns
False; otherwise, it returns True.