Return non-nil if POS is on a link in the current buffer.
POS must be a buffer position in the current buffer or a mouse
event location in the selected window (see `event-start').
However, if `mouse-1-click-in-non-selected-windows' is non-nil,
POS may be a mouse event location in any window.
A clickable link is identified by one of the following methods:
- If the character at POS has a non-nil `follow-link' text or
overlay property, the value of that property determines what to do.
- If there is a local key-binding or a keybinding at position POS
for the `follow-link' event, the binding of that event determines
what to do.
The resulting value determine whether POS is inside a link:
- If the value is `mouse-face', POS is inside a link if there
is a non-nil `mouse-face' property at POS. Return t in this case.
- If the value is a function, FUNC, POS is inside a link if
the call (FUNC POS) returns non-nil. Return the return value
from that call. Arg is (posn-point POS) if POS is a mouse event.
- Otherwise, return the value itself.
The return value is interpreted as follows:
- If it is a string, the mouse-1 event is translated into the
first character of the string, i.e. the action of the mouse-1
click is the local or global binding of that character.
- If it is a vector, the mouse-1 event is translated into the
first element of that vector, i.e. the action of the mouse-1
click is the local or global binding of that event. - Otherwise, the mouse-1 event is translated into a mouse-2 event at the same position. (fn POS)