Re: Could x-show-tip be reimplemented in Elisp? How does one create borderless frames from Elisp?

[martin rudalics]

>> These are overridden by the window manager.  ‘border-width’ is the most
>> obscure of our frame parameters, it's implementation is beyond our
>> control.  You can set it via ‘tooltip-frame-parameters’ and then it is
>> usually honored for X11 tooltips (but not on Windows).
>
> Does this apply to system tooltips, or tooltips implemented using a full 
Emacs frame?

I'm not sure what you mean.  "System tooltips" are only used on GTK
(optionally) and on OS X (unconditionally) and you cannot control their
border width via the ‘border-width’ frame parameter.  "Tooltips
implemented using a full Emacs frame" behave like other frames and for X
these usually obey the ‘border-width’ frame parameter but only at the
time they are created.  You can't change the border width of an existing
frame.

> Indeed, that's what I'd like. x-show-tip works perfectly for me (it
> supports fonts, faces, etc. properly), expect for the fact that
> updating the tooltip text causes it to be closed and reopened.

That's why IMHO tooltips are not useful for your purpose.  What you
probably want is a normal undecorated frame whose lifetime, position,
size, visibility and contents would be completely controlled by you.

martin