Re: Missing frame parameters on tty's

[Eli Zaretskii]

> Date: Thu, 3 Dec 2015 08:30:01 +0000
> Cc: address@hidden
> From: Alan Mackenzie <address@hidden>
> 
> > Code that accesses frame parameters should expect any particular
> > parameter to appear there, it should be resistant in the face of alist
> > elements missing completely.  There are many more frame parameters
> > that will never be present in a parameters alist of TTY frames (or any
> > other frame, for that matter).
> 
> Yes, there are 56 frame parameters on an X Emacs I just fired up, and 19
> on my Linux tty session.  I'm not suggesting the numbers should be made
> equal - rather that the two particular parameters 'top and 'left should
> be present in all frames.

Why single out those two?  Especially since it make no sense at all to
have them on TTY frames.

> > Yes, and since a TTY frame cannot be moved anyway, the code in
> > question should already make a special case for such frames.
> 
> We have an error here because a special case wasn't made, and it is
> understandable that it wasn't made - the best of us are only human, after
> all.  Who on earth would think that only half of the "geometry
> parameters" would be present?

You don't need to think about this specifically.  You need to be
prepared to handle the case that the frame parameter -- any frame
parameter -- is missing from the parameters' alist.

> The thing is, this error is going to happen again, at some stage.  We
> could prevent this now.

But the same could happen with any other parameter that is missing on
TTY frames, no?

> > I hope I explained why I disagree with you.
> 
> I don't think you have.  You haven't pointed out any disadvantage in a
> tty frame having (top . 0) and (left . 0).

I just don't understand what makes these two frame parameters special.