Re: Missing frame parameters on tty's

[Eli Zaretskii <eliz@gnu.org>]

> Date: Wed, 2 Dec 2015 22:15:34 +0000
> From: Alan Mackenzie <acm@muc.de>
> 
> In my initial investigation of bug #19706, an immediate cause of the
> failure is clear - `frameset-move-onscreen' executes:
> 
>     (frame-parameter frame 'left)
> 
> , but on a tty this parameter is nil.  This is insanity, and was an
> accident waiting to happen (it has now happened).

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).

> The correct values of frame parameters 'left and 'top on a tty cannot be
> other than 0.

Yes, and since a TTY frame cannot be moved anyway, the code in
question should already make a special case for such frames.

> There are two ways of fixing bug #19706:
> 
> The first is to put in special case handling for missing frame
> parameters, pray that the same error isn't already programmed into our
> source anywhere else, and trust our highly skilled hackers never to
> blunder into the same trap again.
> 
> The second is to set the frame parameters appropriately for tty's.
> 
> I think I've made it obvious which course I prefer.

I hope I explained why I disagree with you.