Re: [PATCH] Make display-time-mode time zone configurable

[Paul Eggert <eggert@cs.ucla.edu>]

Mark Oteiza wrote:
> On 19/02/16 at 10:02am, Paul Eggert wrote:
>> >On 02/19/2016 09:14 AM, Mark Oteiza wrote:
>>> > >My first thought of a use-case is simply keeping time zone in the mode
>>> > >line the same regardless of what the system time (or local time) may be,
>>> > >akin to not changing one's watch when travelling.
>> >
>> >That's easily done with (setenv "TZ" "America/Los_Angeles"), or whatever you
>> >want the mode-line's time zone to be.
> Sure, if you want to globally change the time zone in emacs and all the
> subprocesses it spawns,

Which is the normal case. Users who want to affect Emacs but not subprocesses 
can call set-time-zone-rule instead of setenv. Admittedly we steer users away 
from that sort of thing, as it leads to confusion.

> which is counter to the purpose of the defcustom
> in the first place--to expose convenient fine control of the displayed
> time zone in display-time-mode.

I'm afraid we're starting to go in circles. I'm curious about why one would want 
to change just the mode-line's time zone, and you're responding that it's 
because one would want to change just the mode-line's time zone. :-)

We needn't add a control knob for every Emacs behavior, only behaviors for which 
the benefit in fine-grained control outweighs the cost in confusion and 
complexity. The cost/benefit tradeoff for this will differ among users. Expert 
users who need this sort of fine-grained control already have it; as far as I 
can see, nonexpert users don't need it enough to justify its complexity.