Re: so-long-mode and line-move-visual

[Phil Sainty]

Hi Eli,

The settings were arrived at by experimentation, and observing
what caused the fewest problems in severe cases.

With the option combo currently set by so-long, Emacs is only
displaying a small portion of a long line, and basic cursor
movements are only moving around within that visible area, so
it's less likely that the user will cause themselves problems
by moving point.  I'm also mostly concerned about the initial
opening of a file (to ensure Emacs doesn't freeze up simply by
visiting something), in which case that small portion is going
to be (typically) the beginning of the line, where performance
is good.

If the settings were otherwise, it can be extremely problematic
to simply move up and down in a buffer.  A nil line-move-visual
risks the user accidentally skipping to the end of an enormous
line (which may be very bad for performance), whereas a non-nil
value protects them from that.

Truncation meanwhile allows multiple enormous lines to be
visible at the same time, which can be terrible.  I've always
used the "one_line.json" example file from the question at
https://emacs.stackexchange.com/q/598 as a test case, and if I
create a multi-line file where each line is a copy of that (plus
a newline), then I can happily open that with default so-long
settings; but if I then M-x toggle-truncate-lines, Emacs freezes
so badly that I have to kill it.

As such, I don't think these defaults should be changed.


-Phil