Re: Native line numbers landed on master

[Ergus <spacibba@aol.com>]

On Wed, Oct 02, 2019 at 11:40:12AM +0200, Juanma Barranquero wrote:
>On Wed, Oct 2, 2019 at 5:42 AM Ergus <spacibba@aol.com> wrote:
>
>> if so, the code does nothing.
>
>That's what I'm asking. Not how to check for an integer, but what to do
>when/if it's not. I don't have the foggiest idea what's usually done with
>errors during redisplay.

Usually the default is not to do anything if the values are invalid,
unset or null. So, if the user sets the values to something that cannot
be converted to a valid int within the valid range then the function
will return false and nothing needs to be done. The "if else" chain will
do nothing or will set the face to the default value (if not
already).

This has a nice side effect to disable your feature easily just setting
the values (or the faces) to nil, but also to for the values zero (which
is invalid) for example.

I think that what Eli tries to avoid is to parse a const pair array,
lisp lists or some other complex lisp data structures from withing the
display engine because it is very error prone, inefficient and hard to
maintain. So we only do that if it is really needed.

But he will confirm in any case.
Best,
Ergus