Re: How do I turn ANSI-terminal colourising off?

On 13/08/2013, at 6:56 PM, Jan Wielemaker wrote:
> There are two ways to control this.  Here are some entries:
> 
>  * message_property/2 allows changing the colour for message `types'.
>  * The Prolog flag color_term can be set to `false`.  That is most
>    likely your best option.

(1) Could we be allowed to use English spelling for this
    as well as Merkin speling?

(2) The documentation really needs an index.  When I got the printed
    copy, I was hoping for an index in that.  The on-line manual's
    search box failed to report color_term when I sought 'color'.

(3) Maybe that's because help(current_prolog_flag) lists a whole lot
    of flags, but 'color_term' is not one of them.  This is in version
    6.5.0.
>> Whatever the default colours are, they should be chosen to *contrast*
>> with the user's Terminal settings, and if it is impractical to detect
>> that, the best default is no colouring.
> 
> I don't think there is a way to get this info.

I am specifically writing about Terminal.app in Mac OS X.
Poking around with AppleScript Editor, I found these
properties that you can ask Terminal for:

  cursor color (color) : The cursor color for the tab.
  background color (color) : The background color for the tab.
  normal text color (color) : The normal text color for the tab.
  bold text color (color) : The bold text color for the tab.

>   Some emulators allow for
> redefining the 16 ANSI colors, which might solve some of the problem, but
> makes it impossible to guess the result of specifying colors.

The way out is to go up.  (One of my favourite sayings.)

There may well be some people who like their code colourised to
tell them things they already know.  (Hey, I can _see_ the percent
sign.  It's right at the beginning of the line.  Why does it have
to be a different colour as well?  I _know_ this line is something
I typed and this other line is _not_ something I typed.  Why do
they have to be different colours?  Why not use colours to tell
me something I _don't_ know?  Why not make the colours _useful_?)

But it passes the bounds of belief that they will all like the *same*
colours.  The answer is obvious.  Let people specify the colours they
want in their ~/.plrc, and if they _don't_ say what colours they want,
give them uncolourised text *and* a note in the banner something like
"See color_term in current_prolog_flag/2 for a colourised interaction."

> But today, quite a few applications color by default
> and I have the impression that most people like it.

Where does green text on a green background *ever* get to be sensible?

> You'll always make some
> people unhappy with whatever default preference you choose ...

Well, that's not what made *me* unhappy.
What made me unhappy was not being able to find anything about it in
the documentation.  If the banner had said "hey there's this new
colourising feature, read about it at <link>", I would have been
*briefly* irritated.  As it was, I lost nearly an hour trying to
figure out what to do, diligently searching documentation, and
*failing*.

There are new features that don't affect anyone who doesn't choose
to use them, and they can stay undocumented while the design is
finalised.  But new features that change the user experience really
do need to be documented.

Having got that off my chest, this is an exceptional case.
If the documentation of SWI Prolog were generally dreadful, this
issue would be a minor point.  But the documentation of SWI Prolog
is almost always _there_ and _useful_.