GNU bug report logs - #1534
Font lock decoration levels mismatch?

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Message #5 received at submit <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Derick Eddington <derick.eddington <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: Font lock decoration levels mismatch?
Date: Wed, 10 Dec 2008 11:51:33 -0800

I'm using:
GNU Emacs 23.0.60.1 (i486-pc-linux-gnu, GTK+ Version 2.14.3) of
2008-10-13 on rothera, modified by Debian

The documentation at "23.6.1 Font Lock Basics" and "23.6.5 Levels of
Font Lock" refers to level numbers starting at 1, but when I customize
the level for a specific mode (one I'm still developing) the number
given to Customize is 0-based not 1-based; i.e., my `font-lock-defaults'
`KEYWORDS' member is like `(level-1 level-2 level-3 level-4)' and, e.g.,
to make Customize use level-3 I have to tell it the number 2.  Should
Customize do 1-based indexing instead so it corresponds to the
documentation, or the documentation use 0-based?

-- 
: Derick
----------------------------------------------------------------

Message #8 received at 1534 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Glenn Morris <rgm <at> gnu.org>
To: Derick Eddington <derick.eddington <at> gmail.com>
Cc: 1534 <at> debbugs.gnu.org
Subject: Re: bug#1534: Font lock decoration levels mismatch?
Date: Thu, 11 Dec 2008 18:52:18 -0500

Derick Eddington wrote:

> The documentation at "23.6.1 Font Lock Basics" and "23.6.5 Levels of
> Font Lock" refers to level numbers starting at 1, but when I customize
> the level for a specific mode (one I'm still developing) the number
> given to Customize is 0-based not 1-based; i.e., my `font-lock-defaults'
> `KEYWORDS' member is like `(level-1 level-2 level-3 level-4)' and, e.g.,
> to make Customize use level-3 I have to tell it the number 2.

I don't really understand the problem. What exactly are you
customizing, and how?

In general, the actual Lisp expression used by Customize is not
terribly important - use a tag instead to give a more human-readable
set of choices (eg "minimum", "medium", "maximum" rather than 1, 2, 3).

Message #13 received at 1534 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Derick Eddington <derick.eddington <at> gmail.com>
To: Glenn Morris <rgm <at> gnu.org>
Cc: 1534 <at> debbugs.gnu.org
Subject: Re: bug#1534: Font lock decoration levels mismatch?
Date: Fri, 12 Dec 2008 10:48:54 -0800

On Thu, 2008-12-11 at 18:52 -0500, Glenn Morris wrote:
> Derick Eddington wrote:
> 
> > The documentation at "23.6.1 Font Lock Basics" and "23.6.5 Levels of
> > Font Lock" refers to level numbers starting at 1, but when I customize
> > the level for a specific mode (one I'm still developing) the number
> > given to Customize is 0-based not 1-based; i.e., my `font-lock-defaults'
> > `KEYWORDS' member is like `(level-1 level-2 level-3 level-4)' and, e.g.,
> > to make Customize use level-3 I have to tell it the number 2.
> 
> I don't really understand the problem. What exactly are you
> customizing, and how?
> 
> In general, the actual Lisp expression used by Customize is not
> terribly important - use a tag instead to give a more human-readable
> set of choices (eg "minimum", "medium", "maximum" rather than 1, 2, 3).

I'm customizing `font-lock-maximum-decoration'.  It's documentation
says:

        Maximum decoration level for fontification.
        If nil, use the default decoration (typically the minimum
        available).
        If t, use the maximum decoration available.
        If a number, use that level of decoration (or if not available
        the maximum).
        If a list, each element should be a cons pair of the form
        (MAJOR-MODE . LEVEL), where MAJOR-MODE is a symbol or t (meaning
        the default).  For example:
         ((c-mode . t) (c++-mode . 2) (t . 1))
        means use the maximum decoration available for buffers in C
        mode, level 2 decoration for buffers in C++ mode, and level 1
        decoration otherwise.

I'm using the last form with an association for my mode.  I have 4
levels.  I haven't yet learned how to use tags with Customize, I'll read
about that.  But for my mode, I think tag names would not be as clear as
just the numbers.  If Customize is going to allow numbers, shouldn't
their indexing base be consistent with the documentation?

When I start customizing it from its default state and activate the
"Value Menu" with "mode specific", I get:

INS DEL Instance:
            Mode:
            (*) all
            ( ) name: nil
            Decoration:
            ( ) default
            (*) maximum
            ( ) level: 1
INS

Which is not the Lisp syntax and is showing a number.

This isn't a big deal to me, but the Emacs' documentation tells me to
report things like this.

-- 
: Derick
----------------------------------------------------------------

Message #16 received at 1534 <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Glenn Morris <rgm <at> gnu.org>
To: Derick Eddington <derick.eddington <at> gmail.com>
Cc: 1534 <at> debbugs.gnu.org
Subject: Re: bug#1534: Font lock decoration levels mismatch?
Date: Fri, 12 Dec 2008 15:34:33 -0500

Derick Eddington wrote:

>> > when I customize the level for a specific mode (one I'm still
>> > developing) the number given to Customize is 0-based not 1-based;
>> > i.e., my `font-lock-defaults' `KEYWORDS' member is like `(level-1
>> > level-2 level-3 level-4)' and, e.g., to make Customize use
>> > level-3 I have to tell it the number 2.
[...]
> I'm customizing `font-lock-maximum-decoration'.  It's documentation says:
[...]
>          ((c-mode . t) (c++-mode . 2) (t . 1))
>         means use the maximum decoration available for buffers in C
>         mode, level 2 decoration for buffers in C++ mode, and level 1
>         decoration otherwise.
[...]
> When I start customizing it from its default state and activate the
> "Value Menu" with "mode specific", I get:
>
> INS DEL Instance:
>             Mode:
>             (*) all
>             ( ) name: nil
>             Decoration:
>             ( ) default
>             (*) maximum
>             ( ) level: 1


OK. So where's the part where you have to say 2 in order to get 3?

If I use customize to say:

mode: all : maximum
mode: name : f90-mode : level 2

Then I get level 2 highlighting in F90 buffers.


Oh, perhaps I see the problem. You said:

  my `font-lock-defaults' `KEYWORDS' member is like `(level-1 level-2
  level-3 level-4)'

There should be a separate element at the start giving the default
highlighting for the mode. See for example f90-mode:

  (set (make-local-variable 'font-lock-defaults)
       '((f90-font-lock-keywords f90-font-lock-keywords-1
                                 f90-font-lock-keywords-2
                                 f90-font-lock-keywords-3
                                 f90-font-lock-keywords-4)
         nil t))


(or grep for "keywords-1" in the lisp sources)

That does indeed look like a documentation bug in the manual...

Message #21 received at 1534-done <at> emacsbugs.donarmstrong.com (full text, mbox):

From: Glenn Morris <rgm <at> gnu.org>
To: 1534-done <at> debbugs.gnu.org
Subject: Re: bug#1534: Font lock decoration levels mismatch?
Date: Fri, 12 Dec 2008 23:21:35 -0500

I have clarified the documentation.


Glenn Morris wrote:

> There should be a separate element at the start giving the default
> highlighting for the mode.

BTW, it's not really the "default" any more. It's the level used when
font-lock-maximum-decoration has a nil value. Nowaways it is t by
default.

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