Re: numerical field in .muttrc for positioning menus

[Kyle Wheeler <kyle-mutt@xxxxxxxxxxxxxx>]

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On Tuesday, November 20 at 12:29 AM, quoth Mauro Sacchetto:
>In my -muttrc I've , for instance:
>set index_format = "(%3C) %Z %-7.7{%b %d} %-20.20F (lin:%4l msg:%2M) %-28.28t 
>%s"
>What is the exact logic of the numerical field, as -7.7
>to obtain the right positioning of the fileds FROM, TOO etc?

It's the same logic as in printf. To quote the applicable parts from 
the man page:

     Each format specification is introduced by the percent character
     (``%''). The remainder of the format specification includes, in
     the following order:

     Zero or more of the following flags:

         -   A minus sign `-' which specifies left adjustment of the
             output in the indicated field;
         ` ' A space specifying that a blank should be left before a
             positive number for a signed format.  A `+' overrides a
             space if both are used;
         0   A zero `0' character indicating that zero-padding should
             be used rather than blank-padding.  A `-' overrides a `0'
             if both are used;

     Field Width:
         An optional digit string specifying a field width; if the
         output string has fewer characters than the field width it
         will be blank-padded on the left (or right, if the
         left-adjustment indicator has been given) to make up the field
         width (note that a leading zero is a flag, but an embedded
         zero is part of a field width);

     Precision:
         An optional period, `.', followed by an optional digit string
         giving a precision which specifies the number of digits to
         appear after the decimal point, for e and f formats, or the
         maximum number of characters to be printed from a string; if
         the digit string is missing, the precision is treated as zero;

Translating that, in the case of something like %-7.8s, we're telling 
mutt that:

     1. We want to print the subject (because it ends in s)
     2. Exactly 7 spaces are to be reserved for the subject (because of
        the 7), but more may be printed if the subject is longer.
     3. The subject must be right-aligned (because of the -).
     4. Only 8 characters may be printed.

To demonstrate the difference, let's take two subjects, "foobarbaz" 
and "morky" to play with. I'll surround them with wockas (><) so that 
you can see where other text would be printed if they were part of a 
longer line. If we print both of them with >%s< we get:

     >foobarbaz<
     >morky<

If we use >%7s< we get:

     >foobarbaz<
     >  morky<

Note that in both cases, 7 spots were reserved, but the longer subject 
printed in its entirety anyway. If we negated it (>%-7s<), we'd get:

     >foobarbaz<
     >morky  <

If we just use the bit after the decimal (>%.7s<), we're limiting how 
many characters can print:

     >foobarb<
     >morky<

Note that without reserving spaces, adding a negative (>%-.7s<) does 
nothing:

     >foobarb<
     >morky<

BUT these two can be combined to simulate a tabulated list. We use the 
first number (to the left of the decimal) to reserve character spaces, 
and the second number (to the right of the decimal) to limit how many 
print. For example, if we use >%7.7s< then it looks like:

     >foobarb<
     >  morky<

Adding a negative (>%-7.7s<) aligns things to the left:

     >foobarb<
     >morky  <

To put that back in context, let's take a look at your $index_format:

set index_format = "(%3C) %Z %-7.7{%b %d} %-20.20F (lin:%4l msg:%2M) %-28.28t 
%s"

Let's pretend that you have an unread message from foo sent on 
November 20th, that's 10 lines long and 1k big, with a subject of "get 
a load of this weird stuff!". That would be displayed like this:

   1 N   Nov 20  foo                  (lin:10   msg:1k) you                     
    get a load of this weird stuff

Let me replace the spaces that were added as padding with underscores 
so you can see them:

__1 N   Nov 20_ foo_________________ (lin:10__ msg:1k) 
you________________________ get a load of this weird stuff

Let's ignore everything after the msg: part, just to keep things 
simple:

__1 N   Nov 20_ foo_________________ (lin:10__ msg:1k)

Here's what it would look like if you used %20.20F instead of %-20.20F:

__1 N   Nov 20_ _________________foo (lin:10__ msg:1k)

It would look exactly the same for this mail if you used %20F instead 
of %-20.20F, but if the sender was foobarbazquxquuxgarply instead of 
foo, here's how it would compare:

__1 N   Nov 20_ foobarbazquxquuxgarp (lin:10__ msg:1k) << %-20.20F
__1 N   Nov 20_ foobarbazquxquuxgarply (lin:10__ msg:1k) << %20F

Does that make sense?

~Kyle
- -- 
If Tyranny and Oppression come to this land, it will be in the guise 
of fighting a foreign enemy.
                                                       -- James Madison
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