Re: regexp font-lock highlighting

[martin rudalics <rudalics@gmx.at>]

 > I fixed shy group handling in this regexp by allowing ?: to be only
 > before `(' instead of before any of `(', `|' or `)'.  You may need to
 > adjust your code before submitting your final patch.

If you intend "after" instead of "before" here I have done that already.

 > Also I tried to extend this regexp to highlight other special backslash
 > constructs like `\<', `\_<', `\w', `\sC', but soon discovered that
 > sometimes there are similar constructs in non-regexp strings that become
 > inappropriately highlighted.  Unless it's possible to detect whether
 > a given string is a regexp or not,

... it hardly ever is ...

 >                                    I think the regexp highlighting
 > code should be split into multi-level font-lock variables
 > font-lock-regexp-keywords-1 and font-lock-regexp-keywords-2.
 > The first variable would highlight only `\\(?:', `\\|' and `\\)' constructs,
 > but the second - all other regexp constructs.  Everyone agreed to see
 > regexp constructs sometimes highlighted in wrong places could use
 > the second level variable.

I tried to implement variants of that but it did not turn out well.
Highlighting backslashes only is more distracting than useful.  Having
`<' or `w' stand out with bold face makes groupings much less readable.

 > I see everyone tends to change the default color of `font-lock-string-face'
 > (which is barely visible on light backgrounds) to a green color.
 > Currently on tty strings are fontified in green, so maybe this is one
 > of the reasons why people prefer green strings.  This indicates that
 > we should change the current "RosyBrown" default to one of the shades
 > of green.

... but leave alone font-lock's statement "... character strings might
be brown, because, err, strings are brown ..."

 > I added two new faces: for a backslash and regexp constructs after
 > a backslash.  The former inherits from escape-glyph to be highlighted
 > like a backslash in escape sequences, the latter is bold by default.
 > I think there is no need for a face for shy groups.  It is fontified
 > now in the same face as other regexp constructs (bold).

... splendid