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Re: Colored output
Re: Colored output
Sun, 27 Jan 2019 19:46:30 +0100
> Le 27 janv. 2019 à 18:39, Bruno Haible <address@hidden> a écrit :
> Hi Akim,
>> I'd like to have colored diagnostics in Bison, I do feel on occasion it would
>> make it easier to spot errors and warnings for instance.
>> AFAICT, gnulib does not feature any module to help do this. Coreutils (ls)
>> and GCC (maybe diffutils too) are probably good sources of inspiration, but
>> am I missing something? Should I look elsewhere first? Would a gnulib
>> make sense?
> There are two approaches to decide which colors to produce:
> (A) In a first step, produce output without colors. In a second step,
> add the colors, usually through regular expressions.
> (B) Add the colors directly when you produce the output, through interleaved
> statements that turn on or off specific attributes.
> I believe that (A) is good for log files, whereas (B) is preferrable for
> more complex syntax, such as JSON, XML, or programming language text.
Yes, I was clearly aiming at (B).
> There are three approaches to defining the colors and attributes for specific
> syntactic roles:
> (I) Hard code the escape sequences in the program.
> (II) Let the user specify terminal-dependent escape sequences, e.g. through
> an environment variable using an obscure syntax, or through a
> configuration file.
> (III) Let the user specify colors and attributes through a CSS file, and
> let the program translate these colors and attribute specifications
> to the terminal-dependent escape sequences.
I was thinking about (II), and would never have thought about (III)
unless I was aware of the existence of a library providing supports
for CSS on a terminal output.
> The advantages of (III), compared to (II), are:
> - The specification is terminal independent.
> - Easier to change for the user.
> (II) is the approach used by the coreutils for 'ls', with a helper program
> called 'dircolors'. 
> Likewise for 'diff' (, option '--palette').
> (III) is the approach used by GNU gettext for 'msgcat' and friends , and
> by GNU source-highlight . No helper program is needed.
> If you want the combination of (B) and (III):
Well, I was going for B.II, but now that you teased me with B.III, I can't
wait for it!
> I'm in the process of extracting
> the color and style code from GNU gettext into a library 'libtextstyle'. You
> can get an impression of it and how it can be used by looking at these links:
> lines 156..226, 449..514.
> But it's not ready yet.
It looks very promising!