URL

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Revision as of 17:08, 15 August 2017 by Wolfgang Schuster (talk | contribs) (moved Url to URL)
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Overview

URLs can be typeset in various ways. You may specify a URL for later reuse via \useURL:

\useURL[aurl]       [http://xkcd.com/149/] [] [I prefer hot dogs.] 

where #1 is the identifier, #2 is the URL you want to point to, and #4 the text to be displayed where the URL is used. #3 can be used for the 'file path' portion of the URL, if you want. This dates back to when hyperlink support in DVI viewers required that split.

Alternatively, you can use only two arguments and the URL will be used as its own text.

\useURL[anotherurl] [http://xkcd.com/224/]

(That way any character may appear inside the URL string without breaking things under certain circumstances, which can happen when you specify the URL itself as the fourth argument.)

Now that you have defined some URLs you are ready to dereference them by their identifier wherever you please. Don't forget to enable interaction for clickable WWW-look-and-feel.

\setupinteraction[state=start]
\starttext
\from[aurl]         % typesets the URL description in color
\from[anotherurl]   % typesets the URL in color
\stoptext

You can use

\url[aurl]

as well, which behaves like \from[#1].

How to Typeset URLs

Example for Mailto #1

\setupinteraction[state=start]                                                                                                                                               
\useurl [mymail] [mailto:nobody@example.zzz] [][visible@mailaddress.zzz]
                       
\starttext                                                                                         

Send your spam to \from[mymail]!                                                                                     

\stoptext     

Example for Mailto #2

\setupinteraction[state=start]                                                                                                                                                                       
\starttext                                                                                                                                                                     
Send your spam to \goto{visible@mailaddress.zzz}[url(mailto:nobody@example.zzz)]                                                                                                                                         
\stoptext     

Example for WWW (\goto)

Another way of typesetting URLs is the \goto: \goto{#1}[#2] command. This expects the description text as first argument and the actual URL as the second one; note that it has to be wrapped in url(#2) to create a clickable link:

\goto{In Lua, array indices start from one.}[url(http://www.xkcd.com/163/)]

Escaping of Special Characters

Note that special characters, eg hash sign, percent sign, must be escaped. Escaping means that the special character will be processed one step later and it prevents annoying error messages during compilation.

The # sign will be replaced by \#,
the % sign will be replaced by \%, etc.

\setupinteraction[state=start]                                                                                                                                               
\useurl [myurl] [www.example.zzz/\#999] []
[www.example.zzz/\#999]                                                                            

Another way of writing special characters is described below, with hyphenated URLs.

Hyphenated URLs

URLs tend to become large monsters under many circumstances but you may have a good reason not to conceal them from the reader. This is where hyphenation comes in handy. ConTeXt provides a dedicated mechanism for chopping them into pieces:

\hyphenatedurl{http://bits.blogs.nytimes.com/2010/03/05/a-former-book-designer-says-good-riddance-to-print/?hpw}

Hyphenation Rules

This has some characters predefined where Hans “likes” URLs to break (see the list at the beginning of lang-url.lua, cf. a message on ntg-context). If you prefer other characters you can add them via:

\sethyphenatedurlnormal{:=?&}
\sethyphenatedurlbefore{?&}
\sethyphenatedurlafter {:=}

URL hyphenation can, of course, be used wherever you need them.

\useURL[yaurl]      [http://xkcd.com/638/] [] [\hyphenatedurl{http://xkcd.com/638/}]
\starttext
\from[yaurl]
\stoptext

Escaping Special Characters

The method for escaping of special characters described above does not work with command \hyphenatedurl, unfortunately. Escaping backslash will undesirably appear on the output.

In this case, all special characters must be rewritten to commands, see the following list:

% --> \letterpercent
# --> \letterhash

A custom symbol can be inserted as well, eg in case of a linebreak:

\def\hyphenatedurlseparator{}

These special commands can be used in other cases, like \useURL, too.


Setting Color and Style

For \url:

\setupurl
   [color=blue,
    style=\tf]

For \goto and \from:

\setupinteraction
   [state=start,
    color=blue,
    style=\tf]

Tips and Tricks

Many Different Hyperrefs

If you need many hyperrefs in your document these definitions may be handy for you

\def\href#1#2{\useURL[#2][{#2}][][{#1}]\goto{\url[#2]}[url(#1)]}                                                                                                               
\def\ahref#1{\color[linkcolor]{\ttx \href{#1}{<#1>}}}                                                                                                                          
\def\fullahref#1{\color[linkcolor]{\ttx \href{#1}{http://#1}}}                                                                                                                 
\def\mailto#1{\useURL[#1][mailto:#1][][#1]\from[{#1}]}                                                                                                                         
\def\MailTo#1#2{\useURL[#1][mailto:#1][][#2]\from[{#1}]}        

Send mail to \MailTo{foo@bar.zzz}{Mr. Foo}

External Links

Create a macro for external links in a colour that is distinct from other document links.

% Enable document colours
\setupcolors[state=start,]

% Internal link colours
\setupinteraction[state=start,color=blue,]

% External link colours
\definecolor[steelblue][h=4682B4]
\define[2]\href{%
  \begingroup
    \setupinteraction[
      style=normal,
      color=steelblue,
    ]%
    \goto{#1}[url(#2)]%
  \endgroup%
}

% Set index colours
\setupcombinedlist[content][
  interaction=all,
  color=red,
]

% Set the table of contents colours
\setuplist[chapter][
  % Text colour
  color=darkcyan,
  % Page number colour
  pagecolor=darkgreen,
]

% Set up the index heading colour
\setupregister[index][
  color=darkgray,
  balance=no,
]

\def\Google{G\color[red]{o}\color[orange]{o}g\color[green]{l}\color[red]{e}}

\starttext
  \completecontent

  \startchapter[title=chapter]
Search \index{source code}{source code} using \href{\Google{} Website}{http://google.com}! Read about
\index{syntax}{syntax}.
  \stopchapter

\placeindex

\stoptext