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### 8.3 Links

Hyperlink info can be added to labels (or parts of labels). This is useful when the resulting image is embedded into web pages. Hyperlinks are not (yet) exported into a PDF or SVG file. Currently link information can be extracted via the `-T ismap` command-line option, which provides an NCSA formatted ismap file. Such files are used by Doxygen, for example, so this feature is most applicable to Doxygen integration. (If you specify a link target as `\ref Name` then Doxygen will point to a function or class named `Name` in the documentation created by Doxygen.)

In the MFC GUI, links are visible and if they represent a URL they are clickable. In the CLI GUI they are not.

To add a hyperlink to a label, use two `\L()` escape in a pair, making the text between them to point to the link target. The target of the link shall be specified as the parameter to the first `\L()` escape. In this case the link target may not contain closing parenthesis37. Using this method it is possible to add several links to (different parts of) the same label.

In signalling charts, you can also use the `url` attribute. This makes the whole label a hyperlink. The value of the attribute is the target of the link. You cannot use both mechanisms to the same label. Note that you can only use the first method to add hyperinks to box tags.

Links also change formatting. In the plain design, they became blue and underlined. In signalling charts, this is governed by the `text.link_format` chart option and attribute. Any formatting escape sequence you specify as value to this chart option or attribute will be applied at the beginning of the link text and de-applied at the end.

#### Footnotes

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If the link target contains opening brace, hashmark, semicolon or symbols, which terminate a colon label, use quotation marks around the label - it is not possible to use escapes such as `\[` inside a link target.

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