For the most complete integration of Mallard with an application, context-sensitive links can be added to the application that link to pages or sections in documentation. For example, a preferences dialog might have a help button which, when clicked, would open a guide page that links to topics about changing the application preferences.
Implementing context-sensitive help implies certain requirements, such as being able to address specific sections in Mallard documentation and a documentation viewer that is able to understand the addressing scheme.
A linking scheme is required in order to reference specific sections or pages of documentation from an external resource. Mallard does not prescribe a linking scheme, so it is a feature that is dependent on the documentation viewer. Yelp is the principal Mallard documentation viewer, and conforms to the draft freedesktop.org help system specification. An example of a link to the index for the hypothetical myproject project looks as follows:
Link URIs assume that the documentation is installed to the system-wide help directory. While it is possible to override this directory locally, it is not recommended. Refer to the help system specification for more information.
To link to a specific page, add a Unix path separator '/' and the page ID to the URI:
No file extensions are required, as Yelp identifies the extension automatically. Additionally, sections on a page can be linked to by adding the section ID to the end of the URI, prefixed with a '#':
You can test the URI by running Yelp with the URI as an argument. For example:
$ yelp help:myproject/mypage
The above command would run Yelp and show the mypage page in the myproject documentation.
Given a linking scheme, applications can link from a specific context to the corresponding part of the documentation. An obvious example is linking from a help button in a hypothetical export dialog to documentation about exporting. Assuming an application myproject, with a Mallard page export, the URI might look as follows:
Application support for the linking scheme depends on the underlying toolkit. For applications using GTK+, the
gtk_show_uri() function accepts a URI as an argument, and opens Yelp with the given URI. For example, the following line of code launches the default help viewer, generally Yelp, with the URI given above:
gtk_show_uri (gdk_screen_get_default (), "help:myproject/export", GDK_CURRENT_TIME, NULL);
Other toolkits should have a similar function for opening URIs, but the details are outside of the scope of this document. Consult the reference documentation of your toolkit for details.
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