1 /******************************************************************************
5 * Copyright (C) 1997-2012 by Dimitri van Heesch.
7 * Permission to use, copy, modify, and distribute this software and its
8 * documentation under the terms of the GNU General Public License is hereby
9 * granted. No representations are made about the suitability of this software
10 * for any purpose. It is provided "as is" without express or implied warranty.
11 * See the GNU General Public License for more details.
13 * Documents produced by Doxygen are derivative works derived from the
14 * input used in their production; they are not affected by this license.
17 /*! \page external Linking to external documentation
19 If your project depends on external libraries or tools, there are several
20 reasons to not include all sources for these with every run of doxygen:
23 <dt>Disk space:<dd> Some documentation may be available outside of the output
24 directory of doxygen already, for instance somewhere on the web.
25 You may want to link to these pages instead of generating the documentation
26 in your local output directory.
27 <dt>Compilation speed:<dd> External projects typically have a different update
28 frequency from your own project. It does not make much sense to let doxygen
29 parse the sources for these external project over and over again, even if
31 <dt>Memory:<dd> For very large source trees, letting doxygen parse all sources
32 may simply take too much of your system's memory. By dividing the sources
33 into several "packages", the sources of one package can be parsed by
34 doxygen, while all other packages that this package depends on, are
35 linked in externally. This saves a lot of memory.
36 <dt>Availability:<dd> For some projects that are documented with doxygen,
37 the sources may just not be available.
38 <dt>Copyright issues:<dd>If the external
39 package and its documentation are copyright someone else, it may be
40 better - or even necessary - to reference it rather than include a
41 copy of it with your project's documentation. When the author forbids
42 redistribution, this is necessary. If the author requires compliance
43 with some license condition as a precondition of redistribution, and
44 you do not want to be bound by those conditions, referring to their
45 copy of their documentation is preferable to including a copy.
49 If any of the above apply, you can use doxygen's tag file mechanism.
50 A tag file is basically a compact representation of the entities found in the
51 external sources. Doxygen can both generate and read tag files.
53 To generate a tag file for your project, simply put the name of the
54 tag file after the \ref cfg_generate_tagfile "GENERATE_TAGFILE" option in
55 the configuration file.
57 To combine the output of one or more external projects with your own project
58 you should specify the name of the tag files after
59 the \ref cfg_tagfiles "TAGFILES" option in the configuration file.
61 A tag file typically only contains a relative location of the documentation from the
62 point where doxygen was run. So when you include a tag file in other project
63 you have to specify where the external documentation is located in relation this project.
64 You can do this in the configuration file by assigning the (relative) location to the
65 tag files specified after the \ref cfg_tagfiles "TAGFILES" configuration
66 option. If you use a relative path it should be relative with respect to
67 the directory where the HTML output of your project is generated; so a relative path
68 from the HTML output directory of a project to the HTML output of the other project that
72 Suppose you have a project \c proj that uses two external
73 projects called \c ext1 and \c ext2.
74 The directory structure looks as follows:
80 | +- html HTML output directory for proj
81 | +- src sources for proj
84 | +- html HTML output directory for ext1
85 | |- ext1.tag tag file for ext1
87 | +- html HTML output directory for ext2
88 | |- ext2.tag tag file for ext2
89 |- proj.cfg doxygen configuration file for proj
90 |- ext1.cfg doxygen configuration file for ext1
91 |- ext2.cfg doxygen configuration file for ext2
95 Then the relevant parts of the configuration files look as follows:
99 OUTPUT_DIRECTORY = proj
101 TAGFILES = ext1/ext1.tag=../../ext1/html \
102 ext2/ext2.tag=../../ext2/html
106 OUTPUT_DIRECTORY = ext1
107 GENERATE_TAGFILE = ext1/ext1.tag
111 OUTPUT_DIRECTORY = ext2
112 GENERATE_TAGFILE = ext2/ext2.tag
116 Go to the <a href="faq.html">next</a> section or return to the
117 <a href="index.html">index</a>.