Why did OpenCV 3 change its documentation tool from sphinx to doxygen

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Main advandages:

• with doxygen it is easier to maintain documentation and to support contrib modules
• reference is always consistent with the code (for example, it can not contain function which have been deleted)
• generator has some built-in correctness checks (for example, if some function have several documented parameters and several undocumented, then generator will produce a warning)

Main disadvantages:

• no pdf documentation yet (doxygen supports this output, but it needs some tuning)
• no java/python documentation yet (doxygen can produce xml, but some cooperation with javadoc/pydoc/epydoc is needed)
• basic search is limited to entity identifiers only, i.e class/method/namespace/tutorial names (Google custom search can be used for full-text search)

Additional advantages:

• doxygen can produce help in some additional formats: rtf, chm (Compiled HTML), qch (Qt help), Eclipse help, XCode DocSets. However, all these methods should be additionally configured and tuned
• basic search works without web server (one can build and use html reference on local machine)
• formula rendering uses MathJax client-side technology
• html documentation can be built really fast comparing to sphinx (1 min vs. 31 min)