Difference between revisions of "Policies/KDE Frameworks Documentation Policy"

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== Introduction ==
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This page has been moved to the [http://community.kde.org/Frameworks/Frameworks_Documentation_Policy community.kde.org wiki], together with the other framework policies.
 
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Classes in the KDE frameworks are used by many Qt and KDE applications, hence, their usage should be as simple as possible. To help in that endeavor it should be fully documented to let any developer use it. New classes that are added to KDE frameworks must comply with this doc, all existing classes are grandfathered in, but need to be updated to comply if they do not. The KDE library documentation is based upon the [http://java.sun.com/j2se/javadoc/writingdoccomments/index.html#styleguide Java documentation specification]. Follow the link for full in depth documentation about that format.
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These guidelines apply not only to classes in KDE frameworks, but also to libraries elsewhere (KDE PIM, for instance, has a large number of support libraries that need documentation). To some extent they also apply to applications, if only so that it is easier for new developers to contribute meaningfully to the application — well-documented code is easy-to-extend code.
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== Files in the Repository Root Dir ==
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The repository root dir must contain two files: <tt>README.md</tt> and <tt>$framework.yaml</tt>.
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=== README.md ===
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The content of this file is used to generate the front page of the framework documentation. It must feature at least the following fields:
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<pre>
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# $FrameworkName
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One line description.
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## Introduction
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Longer description.
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## Links
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- Home page: <https://projects.kde.org/projects/frameworks/$frameworkname>
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- Mailing list: <https://mail.kde.org/mailman/listinfo/kde-frameworks-devel>
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- IRC channel: #kde-devel on Freenode
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- Git repository: <https://projects.kde.org/projects/frameworks/$frameworkname/repository>
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</pre>
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=== $framework.yaml ===
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This file is used by various tools to generate the documentation. It must contain a <tt>tier</tt> key which must be a number indicating the framework tier.
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It may also contain a <tt>framework-dependencies</tt> key containing a list of frameworks this framework depends on. This key is used by KApidox dependency diagram generator to ensure it captures all dependencies. In most situations, this key can be skipped: you only need to add in specific situations, like if you depend on a framework but do not link to any of its targets (because you only use CMake macros provided by the framework) or because a framework dependency is optional but you want to ensure it is mentioned in the diagram.
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For example, the <tt>kded</tt> framework depends on CMake macros provided by the <tt>KInit</tt> framework. Here is what <tt>kded.yaml</tt> looks like:
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<pre>
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tier: 3
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framework-dependencies:
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    - kinit
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</pre>
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== Document the Classes ==
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=== Add a Class Description ===
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Doxygen uses the first sentence of the class to generate a short class description. This sentence should provide the reason for why the class exists and when to use it, i.e. the description should give an simple overview of what the class does. Examples: "KMyWidgetClass is a class to handle lists", "A widget that shows balls bouncing.", "Monitors directory(s) for changes". The first sentence should be able to stand on its own when displayed by an IDE as the short description. Suggestions for when the class should and '''should not''' be used are very helpful, same with referencing classes that are similar, but fill different needs.
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<tt>@author</tt> should be used to show who the author(s) of the class are. If there are more than one <tt>@author</tt> tag, <tt>@par Maintainer: Foo Bar (foo@bar.com)</tt> should be added. This is required so that developers will know whom is the correct person to contact when they find a bug or have a patch.
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=== Provide Example Code ===
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A simple example usage of the class should be provided. Not only does example code show how the functions in the class interact, but they are good summaries and should be placed in the class descriptions. Note that developers will often copy this coder verbatim as a starting point and so great care should be taken to make sure that the code is clean, clear and concise. Good full variable names such as ''stream'' or ''file'' should be chosen instead of abbreviations like ''s'' and ''fl''. <tt>@code</tt> and <tt>@endcode</tt> should be used to mark code examples.
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=== Example Application ===
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If applicable, provide an example application which shows the usage of the class. A test application or existing application that a developer can reference is an excellent resource for developers looking to learn about the class.
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=== Add Screenshots ===
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If the class is a widget add a screenshot. Screenshots provide a simple and easy way for developers to recognize what the class provides. The screenshots should reside in class description. Images can be placed in <tt>docs/pics</tt> and included with <tt>@image</tt>, like this:
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<syntaxhighlight lang="cpp-qt">
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/**
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* ...
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* @image html myclass.png "Image subtitle"
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*/
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</syntaxhighlight>
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=== Document Public and Protected Members ===
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Developers do not read reference documentation like a book, they scan it for the information that they need. This is why it is important that everything is at the place they expect it to be. IDE's might parse the functions and so it is important that the correct meta data is present and not hidden in the description. Functions should use the "@" tags in the following order:
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# <tt>@brief</tt>
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# <tt>@description</tt>
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# <tt>@param</tt>
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# <tt>@return</tt>
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# <tt>@exception</tt>
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# <tt>@see</tt>
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# <tt>@author</tt>
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# <tt>@since</tt>
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<tt>@param</tt>, <tt>@return</tt> etc should be in all lower case. If there is just one sentence then there should be no period at the end. The first word should not be capitalized and there should not be a dash between the parameter name and the description. The "-" is added by the doc processor and if the developer adds one then there might be two in the resulting html/pdf/tex/etc documentation.
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Correct:
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<syntaxhighlight lang="cpp-qt">
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/**
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* ...
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* @param foo the value to convert
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*/
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</syntaxhighlight>
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Incorrect:
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<syntaxhighlight lang="cpp-qt">
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/**
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* ...
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* @param foo The value to convert
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*            ^
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* @param foo the value to convert.
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*                                ^
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* @Param foo the value to convert
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*  ^
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* @param foo-the value to convert
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*          ^
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*/
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</syntaxhighlight>
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Functions that return bool should not use "iff" in <tt>@return</tt> statements.
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Correct:
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<syntaxhighlight lang="cpp-qt">
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/**
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* ...
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* @return @c true if button is on and is a toggle button, @c false otherwise
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*/
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</syntaxhighlight>
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Incorrect:
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<syntaxhighlight lang="cpp-qt">
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/**
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* ...
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* @return @c true **iff** button is on and is a toggle button
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*/
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</syntaxhighlight>
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<tt>@deprecated</tt> should be added to any function or class that should be removed in the next binary incompatible release (3.0, 4.0, 5.0). They should also state the class/function that replaces it.
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=== Document Enumerations ===
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Enums must be documented, and each enumerated value has to be explained. Same policy as functions.
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== Writing Style ==
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Avoid humor and exclamation marks, it is confusing.
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Check spelling and grammar: Documentation represents a project a lot more than you might think. Take the time to give it the proper polish it deserves. For a lot of developers the documentation will not only explain what the class does, but will be the only view into how the class works.
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== Build the API Documentation before Committing any Code ==
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Use [http://quickgit.kde.org/?p=kapidox.git KApidox] to build the doc locally and fix any errors or warnings in the documentation so others do not have to.
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If Doxygen complains about a particular parameter not being documented, document it. A typical example is:
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<syntaxhighlight lang="cpp-qt">
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/**
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* @param msecs the number of milliseconds until the timeout
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*        is signalled
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*/
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void setTimeout(uint msecs, bool repeat);
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</syntaxhighlight>
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Here the second parameter is not documented, and Doxygen will complain. Add the relevant documentation otherwise crucial information about the use of the class is missing.
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If Doxygen complains about <tt>@param</tt> referring to a parameter that isn't there, add the name for the parameter.
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<syntaxhighlight lang="cpp-qt">
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/**
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* @param msecs the number of milliseconds until the timeout
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*        is signalled
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* @param repeat whether the timeout should happen every
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*        @p msecs milliseconds, or just once
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*/
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void setTimeout(uint, bool);
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</syntaxhighlight>
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Here, Doxygen will complain that the names of the parameters do not occur in the function signature. Add the names. The lack of names can be really confusing if you have a method with several parameters of the same type. Probably the documentation lists the parameters in the order they occur in the function signature, but there is no way to tell.
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Sometimes there is a conflict between reducing Doxygen warnings and compile warnings. This happens in interface definitions where you give a default implementation of a method with no real body, like the following:
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<syntaxhighlight lang="cpp-qt">
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virtual void setTimeout(uint, bool) { }
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</syntaxhighlight>
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This compiles fine; Doxygen will complain about missing names, so you add names:
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<syntaxhighlight lang="cpp-qt">
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virtual void setTimeout(uint timeout, bool repeat) { }
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</syntaxhighlight>
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Now the compilation gives warnings because parameters <tt>timeout</tt> and <tt>repeat</tt> are not used in the function body. There is the [https://qt-project.org/doc/qt-5.1/qtcore/qtglobal.html#Q_UNUSED Q_UNUSED] macro to deal with this. It "uses" its argument, which shuts the compiler up.
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<syntaxhighlight lang="cpp-qt">
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virtual void setTimeout(uint timeout, bool repeat)
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{
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    Q_UNUSED(timeout);
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    Q_UNUSED(repeat);
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}
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</syntaxhighlight>
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With the function defined like this, both Doxygen and the C++ compiler are happy. <tt>Q_UNUSED</tt> does not incur any run-time penalty.
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Latest revision as of 08:45, 11 March 2014

This page has been moved to the community.kde.org wiki, together with the other framework policies.


This page was last modified on 11 March 2014, at 08:45. This page has been accessed 890 times. Content is available under Creative Commons License SA 3.0 as well as the GNU Free Documentation License 1.2.
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