How to use doxygen to create UML class diagrams from C++ source

Hmm, this seems to be a bit of an old question, but since I've been messing about with Doxygen configuration last few days, while my head's still full of current info let's have a stab at it -

I think the previous answers almost have it:

The missing option is to add COLLABORATION_GRAPH = YES in the Doxyfile. I assume you can do the equivalent thing somewhere in the doxywizard GUI (I don't use doxywizard).

So, as a more complete example, typical "Doxyfile" options related to UML output that I tend to use are:

EXTRACT_ALL          = YES
CLASS_DIAGRAMS      = YES
HIDE_UNDOC_RELATIONS = NO
HAVE_DOT             = YES
CLASS_GRAPH          = YES
COLLABORATION_GRAPH  = YES
UML_LOOK             = YES
UML_LIMIT_NUM_FIELDS = 50
TEMPLATE_RELATIONS   = YES
DOT_GRAPH_MAX_NODES  = 100
MAX_DOT_GRAPH_DEPTH  = 0
DOT_TRANSPARENT      = YES

These settings will generate both "inheritance" (CLASS_GRAPH=YES) and "collaboration" (COLLABORATION_GRAPH=YES) diagrams.

Depending on your target for "deployment" of the doxygen output, setting DOT_IMAGE_FORMAT = svg may also be of use. With svg output the diagrams are "scalable" instead of the fixed resolution of bitmap formats such as .png. Apparently, if viewing the output in browsers other than IE, there is also INTERACTIVE_SVG = YES which will allow "interactive zooming and panning" of the generated svg diagrams. I did try this some time ago, and the svg output was very visually attractive, but at the time, browser support for svg was still a bit inconsistent, so hopefully that situation may have improved lately.

As other comments have mentioned, some of these settings (DOT_GRAPH_MAX_NODES in particular) do have potential performance impacts, so YMMV.

I tend to hate "RTFM" style answers, so apologies for this sentence, but in this case the Doxygen documentation really is your friend, so check out the Doxygen docs on the above mentioned settings- last time I looked you can find the details at http://www.doxygen.nl/manual/config.html.

Quote from this post (it's written by the author of doxygen himself) :

run doxygen -g and change the following options of the generated Doxyfile:

    EXTRACT_ALL            = YES
    HAVE_DOT               = YES
    UML_LOOK               = YES

run doxygen again

The 2 highest upvoted answers are correct. As of today, the only thing I needed to change (from default settings) was to enable generation using dot instead of the built-in generator.

Some important notes:

• Doxygen will not generate an actual full diagram of all classes in the project. It will generate a separate image for each hierarchy. If you have multiple, unrelated class hierarchies you will get multiple images.
• All these diagrams can be found in html/inherits.html or (from the website navigation) classes => class hierarchy => "Go to the textual class hierarchy".
• This is a C++ question, so let's talk about templates. Especially if you inherit from T.
  • Each template instantiation will be correctly considered a different type by Doxygen. Types which inherit from different instantations will have different parent classes on the diagram.
  • If a class template foo inherits from T and the T template type parameter has a default, such default will be assumed. If there is a type bar which inherits from foo<U> where U is different than the default, bar will have a foo<U> parent. foo<> and bar<U> will not have a common parent.
  • If there are multiple class templates which inherit from at least one of their template parameters, Doxygen will assume a common parent for these class templates as long as the template type parameters have exactly the same names in the code. This incentivizes for consistency in naming.
  • CRTP and reverse CRTP just work.
  • Recursive template inheritance trees are not expanded. Any variant instantiation will be displayed to inherit from variant<Ts...>.
  • Class templates with no instantiations are being drawn. They will have a <...> string in their name representing type and non-type parameters which did not have defaults.
  • Class template full and partial specializations are also being drawn. Doxygen generates correct graphs if specializations inherit from different types.

I think you will need to edit the doxys file and set GENERATE_UML (something like that) to true. And you need to have dot/graphviz installed.