doc/sphinx/doxygen.ini.in: Remove CLASS_DIAGRAM

CLASS_DIAGRAM has been obsolete in newer version of doxygen, and
it's enabled if HAVE_DOT and CLASS_GRAPH are set.

This increase DOT_GRAPH_MAX_NODES to avoid dot complaning,
and include dot/graphviz for doxygen.

Signed-off-by: Marius Vlad <marius.vlad@collabora.com>

doc/sphinx/doxygen.ini.in

@@ -1899,15 +1899,6 @@ EXTERNAL_PAGES         = YES
 # Configuration options related to the dot tool
 #---------------------------------------------------------------------------
 
-# If the CLASS_DIAGRAMS tag is set to YES, doxygen will generate a class diagram
-# (in HTML and LaTeX) for classes with base or super classes. Setting the tag to
-# NO turns the diagrams off. Note that this option also works with HAVE_DOT
-# disabled, but it is recommended to install and use dot, since it yields more
-# powerful graphs.
-# The default value is: YES.
-
-CLASS_DIAGRAMS         = YES
-
 # You can include diagrams made with dia in doxygen documentation. Doxygen will
 # then run dia to produce the diagram and insert it in the documentation. The
 # DIA_PATH tag allows you to specify the directory where the dia binary resides.
@@ -1928,7 +1919,7 @@ HIDE_UNDOC_RELATIONS   = YES
 # set to NO
 # The default value is: YES.
 
-HAVE_DOT               = NO
+HAVE_DOT               = YES
 
 # The DOT_NUM_THREADS specifies the number of dot invocations doxygen is allowed
 # to run in parallel. When set to 0 doxygen will base this on the number of
@@ -2157,7 +2148,7 @@ PLANTUML_INCLUDE_PATH  =
 # Minimum value: 0, maximum value: 10000, default value: 50.
 # This tag requires that the tag HAVE_DOT is set to YES.
 
-DOT_GRAPH_MAX_NODES    = 50
+DOT_GRAPH_MAX_NODES    = 250
 
 # The MAX_DOT_GRAPH_DEPTH tag can be used to set the maximum depth of the graphs
 # generated by dot. A depth value of 3 means that only nodes reachable from the

doc/sphinx/meson.build

@@ -1,5 +1,6 @@
 sphinx = find_program('sphinx-build', required: true)
 doxygen = find_program('doxygen', required: true)
+dot = find_program('dot', required: true)
 breathe = find_program('breathe-apidoc', required: true)
 
 sphinx_c = run_command(sphinx, '--version')