doxygen: If dot exists, use it.

Add some cmake logic to use graphviz/dot to include call graphs in
the generated docs. This helps users understand the details of the
library.

Signed-off-by: Robin Getz <[email protected]>

CMakeLists.txt

@@ -356,6 +356,9 @@ find_package(Doxygen)
 if(DOXYGEN_FOUND)
 	option(WITH_DOC "Generate documentation with Doxygen" ON)
 
+	# It is not an error when 'dot' is not found, just switching off the Doxygen's HAVE_DOT option
+	find_package_handle_standard_args (Dot REQUIRED_VARS DOXYGEN_DOT_EXECUTABLE)
+
 	if (WITH_DOC)
 		configure_file(${CMAKE_CURRENT_SOURCE_DIR}/Doxyfile.in ${CMAKE_CURRENT_BINARY_DIR}/Doxyfile @ONLY)
 		set(HTML_DEST_DIR ${CMAKE_CURRENT_BINARY_DIR}/html)

Doxyfile.in

@@ -716,7 +716,7 @@ EXAMPLE_RECURSIVE      = NO
 # that contain images that are to be included in the documentation (see the
 # \image command).
 
-IMAGE_PATH             =
+IMAGE_PATH             = @CMAKE_SOURCE_DIR@/doc
 
 # The INPUT_FILTER tag can be used to specify a program that doxygen should
 # invoke to filter for each input file. Doxygen will invoke the filter program
@@ -1599,7 +1599,7 @@ HIDE_UNDOC_RELATIONS   = YES
 # set to NO
 # The default value is: NO.
 
-HAVE_DOT               = NO
+HAVE_DOT               = @DOXYGEN_DOT_FOUND@
 
 # 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
@@ -1715,7 +1715,7 @@ INCLUDED_BY_GRAPH      = YES
 # The default value is: NO.
 # This tag requires that the tag HAVE_DOT is set to YES.
 
-CALL_GRAPH             = NO
+CALL_GRAPH             = YES
 
 # If the CALLER_GRAPH tag is set to YES then doxygen will generate a caller
 # dependency graph for every global function or class method.
@@ -1726,7 +1726,7 @@ CALL_GRAPH             = NO
 # The default value is: NO.
 # This tag requires that the tag HAVE_DOT is set to YES.
 
-CALLER_GRAPH           = NO
+CALLER_GRAPH           = YES
 
 # If the GRAPHICAL_HIERARCHY tag is set to YES then doxygen will graphical
 # hierarchy of all classes instead of a textual one.
@@ -1771,7 +1771,7 @@ INTERACTIVE_SVG        = NO
 # found. If left blank, it is assumed the dot tool can be found in the path.
 # This tag requires that the tag HAVE_DOT is set to YES.
 
-DOT_PATH               =
+DOT_PATH               = "@DOXYGEN_DOT_PATH@"
 
 # The DOTFILE_DIRS tag can be used to specify one or more directories that
 # contain dot files that are included in the documentation (see the \dotfile
@@ -1802,7 +1802,7 @@ DIAFILE_DIRS           =
 # 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    = 25
 
 # 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
@@ -1814,7 +1814,7 @@ DOT_GRAPH_MAX_NODES    = 50
 # Minimum value: 0, maximum value: 1000, default value: 0.
 # This tag requires that the tag HAVE_DOT is set to YES.
 
-MAX_DOT_GRAPH_DEPTH    = 0
+MAX_DOT_GRAPH_DEPTH    = 10
 
 # Set the DOT_TRANSPARENT tag to YES to generate images with a transparent
 # background. This is disabled by default, because dot on Windows does not seem
@@ -1826,7 +1826,7 @@ MAX_DOT_GRAPH_DEPTH    = 0
 # The default value is: NO.
 # This tag requires that the tag HAVE_DOT is set to YES.
 
-DOT_TRANSPARENT        = NO
+DOT_TRANSPARENT        = YES
 
 # Set the DOT_MULTI_TARGETS tag to YES allow dot to generate multiple output
 # files in one run (i.e. multiple -o and -T options on the command line). This
@@ -1835,7 +1835,7 @@ DOT_TRANSPARENT        = NO
 # The default value is: NO.
 # This tag requires that the tag HAVE_DOT is set to YES.
 
-DOT_MULTI_TARGETS      = YES
+DOT_MULTI_TARGETS      = NO
 
 # If the GENERATE_LEGEND tag is set to YES doxygen will generate a legend page
 # explaining the meaning of the various boxes and arrows in the dot generated