doc: build and install doxygen api docs

In order to support out of tree builds and avoid hardcoding version
number, generate `doc/config.dox` from configure.

configure

@@ -417,6 +417,15 @@ else
     have_emacs=0
 fi
 
+printf "Checking if doxygen is available... "
+if command -v doxygen > /dev/null 2>&1; then
+    printf "Yes.\n"
+    have_doxygen=1
+else
+    printf "No (so will not install api docs)\n"
+    have_doxygen=0
+fi
+
 printf "Checking if sphinx is available and supports nroff output... "
 if hash sphinx-build > /dev/null 2>&1 && python -m sphinx.writers.manpage > /dev/null 2>&1 ; then
     printf "Yes.\n"
@@ -829,6 +838,9 @@ HAVE_SPHINX=${have_sphinx}
 # Whether there's a rst2man binary available for building documentation
 HAVE_RST2MAN=${have_rst2man}
 
+# Whether there's a doxygen binary available for building api documentation
+HAVE_DOXYGEN=${have_doxygen}
+
 # The directory to which desktop files should be installed
 desktop_dir = \$(prefix)/share/applications
 

doc/Makefile.local

@@ -12,10 +12,12 @@ mkdocdeps := python $(srcdir)/$(dir)/mkdocdeps.py
 
 # Internal variables.
 ALLSPHINXOPTS   := -d $(DOCBUILDDIR)/doctrees $(SPHINXOPTS) $(srcdir)/$(dir)
+APIMAN		:= $(DOCBUILDDIR)/man/man3/notmuch.3
+DOXYFILE	:= $(srcdir)/$(dir)/doxygen.cfg
 
 .PHONY: sphinx-html sphinx-texinfo sphinx-info
 
-.PHONY: install-man build-man
+.PHONY: install-man build-man apidocs install-apidocs
 
 %.gz: %
 	rm -f $@ && gzip --stdout $^ > $@
@@ -56,6 +58,23 @@ else
 endif
 	touch ${MAN_ROFF_FILES} $@
 
+install-man: install-apidocs
+
+ifeq ($(HAVE_DOXYGEN),1)
+MAN_GZIP_FILES += ${APIMAN}.gz
+apidocs: $(APIMAN)
+install-apidocs: apidocs
+	mkdir -p "$(DESTDIR)$(mandir)/man3"
+	install -m0644  $(DOCBUILDDIR)/man/man3/*.3.gz  $(DESTDIR)/$(mandir)/man3
+
+$(APIMAN): $(dir)/config.dox $(srcdir)/$(dir)/doxygen.cfg $(srcdir)/lib/notmuch.h
+	mkdir -p $(DOCBUILDDIR)/man/man3
+	doxygen $(DOXYFILE)
+else
+apidocs:
+install-apidocs:
+endif
+
 # Do not try to build or install man pages if a man page converter is
 # not available.
 ifeq ($(HAVE_SPHINX)$(HAVE_RST2MAN),00)
@@ -74,8 +93,12 @@ install-man: ${MAN_GZIP_FILES}
 	cd $(DESTDIR)/$(mandir)/man1 && ln -sf notmuch.1.gz notmuch-setup.1.gz
 endif
 
+$(dir)/config.dox: version.stamp
+	echo "PROJECT_NAME = \"Notmuch $(VERSION)\"" > $@
+	echo "INPUT=${srcdir}/lib/notmuch.h" >> $@
+
 $(dir)/docdeps.mk: $(dir)/conf.py $(dir)/mkdocdeps.py
 	$(mkdocdeps) $(srcdir)/doc $(DOCBUILDDIR) $@
 
 CLEAN := $(CLEAN) $(DOCBUILDDIR) $(dir)/docdeps.mk $(DOCBUILDDIR)/.roff.stamp
-CLEAN := $(CLEAN) $(MAN_GZIP_FILES) $(MAN_ROFF_FILES) $(dir)/conf.pyc
+CLEAN := $(CLEAN) $(MAN_GZIP_FILES) $(MAN_ROFF_FILES) $(dir)/conf.pyc $(dir)/config.dox

doc/doxygen.cfg

@@ -4,11 +4,11 @@
 # Project related configuration options
 #---------------------------------------------------------------------------
 DOXYFILE_ENCODING      = UTF-8
-PROJECT_NAME           = "Notmuch 0.18"
+@INCLUDE	       =  "doc/config.dox"
 PROJECT_NUMBER         =
 PROJECT_BRIEF          =
 PROJECT_LOGO           =
-OUTPUT_DIRECTORY       =
+OUTPUT_DIRECTORY       = doc/_build
 CREATE_SUBDIRS         = NO
 OUTPUT_LANGUAGE        = English
 BRIEF_MEMBER_DESC      = YES
@@ -96,7 +96,6 @@ WARN_LOGFILE           =
 #---------------------------------------------------------------------------
 # configuration options related to the input files
 #---------------------------------------------------------------------------
-INPUT                  = lib/notmuch.h
 INPUT_ENCODING         = UTF-8
 FILE_PATTERNS          =
 RECURSIVE              = NO