cmake: add python support

FindCython.cmake was taken from
https://github.com/thewtex/cython-cmake-example. The UseCython module
works, but since it is lacking an installation target setup.py will be
used instead.

python/CMakeLists.txt

@@ -1,33 +1,34 @@
 # EXTRA_DIST = cnghttp2.pxd nghttp2.pyx
 
-# XXX consider https://github.com/thewtex/cython-cmake-example
-
 if(ENABLE_PYTHON_BINDINGS)
-  # XXX add ALL? Will always be invoked as target is always out-of-date though.
-  add_custom_target(python
-    COMMAND ${PYTHON_EXECUTABLE} setup.py build
+
+  add_custom_target(python ALL
+    COMMAND "${PYTHON_EXECUTABLE}" setup.py build
+    VERBATIM
     DEPENDS nghttp2.c
   )
 
-  add_custom_target(python-install
-    COMMAND ${PYTHON_EXECUTABLE} setup.py install --prefix=${DESTDIR}${CMAKE_INSTALL_PREFIX}
-  )
+  configure_file(install-python.cmake.in install-python.cmake ESCAPE_QUOTES @ONLY)
+  install(SCRIPT "${CMAKE_CURRENT_BINARY_DIR}/install-python.cmake")
 
-  # XXX cmake does not have an uninstall target, do not bother with this then.
-  # XXX glob patterns like this will probably not work
-  #add_custom_target(python-uninstall
-  #  COMMAND ${CMAKE} -E remove -f ${DESTDIR}${CMAKE_INSTALL_FULL_LIBDIR}/python*/site-packages/nghttp2.so
-  #  COMMAND ${CMAKE} -E remove -f ${DESTDIR}${CMAKE_INSTALL_FULL_LIBDIR}/python*/site-packages/python_nghttp2-*.egg
-  #)
-
-  # XXX cleaner way to advertise the build artifacts? (note nghttp2.c is cleaned automatically)
-  add_custom_target(python-clean
-    COMMAND ${PYTHON_EXECUTABLE} setup.py clean --all
-  )
-
-  # XXX CYTHON_EXECUTABLE is not set!
   add_custom_command(OUTPUT nghttp2.c
-    COMMAND ${CYTHON_EXECUTABLE} -o nghttp2.c nghttp2.pyx
+    COMMAND "${CYTHON_EXECUTABLE}" -o nghttp2.c
+      "${CMAKE_CURRENT_SOURCE_DIR}/nghttp2.pyx"
+    VERBATIM
     DEPENDS nghttp2.pyx
   )
+## This works also, except that the installation target is missing...
+#  include(UseCython)
+#  cython_add_module(python_nghttp2 nghttp2.pyx)
+#  set_target_properties(python_nghttp2 PROPERTIES
+#    OUTPUT_NAME nghttp2
+#  )
+#  target_include_directories(python_nghttp2 PRIVATE
+#    "${CMAKE_SOURCE_DIR}/lib"
+#    "${CMAKE_SOURCE_DIR}/lib/includes"
+#    "${CMAKE_BINARY_DIR}/lib/includes"
+#  )
+#  target_link_libraries(python_nghttp2
+#    nghttp2
+#  )
 endif()

python/install-python.cmake.in

@@ -0,0 +1,10 @@
+get_filename_component(rootdir "$ENV{DESTDIR}" ABSOLUTE)
+if(rootdir STREQUAL "")
+  set(rootdir /)
+endif()
+execute_process(
+  COMMAND "@PYTHON_EXECUTABLE@" setup.py install
+    --skip-build
+    --root=${rootdir} --prefix=${CMAKE_INSTALL_PREFIX}
+  WORKING_DIRECTORY "@CMAKE_CURRENT_BINARY_DIR@"
+)

python/setup.py.in

@@ -39,6 +39,7 @@ setup(
                                            '@top_srcdir@/lib/includes',
                                            '@top_builddir@/lib/includes'],
                              library_dirs=['@top_builddir@/lib/.libs',
+                                           '@top_builddir@/lib',
                                            '@top_builddir@'],
                              libraries=LIBS)],
     long_description='TBD'