Make Vala builds efficient under make, too

And some further finishing touches.

cmake/ValaPrecompile.cmake

@@ -1,7 +1,7 @@
 # - Precompilation of Vala/Genie source files into C sources
 # Makes use of the parallel build ability introduced in Vala 0.11.
-# Might be a bit oversimplified and inefficient but at least it's short.
 # Filenames must be unique within a single compilation unit and that's fine.
+# Props to other Vala module writers, I had to reengineer it to understand it.
 #
 #   vala_precompile (source... - .vala, .gs, .vapi
 #     [DIRECTORY dir]          - Output directory (binary dir by default)
@@ -30,6 +30,7 @@
 # CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 #=============================================================================
 
+cmake_minimum_required (VERSION 2.8.0)
 find_package (Vala 0.11 REQUIRED)
 include (CMakeParseArguments)
 
@@ -43,22 +44,19 @@ endmacro ()
 function (_vala_make_fast file)
 	_vala_parse_source_path ()
 
-	# See `cmake --help-policy CMP0058` for a rather nice explanation.
+	# See `cmake --help-policy CMP0058` for a rather nice explanation
-	# TODO: it says we can fix this situation even for non-Ninja
+	set (_stamp "${output_vapi}")
-	#   (rebuilds are forced even when the external API doesn't change),
+	set (_byproducts)
-	#   just make sure to only use BYPRODUCTS when it's supported by CMake
+	if (NOT "${CMAKE_VERSION}" VERSION_LESS "3.0.2")
-	set (stamp "${output_vapi}")
+		set (_stamp "${output_vapi}.stamp")
-	set (byproducts)
+		set (_byproducts BYPRODUCTS "${output_vapi}")
-	if ("${CMAKE_GENERATOR}" STREQUAL Ninja)
+		set (stamp_target ${stamp_target} "${_stamp}" PARENT_SCOPE)
-		set (stamp "${output_vapi}.stamp")
-		set (byproducts BYPRODUCTS "${output_vapi}")
-		set (stamp_target ${stamp_target} "${stamp}" PARENT_SCOPE)
 	endif ()
 
-	add_custom_command (OUTPUT "${stamp}"
+	add_custom_command (OUTPUT "${_stamp}"
-		${byproducts}
+		${_byproducts}
 		COMMAND ${VALA_COMPILER} "${file}" "--fast-vapi=${output_vapi}"
-		COMMAND ${CMAKE_COMMAND} -E touch "${stamp}"
+		COMMAND ${CMAKE_COMMAND} -E touch "${_stamp}"
 		DEPENDS "${file}"
 		COMMENT "Generating a fast vapi for ${basename}" VERBATIM)
 	set (fast_vapi_deps ${fast_vapi_deps} "${output_vapi}" PARENT_SCOPE)
@@ -70,11 +68,11 @@ function (_vala_make_c file)
 	_vala_parse_source_path ()
 
 	# We need to filter the current file back out or else it creates conflicts
-	set (fast_vapis ${fast_vapi_args})
+	set (_fast_vapis ${fast_vapi_args})
-	list (REMOVE_ITEM fast_vapis "--use-fast-vapi=${output_vapi}")
+	list (REMOVE_ITEM _fast_vapis "--use-fast-vapi=${output_vapi}")
 
 	add_custom_command (OUTPUT "${output_c}"
-		COMMAND ${VALA_COMPILER} "${file}" -C ${compiler_args} ${fast_vapis}
+		COMMAND ${VALA_COMPILER} "${file}" -C ${compiler_args} ${_fast_vapis}
 		COMMAND ${CMAKE_COMMAND} -E touch "${output_c}"
 		DEPENDS "${file}" ${fast_vapi_deps} ${vapis} ${stamp_target}
 		WORKING_DIRECTORY "${directory}"
@@ -121,6 +119,8 @@ function (vala_precompile)
 	foreach (_source ${sources})
 		_vala_make_fast ("${_source}")
 	endforeach ()
+
+	# The target is actually required, or else it may trigger CMP0058
 	if (stamp_target)
 		add_custom_target ("vala_fast_vapis_${counter}" DEPENDS ${stamp_target})
 		set (stamp_target "vala_fast_vapis_${counter}")
@@ -143,14 +143,12 @@ function (vala_precompile)
 # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 
 	set (extra_outputs)
-	set (export_args)
-
 	if (arg_VAPI)
 		if (NOT IS_ABSOLUTE "${arg_VAPI}")
 			set (arg_VAPI "${directory}/${arg_VAPI}")
 		endif ()
 		list (APPEND extra_outputs "${arg_VAPI}")
-		list (APPEND export_args "--internal-vapi=${arg_VAPI}")
+		list (APPEND compiler_args "--internal-vapi=${arg_VAPI}")
 		if (NOT arg_HEADER)
 			message (FATAL_ERROR "HEADER generation required for vapi")
 		endif ()
@@ -160,7 +158,7 @@ function (vala_precompile)
 			set (arg_SYMBOLS "${directory}/${arg_SYMBOLS}")
 		endif ()
 		list (APPEND extra_outputs "${arg_SYMBOLS}")
-		list (APPEND export_args "--symbols=${arg_SYMBOLS}")
+		list (APPEND compiler_args "--symbols=${arg_SYMBOLS}")
 		if (NOT arg_HEADER)
 			message (FATAL_ERROR "HEADER generation required for symbols")
 		endif ()
@@ -177,14 +175,13 @@ function (vala_precompile)
 		list (APPEND extra_outputs
 			"${header_base}${header_ext}"
 			"${header_base}_internal${header_ext}")
-		list (APPEND export_args
+		list (APPEND compiler_args
 			"--header=${header_base}${header_ext}"
 			"--internal-header=${header_base}_internal${header_ext}")
 	endif ()
 	if (extra_outputs)
 		add_custom_command (OUTPUT ${extra_outputs}
-			COMMAND ${VALA_COMPILER}
+			COMMAND ${VALA_COMPILER} -C ${compiler_args} ${fast_vapi_args}
-				-C ${compiler_args} ${export_args} ${fast_vapi_args}
 			DEPENDS ${fast_vapi_deps} ${vapis}
 			COMMENT "Generating vapi/headers/symbols" VERBATIM)
 	endif ()