#external.rules: Support for external (self-configurable) components

#
# This mechanism can be easily used to implement a `visibility'
# functionality to each make component. Use the settings
#
TARGET_FLAGS=-DWITH_$(TARGET)
TARGET_LIB=-l$(TARGET)
#
# in the local Makefiles, such that any C/C++ source can test the
# availability of another library/package with an #ifdef WITH_...
#
TARGETCFG = $(LIB_PATH)/$(TARGET).cfg

remove-config:
	-$(RM) $(LIB_PATH)/$(TARGET).cfg

#
# This target should rarely be used, since it modifies global
# variables which are used for any other make target.
# This target can be used to FORCE visibility to all other
# makefile targets.
#
global-config: $(LIB_PATH) $(VPATH)GNUmakefile
	echo 'INCLUDES+=$(TARGET_INCLUDES)' >> $(TARGETCFG)
	echo 'SYSCFLAGS+=$(TARGET_CFLAGS)' >> $(TARGETCFG)
	echo 'LDFLAGS+=$(TARGET_LDFLAGS)'  >> $(TARGETCFG)

#
# This target sets some target-specific names, which can be used
# by other target makefiles to test, if this package is available.
# This target can be used to make a package visible to another
# package, which knows of the possible existence of this one.
#
visible: $(LIB_PATH) $(VPATH)GNUmakefile
	echo '$(TARGET)_FLAGS=$(TARGET_FLAGS)' >> $(TARGETCFG)
	echo '$(TARGET)_LIB=$(TARGET_LIB)'     >> $(TARGETCFG)

help:: external.help

help.external: external.help

external.help:
	@ echo 'Make targets from external.rules:'
	@ echo '  global-config .... Add target specific flags to the global configuration'
	@ echo '  visible .......... Add target flags (-DWITH_$(TARGET) ...) to the configuration'
	@ echo '  remove-config .... Remove target configuration file'
	@ echo '    Note: Config is stored in $$LIB_PATH/$$TARGET.cfg'
	@ echo '      which is: $(LIB_PATH)/$(TARGET).cfg'
	@ echo

makevars:: makevars.external

external.makevars: makevars.external

makevars.external:
	@ echo 'Make variables used in external.rules:'
	@ echo '  TARGET ........... the name of the configuration, to be used for makefile inclusion'
	@ echo '  LIB_PATH ......... where to create the configuration file'
	@ echo '  VPATH ............ from where this make is invoked'
	@ echo '  TARGETCFG ........ full path name of the make include file for this target'
	@ echo ' For the "global-config" target:'
	@ echo '  TARGET_INCLUDES .. include paths to be added to the global INCLUDES variable'
	@ echo '  TARGET_CFLAGS .... C flags to be added to the global CFLAGS variable'
	@ echo '  TARGET_LDFLAGS ... Linker flags to be added to the global LDFLAGS variable'
	@ echo ' For the "visible" target:'
	@ echo '  TARGET_FLAGS .... The content of the global $(TARGET)_FLAGS variable'
	@ echo '  TARGET_LIB ...... The content of the global $(TARGET)_LIB variable'
	@ echo ''

debug:: debug.external

external.debug: debug.external

debug.external:
	@ echo 'Make variables used in external.rules:'
	@ echo '  TARGET ........... $(TARGET)' 
	@ echo '  LIB_PATH ......... $(LIB_PATH)'
	@ echo '  VPATH ............ $(VPATH)'
	@ echo '  TARGETCFG ........ $(TARGETCFG)'
	@ echo '  TARGET_CFLAGS .... $(TARGET_CFLAGS)'
	@ echo '  TARGET_LDFLAGS ... $(TARGET_LDFLAGS)'
	@ echo '  TARGET_INCLUDES... $(TARGET_INCLUDES)'
	@ echo '  TARGET_FLAGS ..... $(TARGET_FLAGS)'
	@ echo '  TARGET_LIB ....... $(TARGET_LIB)'
	@ echo ''