cmake: Combine installed packages

This change combines previous installed "cmake/LibmultiprocessLibConfig.cmake"
and "cmake/LibmultiprocessBinConfig.cmake" files into a single
"cmake/Libmultiprocess/LibmultiprocessConfig.cmake" file, so it can be imported
with "find_package(Libmultiprocess)". The previous locations which were set in
#97 were not actually
compatible with find_package search behavior by default.

The change also adds some documentation about using the new package to
doc/install.md.

Author: ryanofsky

CMakeLists.txt

@@ -64,16 +64,6 @@ set_target_properties(multiprocess PROPERTIES
 install(TARGETS multiprocess EXPORT LibTargets
   ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR} COMPONENT lib
   PUBLIC_HEADER DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/mp COMPONENT lib)
-include(CMakePackageConfigHelpers)
-configure_package_config_file(
-  ${PROJECT_SOURCE_DIR}/cmake/LibmultiprocessLibConfig.cmake.in
-  LibmultiprocessLibConfig.cmake
-  INSTALL_DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake
-  NO_SET_AND_CHECK_MACRO)
-install(
-  FILES
-    ${CMAKE_CURRENT_BINARY_DIR}/LibmultiprocessLibConfig.cmake
-  DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake COMPONENT lib)
 
 # mpgen code generator
 add_executable(mpgen src/mp/gen.cpp $<TARGET_OBJECTS:util>)
@@ -92,16 +82,6 @@ set_target_properties(mpgen PROPERTIES
 install(TARGETS mpgen EXPORT BinTargets
   RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR} COMPONENT bin
   PUBLIC_HEADER DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/mp COMPONENT bin)
-include(CMakePackageConfigHelpers)
-configure_package_config_file(
-  ${PROJECT_SOURCE_DIR}/cmake/LibmultiprocessBinConfig.cmake.in
-  LibmultiprocessBinConfig.cmake
-  INSTALL_DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake
-  NO_SET_AND_CHECK_MACRO)
-install(
-  FILES
-    ${CMAKE_CURRENT_BINARY_DIR}/LibmultiprocessBinConfig.cmake
-  DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake COMPONENT bin)
 
 # makefile include to invoke mpgen code generator, for downstream Make projects
 install(FILES "include/mpgen.mk"
@@ -126,13 +106,28 @@ install(EXPORT LibTargets
   NAMESPACE Libmultiprocess::
   DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/Libmultiprocess COMPONENT lib)
 
+# CMake find_package config file, for downstream CMake projects
+include(CMakePackageConfigHelpers)
+configure_package_config_file(
+  ${PROJECT_SOURCE_DIR}/cmake/Config.cmake.in
+  LibmultiprocessConfig.cmake
+  INSTALL_DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/Libmultiprocess
+  NO_SET_AND_CHECK_MACRO)
+install(
+  FILES
+    ${CMAKE_CURRENT_BINARY_DIR}/LibmultiprocessConfig.cmake
+  DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/Libmultiprocess
+  COMPONENT common)
+
 # Makefile targets to support "make install-bin" "make install-lib"
 add_custom_target(install-bin
   COMMAND ${CMAKE_COMMAND} -DCOMPONENT=bin -P ${CMAKE_CURRENT_BINARY_DIR}/cmake_install.cmake
+  COMMAND ${CMAKE_COMMAND} -DCOMPONENT=common -P ${CMAKE_CURRENT_BINARY_DIR}/cmake_install.cmake
   VERBATIM)
 add_dependencies(install-bin mpgen)
 add_custom_target(install-lib
   COMMAND ${CMAKE_COMMAND} -DCOMPONENT=lib -P ${CMAKE_CURRENT_BINARY_DIR}/cmake_install.cmake
+  COMMAND ${CMAKE_COMMAND} -DCOMPONENT=common -P ${CMAKE_CURRENT_BINARY_DIR}/cmake_install.cmake
   VERBATIM)
 add_dependencies(install-lib multiprocess)
 

cmake/Config.cmake.in

@@ -0,0 +1,30 @@
+@PACKAGE_INIT@
+
+# CMake find_package compatible package file, for downstream CMake projects
+#
+# Based on https://cmake.org/cmake/help/latest/guide/importing-exporting/index.html#adding-components
+
+set(_Libmultiprocess_supported_components Bin Lib)
+
+# If no components specified, include all components.
+list(LENGTH Libmultiprocess_FIND_COMPONENTS Libmultiprocess_FIND_COMPONENTS_len)
+if(Libmultiprocess_FIND_COMPONENTS_len EQUAL 0)
+    set(Libmultiprocess_FIND_COMPONENTS ${_Libmultiprocess_supported_components})
+endif()
+
+if ("Bin" IN_LIST Libmultiprocess_FIND_COMPONENTS)
+  include("${CMAKE_CURRENT_LIST_DIR}/TargetCapnpSources.cmake")
+endif()
+
+if ("Lib" IN_LIST Libmultiprocess_FIND_COMPONENTS)
+  include(CMakeFindDependencyMacro)
+  find_dependency(CapnProto)
+endif()
+
+foreach(_comp ${Libmultiprocess_FIND_COMPONENTS})
+  if (NOT _comp IN_LIST _Libmultiprocess_supported_components)
+    set(Libmultiprocess_FOUND False)
+    set(Libmultiprocess_NOT_FOUND_MESSAGE "Unsupported component: ${_comp}")
+  endif()
+  include("${CMAKE_CURRENT_LIST_DIR}/${_comp}Targets.cmake")
+endforeach()

cmake/LibmultiprocessBinConfig.cmake.in

@@ -18,3 +18,35 @@ make
 make check # Optionally build and run tests
 make install
 ```
+
+To build with libmultiprocess in a CMake project can specify:
+
+```cmake
+find_package(Libmultiprocess)
+target_capnp_sources(mytarget ${CMAKE_CURRENT_SOURCE_DIR} myschema.capnp)
+```
+
+Which will locate the libmultiprocess cmake package, and call the
+`target_capnp_sources` function to generate C++ files and link them into a
+library or executable target. See `example/CMakeLists.txt` for a complete
+example.
+
+To build with libmultiprocess in a non-CMake project can use installed
+`<prefix>/include/mpgen.mk` Makefile rule to generate C++ files, and
+`<prefix>/lib/pkgconfig/libmultiprocess.pc` pkg-config definition to link
+against the runtime library.
+
+For cross-compilation, it may be useful to build the runtime library and code
+generation binaries separately, which can be done with:
+
+```sh
+make install-bin # install bin/mpgen and related files
+make install-lib # install lib/libmultiprocess.a and related files
+```
+
+It is also possible to import CMake targets separately with:
+
+```cmake
+find_package(Libmultiprocess COMPONENTS Bin)
+find_package(Libmultiprocess COMPONENTS Lib)
+```