Improve installed Cmake Config

Adds automatic dependency finding (if they were used).
Adds a way to require a specific version in the find_package(httplib) call.

You should link against the httplib::httplib IMPORTED target, which is
created automatically.

Author: sum01

CMakeLists.txt

@@ -58,17 +58,58 @@ target_compile_definitions(${PROJECT_NAME} INTERFACE
 	$<$<BOOL:${OPENSSL_FOUND}>:CPPHTTPLIB_OPENSSL_SUPPORT>
 )
 
+# Cmake's find_package search path is different based on the system
+# See https://cmake.org/cmake/help/latest/command/find_package.html for the list
+if(CMAKE_SYSTEM_NAME STREQUAL "Windows")
+	set(_TARGET_INSTALL_CMAKEDIR "${CMAKE_INSTALL_PREFIX}/cmake/${PROJECT_NAME}")
+else()
+	# On Non-Windows, it should be /usr/lib/cmake/<name>/<name>Config.cmake
+	# NOTE: This may or may not work for macOS...
+	set(_TARGET_INSTALL_CMAKEDIR "${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME}")
+endif()
+
+include(CMakePackageConfigHelpers)
+
+# Configures the meta-file httplibConfig.cmake.in to replace variables with paths/values/etc.
+configure_package_config_file("${PROJECT_NAME}Config.cmake.in"
+	"${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake"
+	INSTALL_DESTINATION "${_TARGET_INSTALL_CMAKEDIR}"
+	# Passes the includedir install path
+	PATH_VARS CMAKE_INSTALL_FULL_INCLUDEDIR
+	# There aren't any components, so don't use the macro
+	NO_CHECK_REQUIRED_COMPONENTS_MACRO
+)
 
-install(TARGETS ${PROJECT_NAME} EXPORT httplibConfig
-    ARCHIVE  DESTINATION ${CMAKE_INSTALL_LIBDIR}
-    LIBRARY  DESTINATION ${CMAKE_INSTALL_LIBDIR}
-    RUNTIME  DESTINATION ${CMAKE_INSTALL_BINDIR})
+# Creates the version file for version-checking with find_package(httplib)
+write_basic_package_version_file("${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake"
+	VERSION ${CMAKE_PROJECT_VERSION}
+	# Controls how the version-checking works.
+	# AnyNewerVersion just accepts any version >= the target version.
+	# If SemVer is instead desired behaviour, use SameMajorVersion
+	COMPATIBILITY AnyNewerVersion
+)
 
+# Creates the export httplibTargets.cmake
+# This is strictly what holds compilation requirements
+# and linkage information (doesn't find deps though).
+install(TARGETS ${PROJECT_NAME}
+	EXPORT httplibTargets
+	LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
+	ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
+)
 
-install(EXPORT httplibConfig DESTINATION share/httplib/cmake)
 install(FILES httplib.h DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
 
-export(TARGETS ${PROJECT_NAME} FILE httplibConfig.cmake)
+install(FILES
+		"${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake"
+		"${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake"
+	DESTINATION ${_TARGET_INSTALL_CMAKEDIR}
+)
 
-#add_subdirectory(example)
-#add_subdirectory(test)
+# NOTE: This path changes depending on if it's on Windows or Linux
+install(EXPORT httplibTargets
+	# Puts the targets into the httplib namespace
+	# So this makes httplib::httplib linkable after doing find_package(httplib)
+	NAMESPACE ${PROJECT_NAME}::
+	DESTINATION ${_TARGET_INSTALL_CMAKEDIR}
+)

httplibConfig.cmake.in

@@ -0,0 +1,19 @@
+# Generates a macro to auto-configure everything
+@PACKAGE_INIT@
+
+include(CMakeFindDependencyMacro)
+
+# We add find_dependency calls here to not make the end-user have to call them.
+find_dependency(Threads REQUIRED)
+find_dependency(OpenSSL @_HTTPLIB_OPENSSL_MIN_VER@ QUIET)
+find_dependency(ZLIB QUIET)
+
+# Lets the end-user find the header path if needed
+# This is helpful if you're using Cmake's pre-compiled header feature
+set_and_check(HTTPLIB_HEADER_PATH "@PACKAGE_CMAKE_INSTALL_FULL_INCLUDEDIR@/httplib.h")
+# Lets you check if these options were correctly enabled for your install
+set(HTTPLIB_IS_USING_OPENSSL @OPENSSL_FOUND@)
+set(HTTPLIB_IS_USING_ZLIB @ZLIB_FOUND@)
+
+# Brings in the target library
+include("${CMAKE_CURRENT_LIST_DIR}/httplibTargets.cmake")