enh: Add option to add installation to CMake’s package registry

CMakeLists.txt

@@ -164,6 +164,8 @@ gflags_define (BOOL BUILD_TESTING              "Enable build of the unit tests a
 gflags_define (BOOL INSTALL_HEADERS            "Request installation of headers and other development files."             ON  OFF)
 gflags_define (BOOL INSTALL_SHARED_LIBS        "Request installation of shared libraries."                                ON  ON)
 gflags_define (BOOL INSTALL_STATIC_LIBS        "Request installation of static libraries."                                ON  OFF)
+gflags_define (BOOL REGISTER_BUILD_DIR         "Request entry of build directory in CMake's package registry."            OFF OFF)
+gflags_define (BOOL REGISTER_INSTALL_PREFIX    "Request entry of installed package in CMake's package registry."          ON  OFF)
 
 gflags_property (BUILD_STATIC_LIBS   ADVANCED TRUE)
 gflags_property (INSTALL_HEADERS     ADVANCED TRUE)
@@ -523,7 +525,12 @@ endif ()
 # support direct use of build tree
 set (INSTALL_PREFIX_REL2CONFIG_DIR .)
 export (TARGETS ${TARGETS} FILE "${PROJECT_BINARY_DIR}/${EXPORT_NAME}.cmake")
-export (PACKAGE gflags)
+if (REGISTER_BUILD_DIR)
+  export (PACKAGE ${PACKAGE_NAME})
+endif ()
+if (REGISTER_INSTALL_PREFIX)
+  register_gflags_package(${CONFIG_INSTALL_DIR})
+endif ()
 configure_file (cmake/config.cmake.in "${PROJECT_BINARY_DIR}/${PACKAGE_NAME}-config.cmake" @ONLY)
 
 # ----------------------------------------------------------------------------

cmake/utils.cmake

@@ -161,3 +161,41 @@ macro (add_gflags_test name expected_rc expected_output unexpected_output cmd)
     WORKING_DIRECTORY "${GFLAGS_FLAGFILES_DIR}"
   )
 endmacro ()
+
+# ------------------------------------------------------------------------------
+## Register installed package with CMake
+#
+# This function adds an entry to the CMake registry for packages with the
+# path of the directory where the package configuration file of the installed
+# package is located in order to help CMake find the package in a custom
+# installation prefix. This differs from CMake's export(PACKAGE) command
+# which registers the build directory instead.
+function (register_gflags_package CONFIG_DIR)
+  if (NOT IS_ABSOLUTE "${CONFIG_DIR}")
+    set (CONFIG_DIR "${CMAKE_INSTALL_PREFIX}/${CONFIG_DIR}")
+  endif ()
+  string (MD5 REGISTRY_ENTRY "${CONFIG_DIR}")
+  if (WIN32)
+    install (CODE
+      "execute_process (
+         COMMAND reg add \"HKCU\\\\Software\\\\Kitware\\\\CMake\\\\Packages\\\\${PACKAGE_NAME}\" /v \"${REGISTRY_ENTRY}\" /d \"${CONFIG_DIR}\" /t REG_SZ /f
+         RESULT_VARIABLE RT
+         ERROR_VARIABLE  ERR
+         OUTPUT_QUIET
+       )
+       if (RT EQUAL 0)
+         message (STATUS \"Register:   Added HKEY_CURRENT_USER\\\\Software\\\\Kitware\\\\CMake\\\\Packages\\\\${PACKAGE_NAME}\\\\${REGISTRY_ENTRY}\")
+       else ()
+         string (STRIP \"\${ERR}\" ERR)
+         message (STATUS \"Register:   Failed to add registry entry: \${ERR}\")
+       endif ()"
+    )
+  elseif (IS_DIRECTORY "$ENV{HOME}")
+    file (WRITE "${PROJECT_BINARY_DIR}/${PACKAGE_NAME}-registry-entry" "${CONFIG_DIR}")
+    install (
+      FILES       "${PROJECT_BINARY_DIR}/${PACKAGE_NAME}-registry-entry"
+      DESTINATION "$ENV{HOME}/.cmake/packages/${PACKAGE_NAME}"
+      RENAME      "${REGISTRY_ENTRY}"
+    )
+  endif ()
+endfunction ()