From bfa61ccf64db099f182da72854835a3a6263b981 Mon Sep 17 00:00:00 2001
From: "FeRD (Frank Dana)" <ferdnyc@gmail.com>
Date: Mon, 23 Jan 2023 16:09:54 -0500
Subject: Help: Modernize PackageConfigHelpers example

The example shown in the module documentation for
CMakePackageConfigHelpers was showing its age, by:

1. Hardcoding directory prefixes (`etc/`, `lib/`, etc.) instead of
   using GNUInstallDirs
2. Handwaving `set()` commands (incorrectly!) as:
     `set(VAR dir/ ... CACHE )`
   which should, at the very least, be:
     `set(VAR dir/ CACHE ... )`
3. Installing CMake configuration files to `lib/Foo/cmake/`, when
   current practice favors `${CMAKE_INSTALL_LIBDIR}/cmake/Foo/`

This updated example addresses all of those issues.
---
 Modules/CMakePackageConfigHelpers.cmake | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/Modules/CMakePackageConfigHelpers.cmake b/Modules/CMakePackageConfigHelpers.cmake
index 6f5702a..1dc850a 100644
--- a/Modules/CMakePackageConfigHelpers.cmake
+++ b/Modules/CMakePackageConfigHelpers.cmake
@@ -200,14 +200,16 @@ Example using both :command:`configure_package_config_file` and
 
 .. code-block:: cmake
 
-   set(INCLUDE_INSTALL_DIR include/ ... CACHE )
-   set(LIB_INSTALL_DIR lib/ ... CACHE )
-   set(SYSCONFIG_INSTALL_DIR etc/foo/ ... CACHE )
+   include(GNUInstallDirs)
+   set(INCLUDE_INSTALL_DIR ${CMAKE_INSTALL_INCLUDEDIR}/Foo
+       CACHE PATH "Location of header files" )
+   set(SYSCONFIG_INSTALL_DIR ${CMAKE_INSTALL_SYSCONFDIR}/foo
+       CACHE PATH "Location of configuration files" )
    #...
    include(CMakePackageConfigHelpers)
    configure_package_config_file(FooConfig.cmake.in
      ${CMAKE_CURRENT_BINARY_DIR}/FooConfig.cmake
-     INSTALL_DESTINATION ${LIB_INSTALL_DIR}/Foo/cmake
+     INSTALL_DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/Foo
      PATH_VARS INCLUDE_INSTALL_DIR SYSCONFIG_INSTALL_DIR)
    write_basic_package_version_file(
      ${CMAKE_CURRENT_BINARY_DIR}/FooConfigVersion.cmake
@@ -215,7 +217,7 @@ Example using both :command:`configure_package_config_file` and
      COMPATIBILITY SameMajorVersion )
    install(FILES ${CMAKE_CURRENT_BINARY_DIR}/FooConfig.cmake
                  ${CMAKE_CURRENT_BINARY_DIR}/FooConfigVersion.cmake
-           DESTINATION ${LIB_INSTALL_DIR}/Foo/cmake )
+           DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/Foo )
 
 ``FooConfig.cmake.in``:
 
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