Fix Nix pkg-config support

CMAKE_INSTALL_LIBDIR is an absolute path on Nix (which is a valid
thing to do). In such a case two absolute paths would get appended
resulting in a nonsense path that broke pkg-config support.

CMakeLists.txt

@@ -303,9 +303,12 @@ endif()
 sfml_set_option(SFML_INSTALL_PKGCONFIG_FILES ${SFML_INSTALL_PKGCONFIG_DEFAULT} BOOL "TRUE to automatically install pkg-config files so other projects can find SFML")
 
 if(SFML_INSTALL_PKGCONFIG_FILES)
+    # account for CMAKE_INSTALL_LIBDIR potentially being an absolute path
+    file(RELATIVE_PATH SFML_RELATIVE_INSTALL_LIBDIR ${CMAKE_INSTALL_PREFIX} ${CMAKE_INSTALL_FULL_LIBDIR})
+
     # set pkgconfig install directory
     # this could be e.g. macports on mac or msys2 on windows etc.
-    set(SFML_PKGCONFIG_DIR "/${CMAKE_INSTALL_LIBDIR}/pkgconfig")
+    set(SFML_PKGCONFIG_DIR "/${SFML_RELATIVE_INSTALL_LIBDIR}/pkgconfig")
 
     if(SFML_OS_FREEBSD OR SFML_OS_OPENBSD OR SFML_OS_NETBSD)
         set(SFML_PKGCONFIG_DIR "/libdata/pkgconfig")

changelog.md

@@ -7,6 +7,7 @@
 -   Ensure GNUInstallDirs cache vars are included before first used (#2778, #2779)
 -   [macOS] Fix incorrect variable expansion (#2780)
 -   Issue warning when trying to use UCRT MinGW with precompiled MSVCRT depenencies (#2821)
+-   Fix Nix pkg-config support
 
 ### Audio
 

tools/pkg-config/sfml-all.pc.in

@@ -1,6 +1,6 @@
 prefix=@CMAKE_INSTALL_PREFIX@
 exec_prefix=${prefix}
-libdir=${exec_prefix}/@CMAKE_INSTALL_LIBDIR@
+libdir=${exec_prefix}/@SFML_RELATIVE_INSTALL_LIBDIR@
 includedir=${prefix}/include
 
 Name: SFML-all

tools/pkg-config/sfml-audio.pc.in

@@ -1,6 +1,6 @@
 prefix=@CMAKE_INSTALL_PREFIX@
 exec_prefix=${prefix}
-libdir=${exec_prefix}/@CMAKE_INSTALL_LIBDIR@
+libdir=${exec_prefix}/@SFML_RELATIVE_INSTALL_LIBDIR@
 includedir=${prefix}/include
 
 Name: SFML-audio

tools/pkg-config/sfml-graphics.pc.in

@@ -1,6 +1,6 @@
 prefix=@CMAKE_INSTALL_PREFIX@
 exec_prefix=${prefix}
-libdir=${exec_prefix}/@CMAKE_INSTALL_LIBDIR@
+libdir=${exec_prefix}/@SFML_RELATIVE_INSTALL_LIBDIR@
 includedir=${prefix}/include
 
 Name: SFML-graphics

tools/pkg-config/sfml-network.pc.in

@@ -1,6 +1,6 @@
 prefix=@CMAKE_INSTALL_PREFIX@
 exec_prefix=${prefix}
-libdir=${exec_prefix}/@CMAKE_INSTALL_LIBDIR@
+libdir=${exec_prefix}/@SFML_RELATIVE_INSTALL_LIBDIR@
 includedir=${prefix}/include
 
 Name: SFML-network

tools/pkg-config/sfml-system.pc.in

@@ -1,6 +1,6 @@
 prefix=@CMAKE_INSTALL_PREFIX@
 exec_prefix=${prefix}
-libdir=${exec_prefix}/@CMAKE_INSTALL_LIBDIR@
+libdir=${exec_prefix}/@SFML_RELATIVE_INSTALL_LIBDIR@
 includedir=${prefix}/include
 
 Name: SFML-system

tools/pkg-config/sfml-window.pc.in

@@ -1,6 +1,6 @@
 prefix=@CMAKE_INSTALL_PREFIX@
 exec_prefix=${prefix}
-libdir=${exec_prefix}/@CMAKE_INSTALL_LIBDIR@
+libdir=${exec_prefix}/@SFML_RELATIVE_INSTALL_LIBDIR@
 includedir=${prefix}/include
 
 Name: SFML-window