nixpkgs/pkgs/development/libraries/SDL2/find-headers.patch

diff -ru3 SDL2-2.0.14/sdl2-config.cmake.in SDL2-2.0.14-new/sdl2-config.cmake.in
--- SDL2-2.0.14/sdl2-config.cmake.in	2020-12-21 18:44:36.000000000 +0100
+++ SDL2-2.0.14-new/sdl2-config.cmake.in	2021-01-16 23:53:40.721121792 +0100
@@ -6,7 +6,8 @@
 set(SDL2_PREFIX "@prefix@")
 set(SDL2_EXEC_PREFIX "@prefix@")
 set(SDL2_LIBDIR "@libdir@")
-set(SDL2_INCLUDE_DIRS "@includedir@/SDL2")
+set(SDL2_INCLUDE_DIRS "@includedir@/SDL2" $ENV{SDL2_PATH})
+separate_arguments(SDL2_INCLUDE_DIRS)
 set(SDL2_LIBRARIES "-L${SDL2_LIBDIR} @SDL_RLD_FLAGS@ @SDL_LIBS@")
 string(STRIP "${SDL2_LIBRARIES}" SDL2_LIBRARIES)
 
@@ -20,14 +21,14 @@
 
   add_library(SDL2::SDL2 SHARED IMPORTED)
   set_target_properties(SDL2::SDL2 PROPERTIES
-    INTERFACE_INCLUDE_DIRECTORIES "@includedir@/SDL2"
+    INTERFACE_INCLUDE_DIRECTORIES "${SDL2_INCLUDE_DIRS}"
     IMPORTED_LINK_INTERFACE_LANGUAGES "C"
     IMPORTED_LOCATION "@libdir@/${CMAKE_SHARED_LIBRARY_PREFIX}SDL2${CMAKE_SHARED_LIBRARY_SUFFIX}"
     INTERFACE_LINK_LIBRARIES "${SDL2_EXTRA_LINK_FLAGS}")
 
   add_library(SDL2::SDL2-static STATIC IMPORTED)
   set_target_properties(SDL2::SDL2-static PROPERTIES
-    INTERFACE_INCLUDE_DIRECTORIES "@includedir@/SDL2"
+    INTERFACE_INCLUDE_DIRECTORIES "${SDL2_INCLUDE_DIRS}"
     IMPORTED_LINK_INTERFACE_LANGUAGES "C"
     IMPORTED_LOCATION "@libdir@/${CMAKE_STATIC_LIBRARY_PREFIX}SDL2${CMAKE_STATIC_LIBRARY_SUFFIX}"
     INTERFACE_LINK_LIBRARIES "${SDL2_EXTRA_LINK_FLAGS_STATIC}")
diff -ru3 SDL2-2.0.14/sdl2-config.in SDL2-2.0.14-new/sdl2-config.in
--- SDL2-2.0.14/sdl2-config.in	2020-12-21 18:44:36.000000000 +0100
+++ SDL2-2.0.14-new/sdl2-config.in	2021-01-16 23:57:11.940353171 +0100
@@ -42,7 +42,11 @@
       echo @SDL_VERSION@
       ;;
     --cflags)
-      echo -I@includedir@/SDL2 @SDL_CFLAGS@
+      SDL_CFLAGS=""
+      for i in @includedir@/SDL2 $SDL2_PATH; do
+        SDL_CFLAGS="$SDL_CFLAGS -I$i"
+      done
+      echo $SDL_CFLAGS @SDL_CFLAGS@
       ;;
 @ENABLE_SHARED_TRUE@    --libs)
 @ENABLE_SHARED_TRUE@      echo -L@libdir@ @SDL_RLD_FLAGS@ @SDL_LIBS@