gnu: Add sdl2-image.

* gnu/packages/sdl.scm (propagated-inputs-with-sdl2): New procedure.
(sdl2-image): New variable.

gnu/packages/sdl.scm

@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2013 David Thompson <dthompson2@worcester.edu>
+;;; Copyright © 2013, 2015 David Thompson <dthompson2@worcester.edu>
 ;;; Copyright © 2014 Mark H Weaver <mhw@netris.org>
 ;;; Copyright © 2015 Sou Bunnbu <iyzsong@gmail.com>
 ;;; Copyright © 2015 Alex Kost <alezost@gmail.com>
@@ -20,6 +20,7 @@
 ;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
 
 (define-module (gnu packages sdl)
+  #:use-module (ice-9 match)
   #:use-module (gnu packages)
   #:use-module ((guix licenses) #:hide (freetype))
   #:use-module (guix packages)
@@ -299,6 +300,29 @@ directory.")
     (home-page (package-home-page sdl))
     (license (package-license sdl))))
 
+(define (propagated-inputs-with-sdl2 package)
+  "Replace the \"sdl\" propagated input of PACKAGE with SDL2."
+  (map (match-lambda
+         (("sdl" _)
+          `("sdl2" ,sdl2))
+         (other other))
+       (package-propagated-inputs package)))
+
+(define-public sdl2-image
+  (package (inherit sdl-image)
+    (name "sdl2-image")
+    (version "2.0.0")
+    (source (origin
+              (method url-fetch)
+              (uri
+               (string-append "http://www.libsdl.org/projects/SDL_image/release/SDL2_image-"
+                              version ".tar.gz"))
+              (sha256
+               (base32
+                "0d3jlhkmr0j5a2dd5h6y29jfcsj7mkl16wghm6n3nqqp7g3ib65j"))))
+    (propagated-inputs
+     (propagated-inputs-with-sdl2 sdl-image))))
+
 (define-public guile-sdl
   (package
     (name "guile-sdl")