gnu: Add libmypaint.

* gnu/packages/gimp.scm (libmypaint): New variable.

gnu/packages/gimp.scm

@@ -39,6 +39,7 @@ (define-module (gnu packages gimp)
   #:use-module (gnu packages pdf)
   #:use-module (gnu packages photo)
   #:use-module (gnu packages python)
+  #:use-module (gnu packages web)
   #:use-module (gnu packages xorg))
 
 (define-public babl
@@ -243,3 +244,31 @@ (define-public gimp-fourier
 can draw or apply filters in fourier space and get the modified image with an
 inverse fourier transform.")
     (license license:gpl3+)))
+
+(define-public libmypaint
+  (package
+    (name "libmypaint")
+    (version "1.3.0")
+    (source (origin
+              (method url-fetch)
+              (uri (string-append "https://github.com/mypaint/libmypaint/"
+                                  "releases/download/v" version "/libmypaint-"
+                                  version ".tar.xz"))
+              (sha256
+               (base32
+                "0wd6jk69vmhsq1mdw96v0fh7b28n3glkr5ca466zcq7agzaxj1va"))))
+    (build-system gnu-build-system)
+    (native-inputs
+     `(("intltool" ,intltool)
+       ("pkg-config" ,pkg-config)))
+    ;; As needed by 'libmypaint.pc'.
+    (propagated-inputs
+     `(("json-c" ,json-c)
+       ("gobject-introspection" ,gobject-introspection)))
+    (inputs
+     `(("glib" ,glib)))
+    (synopsis "Artistic brushes library")
+    (description "Libmypaint, also called \"brushlib\", is a library for making
+brushstrokes which is used by MyPaint and GIMP.")
+    (home-page "http://mypaint.org")
+    (license license:isc)))