>From 8cd2b22517e04030970bb33abd980577c15c3f01 Mon Sep 17 00:00:00 2001
From: Pierre Langlois <address@hidden>
Date: Sat, 9 Dec 2017 13:05:21 +0000
Subject: [PATCH 1/2] gnu: libid3tag: Create a pkg-config file.

Cleanup packages depending on libid3tag by allowing pkg-config to find it
automatically.

* gnu/package/mp3.scm (libid3tag)[arguments]: Add a create-pkg-config-file
phase.
* gnu/package/audio.scm (audacity)[arguments]: Do not ID3TAG_CFLAGS and
ID3TAG_LIBS environment variables.
* gnu/package/libusb.scm (gmtp)[arguments]: Remove.
---
 gnu/packages/audio.scm  | 10 ++++------
 gnu/packages/libusb.scm |  8 +-------
 gnu/packages/mp3.scm    | 22 ++++++++++++++++++++++
 3 files changed, 27 insertions(+), 13 deletions(-)

diff --git a/gnu/packages/audio.scm b/gnu/packages/audio.scm
index 4f6e4a409..2273f4606 100644
--- a/gnu/packages/audio.scm
+++ b/gnu/packages/audio.scm
@@ -9,6 +9,7 @@
 ;;; Copyright © 2016 ng0 <address@hidden>
 ;;; Copyright © 2016 Lukas Gradl <address@hidden>
 ;;; Copyright © 2016 Tobias Geerinckx-Rice <address@hidden>
+;;; Copyright © 2017 Pierre Langlois <address@hidden>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -345,8 +346,7 @@ engineers, musicians, soundtrack editors and composers.")
        ("which" ,which)))
     (arguments
      `(#:configure-flags
-       (let ((libid3tag (assoc-ref %build-inputs "libid3tag"))
-             (libmad (assoc-ref %build-inputs "libmad"))
+       (let ((libmad (assoc-ref %build-inputs "libmad"))
              (portmidi (assoc-ref %build-inputs "portmidi")))
          (list
           ;; Loading FFmpeg dynamically is problematic.
@@ -357,10 +357,8 @@ engineers, musicians, soundtrack editors and composers.")
                     '("x64_64" "i686"))
               '()
               '("--enable-sse=no"))
-          ;; portmidi, libid3tag and libmad provide no .pc files, so
-          ;; pkg-config fails to find them.  Force their inclusion.
-          (string-append "ID3TAG_CFLAGS=-I" libid3tag "/include")
-          (string-append "ID3TAG_LIBS=-L" libid3tag "/lib -lid3tag -lz")
+          ;; portmidi and libmad provide no .pc files, so pkg-config fails to
+          ;; find them.  Force their inclusion.
           (string-append "LIBMAD_CFLAGS=-I" libmad "/include")
           (string-append "LIBMAD_LIBS=-L" libmad "/lib -lmad")
           (string-append "PORTMIDI_CFLAGS=-I" portmidi "/include")
diff --git a/gnu/packages/libusb.scm b/gnu/packages/libusb.scm
index 31c7dfa44..94c611b2f 100644
--- a/gnu/packages/libusb.scm
+++ b/gnu/packages/libusb.scm
@@ -6,6 +6,7 @@
 ;;; Copyright © 2016 Efraim Flashner <address@hidden>
 ;;; Copyright © 2016 Theodoros Foradis <address@hidden>
 ;;; Copyright © 2017 Jonathan Brielmaier <address@hidden>
+;;; Copyright © 2017 Pierre Langlois <address@hidden>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -295,13 +296,6 @@ proposed for standardization.")
                (base32
                 "0fyi3pdl2g57vr0p46ip2wwzyap3l0by7iqaqygv0yxfcs79l6xj"))))
     (build-system glib-or-gtk-build-system)
-    (arguments
-     '(#:configure-flags
-       (let ((libid3tag (assoc-ref %build-inputs "libid3tag")))
-         (list
-          ;; libid3tag provides no .pc file, so pkg-config fails to find them.
-          (string-append "ID3TAG_CFLAGS=-I" libid3tag "/include")
-          (string-append "ID3TAG_LIBS=-L" libid3tag "/lib -lid3tag -lz")))))
     (inputs
      `(("gtk+" ,gtk+)
        ("flac" ,flac)
diff --git a/gnu/packages/mp3.scm b/gnu/packages/mp3.scm
index fbb924ba5..dd40fc59f 100644
--- a/gnu/packages/mp3.scm
+++ b/gnu/packages/mp3.scm
@@ -99,6 +99,28 @@ This package contains the library.")
               "0lb1w883dc46dajbdvnia5870brl5lvnlk7g7y58y9wpg5p4znk3"))))
    (build-system gnu-build-system)
    (inputs `(("zlib" ,zlib)))
+   (arguments
+     `(#:phases
+        (modify-phases %standard-phases
+          (add-after 'install 'create-pkg-config-file
+            (lambda* (#:key outputs #:allow-other-keys)
+              (let* ((out (assoc-ref outputs "out"))
+                     (pkgconfig-path (string-append out "/lib/pkgconfig")))
+                (mkdir-p pkgconfig-path)
+                (with-output-to-file
+                  (string-append pkgconfig-path "/id3tag.pc")
+                  (lambda _
+                    (format #t
+                      "address@hidden@
+                       exec_prefix=${prefix}/bin~@
+                       libdir=${prefix}/lib~@
+                       includedir=${prefix}/include~@
+                       Name: ID3TAG~@
+                       Description: libid3tag - ID3 tag manipulation library~@
+                       Version: address@hidden@
+                       Libs: -L${libdir} -lid3tag -lz~@
+                       Cflags: -I${includedir}~%"
+                      out ,version)))))))))
    (synopsis "Library for reading ID3 tags")
    (description
     "Libid3tag is a library for reading ID3 tags, both ID3v1 and the various
-- 
2.15.1