audacious: add vgmstream plugin

pkgs/applications/audio/audacious/plugins.nix

@@ -41,6 +41,7 @@
 , qtmultimedia
 , qtx11extras
 , soxr
+, vgmstream
 , wavpack
 }:
 
@@ -109,6 +110,10 @@ stdenv.mkDerivation rec {
 
   dontWrapQtApps = true;
 
+  postInstall = ''
+    ln -s ${vgmstream.override { buildAudaciousPlugin = true; }}/lib/audacious/Input/* $out/lib/audacious/Input
+  '';
+
   meta = audacious.meta // {
     description = "Plugins for Audacious music player";
   };

pkgs/applications/audio/vgmstream/default.nix

@@ -1,6 +1,7 @@
-{ stdenv, lib, fetchFromGitHub, cmake, pkg-config
-, mpg123, ffmpeg, libvorbis, libao, jansson, speex
+{ stdenv, lib, fetchFromGitHub, cmake, pkg-config, gtk3
+, audacious, mpg123, ffmpeg, libvorbis, libao, jansson, speex
 , nix-update-script
+, buildAudaciousPlugin ? false  # only build cli by default, pkgs.audacious-plugins sets this to enable plugin support
 }:
 
 stdenv.mkDerivation rec {
@@ -19,16 +20,29 @@ stdenv.mkDerivation rec {
     extraArgs = [ "--version-regex" "r(.*)" ];
   };
 
-  nativeBuildInputs = [ cmake pkg-config ];
+  nativeBuildInputs = [
+    cmake
+    pkg-config
+  ] ++ lib.optional buildAudaciousPlugin gtk3;
 
-  buildInputs = [ mpg123 ffmpeg libvorbis libao jansson speex ];
+  buildInputs = [
+    mpg123
+    ffmpeg
+    libvorbis
+    libao
+    jansson
+    speex
+  ] ++ lib.optional buildAudaciousPlugin (audacious.override { audacious-plugins = null; });
+
+  preConfigure = ''
+    substituteInPlace cmake/dependencies/audacious.cmake \
+      --replace "pkg_get_variable(AUDACIOUS_PLUGIN_DIR audacious plugin_dir)" "set(AUDACIOUS_PLUGIN_DIR \"$out/lib/audacious\")"
+  '';
 
   cmakeFlags = [
-    # There's no nice way to build the audacious plugin without a circular dependency
-    "-DBUILD_AUDACIOUS=OFF"
     # It always tries to download it, no option to use the system one
     "-DUSE_CELT=OFF"
-  ];
+  ] ++ lib.optional (! buildAudaciousPlugin) "-DBUILD_AUDACIOUS=OFF";
 
   meta = with lib; {
     description = "A library for playback of various streamed audio formats used in video games";