From 3b4787975ec6684878db2b21dc33dcfdc748d51e Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Fri, 30 Apr 2021 09:28:54 -0400
Subject: Add fallback method for loading shared libraries.

---
 chickadee/audio/mpg123.scm |  2 +-
 chickadee/audio/openal.scm |  2 +-
 chickadee/audio/vorbis.scm |  2 +-
 chickadee/config.scm.in    | 26 +++++++++++++++++++++-----
 chickadee/freetype.scm     |  2 +-
 5 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/chickadee/audio/mpg123.scm b/chickadee/audio/mpg123.scm
index 20ff3ea..45c319a 100644
--- a/chickadee/audio/mpg123.scm
+++ b/chickadee/audio/mpg123.scm
@@ -89,7 +89,7 @@
 ;;;
 
 (define mpg123-func
-  (let ((lib (dynamic-link %libmpg123)))
+  (let ((lib (dynamic-link* %libmpg123)))
     (lambda (return-type function-name arg-types)
       (pointer->procedure return-type
                           (dynamic-func function-name lib)
diff --git a/chickadee/audio/openal.scm b/chickadee/audio/openal.scm
index acffe6a..0f0c947 100644
--- a/chickadee/audio/openal.scm
+++ b/chickadee/audio/openal.scm
@@ -95,7 +95,7 @@
 ;;;
 
 (define openal-func
-  (let ((lib (dynamic-link %libopenal)))
+  (let ((lib (dynamic-link* %libopenal)))
     (lambda (return-type function-name arg-types)
       (pointer->procedure return-type
                           (dynamic-func function-name lib)
diff --git a/chickadee/audio/vorbis.scm b/chickadee/audio/vorbis.scm
index e54e943..92574c8 100644
--- a/chickadee/audio/vorbis.scm
+++ b/chickadee/audio/vorbis.scm
@@ -48,7 +48,7 @@
 ;;;
 
 (define vorbis-func
-  (let ((lib (dynamic-link %libvorbisfile)))
+  (let ((lib (dynamic-link* %libvorbisfile)))
     (lambda (return-type function-name arg-types)
       (pointer->procedure return-type
                           (dynamic-func function-name lib)
diff --git a/chickadee/config.scm.in b/chickadee/config.scm.in
index 76f70ce..d540231 100644
--- a/chickadee/config.scm.in
+++ b/chickadee/config.scm.in
@@ -22,7 +22,10 @@
 ;;; Code:
 
 (define-module (chickadee config)
-  #:export (%datadir
+  #:use-module (ice-9 match)
+  #:use-module (system foreign)
+  #:export (dynamic-link*
+            %datadir
             %chickadee-version
             %libopenal
             %libvorbisfile
@@ -30,15 +33,28 @@
             %libfreetype
             scope-datadir))
 
+;; Try to link against multiple library possibilities, such as the
+;; absolute file name discovered by ./configure or by searching the
+;; library load path as a fallback method.  Useful when restributing
+;; relocatable builds.
+(define (dynamic-link* names)
+  (let loop ((names names))
+    (match names
+      (()
+       (error "could not find library" names))
+      ((name . rest)
+       (or (false-if-exception (dynamic-link name))
+           (loop rest))))))
+
 (define %datadir
   (or (getenv "CHICKADEE_DATADIR") "@chickadee_datadir@/chickadee"))
 
 (define %chickadee-version "@PACKAGE_VERSION@")
 
-(define %libopenal "@OPENAL_LIBDIR@/libopenal")
-(define %libvorbisfile "@VORBIS_LIBDIR@/libvorbisfile")
-(define %libmpg123 "@MPG123_LIBDIR@/libmpg123")
-(define %libfreetype "@FREETYPE_LIBDIR@/libfreetype")
+(define %libopenal '("@OPENAL_LIBDIR@/libopenal" "libopenal"))
+(define %libvorbisfile '("@VORBIS_LIBDIR@/libvorbisfile" "libvorbisfile"))
+(define %libmpg123 '("@MPG123_LIBDIR@/libmpg123" "libmpg123"))
+(define %libfreetype '("@FREETYPE_LIBDIR@/libfreetype" "libfreetype"))
 
 (define (scope-datadir file)
   "Append the Chickadee data directory to FILE."
diff --git a/chickadee/freetype.scm b/chickadee/freetype.scm
index 58a1d08..73c0791 100644
--- a/chickadee/freetype.scm
+++ b/chickadee/freetype.scm
@@ -54,7 +54,7 @@
 ;;; Low-level bindings
 ;;;
 
-(define %lib (dynamic-link %libfreetype))
+(define %lib (dynamic-link* %libfreetype))
 
 (define (freetype-func return-type function-name arg-types)
   (pointer->procedure return-type
-- 
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