Try all of glut32, freeglut, and libfreeglut on Windows

Author: RyanGlScott

GLUT.cabal

@@ -43,12 +43,6 @@ extra-source-files:
    examples/RedBook8/Chapter01/triangles.frag
    examples/RedBook8/Chapter01/triangles.vert
 
-flag freeglut
-  description:
-    When compiling under Windows, use the freeglut library.
-  default: False
-  manual:  True
-
 flag UseNativeWindowsLibraries
   description:
     When compiling under Windows, use the native libraries instead of e.g. the
@@ -100,17 +94,12 @@ library
   ghc-options: -Wall
   if impl(ghc > 8)
     ghc-options: -Wcompat
-  if os(windows) && (flag(freeglut) || flag(UseNativeWindowsLibraries))
+  if os(windows) && flag(UseNativeWindowsLibraries)
     if arch(i386)
       cpp-options: "-DCALLCONV=stdcall"
     else
       cpp-options: "-DCALLCONV=ccall"
     cc-options: "-DUSE_GETPROCADDRESS"
-    if flag(freeglut)
-      cc-options: "-DUSE_FREEGLUT"
-      extra-libraries: freeglut
-    else
-      extra-libraries: glut32
   else
     cpp-options: "-DCALLCONV=ccall"
     cc-options: "-DUSE_DLSYM"

cbits/HsGLUT.c

@@ -85,16 +85,17 @@ hs_GLUT_getProcAddress(const char *name)
 
   if (firstTime) {
     firstTime = 0;
-#if defined(USE_FREEGLUT)
-    handle = LoadLibrary(TEXT("freeglut"));
+    handle = LoadLibrary(TEXT("glut32"));
+
+    // If glut32 isn't present, try freeglut instead
+    if (!handle) {
+      handle = LoadLibrary(TEXT("freeglut"));
+    }
 
     // The MinGW-w64 version of freeglut prefixes "lib" onto the DLL name
     if (!handle) {
       handle = LoadLibrary(TEXT("libfreeglut"));
     }
-#else
-    handle = LoadLibrary(TEXT("glut32"));
-#endif
   }
 
   return handle ? GetProcAddress(handle, name) : NULL;