Make libcanberra support optional

Add a configure switch:

 --with-libcanberra=[yes/no/auto]

(defaulting to auto); if libcanberra is not found or explicitly
disabled, then the default system bell will be used for the bell
sound and no switch workspace sound is played.

https://bugzilla.gnome.org/show_bug.cgi?id=609585

configure.in

@@ -124,7 +124,7 @@ if test "x$GCC" = "xyes"; then
 fi
 changequote([,])dnl
 
-MUTTER_PC_MODULES='gtk+-2.0 >= 2.10.0 pango >= 1.2.0 libcanberra-gtk'
+MUTTER_PC_MODULES='gtk+-2.0 >= 2.10.0 pango >= 1.2.0'
 
 AC_ARG_ENABLE(gconf,
   AC_HELP_STRING([--disable-gconf],
@@ -160,6 +160,11 @@ AC_ARG_WITH(introspection,
                  [disable the use of GObject introspection]),,
   with_introspection=auto)
 
+AC_ARG_WITH(libcanberra,
+  AC_HELP_STRING([--without-libcanberra],
+                 [disable the use of libcanberra for playing sounds]),,
+  with_libcanberra=auto)
+
 AC_ARG_ENABLE(xsync,
   AC_HELP_STRING([--disable-xsync],
                  [disable mutter's use of the XSync extension]),,
@@ -212,6 +217,24 @@ else
   echo "Building without libstartup-notification"
 fi
 
+have_libcanberra=no
+AC_MSG_CHECKING([libcanberra-gtk])
+if test x$with_libcanberra = xno ; then
+  AC_MSG_RESULT([disabled])
+else
+  if $PKG_CONFIG --exists libcanberra-gtk; then
+    have_libcanberra=yes
+    AC_MSG_RESULT(yes)
+    MUTTER_PC_MODULES="$MUTTER_PC_MODULES libcanberra-gtk"
+    AC_DEFINE([HAVE_LIBCANBERRA], 1, [Building with libcanberra for playing sounds])
+  else
+    AC_MSG_RESULT(no)
+    if test x$with_libcanberra = xyes ; then
+      AC_MSG_ERROR([libcanberra forced and libcanberra-gtk was not found])
+    fi
+  fi
+fi
+
 XCOMPOSITE_VERSION=0.2
 
 AC_MSG_CHECKING([Xcomposite >= $XCOMPOSITE_VERSION])
@@ -532,6 +555,7 @@ mutter-$VERSION:
 	XFree86 Xinerama:         ${use_xfree_xinerama}
 	Solaris Xinerama:         ${use_solaris_xinerama}
 	Startup notification:     ${have_startup_notification}
+	libcanberra:              ${have_libcanberra}
 	Introspection:            ${have_introspection}
 	Session management:       ${found_sm}
 	Shape extension:          ${found_shape}

src/core/bell.c

@@ -52,7 +52,9 @@
 #include "bell.h"
 #include "screen-private.h"
 #include "prefs.h"
+#ifdef HAVE_LIBCANBERRA
 #include <canberra-gtk.h>
+#endif
 
 /**
  * Flashes one entire screen.  This is done by making a window the size of the
@@ -287,6 +289,7 @@ meta_bell_notify (MetaDisplay *display,
   if (meta_prefs_get_visual_bell ()) 
     bell_visual_notify (display, xkb_ev);
 
+#ifdef HAVE_LIBCANBERRA
   if (meta_prefs_bell_is_audible ())
     {
       ca_proplist *p;
@@ -326,12 +329,27 @@ meta_bell_notify (MetaDisplay *display,
                               xkb_bell_event->percent);
         }
     }
+#endif /* HAVE_LIBCANBERRA */
 }
 #endif /* HAVE_XKB */
 
 void
 meta_bell_set_audible (MetaDisplay *display, gboolean audible)
 {
+#ifdef HAVE_XKB
+#ifdef HAVE_LIBCANBERRA
+  /* When we are playing sounds using libcanberra support, we handle the
+   * bell whether its an audible bell or a visible bell */
+  gboolean enable_system_bell = FALSE;
+#else
+  gboolean enable_system_bell = audible;
+#endif /* HAVE_LIBCANBERRA */
+
+  XkbChangeEnabledControls (display->xdisplay,
+                            XkbUseCoreKbd,
+                            XkbAudibleBellMask,
+                            enable_system_bell ? XkbAudibleBellMask : 0);
+#endif /* HAVE_XKB */
 }
 
 gboolean
@@ -358,10 +376,7 @@ meta_bell_init (MetaDisplay *display)
 		       XkbUseCoreKbd,
 		       XkbBellNotifyMask,
 		       XkbBellNotifyMask);
-      XkbChangeEnabledControls (display->xdisplay,
-				XkbUseCoreKbd,
-				XkbAudibleBellMask,
-                                0);
+      meta_bell_set_audible (display, meta_prefs_bell_is_audible ());
       if (visual_bell_auto_reset) {
 	XkbSetAutoResetControls (display->xdisplay,
 				 XkbAudibleBellMask,

src/core/workspace.c

@@ -33,7 +33,9 @@
 
 #include <X11/Xatom.h>
 #include <string.h>
+#ifdef HAVE_LIBCANBERRA
 #include <canberra-gtk.h>
+#endif
 
 enum {
   PROP_0,
@@ -444,6 +446,7 @@ static void
 workspace_switch_sound(MetaWorkspace *from,
                        MetaWorkspace *to)
 {
+#ifdef HAVE_LIBCANBERRA
   MetaWorkspaceLayout layout;
   int i, nw, x, y, fi, ti;
   const char *e;
@@ -499,6 +502,7 @@ workspace_switch_sound(MetaWorkspace *from,
 
  finish:
   meta_screen_free_workspace_layout (&layout);
+#endif /* HAVE_LIBCANBERRA */
 }
 
 /**