prefs: Adapt to re-addition of a separate visual-bell option

Commit a228546d merged the visual-bell/visual-bell-type options,
but the change turned out too disruptive for gnome-control-center /
gnome-shell, so gsettings-desktop-schemas commit a5819b2a4e9 re-added
the separate option.

src/core/bell.c

@@ -271,9 +271,6 @@ bell_visual_notify (MetaDisplay *display,
     case G_DESKTOP_VISUAL_BELL_FRAME_FLASH:
       bell_flash_frame (display, xkb_ev); /* does nothing yet */
       break;
-    case G_DESKTOP_VISUAL_BELL_NONE:
-      /* do nothing */
-      break;
     }
 }
 
@@ -281,8 +278,9 @@ void
 meta_bell_notify (MetaDisplay *display, 
 		  XkbAnyEvent *xkb_ev)
 {
-  /* flash something if appropriate */
-  bell_visual_notify (display, xkb_ev);
+  /* flash something */
+  if (meta_prefs_get_visual_bell ())
+    bell_visual_notify (display, xkb_ev);
 
   if (meta_prefs_bell_is_audible ()) 
     {

src/core/prefs.c

@@ -80,6 +80,7 @@ static gboolean application_based = FALSE;
 static gboolean disable_workarounds = FALSE;
 static gboolean auto_raise = FALSE;
 static gboolean auto_raise_delay = 500;
+static gboolean bell_is_visible = FALSE;
 static gboolean bell_is_audible = TRUE;
 static gboolean reduced_resources = FALSE;
 static gboolean gnome_accessibility = FALSE;
@@ -288,6 +289,14 @@ static MetaBoolPreference preferences_bool[] =
       &auto_raise,
       FALSE,
     },
+    {
+      { "visual-bell",
+        SCHEMA_GENERAL,
+        META_PREF_VISUAL_BELL,
+      },
+      &bell_is_visible, /* FIXME: change the name: it's confusing */
+      FALSE,
+    },
     {
       { "audible-bell",
         SCHEMA_GENERAL,
@@ -1655,6 +1664,12 @@ meta_prefs_get_button_layout (MetaButtonLayout *button_layout_p)
   *button_layout_p = button_layout;
 }
 
+gboolean
+meta_prefs_get_visual_bell (void)
+{
+  return bell_is_visible;
+}
+
 gboolean
 meta_prefs_bell_is_audible (void)
 {

src/include/prefs.h

@@ -201,6 +201,7 @@ void meta_prefs_get_window_binding (const char          *name,
                                     unsigned int        *keysym,
                                     MetaVirtualModifier *modifiers);
 
+gboolean           meta_prefs_get_visual_bell      (void);
 gboolean           meta_prefs_bell_is_audible      (void);
 GDesktopVisualBellType meta_prefs_get_visual_bell_type (void);