Bug#569678: grub-pc: does not clear serial console

[Colin Watson]

On Wed, Jan 05, 2011 at 12:25:08PM +0100, Vladimir 'φ-coder/phcoder' Serbinenko wrote:
> tag 569678 fixed-upstream
> thanks
> managed to recreate. Added forced cls on output initialisation. This
> fixed it.

Thanks.  This fix seems to me like it might be a bit over-the-top,
though; won't it mean that we'll *always* have a screen clear on VGA
console output as well?  IME, that tends to produce unnecessary flicker
if the menu isn't being displayed.

I know that normal mode clears the screen unconditionally as well, but
that's easily fixed:

Index: b/grub-core/normal/menu.c
===================================================================
--- a/grub-core/normal/menu.c
+++ b/grub-core/normal/menu.c
@@ -597,6 +597,7 @@
       int boot_entry;
       grub_menu_entry_t e;
       int auto_boot;
+      int initial_timeout = grub_menu_get_timeout ();
 
       boot_entry = run_menu (menu, nested, &auto_boot);
       if (boot_entry < 0)
@@ -606,7 +607,9 @@
       if (! e)
 	continue; /* Menu is empty.  */
 
-      grub_cls ();
+      /* Only clear the screen if we drew the menu in the first place.  */
+      if (initial_timeout != 0)
+	grub_cls ();
 
       if (auto_boot)
 	grub_menu_execute_with_fallback (menu, e, &execution_callback, 0);

-- 
Colin Watson                                       [cjwatson at debian.org]