efi/console: Properly clear leftover artifacts from the screen

A regression in GRUB 2.12 causes the GRUB screen to become cluttered
with artifacts from the previous screen whether it's the UEFI post UI,
UEFI shell or any graphical UI running before GRUB. This issue occurs
in situations like booting GRUB from the UEFI shell and going straight
to the rescue or command shell causing visual discomfort.

The regression was introduced by commit 2d7c3abd8 (efi/console: Do not
set text-mode until it is actually needed). To address the screen
flickering issue this commit suppresses the text-mode setting until the
first output is requested. Before text-mode is set any attempt to clear
the screen has no effect. This inactive period renders the clear screen
ineffective in early boot stages, potentially leaving leftover artifacts
that will clutter the GRUB console display, as there is no guarantee
there will always be a clear screen after the first output.

The issue is fixed by ensuring grub_console_cls() to work through lazy
mode-setting, while also avoiding screen clearing for the hidden menu
which the flicker-free patch aims to improve.

Fixes: 2d7c3abd8 (efi/console: Do not set text-mode until we actually need it)
Signed-off-by: Michael Chang <mchang@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

diff --git a/grub-core/normal/menu.c b/grub-core/normal/menu.c
index 6a90e091f22367cd45d83fa748a1d45cf9e38ae6..f24544b278396c1fab16f6f01ebed3408d3a339d 100644 (file)
--- a/grub-core/normal/menu.c
+++ b/grub-core/normal/menu.c
@@ -881,13 +881,14 @@ show_menu (grub_menu_t menu, int nested, int autobooted)
       if (! e)
        continue; /* Menu is empty.  */
 
-      grub_cls ();
-
       if (auto_boot)
        grub_menu_execute_with_fallback (menu, e, autobooted,
                                         &execution_callback, &notify_boot);
       else
-       grub_menu_execute_entry (e, 0);
+       {
+         grub_cls ();
+         grub_menu_execute_entry (e, 0);
+       }
       if (autobooted)
        break;
     }

diff --git a/grub-core/term/efi/console.c b/grub-core/term/efi/console.c
index bb587f39da027f0423479a2b252279b9306f03f5..258b52737fdcbe0937f0480442885bb76ece4d3f 100644 (file)
--- a/grub-core/term/efi/console.c
+++ b/grub-core/term/efi/console.c
@@ -432,7 +432,7 @@ grub_console_cls (struct grub_term_output *term __attribute__ ((unused)))
   grub_efi_simple_text_output_interface_t *o;
   grub_efi_int32_t orig_attr;
 
-  if (grub_efi_is_finished || text_mode != GRUB_TEXT_MODE_AVAILABLE)
+  if (grub_prepare_for_text_output (term) != GRUB_ERR_NONE)
     return;
 
   o = grub_efi_system_table->con_out;