[bug #60114] The "Backspace" key doesn't work correctly in the superuser authentication prompt.

[Egor Ignatov]

URL:
  <https://savannah.gnu.org/bugs/?60114>

                 Summary: The "Backspace" key doesn't work correctly in the
superuser authentication prompt.
                 Project: GNU GRUB
            Submitted by: egori
            Submitted on: Thu 25 Feb 2021 11:55:10 AM UTC
                Category: User Interface
                Severity: Major
                Priority: 5 - Normal
              Item Group: Software Error
                  Status: None
                 Privacy: Public
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
                 Release: 
                 Release: Git master
         Discussion Lock: Any
         Reproducibility: Every Time
         Planned Release: None

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Details:

Description:
In the superuser login prompt pressing backspace deletes the character in the
internal buffer, but on the terminal screen it moves the cursor right
instead.

Details:
So "grub-core/normal/auth.c:grub_username_get" uses 'grub_printf ("\b \b");'
to clear a character on the screen. grub_printf sends characters all the way
down to the "grub-core/term/gfxterm.c:grub_gfxterm_putchar". In theory
grub_gfxterm_putchar handles '\b' correctly, but it doesn't receive it. The
'\b' char gets lost some were in between this two functions. I suspect it's
because of how unicode characters are processed. So I guess that
"grub-core/normal/term.c:print_ucs4_real" function does not print '\b'.




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