Bug#944679: extlinux: Visual bugs while editing a long kernel command line

[Lukas Schwaighofer <lukas@schwaighofer.name>]

Control: tags -1 + moreinfo

Hi Mikhail,

apologies for the long delay, there was a lot going on the before winter
holidays.

On Wed, 13 Nov 2019 17:59:13 +0100
Mikhail Morfikov <mmorfikov@gmail.com> wrote:

> My current kernel command line is about 400-character long. When it
> was shorter, I didn't have any issues when I wanted to edit this line
> in the bootloader screen by selecting some entry and pressing "E".
> 
> I recently added some other kernel parameters to the cmd line, and I
> noticed many visual bugs in the bootloader screen. Basically with
> each cursor movement (back and forth), I get an extra text line in
> the screen output (copy of the current line scrolled up). Also
> characters in the cmd line disappear or change when I move the cursor
> back. The visual bugs make it almost impossible to edit the kernel
> cmd line. Also When I press the backspace key (or the back arrow key)
> for a longer period of time (let's assume I want to delete some
> parameters entirely from the line), I hear the hardware beeper which
> is really annoying.
> 
> I found out that the problem appears when I have more than 4 lines of
> text on the screen when editing the cmd line. So fifth (and next
> ones) will trigger the visual bugs, while 4 (and less) won't.

I'll look into this and try to reproduce this within the next few days.
To speed things up, can you provide me with your configuration?

If you're able to perform some test, can you check whether the
behavior is consistent when using a different UI modules (menu.c32 or
vesamenu.c32).

Thanks
Lukas