No scrolling for long input lines

No scrolling for long input lines

[Andy Goth]

(I said I would research this some more, but I haven't had a chance, and I won't get one for a couple days, so rather than wait, I am simply posting what I know.)

In GRUB 1.96, typing an input line longer than the screen is wide does not cause the screen to scroll.  Effectively this means once I get to the bottom of the screen, anything I type that's longer than 80 characters (less prompt) I have to type blind.  Aside from not being able to see what I type, everything behaves normally.

My GRUB configuration is plain vanilla.  GRUB's on a FAT12 floppy read in using biosdisk, there's no grub.cfg file, and I directly type in insmod, ls, linux, initrd, boot, and all that jazz.  I haven't made any modifications to the source, and I'm using the 1.96 release I found on alpha.gnu.org.  I have the biosdisk and fat modules compiled into the GRUB image.

-- 
Andy Goth | http://andy.junkdrome.org/
unununium@{aircanopy.net,openverse.com}

Re: No scrolling for long input lines

[Felix Zielcke]

--------------------------------------------------
From: "Andy Goth" <unununium@aircanopy.net>
Sent: Tuesday, October 07, 2008 7:40 PM
To: <grub-devel@gnu.org>
Subject: No scrolling for long input lines

> I haven't made any modifications to the source, and I'm using the 1.96 release I found on alpha.gnu.org.  I have the biosdisk and 
> fat modules compiled into the GRUB image.

Hi,

it would be always better if you check with the current SVN version things that you want to report if they still apply.
grub2 is actively developed and the 1.96 release is from February whereas last change on SVN is currently 2 days old. 

Re: No scrolling for long input lines

[Andy Goth]

Felix Zielcke <fzielcke@z-51.de> wrote:
> it would be always better if you check with the current SVN version things
> that you want to report if they still apply.
___________
I'll test the current SVN this Friday, or perhaps Thursday night at the earliest.  Until then I'm on international business travel.

-- 
Andy Goth | http://andy.junkdrome.org/
unununium@{aircanopy.net,openverse.com}

Re: No scrolling for long input lines

[Andy Goth]

"Andy Goth" <unununium@aircanopy.net> wrote:
> I'll test the current SVN this Friday, or perhaps Thursday night at
> the earliest.

Actually I did spend time tonight investigating.  I needed to get the latest SVN for another reason (about which I have questions I'll ask in a few days), so I went ahead and looked into my scrolling input problem.

Yup, still there.  Today's SVN is affected.

The problem is present when actually booting using GRUB (ordinary VGA text mode), but it all works fine in grub-emu.

Wait, I take that back.  In grub-emu, typing very long lines (that wrap and *cause the screen to scroll*) results in the text wrapping at column 80 instead of column 79, so that there is *not* a white space character in the rightmost column.  Pressing Ctrl-U from such a line will only erase only the bottom line of text, except for the first six characters (which presumably correspond to "grub> ").

Something's flaky!  However, this grub-emu stuff might be unrelated to the problem I've been having with the actual boot loader.

I also add that in grub-emu, the carriage doesn't return after printing an error message, so I get a stairstep effect.  With such an indented prompt, issuing a command like "ls" causes output to be printed to the *left* of the prompt.

Enough about grub-emu.  In the actual boot loader, I noticed that the pattern seems to be: it will scroll the screen if inserting text will cause the last character to overflow the right edge of the screen.  That sounds like the way it should be, right?  The problem is that only currently visible characters appear to be checked for overflow.  This doesn't include the character being typed or characters that previously have failed to scroll onscreen.

Test cases:

1. Near the top of the screen, type a bunch of text and overflow the edge.  Works fine.
2. Hold down enter until the screen starts scrolling.  Works fine.
3. Type a bunch of text and overflow the edge.  Fails to scroll!
4. Use the left arrow key one or two times and type text.  Fails to scroll!
5. Use the left arrow key until the cursor is onscreen, and type text.  Everything scrolls into view.

I'd absolutely love to debug all this and provide patches, but I really don't have time right now.  In fact I didn't have time to do the research I did; I should have been sleeping. :^(

-- 
Andy Goth | http://andy.junkdrome.org/
unununium@{aircanopy.net,openverse.com}

Re: No scrolling for long input lines

[Vesa Jääskeläinen]

Andy Goth wrote:
> "Andy Goth" <unununium@aircanopy.net> wrote:
>> I'll test the current SVN this Friday, or perhaps Thursday night at
>> the earliest.
> 
> Actually I did spend time tonight investigating.  I needed to get the latest SVN for another reason (about which I have questions I'll ask in a few days), so I went ahead and looked into my scrolling input problem.
> 
> Yup, still there.  Today's SVN is affected.
> 
> The problem is present when actually booting using GRUB (ordinary VGA text mode), but it all works fine in grub-emu.
> 
> Wait, I take that back.  In grub-emu, typing very long lines (that wrap and *cause the screen to scroll*) results in the text wrapping at column 80 instead of column 79, so that there is *not* a white space character in the rightmost column.  Pressing Ctrl-U from such a line will only erase only the bottom line of text, except for the first six characters (which presumably correspond to "grub> ").
> 
> Something's flaky!  However, this grub-emu stuff might be unrelated to the problem I've been having with the actual boot loader.
> 
> I also add that in grub-emu, the carriage doesn't return after printing an error message, so I get a stairstep effect.  With such an indented prompt, issuing a command like "ls" causes output to be printed to the *left* of the prompt.
> 
> Enough about grub-emu.  In the actual boot loader, I noticed that the pattern seems to be: it will scroll the screen if inserting text will cause the last character to overflow the right edge of the screen.  That sounds like the way it should be, right?  The problem is that only currently visible characters appear to be checked for overflow.  This doesn't include the character being typed or characters that previously have failed to scroll onscreen.
> 
> Test cases:
> 
> 1. Near the top of the screen, type a bunch of text and overflow the edge.  Works fine.
> 2. Hold down enter until the screen starts scrolling.  Works fine.
> 3. Type a bunch of text and overflow the edge.  Fails to scroll!
> 4. Use the left arrow key one or two times and type text.  Fails to scroll!
> 5. Use the left arrow key until the cursor is onscreen, and type text.  Everything scrolls into view.
> 
> I'd absolutely love to debug all this and provide patches, but I really don't have time right now.  In fact I didn't have time to do the research I did; I should have been sleeping. :^(

This seems to be BIOS issue in a way. In startup.S
grub_console_real_putchar there is quite good comment about what are
BIOS limitations.

Choices are to modify this code here, or make better bios console terminal.

Re: No scrolling for long input lines

[Robert Millan]

On Wed, Oct 08, 2008 at 07:40:38PM +0300, Vesa Jääskeläinen wrote:
> grub_console_real_putchar there is quite good comment about what are
> BIOS limitations.
> 
> Choices are to modify this code here, or make better bios console terminal.

Would vga_text.c solve the problem?  VGA text is alwats garanteed to work on
BIOS.

Perhaps we could have kernel use bios console, and normal mode switch to
vga_text.c somehow.

-- 
Robert Millan

  The DRM opt-in fallacy: "Your data belongs to us. We will decide when (and
  how) you may access your data; but nobody's threatening your freedom: we
  still allow you to remove your data and not access it at all."

Re: No scrolling for long input lines

[Robert Millan]

On Tue, Oct 07, 2008 at 12:40:46PM -0500, Andy Goth wrote:
> (I said I would research this some more, but I haven't had a chance, and I won't get one for a couple days, so rather than wait, I am simply posting what I know.)
> 
> In GRUB 1.96, typing an input line longer than the screen is wide does not cause the screen to scroll.  Effectively this means once I get to the bottom of the screen, anything I type that's longer than 80 characters (less prompt) I have to type blind.  Aside from not being able to see what I type, everything behaves normally.
> 
> My GRUB configuration is plain vanilla.  GRUB's on a FAT12 floppy read in using biosdisk, there's no grub.cfg file, and I directly type in insmod, ls, linux, initrd, boot, and all that jazz.  I haven't made any modifications to the source, and I'm using the 1.96 release I found on alpha.gnu.org.  I have the biosdisk and fat modules compiled into the GRUB image.

Andy, I just sent a patch (mail titled "split/refurbish vga_text.mod") which
would allow you to use vga_text.c as a terminal output driver:

  insmod vga_text
  terminal_output vga_text

I think this should solve your problem.  Could you test it?

-- 
Robert Millan

  The DRM opt-in fallacy: "Your data belongs to us. We will decide when (and
  how) you may access your data; but nobody's threatening your freedom: we
  still allow you to remove your data and not access it at all."