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Re: No scrolling for long input lines

From: Andy Goth
Subject: Re: No scrolling for long input lines
Date: Tue, 7 Oct 2008 23:12:31 -0500 (CDT)

"Andy Goth" <address@hidden> 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 

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 |

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