Re: [PATCH] Clear out gfxterm's virtual text_buffer - fixes junk at end of lines

[Joe Auricchio]

On 18 Jul, 2009, at 11:58 , Robert Millan wrote:
> On Sat, Jul 18, 2009 at 12:15:04AM -0700, Joe Auricchio wrote:
> > This fixes a 100% reproducible and very annoying bug I've found:  
> > Switch
> > to gfxterm and until your clear the screen or scroll, the last  
> > position
> > of every line has a random junk character in random foreground and
> > background color. I believe the root cause is that the  
> > virtual_screen's
> > text_buffer is uninitialized; as the cursor reaches a new position,  
> > the
> > uninitialized junk data is drawn to the screen. Really, the entire  
> > screen
> > is junk, but it's never marked dirty so it's never drawn. So let's  
> > just
> > clear out the whole text_buffer when we set up the screen.
>
> But grub_virtual_screen_free() already set the whole structure to 0  
> at the
> beginning of grub_virtual_screen_setup().
>
> Does a zero-filled screen result in garbage, or is something else  
> overwriting
> it?

grub_virtual_screen_free sets all of virtual_screen to 0, but not  
virtual_screen.text_buffer. text_buffer just gets grub_freed. Later in  
grub_virtual_screen_setup, a new text_buffer is grub_malloced. It's  
this new text_buffer that my patch clears out.

-joe