[BRLTTY] Was: Re: Linux console hacking > scroll back buffer

[Nicolas Pitre]

On Thu, 22 May 2025, Didier Spaier wrote:

> Salut Nicolas,
> 
> at the risk of beating a dead horse...
> 
> Maybe your technical and communication skills could help the scroll back buffer
> of Linux virtual terminals (or consoles) to make a come back?

That's not that simple.

Initially, the Linux text console was implemented directly inside the 
VGA graphic card's memory. And to make scrolling blazingly fast, the 
base pointer for the beginning of the text screen was simply moved to 
the next screen row rather than moving the whole screen content by one 
row. So there were never any explicit scrollback buffer per se, simply 
that the moving of the text start pointer left previous screen line 
content behind in memory. Eventually the screen character grid would 
reach the top of the VGA memory, meaning the pointer and screen content 
had to be moved back to the start of memory. Still, while the pointer 
was halfway through the VGA memory, simply moving it back temporarily 
provided that scrollback buffer feature.

So to say that if you still have VGA compatible hardware and a screen 
size that is close enough to the default 80x25 then the scrollback 
buffer functionality is probably still there. If your video hardware 
requires that the console be implemented in a pixel frame buffer then 
there is no scrollback buffer in that case and there never was any.


Nicolas