Re: some console code checked in

[Niels Möller]

Marcus Brinkmann <Marcus.Brinkmann@ruhr-uni-bochum.de> writes:

> On Mon, Mar 18, 2002 at 03:12:54AM -0500, Roland McGrath wrote:
> > I think all the terminal emulation stuff belongs in the common layer and
> > not in the vga code.  All that stuff would be the same for a different sort
> > of output device.  Each output device can just have a few calls for move
> > cursor, scroll, clear space, write chars, etc.
> 
> I have considered it, that is how it was done in colortext.  It is a nice 
> idea,
> but I think it is based on wrong assumptiond about the display drivers/
> It assumes that all display drivers basically have the same features, and
> work roughly the same way.  But if you look what there is outside of
> framebuffer and VGA text hardware,

framebuffer and vga are two quite important cases. I remember
discussion on how to get the linux-68k amiga console driver do
scrolling by fiddling with the copper list instead of actually
scrolling the bitmaps ;-). Even in this non-vga, non-fb case,
scrolling was important.

> there is lots of stuff that works quite differently (Braille
> terminals, Text-to-Speech, "intelligent" terminals doing their own
> escape sequences handling).

I have no idea how "scroll-region" escape codes should be implemented
on a text-to-speech terminal (my best guess is "not at all"), but
scrolling is still a common and important operation for the devices
that do support it.

If every device has some pointers for the basic operations, strange
devices can leave some of the pointers as NULL, and for each NULL
operation, the console code has to figure out how to do without that
feature.

/Niels