Re: console update

[Marcus Brinkmann]

On Tue, Jun 18, 2002 at 11:35:20PM +0000, Adam Olsen wrote:
> Could you explain the difference between double-width characters and
> variable-width fonts, with regards to how curses and such handle them?

In Unicode, some characters are defined to be as wide as two normal
characters.  Applications which want to use them can take this into account
when calculating positions of glyphs/characters. Same for bidirectional
writing.

> It seems to me that in both cases the answer is to simply avoid them.

No, the answer is to support them, as it is well defined which those
characters are :)

> And if you can optionally put tabs on the screen, you could optionally
> use a variable-width font, you just have to make sure to avoid it when
> it causes problems.

Good that you remind me of tabs.  "some text<tab>" is not well defined with
variable spaced fonts, as you don't know over how many tabs "some text"
stretches.
 
> > Is there a terminal emulator for X that uses variables space fonts?  I would
> > like to try it out.  But I can imagine a hell lot of display problems caused
> > by app-unawareness, starting from ASCII art to graphic characters (box
> > drawing) and overwriting text.  Eg,
> 
> I just checked, and you can tell gnome-terminal to use a
> variable-width font, but it seems to really screw things up.  It
> doesn't seem to be erasing old characters properly.
> 
> But, I see no reason to *require* a fixed width font.  So what if it
> screws up some ascii art, many apps would work fine.  Just as long as
> you can disable it when you need to.

On Tue, Jun 18, 2002 at 07:40:51PM -0400, Joshua Judson Rosen wrote:
> I've used variable-width fonts in gnome-terminal--things tend to get
> pretty ugly...
> 
> ... which is not to say that a user shouldn't be allowed to choose for
> things to be ugly like that :)

You both say it doesn't work, as it screws things up, and on the other hand
you say it should be allowed.

The console server could not do the line wrapping, as it doesn't know how
wide the characters are (imagine two clients with different fonts).  In
consequence, it could not do the escape character interpretation in most
cases, and would have to replay arbitrary long sequences of output to
support this.  Which is not what you want.

Thanks,
Marcus


-- 
`Rhubarb is no Egyptian god.' Debian http://www.debian.org brinkmd@debian.org
Marcus Brinkmann              GNU    http://www.gnu.org    marcus@gnu.org
Marcus.Brinkmann@ruhr-uni-bochum.de
http://www.marcus-brinkmann.de