How to draw pixel ?

How to draw pixel ?

[Andy Stewart]

Hi all,

Have a exist function or package to draw pixel?
I need draw pixel vertically line in emacs buffer.

Thanks!

  -- Andy

RE: How to draw pixel ?

[Drew Adams]

> function to draw pixel vertically line in emacs buffer

I don't have a direct answer to your question, but you might also take a look at
the code in vline.el. It draws a vertical line using character composition with
the character ?|.
http://www.emacswiki.org/emacs/vline.el

Re: How to draw pixel ?

[Andy Stewart]

Hi Drew,

"Drew Adams" <drew.adams@oracle.com> writes:

>> function to draw pixel vertically line in emacs buffer
>
> I don't have a direct answer to your question, but you might also take a look at
> the code in vline.el. It draws a vertical line using character composition with
> the character ?|.
> http://www.emacswiki.org/emacs/vline.el
I know vline.el.
But this overlay have display problem with multi-byte language (such as Chinese),
when Chinese character's width is not *two times* of English character's
width.

I have uploae screenshot for describe this problem.
Screenshot at http://www.emacswiki.org/emacs/VlineProblemWithChinese

Then you will see the problem.

Regards,

  -- Andy

RE: How to draw pixel ?

[Drew Adams]

> >> function to draw pixel vertically line in emacs buffer
> >
> > I don't have a direct answer to your question, but you 
> > might also take a look at the code in vline.el. It draws
> > a vertical line using character composition with
> > the character ?|.
> > http://www.emacswiki.org/emacs/vline.el
>
> I know vline.el.
> But this overlay have display problem with multi-byte 
> language (such as Chinese), when Chinese character's width
> is not *two times* of English character's width.
> 
> I have attached screenshot for describe this problem.
> Then you will see the problem.

I probably can't help with this - I'm no expert on multi-byte stuff, character
composition, or use of graphics with Emacs.

But make sure of one thing: did you first set option `vline-style' to `compose'?
If it is not `compose', then a face is simply applied to the existing character.
If it is `compose', then the existing character is composed with character ?|.
The latter effect is of drawing a thin vertical line through the character.

Your screenshot looks like what one gets when the option has value `face'
instead. (But maybe that's just a coincidence, and the appearance is due here to
multi-byte characters.)