narrow color bar using display properties

narrow color bar using display properties

[Eric Abrahamsen]

I've got my cursor-type set to a colored bar, and looking at it today I
thought it would be very nice if I could create a similar effect with
code: presumably using text properties (I'm guessing the display
property) to lay a bar of color (either background color or a
transparent foreground color) over existing text, only a couple of
pixels wide and aligned left, without otherwise disturbing the placement
of the text beneath.

Right now the most promising approach seems to be the image display
property (presumably I could use the :data specification just to draw a
block of colored pixels), except that if I understand it correctly that
will replace the underlying text, not add to it.

Does anyone have advice on achieving this?

Thanks,
Eric

Re: narrow color bar using display properties

[Michael Heerdegen]

Eric Abrahamsen <eric@ericabrahamsen.net> writes:

> I've got my cursor-type set to a colored bar, and looking at it today I
> thought it would be very nice if I could create a similar effect with
> code: presumably using text properties (I'm guessing the display
> property) to lay a bar of color (either background color or a
> transparent foreground color) over existing text, only a couple of
> pixels wide and aligned left, without otherwise disturbing the placement
> of the text beneath.
>
> Right now the most promising approach seems to be the image display
> property (presumably I could use the :data specification just to draw a
> block of colored pixels), except that if I understand it correctly that
> will replace the underlying text, not add to it.
>
> Does anyone have advice on achieving this?

You may want to try using faces using the stipple attribute (see (elisp)
Face Attributes) and use them in text properties or overlays.

Using stipple is easy, e.g. like this:

  (defface test '((t (:stipple "hlines2"))) "Doc...")

The downside: stipple doesn't work in Windows AFAIK.


Regards,

Michael.

Re: narrow color bar using display properties

[Stefan Monnier]

> I've got my cursor-type set to a colored bar, and looking at it today I
> thought it would be very nice if I could create a similar effect with
> code: presumably using text properties (I'm guessing the display
> property) to lay a bar of color (either background color or a
> transparent foreground color) over existing text, only a couple of
> pixels wide and aligned left, without otherwise disturbing the placement
> of the text beneath.

I can't think of any way to get this effect with the current display
tricks provided to Elisp.


        Stefan

Re: narrow color bar using display properties

[Eli Zaretskii]

> From: Eric Abrahamsen <eric@ericabrahamsen.net>
> Date: Tue, 05 Mar 2013 14:26:45 +0800
> 
> I've got my cursor-type set to a colored bar, and looking at it today I
> thought it would be very nice if I could create a similar effect with
> code: presumably using text properties (I'm guessing the display
> property) to lay a bar of color (either background color or a
> transparent foreground color) over existing text, only a couple of
> pixels wide and aligned left, without otherwise disturbing the placement
> of the text beneath.

I don't get it: do you mean to have a color bar to the left of _every_
character in a region of text?  Why would want something like that?
Or did I misunderstand what you want?

Re: narrow color bar using display properties

[Peter Dyballa]

Am 05.03.2013 um 18:49 schrieb Eli Zaretskii:

> I don't get it: do you mean to have a color bar to the left of _every_
> character in a region of text?

I think Eric has a horizontal bar cursor and wants to "underline" text…

--
Greetings

  Pete

The future will be much better tomorrow.
				– George W. Bush

Re: narrow color bar using display properties

[Dan Espen]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Eric Abrahamsen <eric@ericabrahamsen.net>
>> Date: Tue, 05 Mar 2013 14:26:45 +0800
>> 
>> I've got my cursor-type set to a colored bar, and looking at it today I
>> thought it would be very nice if I could create a similar effect with
>> code: presumably using text properties (I'm guessing the display
>> property) to lay a bar of color (either background color or a
>> transparent foreground color) over existing text, only a couple of
>> pixels wide and aligned left, without otherwise disturbing the placement
>> of the text beneath.
>
> I don't get it: do you mean to have a color bar to the left of _every_
> character in a region of text?  Why would want something like that?
> Or did I misunderstand what you want?

I'm not sure what the OP wants either, but if you've ever seen
an IBM 5251 with the "column separator" attribute that would be one
explanation.  But column separators formed a bucket around an
input character:

| |
|_|

Actually pretty nice for indicating input fields vs. protected fields.

-- 
Dan Espen

Re: narrow color bar using display properties

[Eli Zaretskii]

> From: Peter Dyballa <Peter_Dyballa@Web.DE>
> Date: Tue, 5 Mar 2013 19:16:27 +0100
> Cc: help-gnu-emacs@gnu.org
> 
> I think Eric has a horizontal bar cursor and wants to "underline" text…

Then what's wrong with a underline font/face?

RE: narrow color bar using display properties

[Drew Adams]

> > I don't get it: do you mean to have a color bar to the left 
> > of _every_ character in a region of text?
> 
> I think Eric has a horizontal bar cursor and wants to 
> "underline" text.

Really?  In that case, I don't understand Stefan's message saying that you can't
do that with Emacs.

You can easily use a face that has attribute `underline' and/or `overline' as a
text property or overlay.  And the line(s) can be any color.

(Like Eli, I too did (do?) not understand what the request is.)

Re: narrow color bar using display properties

[Eric Abrahamsen]

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

>> > I don't get it: do you mean to have a color bar to the left 
>> > of _every_ character in a region of text?
>> 
>> I think Eric has a horizontal bar cursor and wants to 
>> "underline" text.
>
> Really?  In that case, I don't understand Stefan's message saying that you can't
> do that with Emacs.
>
> You can easily use a face that has attribute `underline' and/or `overline' as a
> text property or overlay.  And the line(s) can be any color.
>
> (Like Eli, I too did (do?) not understand what the request is.)

Ha, sorry to create confusion, I thought I'd articulated myself well! I
do want a color bar to the left of a series of characters, but
vertically-aligned characters, creating a multi-line vertical bar (I'm
trying to prettify Org Agenda's display of multi-day agenda items).

Initial experimentation indicates that Michael Heerdegen's stipple
suggestion might do the trick!

Thanks,
Eric