Vector graphics overlays

Vector graphics overlays

[Elias Mårtenson]

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A few times now, when developing Emacs modes, I have found myself wishing
that there was a way of doing graphical overlays on top of the text in a
buffer.

In one case, I wanted to draw arrows connecting elements in a Common Lisp
buffer in order to visually connect related symbols with arrows.

In other cases I have wanted to highlight sections of text using symbols
and graphics that floats on top (semi-transparent) of the text being edited.

I figured that one way of dealing with this would be to have the ability to
overlay SVG graphics on top of the text being edited. I was about to start
actually implementing this when someone pointed out to me that this would
be completely incompatible with running Emacs in text mode (although I was
thinking to myself that so is inline images, and that's a supported
feature).

What is the opinion about this? Is this something that has been discussed
previously, and if so, what was the outcome?

Regards,
Elias

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Re: Vector graphics overlays

[Eli Zaretskii]

> Date: Sat, 22 Mar 2014 13:15:44 +0800
> From: Elias Mårtenson <lokedhs@gmail.com>
> 
> I figured that one way of dealing with this would be to have the ability to
> overlay SVG graphics on top of the text being edited. I was about to start
> actually implementing this when someone pointed out to me that this would
> be completely incompatible with running Emacs in text mode (although I was
> thinking to myself that so is inline images, and that's a supported
> feature).
> 
> What is the opinion about this? Is this something that has been discussed
> previously, and if so, what was the outcome?

The question you should ask yourself is whether not showing the image
will fatally hamper whatever features you want to build on top of
that.  If it will (I don't think so), then perhaps some ASCII art
replacement for the image is in order.  If not, then this feature will
simply be unavailable on text terminals.

Re: Vector graphics overlays

[Elias Mårtenson]

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On 22 March 2014 15:53, Eli Zaretskii <eliz@gnu.org> wrote:


> The question you should ask yourself is whether not showing the image
> will fatally hamper whatever features you want to build on top of
> that.  If it will (I don't think so), then perhaps some ASCII art
> replacement for the image is in order.  If not, then this feature will
> simply be unavailable on text terminals.
>

So are you saying that if this feature in built, there would be no
principal objections to including it in Emacs?

Regards,
Elias

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Re: Vector graphics overlays

[Eli Zaretskii]

> Date: Sat, 22 Mar 2014 19:08:05 +0800
> From: Elias Mårtenson <lokedhs@gmail.com>
> Cc: emacs-devel@gnu.org
> 
> > The question you should ask yourself is whether not showing the image
> > will fatally hamper whatever features you want to build on top of
> > that.  If it will (I don't think so), then perhaps some ASCII art
> > replacement for the image is in order.  If not, then this feature will
> > simply be unavailable on text terminals.
> >
> 
> So are you saying that if this feature in built, there would be no
> principal objections to including it in Emacs?

Not because it cannot display images on text terminals, no.

Re: Vector graphics overlays

[joakim]

Elias Mårtenson <lokedhs@gmail.com> writes:

> On 22 March 2014 15:53, Eli Zaretskii <eliz@gnu.org> wrote:
>
>     The question you should ask yourself is whether not showing the
>     image
>     will fatally hamper whatever features you want to build on top of
>     that. If it will (I don't think so), then perhaps some ASCII art
>     replacement for the image is in order. If not, then this feature
>     will
>     simply be unavailable on text terminals.
>     
>
> So are you saying that if this feature in built, there would be no
> principal objections to including it in Emacs?

I'm not sure what you want do achieve, but perhaps the Xwidget branch
can be of interest. In the branch its possible to embedd a webkit
browser in an emacs window, similar to an image. So, you could show svg
graphics in the webkit component.

There is also initial support to manage the DOM inside the component
from Elisp.

I also had some proof of concept support for other graphical
containers, such as a Clutter view.

>
> Regards,
> Elias
>

-- 
Joakim Verona

Re: Vector graphics overlays

[Elias Mårtenson]

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On 22 March 2014 22:42, <joakim@verona.se> wrote:


> I'm not sure what you want do achieve, but perhaps the Xwidget branch
> can be of interest. In the branch its possible to embedd a webkit
> browser in an emacs window, similar to an image. So, you could show svg
> graphics in the webkit component.
>

What I want to do is more than just show graphics. I want to show overlay
graphics on top of the text. In fact, the graphics will actually (seem to)
interact with the text. In its simplest form, you might envision a box
around some text, or an arrow drawn on top of the text, pointing at a given
word.

That said, if Xwidget can provide a way to draw its stuff *on top of* the
text being edited, then it could possibly do exactly what I want.

Regards,
Elias

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Re: Vector graphics overlays

[joakim]

Elias Mårtenson <lokedhs@gmail.com> writes:

> On 22 March 2014 22:42, <joakim@verona.se> wrote:
>
>     
>     I'm not sure what you want do achieve, but perhaps the Xwidget
>     branch
>     
>     can be of interest. In the branch its possible to embedd a webkit
>     browser in an emacs window, similar to an image. So, you could
>     show svg
>     graphics in the webkit component.
>     
>
> What I want to do is more than just show graphics. I want to show
> overlay graphics on top of the text. In fact, the graphics will
> actually (seem to) interact with the text. In its simplest form, you
> might envision a box around some text, or an arrow drawn on top of the
> text, pointing at a given word.
>
> That said, if Xwidget can provide a way to draw its stuff on top of
> the text being edited, then it could possibly do exactly what I want.

You get a browser inside emacs. So, you can mix graphics and text as you
can in a browser.

The component doesnt overlay transparently on top of the emacs buffer
though. You get a component that is part of a buffer like an image,
except it is interactive.

It should be possible to do some alpha blending trickery though, if
thats what you really want.

The way the xwidget branch works, it uses offscreen buffers to create
bitmaps that are blitted to screen. This is to integrate with the emacs
display engine. One could perhaps fetch the offscreen content of an
emacs buffer to the mix.

(Your name sounds Swedish so we could discuss this off-list in Swedish
if you are further interested in this aproach)

>
> Regards,
> Elias
>

-- 
Joakim Verona

Re: Vector graphics overlays

[Stefan]

> A few times now, when developing Emacs modes, I have found myself wishing
> that there was a way of doing graphical overlays on top of the text in a
> buffer.

See also http://comments.gmane.org/gmane.emacs.devel/163377.

I'd welcome such a feature.  The fact that it wouldn't work in a tty is
not a reason to turn it down.


        Stefan