Re: Embedding icons in Pango text, the "right" way?

[Behdad Esfahbod]

See:
https://github.com/GNOME/pango/blob/master/examples/cairoshape.c

On Aug 11, 2016 8:04 AM, "Andy Meneely"  wrote:

> Hi,
>   I maintain a Ruby gem that uses Pango heavily (
> https://github.com/andymeneely/squib/). One of the key features is to be
> able to draw an icon into the text such that it flows just like any other
> word. Carving out the space in the Pango layout has proven to be a
> finicky challenge. (Once we carve out the proper space in the layout, we
> use Cairo to paint the image separately.)
>
> What is the proper way to carve out space for image? We need this space to
> flow like any other word.
>
> The way we currently carve out space is a bit hacky (
> https://github.com/andymeneely/squib/blob/master/lib/squib/
> graphics/text.rb#L98). We (1) replace the key with a control character,
> then (2) change the letter spacing of the middle character to the width we
> need. This fails on some platforms and not others.
>
> If we created a zero-sized regular character (e.g "a"), then stroking path
> will fail because a zero-sized font invalidates the matrix math. Plus, we
> get strange behavior happening when the text is ONLY an embedded icon of a
> zero-sized font (i.e. we get a warning that the font can't be found).
>
> So I've never been happy with the way we implement this and I'm convinced
> Pango provides a better way. I see the AttrShape struct - should I be
> using that? How do I set attributes for just one character? I've been
> scouring the docs and mailing lists archives and I'm not grasping exactly
> how attribute lists work, so that's why I went with markup.
>
> If you have solutions in just C, or in another scripting language, I can
> port it.
>
> Thanks!
>
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>
>
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Re: Embedding icons in Pango text, the "right" way?

[Andy Meneely]

On Fri, Aug 12, 2016 at 5:26 AM, Stefan Salewski  wrote:

> On Thu, 2016-08-11 at 11:04 -0400, Andy Meneely wrote:
> > One of the key features is to be able to draw an icon
> > into the text
>
> You do know that GTK3 textview is doing exactly that?
>
> See GTK3 gtk3-demo program, textview, "Multiple Views". No idea how
> that works internally, sorry.
>

Ah, I was not aware of those. I don't use gtk in my project, so I didn't
think to look there. I haven't found gtk's exact implementation, but that
information led me to figure out how to create a Shape attribute and add it
to the to the AttrList and hook in a "shape renderer" with a
Pango::Rectangle.

I'll post a minimal solution here for posterity once I get the details
ironed out.

Thanks!
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Re: Embedding icons in Pango text, the "right" way?

[Stefan Salewski]

On Thu, 2016-08-11 at 11:04 -0400, Andy Meneely wrote:
> One of the key features is to be able to draw an icon
> into the text

You do know that GTK3 textview is doing exactly that?

See GTK3 gtk3-demo program, textview, "Multiple Views". No idea how
that works internally, sorry.
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Embedding icons in Pango text, the "right" way?

[Andy Meneely]

Hi,
  I maintain a Ruby gem that uses Pango heavily (https://github.com/
andymeneely/squib/). One of the key features is to be able to draw an icon
into the text such that it flows just like any other word. Carving out the
space in the Pango layout has proven to be a finicky challenge. (Once we
carve out the proper space in the layout, we use Cairo to paint the image
separately.)

What is the proper way to carve out space for image? We need this space to
flow like any other word.

The way we currently carve out space is a bit hacky (https://github.com/
andymeneely/squib/blob/master/lib/squib/graphics/text.rb#L98). We (1)
replace the key with a control character, then (2) change the letter
spacing of the middle character to the width we need. This fails on some
platforms and not others.

If we created a zero-sized regular character (e.g "a"), then stroking path
will fail because a zero-sized font invalidates the matrix math. Plus, we
get strange behavior happening when the text is ONLY an embedded icon of a
zero-sized font (i.e. we get a warning that the font can't be found).

So I've never been happy with the way we implement this and I'm convinced
Pango provides a better way. I see the AttrShape struct - should I be using
that? How do I set attributes for just one character? I've been scouring
the docs and mailing lists archives and I'm not grasping exactly how
attribute lists work, so that's why I went with markup.

If you have solutions in just C, or in another scripting language, I can
port it.

Thanks!
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