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

[Andy Meneely <andy meneely gmail com>]

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!