I am working in this direction (mentally) though it might be quite a while before I have a solution. As maybe you already know, FoldingText does this for lots of syntax, including URLs.
And it works, but still feels a bit odd to me having syntax, urls, etc show hide as you move cursor through text. Another approach is to use a more "rich text" approach. Where the URL is shown in a popup panel. I'm leaning in that direction at the moment. But will be quite a while before I actually start coding a solution. The sequence of things is:
- Build next text engine. 2. Build WriteRoom 4 with new text engine. 3. Build TaskPaper 4 with new text engine. At the moment I'm still on step one. Making progress, but finish line is months not weeks out.