Re: Fill column indicator functionality

[Clément Pit-Claudel]

On 15/03/2019 03.30, Eli Zaretskii wrote:
> Does this answer your question?

It does, thanks. It's a very thorough answer. Thanks for taking the time, Eli!

> The continuous line idea does have one advantage: it seamlessly
> supports lines of variable height.  But that use case is rare, and I
> think we will be able to support them with the glyph-based
> implementation as well.

This was actually going to be my follow-up question :) I see lines of variable 
height in many of most of my Emacs mode, through a combination of factors:

- Font switches due to symbols picked by prettify-symbols-mode not being 
available in my main programming font
- Variable-pitch fonts being used by AucTeX for section and paragraph titles 
- Varying font sizes to indicate nesting depth in Org-mode
- Changing line spacing to separate top-level items in org-mode

Is there actually a good way to support all this?  Maybe using a very thin 
space and a face with a :background on it would do.  Or maybe it will be 
possible to put a 'display (space …) property on the line character so that it 
displays as a 1-px wide line?

Also, as a second follow-up question: we already have code to draw boxes around 
characters; would it be hard to extend that code to allow customization of 
which sides to draw? Alternatively, would it be hard to add a vertical 
strike-through face property? (I've used horizontal strike-through as a way to 
display horizontal lines in the past)

Cheers,
Clément.