Re: Drawing UI elements behind text

[JD Smith <jdtsmith@gmail.com>]

> On Nov 10, 2024, at 11:39 AM, Cecilio Pardo <cpardo@imayhem.com> wrote:
> 
> Hello,
> 
> I am working on a mechanism to draw things on the background, behind
> the text of a buffer.
> 
> This would allow to draw UI elements (such as indent lines or a fill
> column indicator) and eye candy like background images or colored
> windows.

I support this idea.  For indent-bars, I use display :stipple as a "separate band" of graphical information that can lie atop text in a buffer, but remain independent of it.  Stipples are flexible and very performant, but have a few issues:

- There is inconsistent stipple support across emacs versions.
- Stipple patterns begin at the frame origin, so up-to-date window-specific remapping is required to prevent unwanted pattern aliasing.  
- Aligning stipples vertically requires fixed space content.

More commonly, modes also make use of :box styling, e.g. for producing boxed "labels", as in org-modern.

An API for drawing simple styled lines, rounded corners, boxes etc. — either in absolute window coordinates, or associated with, but "behind" text in the buffer — would represent a real step forward.