Re: Drawing UI elements behind text

[Cecilio Pardo <cpardo@imayhem.com>]

On 25/11/2024 0:37, JD Smith wrote:
> 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.

Stipples also disable the scrolling of buffer pixels, affecting 
performance of redisplay.

> 
> 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.

I haven't found a way to draw behind the text that is not too 
complicated or affects redisplay too much. So now the idea is drawing 
over the text. For the applications I have in mind this works equally well.

The starting drawing elements are going to be vertical and horizontal 
segments, with color (maybe with alpha), width and different patterns. 
They can be placed on pixel positions or character positions when using 
fixed size fonts, using floating point numbers so you can put, for 
example, indent lines in the middle of characters.

They are associated with a buffer, and have a 'source' marker so the 
facility can be shared by several programs.

Any ideas for more elements or applications are welcome.

--
Cecilio Pardo.