Re: Drawing UI elements behind text

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sun, 10 Nov 2024 11:29:27 -0800
> Cc: cpardo@imayhem.com, emacs-devel@gnu.org
> From: Jim Porter <jporterbugs@gmail.com>
> 
> On 11/10/2024 11:22 AM, Eli Zaretskii wrote:
> > Once the display engine knows at what X coordinate the image slice
> > should start, it can stop laying out other display elements and switch
> > to the slice when that X coordinate is reached.
> 
> I was thinking more about the Y coordinates and having gaps between 
> consecutive slices if we made a mistake. That's probably fixable, but it 
> seems like it would require a lot of care to avoid bugs.

Yes, it requires care.

> >> Or what about applying text scaling?
> > 
> > How is this different from what we do today when text-scaling happens
> > in a buffer where images are displayed together with text?
> 
> I'm just worried about this due to seeing some similar bugs come up in 
> the visual-wrap-prefix-mode code.

Bugs will always be with us, no way around that.

> >> I suppose if we deemed this feature important, we could probably address
> >> all of those, but I'm not sure it's worth the effort.
> > 
> > What alternative do we have?  Showing the images alongside text
> > without letting the images scroll with the text (vertically and
> > horizontally) will not fly.  How do you scroll the images with the
> > text except by displaying them as part of the "normal" display layout?
> 
> Personally, I'm ok with saying we just don't support laying out images 
> like this in EWW. For it to have a practical effect, we'd probably need 
> to have more-complete CSS support anyway. That's not easy either (though 
> I have some ideas about how we could do it if we thought it would be 
> worthwhile).

This entire sub-thread is about how to provide such a feature;
leaving it unsupported is easy.  If we do want to provide it, I think
going the image-slice way is a better alternative.