Re: Introducing emacs-webkit and more thoughts on Emacs rendering (was Rethinking the design of xwidgets)

[Eli Zaretskii]

> From: Akira Kyle <akira@akirakyle.com>
> Cc: larsi@gnus.org, emacs-devel@gnu.org
> Date: Mon, 30 Nov 2020 10:03:55 -0700
> 
> > No complexity at all, it's almost trivial, because the display
> > code already does that.  As for "satisfactorily" part: what can be
> > unsatisfactory about displaying the widget on the next screen
> > line?
> 
> That's fine, and would be the expected behavior when lines are 
> supposed to wrap. But when lines are not wrapped, I would not 
> expect a display element to disappear as soon as one pixel of it 
> exceeds the window border.

And yet that's exactly what happens with other display elements, for
example wide characters on TTY display.

Again, AFAIU we are talking about rare use cases, which you said
cannot be displayed in any other way, so what do you expect Emacs to
do in such restrictive situations??

> Already I find the way redisplay doesn't like to display images
> clipped at the top of the window jarring.

Not sure what you are talking about, but I'm sure whatever is jarring
can be fixed by relatively simple augmentations to the display code.

> If I wanted to zoom into the widget if it was displaying something
> detailed, I wouldn't want it to suddenly disappear.

It doesn't have to, we can scroll the window instead, so that the
enlarged widget is brought into the viewport.

Again, what else do you expect Emacs to do when you yourself said
these widgets don't allow any other solution??

> I think Emacs needs to be able to clip the elements its displays in
> order to not end up with what I would call surprising and
> frustrating behavior.

But you yourself said this is not allowed in these cases, so how can
Emacs do what is not allowed??

> >> What if `window-resize-pixelwise` or `frame-resize-pixelwise`
> >> non-nil and the element is on the last, partially clipped line?
> >
> > We don't display it.  How is this different from a any other large
> > display element that cannot be shown in the viewport?
> 
> Images are the only other large display element that I'm aware of 
> and images are clipped in such cases

But you yourself said that clipping these widgets is impossible.  What
am I missing in this discussion?