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: Sun, 29 Nov 2020 20:54:01 -0700
> 
> > Anyway, this just tells me that GTK is not a good starting point
> > for embedding widgets.  Do other projects build embedded widgets
> > on such shaky grounds?
> 
> I wouldn't say GTK isn't good for embedding widgets. In fact I'd 
> say it's probably great if you're wanting to extend an existing 
> GTK app with custom widgets. The problem is Emacs, despite using 
> GTK as a toolkit, isn't really a GTK app.

First, which of the problems you mentioned are related to Emacs not
being a GTK application?

And second, there's a branch in our repository where Emacs _is_ made
to be a GTK application, AFAIU.

> > This is solvable.  We already have similar situation in the
> > display engine, where some display element cannot be usefully
> > "clipped".  We either don't display it at all or display it on the
> > next screen line, depending on the wrap mode.
> 
> I don't doubt its solvable, but how satisfactorily and at what 
> complexity?

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?

> What if the element is large and 99% of it could be visible? What if
> the element is wider than the window?

These are marginal cases: you are talking about very large widgets
that in addition refuse to be resized.  How many are like that?  And
what else can we do with widgets that are (1) large, (2) won't resize,
and (3) cannot be clipped?

The perfect should not be the enemy of the good, right?

> 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?