bug#66068: 30.0.50; xwidget-webkit-browse-url makes Emacs abort

[Po Lu via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Eli Zaretskii <eliz@gnu.org> writes:

> The backtrace seems to say that there was some X error:
>
>   X protocol error: GLXBadWindow on protocol request 151
>   Serial no: 4286
>   Failing resource ID (if any): 0x3c001c5
>   Minor code: 32
>
> I guess we now need to understand what window triggered the "bad
> window" error and why?

I've commented on precisely the same bug in the past; if someone can
unearth that bug number, this bug ought to be merged with it.

It boils down to how the WebKitGTK developers have elected to cease
supporting off-screen windows, by presuming that every window holding a
WebView widget is an X server window eligible for an OpenGL context.
Emacs requires placing these widgets within offscreen windows managed by
GTK, for each xwidget might be displayed in multiple distinct windows,
and its contents must be captured and reproduced within all of them if
that be the case.

To put this another way, WebKitGTK doesn't support displaying a single
widget more than once anymore.  There is another library designed for
such use-cases as that of Emacs, based on the same WebKit library as
WebKitGTK, by the name of WPE.  The solution to this bug, in my
estimation, is rewriting xwidgets for that library... any volunteers?

BTW, please pardon my belated response to this bug.  Time remains scarce
for me.