bug#72104: [PATCH] xwidget: Fix xwidget-at misinterpreting non-xwidget text-properties

[George Huebner <george@feyor.sh>]

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Tags: patch

xwidget-at assumes the text-property at `point-min` either doesn't 
exist or is an xwidget, and can improperly access fields. This 
patch just returns nil if the text-property isn't an xwidget.

This is definitely an edge case; I use a package called org-modern 
where headlines are formatted with text-properties, which is how I 
found the bug:
Debugger entered--Lisp error: (wrong-type-argument listp #("◉" 0 1 
(face org-modern-symbol)))
  xwidget-at(1)
  xwidget-webkit-current-session()


In GNU Emacs 29.1 (build 1, aarch64-apple-darwin23.4.0, Carbon 
Version
170 AppKit 2487.5)
Windowing system distributor 'Apple Inc.', version 14.4.0
System Description:  macOS 14.4

Configured using:
 'configure
 --prefix=/nix/store/ismv7jzf3hcqziq5bpjfs54zd4qfjjn7-emacs-mac-macport-29.1
 --disable-build-details --with-modules --without-gif 
 --without-jpeg
 --without-png --without-tiff --without-x --without-xpm
 '--enable-mac-app=$$out/Applications' --with-gnutls --with-mac
 --with-xml2 --without-ns --with-compress-install
 --with-toolkit-scroll-bars --with-native-compilation
 --without-imagemagick --with-mailutils --without-small-ja-dic
 --with-tree-sitter --without-xinput2 --without-xwidgets 
 --without-dbus
 --without-selinux --with-xwidgets'

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From 48a662563bc6e7c5bc63dc63da4e0c36909b6cc2 Mon Sep 17 00:00:00 2001
From: George Huebner <george@feyor.sh>
Date: Sun, 14 Jul 2024 01:46:07 -0500
Subject: [PATCH] xwidget: Fix xwidget-at misinterpreting non-xwidget
 text-properties

xwidget-open wrongly assumes the the text-property at min-position is an
xwidget, if it exists; the fix is just returning nil if the
text-property isn't an xwidget.
---
 lisp/xwidget.el | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lisp/xwidget.el b/lisp/xwidget.el
index bf5987d..c5a84db 100644
--- a/lisp/xwidget.el
+++ b/lisp/xwidget.el
@@ -81,7 +81,7 @@ This returns the result of `make-xwidget'."
 (defun xwidget-at (pos)
   "Return xwidget at POS."
   (let* ((disp (get-text-property pos 'display))
-         (xw (car (cdr (cdr disp)))))
+         (xw (ignore-errors (car (cdr (cdr disp))))))
     (when (xwidget-live-p xw) xw)))
 
 
-- 
2.44.1