Handle xwidgets like processes and delete them when their buffer is killed.

* lisp/xwidget.el (xwidget-kill-buffer-query-function): New function to
query a user before killing a buffer with xwidgets in it.

This function is stored in `kill-buffer-query-functions' and called from
`kill-buffer'.
* src/buffer.c (Fkill_buffer): Call `kill_buffer_xwidgets'.
* src/xwidget.c (kill_buffer_xwidgets): Delete xwidgets attached to the
specified buffer.
* src/xwidget.h (kill_buffer_xwidgets): Add definition.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/xwidget.h b/src/xwidget.h
index 3ca9dbe0e1a..530b087796c 100644
--- a/src/xwidget.h
+++ b/src/xwidget.h
@@ -107,4 +107,6 @@ struct xwidget* lookup_xwidget (Lisp_Object  spec);
 #define XG_XWIDGET "emacs_xwidget"
 #define XG_XWIDGET_VIEW "emacs_xwidget_view"
 void      xwidget_view_delete_all_in_window(  struct window *w );
+
+void kill_buffer_xwidgets (Lisp_Object buffer);
 #endif  /* XWIDGET_H_INCLUDED */