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.

lisp/xwidget.el

@@ -454,6 +454,16 @@ It can be retrieved with `(xwidget-get XWIDGET PROPNAME)'."
 ;;(add-hook 'window-configuration-change-hook 'xwidget-cleanup)
 (add-hook 'window-configuration-change-hook 'xwidget-delete-zombies)
 
+(defun xwidget-kill-buffer-query-function ()
+  "Ask beforek illing a buffer that has xwidgets."
+  (let ((xwidgets (get-buffer-xwidgets (current-buffer))))
+    (or (not xwidgets)
+        (yes-or-no-p
+         (format "Buffer %S has xwidgets; kill it? "
+                 (buffer-name (current-buffer)))))))
+
+(add-hook 'kill-buffer-query-functions 'xwidget-kill-buffer-query-function)
+
 ;;killflash is sadly not reliable yet.
 (defvar xwidget-webkit-kill-flash-oneshot t)
 (defun xwidget-webkit-kill-flash ()

src/buffer.c

@@ -44,6 +44,10 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include "keymap.h"
 #include "frame.h"
 
+#ifdef HAVE_XWIDGETS
+#include "xwidget.h"
+#endif  /* HAVE_XWIDGETS */
+
 struct buffer *current_buffer;		/* The current buffer.  */
 
 /* First buffer in chain of all buffers (in reverse order of creation).
@@ -1835,6 +1839,11 @@ cleaning up all windows currently displaying the buffer to be killed. */)
   kill_buffer_processes (buffer);
   UNGCPRO;
 
+#ifdef HAVE_XWIDGETS
+  GCPRO1 (buffer);
+  kill_buffer_xwidgets (buffer);
+  UNGCPRO;
+#endif  /* HAVE_XWIDGETS */
   /* Killing buffer processes may run sentinels which may have killed
      our buffer.  */
   if (!BUFFER_LIVE_P (b))

src/xwidget.c

@@ -202,7 +202,7 @@ TYPE is a symbol which can take one of the following values:
   //should work a bit like "make-button"(make-button BEG END &rest PROPERTIES)
   // arg "type" and fwd should be keyword args eventually
   //(make-xwidget 3 3 'button "oei" 31 31 nil)
-  //(xwidget-info (car xwidget-alist))
+  //(xwidget-info (car xwidget-list))
   struct xwidget* xw = allocate_xwidget();
   Lisp_Object val;
   xw->type = type;
@@ -1619,7 +1619,7 @@ syms_of_xwidget (void)
 
   DEFSYM (QCplist, ":plist");
 
-  DEFVAR_LISP ("xwidget-alist", Vxwidget_list, doc: /*xwidgets list*/);
+  DEFVAR_LISP ("xwidget-list", Vxwidget_list, doc: /*xwidgets list*/);
   Vxwidget_list = Qnil;
 
   DEFVAR_LISP ("xwidget-view-alist", Vxwidget_view_alist, doc: /*xwidget views list*/);
@@ -1845,4 +1845,18 @@ xwidget_end_redisplay (struct window *w, struct glyph_matrix *matrix)
     }
 }
 
+/* Kill all xwidget in BUFFER. */
+void
+kill_buffer_xwidgets (Lisp_Object buffer)
+{
+    Lisp_Object tail, xw;
+
+    for (tail = Fget_buffer_xwidgets (buffer); CONSP (tail); tail = XCDR (tail))
+        {
+            xw = XCAR (tail);
+            Vxwidget_list = Fdelq (xw, Vxwidget_list);
+            /* TODO free the GTK things in xw */
+        }
+}
+
 #endif  /* HAVE_XWIDGETS */

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 */