Re: Calling interactive lisp functions from C

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sun, 22 Sep 2024 18:38:53 +0200
> From:  Noé Lopez via "Emacs development discussions." <emacs-devel@gnu.org>
> 
> I am trying to call the read-file-name function from a C WebKit
> callback, in this case it is the « run-file-chooser » signal.
> 
> I came up with this code which works when selecting a file, but aborts
> emacs when hitting the « cancel » button of the file chooser dialog.
> 
> static gboolean wpe_run_file_chooser_cb (WebKitWebView *webview,
> 					 WebKitFileChooserRequest *request,
> 					 struct xwidget *xw)
> {
>   /* use read-file-name if only one file is needed, useful for keyboard
>      only usage. */
>   if (!webkit_file_chooser_request_get_select_multiple (request))
>     {
>       /* TODO: we can use webkit_file_chooser_request_get_selected_files
>        * to find a default file name for the prompt. */
>       Lisp_Object file = call4 (Qread_file_name,
> 				build_string ("Select file"),
> 				Qnil,
> 				Qnil,
> 				Qt);
>       if (EQ (file, Qnil))
> 	{
> 	  webkit_file_chooser_request_cancel (request);
> 	  g_message ("canceled file request");
> 	}
>       const char *const selected_files[] = { SSDATA (file), NULL };
>       webkit_file_chooser_request_select_files (request, selected_files);
>       return TRUE;
>     }
>   return TRUE;
> }
> 
> The callback is activated from a click action in the WebKit buffer, so
> « waiting_for_input » is true, causing signal_or_quit to abort.  Using
> clear_waiting_for_input changes it to a segmentation fault.
> 
> What can I do to catch the quit signal?  Ideally I need to call a
> function to notify WebKit of the cancelation, or it will hang.

Did you try to bind inhibit-quit to the value t?

An alternative is not to call read-file-name directly, but instead
queue an input event that will invoke a command when processed, and
the command will call read-file-name.