Re: Calling interactive lisp functions from C

["Noé Lopez via Emacs development discussions." <emacs-devel@gnu.org>]

Eli Zaretskii <eliz@gnu.org> writes:

>> 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?

Yes, but Fx_file_dialox, called from read-file-name calls quit directly
without checking inhibit-quit.

> 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.

That is probably best, if WebKit supports asynchronous answering for
that signal.  I will look into it.

Thanks.