Key press synthesis (for WebKitGTK)

[Pierre Neidhardt <mail ambrevar xyz>]

Hi all!

I'm working on the GTK port of Next browser (http://next.atlas.engineer/,
source: https://source.atlas.engineer/public/next).

I have a window with a WebKitGTK view in it.

I intercept all key-press-events and send them to a third-party Lisp program via
XML-RPC.

Whenever the Lisp program does not recognize the key bindings, it notifies the
GTK program.  From there, GTK must forward the key press to the WebKit view.

Example:

- The focus is on a text field on a web page.
- I press "a".
- "a" is sent to the Lisp third party program.
- Lisp does not know what to do with "a", and sends a message back to the GTK program.
- The GTK program must insert "a" in the text field in the WebKit view.


To achieve that, I think I need to synthesize a key press event during the last
step.
(Unless someone can think of a direct way to forward a key press to the WebKit
view.)

Here is what I've got:

- In the widget creation function:

--8<---------------cut here---------------start------------->8---
        g_signal_connect(buffer->web_view, "key-press-event", G_CALLBACK(window_send_event), window);
--8<---------------cut here---------------end--------------->8---

A 'window_send_event' callback for all key-presses.  I use Libsoup to send an
XML-RPC message containing the keypress to the Lisp program:

--8<---------------cut here---------------start------------->8---
void window_send_event(GtkWidget *widget, GdkEventKey *event, gpointer data) {
  // ...  Some provision to avoid infinite loops...

        WindowEvent *window_event = g_new(WindowEvent, 1);
        Window *window = (Window *)data;
        window_event->window = window;
        window_event->event = event;

        g_debug("Sending keypress XML-RPC message for window %p", window_event->window);
        soup_session_queue_message(xmlrpc_env, msg, &window_event_callback, window_event);
}
--8<---------------cut here---------------end--------------->8---

And finally, the callback when the response arrives from the Lisp program:

--8<---------------cut here---------------start------------->8---
void window_event_callback(SoupSession *_session, SoupMessage *msg, gpointer data) {
        // ...
        if (!g_variant_get_boolean(consumed)) {
                g_debug("Event not consumed, forwarding to GTK");

                WindowEvent *window_event = (WindowEvent *)data;

                GdkDevice *device = NULL;
                GdkDisplay *display = gdk_display_get_default();
                GdkSeat *seat = gdk_display_get_default_seat(display);
                device = gdk_seat_get_keyboard(seat);

                GdkEvent *event = gdk_event_new(GDK_KEY_PRESS);
                event->key = *(window_event->event);
                event->key.string = g_strdup(window_event->event->string);
                event->key.time = gtk_get_current_event_time();
                event->key.window = 
g_object_ref(gtk_widget_get_window(GTK_WIDGET(window_event->window->base)));
                gdk_event_set_device(event, device);

                gtk_main_do_event(event);
                gdk_event_free(event);

                g_debug("Event emitted");
        }
}
--8<---------------cut here---------------end--------------->8---

The

--8<---------------cut here---------------start------------->8---
                gtk_main_do_event(event);
--8<---------------cut here---------------end--------------->8---
    
call is not caught anywhere though.  Any idea why?

I've tried with different event settings and sometimes I get

--8<---------------cut here---------------start------------->8---
(next-gtk-webkit:10768): GLib-GObject-WARNING **: 15:31:27.027: gsignal.c:2172: signal id '68' cannot be 
chained from current emission stage for instance '0x1c3a2a0'
--8<---------------cut here---------------end--------------->8---

I don't understand the above error message.  Any idea what could issue it?

Any clue, anyone?

Cheers!

-- 
Pierre Neidhardt
https://ambrevar.xyz/