Re: Key press synthesis (for WebKitGTK)

[Gergely Polonkai <gergely polonkai eu>]

Hello,

from the manual
(https://developer.gnome.org/gtk3/stable/GtkWidget.html#GtkWidget-key-press-event),
the signature of key-press-event handlers is:

```
gboolean
user_function (GtkWidget *widget,
               GdkEvent  *event,
               gpointer   user_data)
```

> From the same manual:

> Returns
>
> TRUE to stop other handlers from being invoked for the event. FALSE to
> propagate the event further.

So if you change your handler’s return type from `void` to `gboolean`
and return `FALSE` if the lisp thingy doesn’t understand your key, it
will be automatically propagated to the next handler (which, hopefully,
will insert your "a" key.

Best,
Gergely

Pierre Neidhardt writes:

> 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!