bring_to_front_and_focus implementation on gtk

[Kartoffelsaft]

This should be a working implementation of the bring_to_front_and_focus function for the WindowHandle mentioned in #295.

Also, I noticed that this focus function has a documentation comment above it but the function below just has a regular comment. I didn't bother to change it as it seemed unrelated to what I was doing, and I didn't know if that was intentional. The documentation seems to have gotten it anyway.

[cmyr]

Thanks for the patch!

I would trust the GTK docs on this, and use present_with_time instead. From a quick reading it looks like the 'timestamp' is generally something that is associated with an event; it also says that we can pass GDK_CURRENT_TIME to use the current timestamp, so I would try that?

[jneem]

This gtk API is probably derived from the x11 API, where when you request input focus you're supposed to supply the timestamp of the event that made you want to request input focus. As I recently learned in #1045, you aren't allowed to use the current time; it has something to do with focus stealing prevention. The relevant snippet from ICCCM is

Clients that use a SetInputFocus request must set the time field to the timestamp of the event that caused them to make the attempt. [...] Note that clients must not use CurrentTime in the time field.

The underlying issue here is that the druid-shell API doesn't allow for a meaningful timestamp. But given that constraint, there's actually no difference between present and present_with_time(GDK_CURRENT_TIME). I just checked the gtk source:

void
gtk_window_present (GtkWindow *window)
{
  gtk_window_present_with_time (window, GDK_CURRENT_TIME);
} 

[Kartoffelsaft]

Given what @jneem said, I think it should be left at present, as using present_with_time implies that we know what timestamp to use, which we don't. That said, I do think that a // TODO: should be added to indicate that present_with_time should be used if and when the timestamp could be known.

And having looked at the GTK source myself, it does do some conversion so that it doesn't break the X11 side of things:

gtk_window_present_with_time (GtkWindow *window,
			      guint32    timestamp)
{
// ...
      if (timestamp == GDK_CURRENT_TIME)
        {
// #ifdef ...
	      timestamp = gdk_x11_display_get_user_time (display);
// #endif ...
	    timestamp = gtk_get_current_event_time ();
        }

[cmyr]

Okay, thanks for the explanation!