void
Editor::close_region_gaps ()
{
	list <boost::shared_ptr<Playlist > > used_playlists;

	RegionSelection rs = get_regions_from_selection_and_entered ();

	if (!_session || rs.empty()) {
		return;
	}

	Dialog dialog (_("Close Region Gaps"));

	Table table (2, 3);
	table.set_spacings (12);
	table.set_border_width (12);
	Label* l = manage (left_aligned_label (_("Crossfade length")));
	table.attach (*l, 0, 1, 0, 1);

	SpinButton spin_crossfade (1, 0);
	spin_crossfade.set_range (0, 15);
	spin_crossfade.set_increments (1, 1);
	spin_crossfade.set_value (5);
	table.attach (spin_crossfade, 1, 2, 0, 1);

	table.attach (*manage (new Label (_("ms"))), 2, 3, 0, 1);

	l = manage (left_aligned_label (_("Pull-back length")));
	table.attach (*l, 0, 1, 1, 2);

	SpinButton spin_pullback (1, 0);
	spin_pullback.set_range (0, 100);
	spin_pullback.set_increments (1, 1);
	spin_pullback.set_value(10);
	table.attach (spin_pullback, 1, 2, 1, 2);

	table.attach (*manage (new Label (_("ms"))), 2, 3, 1, 2);

	dialog.get_vbox()->pack_start (table);
	dialog.add_button (Stock::CANCEL, RESPONSE_CANCEL);
	dialog.add_button (_("Ok"), RESPONSE_ACCEPT);
	dialog.show_all ();

	if (dialog.run () == RESPONSE_CANCEL) {
		return;
	}

	framepos_t crossfade_len = spin_crossfade.get_value();
	framepos_t pull_back_frames = spin_pullback.get_value();

	crossfade_len = lrintf (crossfade_len * _session->frame_rate()/1000);
	pull_back_frames = lrintf (pull_back_frames * _session->frame_rate()/1000);

	/* Iterate over the region list and make adjacent regions overlap by crossfade_len_ms */

	begin_reversible_command (_("close region gaps"));

	int idx = 0;
	boost::shared_ptr<Region> last_region;

	rs.sort_by_position_and_track();
	
	for (RegionSelection::iterator r = rs.begin(); r != rs.end(); ++r) {

		boost::shared_ptr<Playlist> pl = (*r)->region()->playlist();

		if (!pl->frozen()) {
			/* we haven't seen this playlist before */

			/* remember used playlists so we can thaw them later */
			used_playlists.push_back(pl);
			pl->freeze();
		}

		framepos_t position = (*r)->region()->position();
                

		if (idx == 0 || position < last_region->position()){
			last_region = (*r)->region();
			idx++;
			continue;
		}
                
                framepos_t last_region_position = last_region->position();
                framecnt_t last_region_length = last_region->length();
                framepos_t last_region_end = (last_region_position + last_region_length);
                
                if ((last_region_end - pull_back_frames) > (position - crossfade_len)){
                    (*r)->region()->trim_front( (position - pull_back_frames));
                    last_region->trim_end( (position - pull_back_frames + crossfade_len));
                } else {
                    (*r)->region()->trim_front( (last_region_end - pull_back_frames - crossfade_len));
                    last_region->trim_end( (last_region_end - pull_back_frames));
                }
		last_region = (*r)->region();

		idx++;
	}

	while (used_playlists.size() > 0) {
		list <boost::shared_ptr<Playlist > >::iterator i = used_playlists.begin();
		(*i)->thaw();
		used_playlists.pop_front();
	}

	commit_reversible_command ();
}