on.keychord_press = function(chord, key)
	if chord == 'C-=' then
		-- zoom in
		Viewport.zoom = Viewport.zoom+0.1
	elseif chord == 'C--' then
		-- zoom out
		Viewport.zoom = Viewport.zoom-0.1
	elseif chord == 'C-0' then
		-- reset zoom
		Viewport.zoom = 1.0
	elseif Cursor_node then
		edit.keychord_press(Cursor_node.editor, chord, key)
	end
end