code: private void checkBeginSelection(Cursor cursor, SelectorModel model)
      {
          final boolean canClick = !model.getClickableArea().contains(cursor.getScreenX(), cursor.getScreenY());
          if (!model.isSelecting() && !canClick)
          {
              model.setSelecting(true);
              startX = cursor.getX();
              startY = cursor.getY();
  
              for (final SelectorListener listener : listeners)
              {
                  listener.notifySelectionStarted(Geom.createArea(startX, startY, 0, 0));
              }
          }
      }
docs: Check if can begin selection. Notify listeners if started.
  
  @param cursor The cursor reference.
  @param model The selector model.