artist_port basic_text_box::key

[johannphilippe]

In text.cpp, line 376 :

      auto next_char = [this, &_text]()
      {
         if (_text.size() > 1 && _select_end < static_cast<int>(_text.size()))
            ++_select_end;
      };

Where _text.size() > 1 should probably be changed to _text.size() > 0 to allow moving caret to right when there is only one character in the box.