docs: private void updateStyle() {
          CaptionStyle cs = captionStyle == null ? CaptionStyle.HIDDEN : captionStyle;
          String background = null;
          
          switch (cs) {
              case FRAME:
                  break;
              
              case TITLE:
                  break;
              
              case LEFT:
                  background = getGradValue(color1, color2);
                  break;
              
              case RIGHT:
                  background = getGradValue(color2, color1);
                  break;
              
              case CENTER:
                  background = getGradValue(color1, color2, color1);
                  break;
              
          }
          
          panel.addClass("sharedForms-captioned sharedForms-captioned-caption-" + cs.name().toLowerCase());
          String css = "##{id}-titlebar ";
          
          if (cs == CaptionStyle.HIDDEN) {
              css += "{display:none}";
          } else {
              css += "{background: " + background + "}";
          }
          
          panel.setCss(css);
      }