groupbar: various visual improvements

added rounding, round at edges, and indicator height

src/render/pass/RectPassElement.hpp

@@ -10,6 +10,7 @@ class CRectPassElement : public IPassElement {
         float      roundingPower = 2.0f;
         bool       blur = false, xray = false;
         float      blurA = 1.F;
+        CBox       clipBox;
     };
 
     CRectPassElement(const SRectData& data);