scroll: click on button step 1

src/base/fresnel.renderer.pas

@@ -437,8 +437,10 @@ begin
       writeln('TRendererScrollBar.MouseHandler Mouse Down ',Parent.Name,' Horz=',Horizontal,' Hit=',MouseDownHit,' p=',FloatToCSSStr(MouseDownGrabPos));
       {$ENDIF}
       case MouseDownHit of
-      TSBHit.hButtonLT: ;
-      TSBHit.hButtonRB: ;
+      TSBHit.hButtonLT:
+        NewPos:=Position-1;
+      TSBHit.hButtonRB:
+        NewPos:=Position+1;
       TSBHit.hThumb:
         begin
           SetPointerCapture((MouseEvt as TFresnelMouseDownEvent).PointerId);