The ReadOnly property makes the control read only. Use the Enabled property to disable the control. Use the Locked property to lock an editor. If the control is read only, the Edit or Change event is not fired. Use the CellEditorVisible property to hide the cell's editor. Use the SelectableItem property to specify the user can select an item. 

The ReadOnly property of the control mostly refers ot the List/Columns section of the control, and it is not applied to the Chart section. 

You can use the following properties to prevent changes in the Chart section.

• AllowCreateBar property on False, prevents the user to create new bars in the chart panel.
• BarsAllowSizing property on False, prevents the user to move or resize any bar on the chart.
• AllowLinkBars property on False, prevents the user to link bars, at runtime