Why does overriding doubleclicked() method of ITextDoubleClickStrategy in eclipse remove syntax highlighting?

Why does overriding doubleclicked() method of ITextDoubleClickStrategy in
eclipse remove syntax highlighting?

I am implementing custom sql editor using eclipse rcp. My requirement is
to highlight keywords when user double clicks on a word.
Problem is that already existing feature for syntax highlighting is gone
when I override doubleclicked() method by extending
DefaultTextDoubleClickStrategy and implementing ITextDoubleClickStrategy.
Why does overriding doubleclicked() method turns off syntax highlighting?
What is the solution for this?
Any help is greatly appreciated.