I have a ComboBox that allows selection of the given items, and an icon that accepts the selection:

the functionality is all fine.
I'm looking for the effect to get the search icon into the comboBox. like in Vaadin Icons:

How is this done?
I tried
comboBox.setIcon(new ThemeResource("search.png"));
it didn't do any change.
backend developer here - not good on front-end tools.
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EDIT:
one thing i can think of is to make the border of ComboBox disappear (don't know yet how), and make a border on the component that contains both the icon and the comboBox.
is there another/better way?