Hi, in Vaadin 8 you could style component e.g. Button by adding style and using ValoTheme static final property.
Button viewBtn = new Button("Detail", VaadinIcons.EYE);
viewBtn.addStyleName(ValoTheme.BUTTON_ICON_ONLY);
viewBtn.addStyleName(ValoTheme.BUTTON_BORDERLESS);
How can you achieve this in Vaadin 10?