private void updateVisibleState() {
        setVisible(helpContent != null
                && !SafeHtmlUtils.EMPTY_SAFE_HTML.equals(helpContent)
                && !NullSafe.isBlankString(helpContent.asString()));
    }
Show the help popup. Useful if you want to trigger the help popup from a keydown
on some other widget, e.g. a form group.
stroom-core-client-widget/src/main/java/stroom/widget/help/client/HelpButton.java