private void updateScrollMargin() {
        if (editor.isAttached() && scrollMarginDirty) {
            editor.setScrollMargin(
                    scrollMargin.getTop(),
                    scrollMargin.getBottom(),
                    scrollMargin.getLeft(),
                    scrollMargin.getRight());
            scrollMarginDirty = false;
        }
    }
@param lineNo One based
@param colNo  One based
stroom-core-client-widget/src/main/java/stroom/editor/client/view/Editor.java