@Override
        public void advanceCharactersBackwards() {
            doWithConfig(sourceConfig -> {
                final long maxChars = sourceConfig.getMaxCharactersPerFetch();
                final long newCharOffset = Math.max(0,
                        receivedSourceLocation.getDataRange().getCharOffsetFrom() - maxChars - 1);
                setDataRange(DataRange.fromCharOffset(newCharOffset, maxChars));
            });
        }
Used for navigating standard char based data using char offsets.
stroom-core-client/src/main/java/stroom/data/client/presenter/SourcePresenter.java