if (region == null || fRightDocument == null || fLeftDocument == null)
return;
RangeDifference diff= region.getDifference();
int rOffset= fRightDocument.getLineOffset(diff.rightStart());
int rLength= fRightDocument.getLineOffset(diff.rightEnd() - 1) + fRightDocument.getLineLength(diff.rightEnd() - 1) - rOffset;
int lOffset= fLeftDocument.getLineOffset(diff.leftStart());
int lLength= fLeftDocument.getLineOffset(diff.leftEnd() - 1) + fLeftDocument.getLineLength(diff.leftEnd() - 1) - lOffset;
fRightDocument.replace(rOffset, rLength, fLeftDocument.get(lOffset, lLength));
}