synchronized void returnPressed() {
Document doc = getDocument();
int len = doc.getLength();
Segment segment = new Segment();
try {
doc.getText(outputMark, len - outputMark, segment);
} catch(javax.swing.text.BadLocationException ignored) {
ignored.printStackTrace();
}
if(segment.count > 0) {
history.addElement(segment.toString());
}
historyIndex = history.size();
inPipe.write(segment.array, segment.offset, segment.count);
append("\n");
outputMark = doc.getLength();