protected void updateByOpTree(javax.swing.text.DocumentFilter.FilterBypass fb) {
String oldStr = JMathTextField.this.getText();
String newStr = operatorTree.toString();
int commonStart = Utils.equalStartLen(oldStr, newStr);
int commonEnd = Utils.equalEndLen(oldStr, newStr);
if (commonEnd + commonStart >= Math.min(oldStr.length(), newStr.length()))
commonEnd = Math.min(oldStr.length(), newStr.length()) - commonStart;
try {
fb.replace(
commonStart,
oldStr.length() - commonEnd - commonStart,
newStr.substring(commonStart, newStr.length() - commonEnd),
null);
} catch (BadLocationException e) {
// this should not happen. we should have checked this. this whole function should be safe
throw new AssertionError(e);
}
}
