OutOfMemoryError even when UndoManager limit is set to 0

[pmouawad]

Hi,
We are using RSyntaxTextArea and faced in the past this:
#19
So we implemented the proposed method.
We recently had a bug report:
https://issues.apache.org/bugzilla/show_bug.cgi?id=57440
As per comment of last 9 days we implemented a fix.

But it seems RUndoManager keeps piling up in org.fife.ui.rtextarea.RUndoManager$RCompoundEdit a huge number of javax.swing.text.AbstractDocument$DefaultDocumentEvent.

See screenshots:

See code:
https://github.com/apache/jmeter/blob/trunk/src/core/org/apache/jmeter/gui/util/JSyntaxTextArea.java

https://github.com/apache/jmeter/blob/trunk/src/core/org/apache/jmeter/gui/LoggerPanel.java

Thanks

[pmouawad]

Hi,
I traced what is happening.
When we call this piece of code:
Document doc;
try {
doc = textArea.getDocument();
Element root = doc.getDefaultRootElement();
int lineCount = root.getElementCount();
if (lineCount>LOGGER_PANEL_MAX_LINES_COUNT) {
int end = root.getElement(lineCount-LOGGER_PANEL_MAX_LINES_COUNT-1).getEndOffset();
doc.remove(0, end);
}
doc.insertString(doc.getLength(), format.format(logEvent), null);
textArea.setCaretPosition(doc.getLength()-1);
} catch (BadLocationException e) {
// NOOP
}

doc.insertString ends up calling RUndoManager#startCompoundEdit which leads to OOM.

I am wondering why RUndoManager does this when limit is set to 0.
Seems to be the bug.

[bobbylight]

Looking back at old, unclosed threads...

It looks like setting the limit of undos to 0 actually disables the limit (this is in Swing's UndoManager class), so my suggestion way back when was way off-base.

I can think of two workarounds for you until a solution is put into RSTA:

1. Set your undo limit to 1 instead of 0. As long as your editor is read-only, users should not be able to trigger undo actions, and RSTA's memory usage should not grow indefinitely.
2. Create a subclass of RUndoManager, override methods to make it do nothing (perhaps undo(), redo(), and undoableEditHappened()), then create an RSyntaxTextArea subclass, overriding the createUndoManager() method to return your do-nothing implementation.