Cursor states are not correctly restored after clearing undo stack (doesn't affect wodo)

[peitschie]

The undo stack can be cleared by calling setInitialState() on the gui.TrivialUndoManager component. However, the cursor-extraction logic incorrectly assumes that last OpMoveCursor operation is the current location of the cursor, which is not the case if text editing has occurred.

See comment and related block of code in e6cb301 and workaround code in pr #900 (saveCurrentCursorPositions).

[vandenoever]

Could you write a small test case / unit test and add it to tests/gui/TrivialUndoManagerTests.js, perhaps in a new list this.brokenTests?

[peitschie]

Could you write a small test case / unit test and add it to tests/gui/TrivialUndoManagerTests.js, perhaps in a new list this.brokenTests?

It's not really a high priority for me at the moment...

[vandenoever]

Can you describe the issue a bit more, then I'll have a go at a unit test for the issue.

[kossebau]

Issue as I again understand it (sleeping works wonders):
if the trivialundomanager is asked to dump its current stack of states (on a given document), it still needs to have an initial state transition after that dump which describes the current cursor positions. Because added cursors would be positioned at the beginning of the document, and the diff to the current existing state of the document can be described by adding matching cursor ops as that initial state transition.
Problem now is that the current code simply takes that last cursor move ops from the old stack to get the cursor ops for the new initial state transition. Which might not really match the current state of the document, because since that cursor move op was done, other ops might have removed/added things in front of the cursor, thus invalidating the position as used in the last cursor op.