how do i use undo and redo?

[monopx-top]

the signatures are:
UndoRedoResult try_undo(CharOffset op_offset);
and
UndoRedoResult try_redo(CharOffset op_offset);

do the functions change the tree directly or do I have to do something with the result?
what is the op_offset for?
Can I get an example of how to use it please?

[cdacamar]

Were you able to check out the test file? There are quite a few examples of how to use both APIs:

fredbuf/fredbuf-test.cpp

Line 371 in 2ff26d5

auto r = tree.try_undo(CharOffset{ 0 });

As for what the offset is for, it tells the undo structure where that undo/redo operation was invoked and stores it if the operation is successful so that it will be returned when the corresponding operation is invoked again.