Undo doesn't work properly

[Duskfall]

Steps to reproduce

1. Open ​http://ckeditor.com/demo
2. Clear all text inside
3. Type a small text like "test"
4. Select the "test text and copy it Ctrl + C
5. Paste the selected text multiple times. At lease 4-5 lines
6. Undo the input by pressing Ctrl + Z

Expected result

Undo all text

Actual result

The text is not undoed completely only partially

Other details (browser, OS, CKEditor version, installed plugins)

Tested on Firefox 49.0.1, Chrome 52.0.2743.116 m (64-bit) and IE 11

[Jakub Ś]

It has always worked that way - this is by design.

There is a fixed number of characters recorded in one undo step: ​https://github.com/ckeditor/ckeditor-dev/blob/master/plugins/undo/plugin.js#L240-L245

[Duskfall]

Is there a documentation or a reason why there is a limit in that? Did it fix some bug or something or shall I freely play with the value? Thanks

[Jakub Ś]

We definitely don't recommend changing the core code of the editor but you can experiment it with if you like. I'm not aware of any bug that has been fixed by that value.