Undo snapshot is overwritten on selectionChange

[jacekbogdanski]

Type of report

Bug

Provide detailed reproduction steps (if any)

1. Open https://ckeditor.com/latest/samples
2. Change editor content.
3. Make sure that there is at least a single undo step (undo button is not disabled).
4. Start clicking around inside editor (at least 20x) changing a selection.
5. Click undo button.

Expected result

Undo button is enabled and undoes the last change.

Actual result

Undo button is disabled.

Other details

• Installed CKEditor plugins: Undo

[jacekbogdanski]

It looks like the issue is caused by copyformatting plugin. applyFormatting command is executed on mouseup event. The command is integrated with undo by default, so undo plugin listen on the command execution and creates a snapshot any time it has been used. It should be integrated with undo plugin, however, a snapshot should be created only if content really changed.

https://github.com/ckeditor/ckeditor-dev/blob/d931efee7bb8875e489c172fa3e20de8e8209aef/plugins/copyformatting/plugin.js#L103-L107

I already checked against regression and the only regression I found is the addition of the applyFormatting plugin into the default config file: 9f97b19

[engineering-this]

There is another related issue.

1. Open sample: http://cdn.ckeditor.com/4.11.2/full-all/samples/
2. Focus editor and type one letter.
3. Press undo.
4. Change editor selection with mouse.

Expected

Redo button is active.

Actual

Redo button is inactive.

[Comandeer]

Merged into 4.11.3.