Various issues when undoing when at the bottom of snapshots stack

[Olek Nowodziński]

Surprisingly, for some reason, when multiple inline editor are in use (/samples/inlineall.html), they share (actually: abuse) one another's undo stack. It happens when CTRL+Z is pressed and there are no snapshots left on the current stack.

It doesn't look like a feature, really, and since the issue can be reproduced since 4.0 in different browsers, it's time we fixed it.

See attached video (recorded in FF) to know more.

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Another TC. On IE open the inline all sample, focus one of the editors with more complex contents, type something and press CTRL+Z multiple times. Textfified version of the initial contents will be loaded.

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Another TC in FF:

1. ​http://ckeditor4.t/ckeditor/samples/replacebyclass.html
2. Put the caret

   Apollo 11^
   

3. Type "moo"
4. C-z

   ^Apollo 11
   

5. C-z

   ^
   Apollo 11
   

Expected

^Apollo 11

but another, native undo snapshot reverts the selection to the position initially set by the browser.

The reason

It seems that editor does not prevent the native undo if it reached the bottom of snapshots stack. It allows browser to do stuff and weird things happen.

[Piotrek Koszuliński]

cc