Bug in undo/redo with additional new lines

[theuserbl]

That little bug exists on Windows and Linux. In version 2.0.0 and 1.2.0.

First open a file with color emojis

Then writing fast and wild some "text".

Then Undo with Ctrl+Z or over the menu

And then redo with Ctrl+Y or over the menu

After the redo you have one or more new lines.
Possible with one single letter, which was before part of the longer "word"

[lhecker]

It would be very helpful if you submit issues like this:

Steps to reproduce

• Create a new file with the contents

  foo
  bar
  

• Close and reopen the file
• Write Enter, "abc", Enter, "def" at the end
• Prses Ctrl-Z, Ctrl-Y

Expected

foo
bar

abc
def

Actual

...

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Writing it this way makes it faster for us maintainers to read the issue and reproduce it. 🙂
I won't have time to immediately investigate this and contributions would be welcome.

Long-term I intend to address this fundamentally by using a piece table instead of a gap buffer.