Bug: Undo after deleting styled text causes throw of exception

[gandalfas]

Expected Behavior

If you delete a character from styled text, and then Undo, it should work without throwing an exception.

Actual Behavior

An exception is thrown, under these conditions:

• The styled text must be on a line where there are two styles present, e.g. bold followed by italics.
• And the deletion must occur on the second styled text.

Variations

• if the Delete key + undo is done on the first styled text of that line, it works fine.
• if the line is all bold or all italics, then Delete key + undo works fine on any word on the line.

Reproducible Demo

• Run the demo program RichTextDemo (provided in your download area), so that stdout and stderr will appear (e.g., under an IDE)
• Open sample.rtfx
• go to line 3, the italicized line, copy the word 'Italicized' and paste it onto end of line 2, the bold line. now we have two different styles on the line.
• click within 'Italicized' on line 2
• hit the Delete key
• hit Ctl-Z
• at this point the exception is thrown:

---

Exception in thread "JavaFX Application Thread" java.lang.IllegalArgumentException: Unexpected change received.

Expected:
[RichTextChange{
position: 43
removed: Par[; StyledSegment(segment=left() style=true,12,Serif,0x000000ff)]
inserted: Par[; StyledSegment(segment=left(c) style=true,12,Serif,0x000000ff)]
}]

Received:
[RichTextChange{
position: 43
removed: Par[; StyledSegment(segment=left() style=true,12,Serif,0x000000ff)]
inserted: Par[; StyledSegment(segment=left(c) style=true,12,Serif,0x000000ff)]
}]

at org.fxmisc.undo.impl.UndoManagerImpl.changeObserved(UndoManagerImpl.java:234)
at org.reactfx.util.QueuingStreamNotifications.lambda$head$0(NotificationAccumulator.java:217)
at org.reactfx.ObservableBase.notifyObservers(ObservableBase.java:68)
at org.reactfx.SuspendableBase.resume(SuspendableBase.java:64)
at org.reactfx.CloseableOnceGuard.close(Guard.java:49)
at org.reactfx.MultiGuard.close(Guard.java:83)
    (rest of stack deleted)

---

Environment info:

• RichTextFX Version: 0.10.0
• Flowless 0.6.1
• ReactFX 2.0-M5
• UndoFX 2.1.0
• WellBehavedFX 0.3.3
• Operating System: Windows 10
• Java version: 8u181

---

[Jugen]

@Kim4444 Thanks for reporting the bug and providing clear steps to reproduce.
I did some debugging and have found the problem to be here, so will submit a PR soon.

[gandalfas]

@Jugen excellent news! thanks so much for your quick investigation!

[Jugen]

Fixed by PR #817