Strange Behavior Putting Drawing Events onto the Undo Stack

[NickDefo]

There appears to be an issue with how drawing events get added to the undo stack. If you hit undo after a drawing event, but before a time slice is placed onto the undo stack you will undo the drawing event, but immediately have a new drawing event placed onto the undo stack, which contains the previous undo event. This bug appears to have been documented and fixed in issue 174, but it was either reintroduced, or the fix did not make it into the Windows build.

This imgur album shows the described issue: http://imgur.com/a/wtSLt (I could not attach the gifs due to the file size)

Basic system details
MyPaint version: 1.2.1+gitexport.bcf5a28d
Also reproducable on current alpha, 1.3.0-alpha+git.70ce73d9
Operating system: Windows 10 64 bit

Steps to reproduce

1. Start MyPaint
2. Begin drawing strokes in rapid succession for a few seconds
3. After several seconds, hit undo shortly after the last stroke you drew.
4. Watch the undo/redo arrows in the upper left corner of the screen - You will see the Redo arrow light up and show you that you have something to redo in the Undo/Redo stack, and then it will immediately gray out, as a new undo event is pushed onto the stack for the last few strokes that you drew.
5. Hit undo: you will restore everything that you had just tried to undo in step 3.

This problem can be exacerbated if you made strokes between when you hit undo, and when the undo event was pushed onto the stack, as these strokes will leave the undo/redo stack in a broken state.

Note: Because this is a timing-dependent bug, it may take a few attempts to reproduce the issue. It all depends on whether or not a slice of pen events were being added to the undo/redo stack before or after you hit undo.

[achadwick]

Thnaks for the report @NickDefo !

Is it still happening with the latest alpha build? You can get that on the AppVeyor button on the main page, or from https://ci.appveyor.com/project/achadwick/mypaint/branch/master. To download it, click the build for your preferred environment, then the Artifacts tab, and grab the installer exe or the standalone zipfile (either's fine for testing this).

[NickDefo]

Yep, still occurring with the latest alpha build - Sorry for not calling that out more clearly in the original post.