If the user clicks on the spin box that has an On Mouse Leave event and then drags the mouse around the leave event will fire off as if the mouse position is still being updated to the screen (the mouse is hidden when clicking and dragging on a spin box). This causes two issues.

Issue one: There is a continuity error because the mouse enter event does not fire during this error, only the the event leave. Meaning that you can have multiple leave events firing off without a ever getting a mouse enter event.

Issues two: The mouse when release always shows up as the spot that the user originally clicked on the spin box. This means the expected behavior is for the event leave to not fire off while using the spin box

Steps to Reproduce
  1. Open the editor
  2. Create a new blueprint widget
    Right click content browser > User Interface > Widget Blueprint
  3. Name it Spinbox
  4. Create a new blueprint widget
    Right click content browser > User Interface > Widget Blueprint
  5. Name it Holder
  6. Open "Spinbox" widget
  7. Delete the Canvas panel
  8. Add a Spin box widget to the designer tab
  9. Go to the event graph
  10. Create the blueprint in the attached image
  11. Compile and save
  12. Open the "Holder" Widget blueprint
  13. Add the "Spinbox" widget to the designer tab via the User create section
  14. Compile and save
  15. Open the level blueprint
  16. Add the widget "Holder" to the screen
    Event Begin play > Create Widget > Select "Holder" from the drop down > Add to viewport
  17. Compile
  18. Play in editor
  19. Press Shif+F1 to show mouse
  20. Move the mouse into and out of the spin box
  21. Notice "Enter" and "Leave" are printed out appropriately
  22. Click and drag on the spin box in the manner shown in the other attached image
  23. Notice that the Event On Mouse Leave fires off but the Enter event does not

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Cannot Reproduce
ComponentUE - Editor - UI Systems
Affects Versions4.7.54.8
CreatedApr 13, 2015
ResolvedAug 11, 2016
UpdatedJul 14, 2021