This appears to be a bug as the functionality is essentially broken. The validation editors including those shown in the demo, will appear offscreen and inaccessible if in the last visible column in a horizontally scrolling spreadsheet.
See dojo here.
Steps to reproduce:
- Create a spreadsheet that has a horizontal scroll.
- In the last column apply cells with validations and/or a custom editor.
- Render the spreadsheet and scroll to the right.
- Notice the editor buttons appear off-screen, there is no way to access them.
The buttons should appear on the left of the cell instead of the right if they are not accessible (that is, they fall on the last visible column).