Odd 'flickering' (unstable display) in table: possible scrollbar issue

Using the latest Preview version of 3D Slicer (4.13.0 2022-01-19) in the Segment Editor I encountered some weird behaviour in the table of segments.
I had eight (8) segments defined, and I clicked the Threshold tool and scrolled down.
The table entries perpetually flicked between two states, at a frequency of ~once every 3–4 seconds,

My best guess is that there might be two conflicting instructions in the underlying code for the table:

  • one saying “a scrollbar needs to be added”,
  • the other saying “a scrollbar is not needed”,

I speculate that the problem arises because

  • when the scrollbar is present the vertical spacing of the list of segment is compressed, meaning that a scrollbar is not needed; but
  • when the scrollbar is not present the vertical spacing of the list of segment is expanded, meaning that a scrollbar is needed.


Upon further consideration, I don’t think clicking the Threshold effect or scrolling down had anything to do with it. The behaviour likely commenced after adding the eighth segment.

Adding a ninth segment stopped the flickering.
Surprisingly, removing the same ninth segment did not cause the flickering to instantly resume.

Later on I applied the Threshold effect, causing its dialogue to be dismissed. And then I clicked again on the Threshold effect: this did actually cause the flickering to start (with eight segments)! Cancelling the Threshold effect caused the flickering to stop.