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

**URL:** <https://discourse.slicer.org/t/odd-flickering-unstable-display-in-table-possible-scrollbar-issue/21555>\
**Category:** Support\
**Tags:** gui\
**Created:** [January 21, 2022, 5:43am UTC](https://discourse.slicer.org/t/odd-flickering-unstable-display-in-table-possible-scrollbar-issue/21555 "2022-01-21T05:43:53Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![DIV](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/div/32/12816_2.png) [@DIV](https://discourse.slicer.org/u/DIV)\
**Post date:** [January 21, 2022, 5:43am UTC](https://discourse.slicer.org/t/odd-flickering-unstable-display-in-table-possible-scrollbar-issue/21555/1 "2022-01-21T05:43:53Z")

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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,

 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/f/6/f6e35562304f7fc068eba722710e85bfc1ee0750.png)  
 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/d/3/d358811fdfe76714ec71daf404db48e94e9be44b.png)

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.

—DIV

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<div class="post-metadata">

**Author:** ![DIV](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/div/32/12816_2.png) [@DIV](https://discourse.slicer.org/u/DIV)\
**Post date:** [January 21, 2022, 5:45am UTC](https://discourse.slicer.org/t/odd-flickering-unstable-display-in-table-possible-scrollbar-issue/21555/2 "2022-01-21T05:45:30Z")

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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.