# Observe annotation ruler size change
**URL:** https://discourse.slicer.org/t/observe-annotation-ruler-size-change/5039
**Category:** Development
**Created:** [December 11, 2018, 12:30pm UTC](https://discourse.slicer.org/t/observe-annotation-ruler-size-change/5039 "2018-12-11T12:30:00Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@giancu](https://discourse.slicer.org/u/giancu)
#### Post date: [December 11, 2018, 12:30pm UTC](https://discourse.slicer.org/t/observe-annotation-ruler-size-change/5039/1 "2018-12-11T12:30:00Z")
Hi. I try to capture the change in size of a vtkMRMLAnnotationRulerNode. Is there any event (signal) which is triggered in such a situation? I am using the nice LineProfile example of Andras, but I would like to be able to update the line profile chart “on line” when changing the annotation ruler.
Thanks in advance.
Cheers Gheorghe
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### Author:  [@lassoan](https://discourse.slicer.org/u/lassoan)
#### Post date: [December 11, 2018, 9:12pm UTC](https://discourse.slicer.org/t/observe-annotation-ruler-size-change/5039/2 "2018-12-11T21:12:04Z")
A completely reworked version of the line profile plot module is available:
> **[GitHub - lassoan/SlicerLineProfile: Extension for 3D Slicer to compute...](https://github.com/lassoan/SlicerLineProfile)**
>
> Extension for 3D Slicer to compute intensity profile of a volume along a line - GitHub - lassoan/SlicerLineProfile: Extension for 3D Slicer to compute intensity profile of a volume along a line
It can update the profile in real-time as you modify the ruler (just click the checkbox on the “Compute…” button). It also makes available the sampled intensity values in a table, and uses new plotting infrastructure.
[https://github.com/lassoan/SlicerLineProfile/blob/master/LineProfileScreenshot01.png?raw=true](https://github.com/lassoan/SlicerLineProfile/blob/master/LineProfileScreenshot01.png?raw=true)
It would be ready to be submitted to the extension manager (so that you can install using a single click) but I did not have time to create an icon for the extension. If anybody could draw a nice icon to replace the [current placeholder](https://github.com/lassoan/SlicerLineProfile/blob/master/LineProfile.png) then please do and send a pull request. Thanks!
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### Author:  [@giancu](https://discourse.slicer.org/u/giancu)
#### Post date: [January 7, 2019, 9:25am UTC](https://discourse.slicer.org/t/observe-annotation-ruler-size-change/5039/3 "2019-01-07T09:25:02Z")
You’re the best. Work like a charm. Thank you.
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### Author:  [@giancu](https://discourse.slicer.org/u/giancu)
#### Post date: [January 7, 2019, 9:40am UTC](https://discourse.slicer.org/t/observe-annotation-ruler-size-change/5039/4 "2019-01-07T09:40:17Z")
Is looks like sometimes the update speed is not always the same. Moving the mouse does not always update the plot. Can I adapt the update parameters? Luckily the values saved in the table are always correct.
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### Author:  [@lassoan](https://discourse.slicer.org/u/lassoan)
#### Post date: [January 7, 2019, 1:48pm UTC](https://discourse.slicer.org/t/observe-annotation-ruler-size-change/5039/5 "2019-01-07T13:48:26Z")
> [@giancu](#):
>
> Can I adapt the update parameters?
Can you give more details about what you would like to do exactly?