# Couldn't Register customized DisplayableManager to extension module

**URL:** <https://discourse.slicer.org/t/couldnt-register-customized-displayablemanager-to-extension-module/28560>\
**Category:** Development\
**Created:** [March 24, 2023, 5:20pm UTC](https://discourse.slicer.org/t/couldnt-register-customized-displayablemanager-to-extension-module/28560 "2023-03-24T17:20:51Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![RuoyanMeng](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/ruoyanmeng/32/12403_2.png) [@RuoyanMeng](https://discourse.slicer.org/u/RuoyanMeng)\
**Post date:** [March 24, 2023, 5:20pm UTC](https://discourse.slicer.org/t/couldnt-register-customized-displayablemanager-to-extension-module/28560/1 "2023-03-24T17:20:52Z")

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Hi, I tried to customize a slice DisplayableManager and register it to vtkMRMLSliceViewDisplayableManagerFactory. But after successfully compiling our extension, When starting the 3D slicer, it will report _ **“/Slicer/Slicer-SuperBuild-Debug/VTK/Common/Core/vtkDebugLeaks.cxx, line 272, Deleting unknown object: vtkMRMLLiverResectionsDisplayableManager”** _  
And the following error is _**“/Slicer/Libs/MRML/DisplayableManager/vtkMRMLDisplayableManagerFactory.cxx, line 136, vtkMRMLSliceViewDisplayableManagerFactory (0x555584f96130): RegisterDisplayableManager - vtkMRMLLiverResectionsDisplayableManager is not a displayable manager. Failed to register”**_

For creating customized DisplayableManager I referenced slicer markups’ [MRMLDM](https://github.com/Slicer/Slicer/tree/fbc2ede79060e2e2c653ddb2f0b7d2bba9fab16b/Modules/Loadable/Markups/MRMLDM)

Could you share your thoughts on possible reasons lead this error? Thank you so much.

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**Author:** ![lassoan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/lassoan/32/13_2.png) [@lassoan](https://discourse.slicer.org/u/lassoan)\
**Post date:** [March 26, 2023, 4:32am UTC](https://discourse.slicer.org/t/couldnt-register-customized-displayablemanager-to-extension-module/28560/2 "2023-03-26T04:32:01Z")

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If you want to create custom markups then you don’t need to implement a custom displayable manager. See complete example [in ExtraMarkups extension](https://github.com/chir-set/SlicerExtraMarkups).

Also check out the Liver extension’s [advanced liver resection planning and visualization tools](https://github.com/ALive-research/Slicer-Liver) already exist in Slicer. Maybe it is a better starting point.

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**Author:** ![Mik](https://avatars.discourse-cdn.com/v4/letter/m/958977/32.png) [@Mik](https://discourse.slicer.org/u/Mik)\
**Post date:** [March 27, 2023, 9:39am UTC](https://discourse.slicer.org/t/couldnt-register-customized-displayablemanager-to-extension-module/28560/3 "2023-03-27T09:39:24Z")

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Did you [initiate](https://github.com/Slicer/Slicer/blob/main/Modules/Loadable/Colors/qSlicerColorsModule.cxx#L51-L53) and [register](https://github.com/Slicer/Slicer/blob/main/Modules/Loadable/Colors/qSlicerColorsModule.cxx#L98-L102) your displayable manager in a module source file?

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**Author:** ![RuoyanMeng](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/ruoyanmeng/32/12403_2.png) [@RuoyanMeng](https://discourse.slicer.org/u/RuoyanMeng)\
**Post date:** [March 27, 2023, 9:40am UTC](https://discourse.slicer.org/t/couldnt-register-customized-displayablemanager-to-extension-module/28560/4 "2023-03-27T09:40:09Z")

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Hi, Thank you for your input! Actually, I am one of the Slicer-Liver extension developers, I would like to add a new feature for visualizing the cutting lines between the resection surface and 3D Slicer slice views. I thought it might be easier to do it within DisplayableManager.

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<div class="post-metadata">

**Author:** ![RuoyanMeng](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/ruoyanmeng/32/12403_2.png) [@RuoyanMeng](https://discourse.slicer.org/u/RuoyanMeng)\
**Post date:** [March 27, 2023, 9:47am UTC](https://discourse.slicer.org/t/couldnt-register-customized-displayablemanager-to-extension-module/28560/5 "2023-03-27T09:47:19Z")

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Thank you so much for pointing this out, I did ignore the initiating process! Now everything works fine!