# Question : extension wizard with CmakeList.txt

**URL:** <https://discourse.slicer.org/t/question-extension-wizard-with-cmakelist-txt/29939>\
**Category:** Development\
**Tags:** python\
**Created:** [June 9, 2023, 10:46am UTC](https://discourse.slicer.org/t/question-extension-wizard-with-cmakelist-txt/29939 "2023-06-09T10:46:23Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![dsa934](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/dsa934/32/17907_2.png) [@dsa934](https://discourse.slicer.org/u/dsa934)\
**Post date:** [June 9, 2023, 10:46am UTC](https://discourse.slicer.org/t/question-extension-wizard-with-cmakelist-txt/29939/1 "2023-06-09T10:46:23Z")

</div>

Operating system: window 10  
Slicer version: 5.2.1

 ![image](https://us1.discourse-cdn.com/flex002/uploads/slicer/original/3X/7/4/7498ed11f885ddcddbf243b84d636998a50d5812.png)

Q1. Why is the cmake file always divided into two when I create a module through the extension wizard? Is there any reason not to do it with one?

Q2.Does anyone know about the CUSTOMSLICER build error?

> [@Build Error & CustomSlicer's Purpose](https://discourse.slicer.org/t/build-error-customslicers-purpose/29910):
>
> Operating system: window 10 Slicer version: 5.2.1 Hi all, [image] Q1. When the Cmake → build process was performed for each of three slicer5.2.1, slicer5.2.2, and CustomSlicer, the same permission error for the vtk folder occurred. What to do in this case? Q2. I’ve heard that CustomSlicer allows you to customize many things without changing the slicer’s core, but is the ‘many’ mentioned here only about the GUI?

> [@About creating Customslicer](https://discourse.slicer.org/t/about-creating-customslicer/29821/19):
>
> Please confirm if I am misunderstanding the slicer. New function: Can be implemented by adding a module through ‘extension wizard’ Modification of existing functions: There is a way to customize without modifying the sclier core. So why does CustomSlicer (SlicerCAT) exist? Is the purpose of using it to customize the logo, GUI environment, etc. to suit my purpose without simply changing the slicer core? For example, there are two ways to save work in slicer as far as I know. Click the Save…

---

<div class="post-metadata">

**Author:** ![jamesobutler](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/jamesobutler/32/7511_2.png) [@jamesobutler](https://discourse.slicer.org/u/jamesobutler)\
**Post date:** [June 9, 2023, 11:33am UTC](https://discourse.slicer.org/t/question-extension-wizard-with-cmakelist-txt/29939/2 "2023-06-09T11:33:39Z")

</div>

> [@dsa934](#):
>
> Q1. Why is the cmake file always divided into two when I create a module through the extension wizard? Is there any reason not to do it with one?

The top level one is used for instructing how to build the Slicer Extension. The one inside the directory “VisualInspection” is used for instructing how to build the individual Slicer module. A Slicer extension can have multiple Slicer modules. Through the Extension Wizard you can see what it is like when you add multiple modules to your extension. You can also take a look at other Slicer extensions as examples.

Here is SlicerOpenIGTLink which has a mix of scripted loadable modules (python) and regular loadable modules (c++).

> **[GitHub - openigtlink/SlicerOpenIGTLink: OpenIGTLinkIF module as an Slicer...](https://github.com/openigtlink/SlicerOpenIGTLink)**
>
> OpenIGTLinkIF module as an Slicer Extension. Contribute to openigtlink/SlicerOpenIGTLink development by creating an account on GitHub.