Documentation/Nightly/Developers/FAQ/Extensions

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Extensions

What is an extension ?

Extensions in the Extension manager.

An extension could be seen as a delivery package bundling together one or more Slicer modules. After installing an extension, the associated modules will be presented to the user as built-in ones

The Slicer community maintains a website referred to as the Slicer Extensions Catalog to support finding, downloading and installing of extensions. Access to this website is integral to Slicer and facilitated by the Extensions Manager functionality built into the distributed program.

The Catalog classifies extensions into three levels of compliance:

  1. Category 1: Fully compliant Slicer Extensions: Slicer license, open source, maintained.
  2. Category 2: Open source, contact exists.
  3. Category 3: All other extensions (work in progress, beta, closed source etc).

To publish extensions, developers should consider reading the following pages:

Is --launch flag available for a MacOSX installed Slicer.app ?

On MacOSx, running Slicer with the --help argument does NOT list the usual launcher related options. 

$ ./Slicer.app/Contents/MacOS/Slicer --help
Usage
 Slicer [options]
 
 Options
   --, --ignore-rest                     Ignores the rest of the labeled arguments following this flag. (default: false)
   -h, --help                            Display available command line arguments.
   [...]
   --version                             Displays version information and exits.

To provide some background information, when generating the package that will be distributed, an application bundle Slicer.app is created. As explained here, a bundle is a directory with a standardized hierarchical structure that holds executable code and the resources used by that code. It means that since all libraries contained within a bundle are referenced relatively to the location of either the CLI or the Slicer executable, the use of launcher does NOT make sens.

To help fixing-up the libraries, executables and plugins so that they reference each other in a relative way, CMake provides us with the BundleUtilities module.

This module is used in two situations:

  1. Fixup of Slicer application itself. See SlicerCPack.cmake#L36-68 and SlicerCPackBundleFixup.cmake.in
  2. Fixup of an extension package. See SlicerExtensionCPack.cmake#L126-143 and SlicerExtensionCPackBundleFixup.cmake.in

What is the difference between Documentation/Nightly/Modules and Documentation/Nightly/Extensions ?

As suggested by the namespace names:

  • All module documentation pages should be located under Documentation/Nightly/Modules
  • All extension documentation pages should be located under Documentation/Nightly/Extensions


For example, if an an extension named DoSomethingGreat bundles three modules ModuleA, ModuleB and ModuleC. The following pages should be created:

  • Documentation/Nightly/Extensions/DoSomethingGreat
  • Documentation/Nightly/Modules/ModuleA
  • Documentation/Nightly/Modules/ModuleB
  • Documentation/Nightly/Modules/ModuleC


In case your extension bundles only one module, the extension name is expected to match the module name. For example, if your extension is named DoSomethingAwesome, the associated module is expected to be named DoSomethingAwesome. The following pages will then be created:

  • Documentation/Nightly/Extensions/DoSomethingAwesome
  • Documentation/Nightly/Modules/DoSomethingAwesome

where page Extensions/DoSomethingAwesome redirect to page Modules/DoSomethingAwesome.


To setup a redirection, simply add the following text to page Extensions/DoSomethingAwesome: 

#REDIRECT [[Documentation/Nightly/Modules/DoSomethingAwesome]]

For an example, see here

More details about redirection are available here: http://www.mediawiki.org/wiki/Help:Redirects

Which URL should be associated with EXTENSION_HOMEPAGE metadata ?

Extensions available through the Slicer Extensions Catalog are expected to have a page created under the Nightly documentation namespace. The corresponding URL should be associated with the EXTENSION_HOMEPAGE metadata.

For example:

  • set(EXTENSION_HOMEPAGE "http://slicer.org/slicerWiki/index.php/Documentation/Nightly/Extensions/DoSomethingGreat")
  • set(EXTENSION_HOMEPAGE "http://slicer.org/slicerWiki/index.php/Documentation/Nightly/Extensions/DoSomethingAwesome")

Note that this also apply for extension bundling only one module. Indeed, in this case the page will redirect to the appropriate module page. For example: http://www.slicer.org/slicerWiki/index.php/Documentation/Nightly/Extensions/SkullStripper

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