Documentation/Nightly/Developers/FAQ/Extensions

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:

• Bundle module(s) into a Slicer extension
• Build, test, package and distribute extensions

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