View source for Documentation/4.8/Developers/Modules

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</noinclude>Slicer supports three types of modules: [[Documentation/{{documentation/version}}/Developers/Modules#Command_Line_Interface_.28CLI.29|Command Line Interface (CLI)]], [[Documentation/{{documentation/version}}/Developers/Modules#Loadable_Modules|Loadable Modules]] and [[Documentation/{{documentation/version}}/Developers/Modules#Scripted_Modules|Scripted Modules]].

While the developer has to choose between one of the three types to implement its module, the end user will <b>NOT</b> notice the difference as they all share the same look & feel. 

The choice for a given type of module is usually based on the type of inputs/parameters for a given module.

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= Command Line Interface (CLI) =
CLIs are standalone executables with a limited input/output arguments complexity (simple argument types, no user interactions...). They are typically implemented using [http://www.itk.org ITK].
* Shared lib or executable
* UI automatically generated
* Where to start ?
# Create initial skeleton using the [[Documentation/{{documentation/version}}/Developers/ExtensionWizard|Extension Wizard]]
# Read [[Documentation/{{documentation/version}}/Developers/Build_Module|Compiling slicer modules outside of the slicer source tree.]]
# Learn from [http://viewvc.slicer.org/viewvc.cgi/Slicer4/trunk/Modules/CLI/ existing modules]
* Links:
**[[Documentation/{{documentation/version}}/Training#Developing_and_contributing_extensions_for_3D_Slicer|Developing and contributing extensions for 3D Slicer]]
** [[Documentation/{{documentation/version}}/Developers/SlicerExecutionModel|Slicer execution model]]
** [http://www.na-mic.org/Wiki/index.php/File:Slicer4_CLI.ppt CLI in Slicer4] (presentation of 2012 NAMIC AHM)

= Loadable Modules =
Loadable modules are [http://en.wikipedia.org/wiki/C%2B%2B C++] plugins that are built against Slicer. They define custom GUIs for their specific behavior as they have full control over the application.
* C++ shared library
* Full control over the UI (based on [http://qt.nokia.com/products/ Qt]) and Slicer internals (MRML, logics, display managers...)
* Optimized for heavy computations
* Where to start ?
# Create initial skeleton using the [[Documentation/{{documentation/version}}/Developers/ExtensionWizard|Extension Wizard]]
# Read [[Documentation/{{documentation/version}}/Developers/Build_Module|Compiling slicer modules outside of the slicer source tree.]]
# Learn from [http://viewvc.slicer.org/viewvc.cgi/Slicer4/trunk/Modules/Loadable/ existing modules]
* Links:
**[[Documentation/{{documentation/version}}/Training#Developing_and_contributing_extensions_for_3D_Slicer|Developing and contributing extensions for 3D Slicer]]
**[http://www.na-mic.org/Wiki/index.php/File:LoadableModules.pptx Loadable modules] (presentation of 2012 NAMIC AHM)
**[[Documentation/{{documentation/version}}/Developers/Tutorials/CreateLoadableModule|How to write a loadable module]]

= Scripted Modules =
Scripted modules are written in [http://www.python.org/ Python]. 

An extensive tutorial and reference page was created [http://www.na-mic.org/Wiki/index.php/2013_Project_Week_Breakout_Session:Slicer4Python for the Slicer/Python breakout session at the NA-MIC 2014 Summer Project Week].  Please read through this and many of your questions will be answered.

Several tutorials for developers are available from the Slicer Training page: https://www.slicer.org/wiki/Documentation/Nightly/Training#Tutorials_for_software_developers  
* Python Console
* Full access to the API: [http://www.vtk.org VTK], [http://qt.nokia.com/products/ Qt], [http://slicer.org/doc/html/annotated.html MRML and Slicer],[http://www.itk.org/SimpleITKDoxygen/html/classes.html SimpleITK] are fully wrapped
* Recommended for fast prototyping and custom workflow development
* Where to start?
# Read the [http://www.na-mic.org/Wiki/index.php/2013_Project_Week_Breakout_Session:Slicer4Python  Slicer/Python breakout session at the NA-MIC 2014 Summer Project Week] tutorial.
# Create initial skeleton using the [[Documentation/{{documentation/version}}/Developers/ExtensionWizard|Extension Wizard]]
# [[Media:SlicerModulesProgrammingBeyondBasics.pdf|Python scripted module design - beyond basics]]: role of widget, logic, MRML classes, using MRML node for storing module parameters, etc. (editable version: [[File:SlicerModulesProgrammingBeyondBasics.pptx]])
# Learn from [http://viewvc.slicer.org/viewvc.cgi/Slicer4/trunk/Modules/Scripted/ existing modules]
* More information:
**[[Documentation/{{documentation/version}}/Training#Developing_and_contributing_extensions_for_3D_Slicer|Developing and contributing extensions for 3D Slicer]]
** [[Documentation/{{documentation/version}}/Developers/Python_scripting|Python Scripting]]
** [[Documentation/{{documentation/version}}/Training#Slicer4_Programming_Tutorial|Python Scripting Tutorial]]
** [[Documentation/{{documentation/version}}/ScriptRepository|Community contributed examples]]
** [[Documentation/{{documentation/version}}/Developers/Slicelets|Developing slicelets: standalone applications with simplified, fully customized user interface]]

=Module Factory=
Loading modules into slicer happens in multiple steps:
*module factories must be registered into the factory manager
* directories where the modules to load are located must be passed to the factory manager
* Optionally specify module names to ignore
* scan the directories and test which file is a module and register it (not instantiated yet) 
* Instantiate all the register modules
* Connect each module with the scene and the application
More details can be found in the [http://slicer.org/doc/html/classqSlicerAbstractModuleFactoryManager.html online doc]

=Association of MRML nodes to modules=

Modules can be associated with MRML nodes, which for example allows determining what module can be used to edit a certain MRML node. A module can either specify the list of node types that it supports by overriding [https://www.slicer.org/doc/html/classqSlicerAbstractCoreModule.html#a932cfab8cb00c2e770b95a97fce92670 qSlicerAbstractCoreModule::associatedNodeTypes()] method or a module can call [https://www.slicer.org/doc/html/classqSlicerCoreApplication.html#a748d8b0ab3914bded820337534a1aa76 qSlicerCoreApplication::addModuleAssociatedNodeTypes()] to associate any node type with any module.

Multiple modules can be associated with the same MRML node type. The best module for editing a specific node instance is determined run-time. The application framework calls [https://www.slicer.org/doc/html/classqSlicerAbstractModuleWidget.html#a8e1bdbc248688677af5cd91f0849d44e qSlicerAbstractModuleWidget::nodeEditable()] for each associated module candidate and will activate the one that has the highest confidence in handling the node.

To select a MRML node as the "active" or "edited" node in a module the module widget's [https://www.slicer.org/doc/html/classqSlicerAbstractModuleRepresentation.html#adfd05c2484d8cab8e3e9cda09e45d227 qSlicerAbstractModuleWidget::setEditedNode()] method is called.

=ToDo - Planned developments=
* Transform all core modules into Loadable modules.
** the factory manager only support file based modules, core modules are not file based (linked into the core factory itself)
* Move factory registration in qSlicerApplication (or a general application library) to support module discovery/loading without needing to instantiate Slicer.
** Currently can't be moved into qSlicerApplication as the CLI factories that are in QTCLI depend on QTGUI
** QtTesting is also limited with the QTCLI dependency on QtGUI (->qSlicerApplication would need to access QtTesting code from QtCli)
** Proposed architecture
 Base
   Application -> classes that are useful to build an application (mix of qSlicerCoreApplication, qSlicerApplication, Main.cxx...)
   Core -> formally QtCore
   Modules -> contains the factories and module specific code
      Loadable
      CLI
      Scripted
   Scripted -> all that is python specific
      Cxx
      Python
   Widgets -> formally QtGUI
* Add category hierarchy in the Settings module panel
* Register factory settings/command-options(e.g. disable-loadable-modules) when registering module factories
** To have the settings panel be generic but have the code proper of each registered factory somewhere else
* Add mechanism for modules to register dialogs (toolbars that open dialogs),  e.g. the sceneview module needs to register the sceneView dialog into an icon.
* <s>Ignore modules from the launcher command line.</s> {{done}}
* cloning" of module panels at run time. See [http://massmail.spl.harvard.edu/public-archives/slicer-devel/2012/008965.html "here] and [http://massmail.spl.harvard.edu/public-archives/slicer-devel/2012/008039.html here]
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