BUG: Python factory registration fixups

Several fixes addressing previous commit:
- Classes grouping FFT factory registrations are now named `InitFactory`
  to better discriminate between factory overrides vs initializers
- Static initialization with `RegisterInternalFactoryOnce` is replaced
  with nonstatic `RegisterOneFactory` method
- Python factory load-time registration is streamlined

CMake/ITKFactoryRegistration.cmake

@@ -14,7 +14,7 @@
 # Overview: Static registration of ITK factories
 # ----------------------------------------------
 #
-# For each factory type (Image, Transform, Mesh, FFT, ...), a
+# For each factory type (Image, Transform, Mesh, FFTImageFilterInit, ...), a
 # registration manager header named
 # `itk<factory_type>FactoryRegisterManager.h` is configured.
 #
@@ -32,8 +32,14 @@
 # a list in a CMake variable named after `LIST_OF_<factory_type>IO_FORMATS`
 # generated by this file.
 #
-# For the FFT factories, each FFT filter which has a factory needs to
-# be included.
+# "Init factories" (such as "VnlFFTImageFilterInitFactory") are intended to reduce
+# overhead. They have the sole purpose of registering multiple factories with the
+# object factory singleton at once. Init factories do not inherit from
+# ObjectFactoryBase, cannot define initialization overrides, and will never be
+# added to the global singleton list of object factories.
+#
+# For the FFTImageFilterInitFactory classes, each FFT filter which has a factory needs to
+# be included in its initialization list.
 #
 #
 #
@@ -52,7 +58,7 @@
 # Setting variable `ITK_NO_<factory_name_uc>_FACTORY_REGISTER_MANAGER` to `ON` prior calling
 # `include(${ITK_USE_FILE})` disables the static registration.
 # Here <factory_name_uc> is the upper case name of the factory. For example,
-# `IMAGEIO`, `MESHIO`, `TRANSFORMIO`, or `FFTIMAGEFILTER`.
+# `IMAGEIO`, `MESHIO`, `TRANSFORMIO`, or `FFTIMAGEFILTERINIT`.
 #
 # All factories can be disabled with the following CMake code:
 #  foreach(_factory_name ${ITK_FACTORY_LIST})

CMake/itkFFTImageFilterFactoryRegisterManager.h.in → CMake/itkFFTImageFilterInitFactoryRegisterManager.h.in

@@ -16,8 +16,8 @@
  *
  *=========================================================================*/
 
-#ifndef itkFFTImageFilterFactoryRegisterManager_h
-#define itkFFTImageFilterFactoryRegisterManager_h
+#ifndef itkFFTImageFilterInitFactoryRegisterManager_h
+#define itkFFTImageFilterInitFactoryRegisterManager_h
 
 namespace itk {
 
@@ -27,10 +27,10 @@ namespace itk {
 //
 @LIST_OF_FACTORIES_REGISTRATION@
 
-class FFTImageFilterFactoryRegisterManager
+class FFTImageFilterInitFactoryRegisterManager
 {
   public:
-  explicit FFTImageFilterFactoryRegisterManager(void (* const list[])(void))
+  explicit FFTImageFilterInitFactoryRegisterManager(void (* const list[])(void))
   {
     for(;*list != nullptr; ++list)
       {
@@ -44,10 +44,10 @@ class FFTImageFilterFactoryRegisterManager
 // application translation units. Note that this code will be expanded in the
 // ITK-based applications and not in ITK itself.
 //
-void (* const FFTImageFilterFactoryRegisterRegisterList[])(void) = {
+void (* const FFTImageFilterInitFactoryRegisterList[])(void) = {
   @LIST_OF_FACTORY_NAMES@
   nullptr};
-const FFTImageFilterFactoryRegisterManager FFTImageFilterFactoryRegisterManagerInstance(FFTImageFilterFactoryRegisterRegisterList);
+const FFTImageFilterInitFactoryRegisterManager FFTImageFilterInitFactoryRegisterManagerInstance(FFTImageFilterInitFactoryRegisterList);
 
 }
 

CMakeLists.txt

@@ -582,7 +582,7 @@ install(FILES ${ITK_BINARY_DIR}/CMakeFiles/ITKConfig.cmake
               CMake/ITKModuleAPI.cmake
               CMake/UseITK.cmake
               CMake/ITKFactoryRegistration.cmake
-              CMake/itkFFTImageFilterFactoryRegisterManager.h.in
+              CMake/itkFFTImageFilterInitFactoryRegisterManager.h.in
               CMake/itkImageIOFactoryRegisterManager.h.in
               CMake/itkTransformIOFactoryRegisterManager.h.in
               CMake/itkMeshIOFactoryRegisterManager.h.in

Modules/Filtering/FFT/include/itkComplexToComplex1DFFTImageFilter.h

@@ -119,8 +119,8 @@ class ITK_TEMPLATE_EXPORT ComplexToComplex1DFFTImageFilter : public ImageToImage
 #  include "itkComplexToComplex1DFFTImageFilter.hxx"
 #endif
 
-#ifdef ITK_FFTIMAGEFILTER_FACTORY_REGISTER_MANAGER
-#  include "itkFFTImageFilterFactoryRegisterManager.h"
+#ifdef ITK_FFTIMAGEFILTERINIT_FACTORY_REGISTER_MANAGER
+#  include "itkFFTImageFilterInitFactoryRegisterManager.h"
 #endif
 
 #endif // itkComplexToComplex1DFFTImageFilter_h

Modules/Filtering/FFT/include/itkComplexToComplexFFTImageFilter.h

@@ -134,8 +134,8 @@ class ITK_TEMPLATE_EXPORT ComplexToComplexFFTImageFilter : public ImageToImageFi
 #  include "itkComplexToComplexFFTImageFilter.hxx"
 #endif
 
-#ifdef ITK_FFTIMAGEFILTER_FACTORY_REGISTER_MANAGER
-#  include "itkFFTImageFilterFactoryRegisterManager.h"
+#ifdef ITK_FFTIMAGEFILTERINIT_FACTORY_REGISTER_MANAGER
+#  include "itkFFTImageFilterInitFactoryRegisterManager.h"
 #endif
 
 #endif

Modules/Filtering/FFT/include/itkVnlFFTImageFilterFactory.h → Modules/Filtering/FFT/include/itkFFTWFFTImageFilterInitFactory.h

@@ -15,55 +15,58 @@
  *  limitations under the License.
  *
  *=========================================================================*/
-#ifndef itkVnlFFTImageFilterFactory_h
-#define itkVnlFFTImageFilterFactory_h
+#ifndef itkFFTWFFTImageFilterInitFactory_h
+#define itkFFTWFFTImageFilterInitFactory_h
 #include "ITKFFTExport.h"
 
-#include "itkObjectFactoryBase.h"
+#include "itkLightObject.h"
 
 namespace itk
 {
 /**
- *\class VnlFFTImageFilterFactory
- * \brief Create instances of Vnl FFT ImageFilter objects using an object factory.
+ *\class FFTWFFTImageFilterInitFactory
+ * \brief Initialize FFTW FFT image filter factory backends.
+ *
+ * The purpose of FFTWFFTImageFilterInitFactory is to perform
+ * one-time registration of factory objects that handle
+ * creation of FFTW-backend FFT image filter classes
+ * through the ITK object factory singleton mechanism.
+ *
  * \ingroup ITKFFT
  */
-class ITKFFT_EXPORT VnlFFTImageFilterFactory : public ObjectFactoryBase
+class ITKFFT_EXPORT FFTWFFTImageFilterInitFactory : public LightObject
 {
 public:
-  ITK_DISALLOW_COPY_AND_MOVE(VnlFFTImageFilterFactory);
+  ITK_DISALLOW_COPY_AND_MOVE(FFTWFFTImageFilterInitFactory);
 
   /** Standard class type aliases. */
-  using Self = VnlFFTImageFilterFactory;
-  using Superclass = ObjectFactoryBase;
+  using Self = FFTWFFTImageFilterInitFactory;
+  using Superclass = LightObject;
   using Pointer = SmartPointer<Self>;
   using ConstPointer = SmartPointer<const Self>;
 
-  /** Class methods used to interface with the registered factories. */
-  const char *
-  GetITKSourceVersion() const override;
-
-  const char *
-  GetDescription() const override;
-
   /** Method for class instantiation. */
   itkFactorylessNewMacro(Self);
 
   /** Run-time type information (and related methods). */
-  itkTypeMacro(VnlFFTImageFilterFactory, ObjectFactoryBase);
+  itkTypeMacro(FFTWFFTImageFilterInitFactory, LightObject);
 
-  /** Register one factory of this type  */
+  /** Register one factory of this type.
+   * The purpose of an InitFactory is to simply load other factories
+   * in its constructor, so nothing is returned here.
+   * Method is required for factory to load correct in Python.  */
   static void
   RegisterOneFactory()
   {
-    auto factory = VnlFFTImageFilterFactory::New();
-
-    ObjectFactoryBase::RegisterFactoryInternal(factory);
+    RegisterFactories();
   }
 
+  static void
+  RegisterFactories();
+
 protected:
-  VnlFFTImageFilterFactory();
-  ~VnlFFTImageFilterFactory() override;
+  FFTWFFTImageFilterInitFactory();
+  ~FFTWFFTImageFilterInitFactory() override;
 };
 } // end namespace itk
 

Modules/Filtering/FFT/include/itkForward1DFFTImageFilter.h

@@ -104,8 +104,8 @@ class ITK_TEMPLATE_EXPORT Forward1DFFTImageFilter : public ImageToImageFilter<TI
 #  include "itkForward1DFFTImageFilter.hxx"
 #endif
 
-#ifdef ITK_FFTIMAGEFILTER_FACTORY_REGISTER_MANAGER
-#  include "itkFFTImageFilterFactoryRegisterManager.h"
+#ifdef ITK_FFTIMAGEFILTERINIT_FACTORY_REGISTER_MANAGER
+#  include "itkFFTImageFilterInitFactoryRegisterManager.h"
 #endif
 
 #endif // itkForward1DFFTImageFilter_h

Modules/Filtering/FFT/include/itkForwardFFTImageFilter.h

@@ -116,8 +116,8 @@ class ITK_TEMPLATE_EXPORT ForwardFFTImageFilter : public ImageToImageFilter<TInp
 #  include "itkForwardFFTImageFilter.hxx"
 #endif
 
-#ifdef ITK_FFTIMAGEFILTER_FACTORY_REGISTER_MANAGER
-#  include "itkFFTImageFilterFactoryRegisterManager.h"
+#ifdef ITK_FFTIMAGEFILTERINIT_FACTORY_REGISTER_MANAGER
+#  include "itkFFTImageFilterInitFactoryRegisterManager.h"
 #endif
 
 #endif

Modules/Filtering/FFT/include/itkHalfHermitianToRealInverseFFTImageFilter.h

@@ -118,8 +118,8 @@ class ITK_TEMPLATE_EXPORT HalfHermitianToRealInverseFFTImageFilter
 #  include "itkHalfHermitianToRealInverseFFTImageFilter.hxx"
 #endif
 
-#ifdef ITK_FFTIMAGEFILTER_FACTORY_REGISTER_MANAGER
-#  include "itkFFTImageFilterFactoryRegisterManager.h"
+#ifdef ITK_FFTIMAGEFILTERINIT_FACTORY_REGISTER_MANAGER
+#  include "itkFFTImageFilterInitFactoryRegisterManager.h"
 #endif
 
 #endif

Modules/Filtering/FFT/include/itkInverse1DFFTImageFilter.h

@@ -99,8 +99,8 @@ class ITK_TEMPLATE_EXPORT Inverse1DFFTImageFilter : public ImageToImageFilter<TI
 #  include "itkInverse1DFFTImageFilter.hxx"
 #endif
 
-#ifdef ITK_FFTIMAGEFILTER_FACTORY_REGISTER_MANAGER
-#  include "itkFFTImageFilterFactoryRegisterManager.h"
+#ifdef ITK_FFTIMAGEFILTERINIT_FACTORY_REGISTER_MANAGER
+#  include "itkFFTImageFilterInitFactoryRegisterManager.h"
 #endif
 
 #endif // itkInverse1DFFTImageFilter_h

Modules/Filtering/FFT/include/itkInverseFFTImageFilter.h

@@ -102,8 +102,8 @@ class ITK_TEMPLATE_EXPORT InverseFFTImageFilter : public ImageToImageFilter<TInp
 #  include "itkInverseFFTImageFilter.hxx"
 #endif
 
-#ifdef ITK_FFTIMAGEFILTER_FACTORY_REGISTER_MANAGER
-#  include "itkFFTImageFilterFactoryRegisterManager.h"
+#ifdef ITK_FFTIMAGEFILTERINIT_FACTORY_REGISTER_MANAGER
+#  include "itkFFTImageFilterInitFactoryRegisterManager.h"
 #endif
 
 #endif

Modules/Filtering/FFT/include/itkRealToHalfHermitianForwardFFTImageFilter.h

@@ -120,8 +120,8 @@ class ITK_TEMPLATE_EXPORT RealToHalfHermitianForwardFFTImageFilter
 #  include "itkRealToHalfHermitianForwardFFTImageFilter.hxx"
 #endif
 
-#ifdef ITK_FFTIMAGEFILTER_FACTORY_REGISTER_MANAGER
-#  include "itkFFTImageFilterFactoryRegisterManager.h"
+#ifdef ITK_FFTIMAGEFILTERINIT_FACTORY_REGISTER_MANAGER
+#  include "itkFFTImageFilterInitFactoryRegisterManager.h"
 #endif
 
 #endif

Modules/Filtering/FFT/include/itkFFTWFFTImageFilterFactory.h → Modules/Filtering/FFT/include/itkVnlFFTImageFilterInitFactory.h

@@ -15,55 +15,56 @@
  *  limitations under the License.
  *
  *=========================================================================*/
-#ifndef itkFFTWFFTImageFilterFactory_h
-#define itkFFTWFFTImageFilterFactory_h
+#ifndef itkVnlFFTImageFilterInitFactory_h
+#define itkVnlFFTImageFilterInitFactory_h
 #include "ITKFFTExport.h"
 
-#include "itkObjectFactoryBase.h"
+#include "itkLightObject.h"
 
 namespace itk
 {
 /**
- *\class FFTWFFTImageFilterFactory
- * \brief Create instances of FFTW FFT ImageFilter objects using an object factory.
+ *\class VnlFFTImageFilterInitFactory
+ * \brief Initialize Vnl FFT image filter factory backends.
+ *
+ * The purpose of VnlFFTImageFilterInitFactory is to perform
+ * one-time registration of factory objects that handle
+ * creation of Vnl-backend FFT image filter classes
+ * through the ITK object factory singleton mechanism.
+ *
  * \ingroup ITKFFT
  */
-class ITKFFT_EXPORT FFTWFFTImageFilterFactory : public ObjectFactoryBase
+class ITKFFT_EXPORT VnlFFTImageFilterInitFactory : public LightObject
 {
 public:
-  ITK_DISALLOW_COPY_AND_MOVE(FFTWFFTImageFilterFactory);
+  ITK_DISALLOW_COPY_AND_MOVE(VnlFFTImageFilterInitFactory);
 
   /** Standard class type aliases. */
-  using Self = FFTWFFTImageFilterFactory;
-  using Superclass = ObjectFactoryBase;
+  using Self = VnlFFTImageFilterInitFactory;
+  using Superclass = LightObject;
   using Pointer = SmartPointer<Self>;
   using ConstPointer = SmartPointer<const Self>;
 
-  /** Class methods used to interface with the registered factories. */
-  const char *
-  GetITKSourceVersion() const override;
-
-  const char *
-  GetDescription() const override;
-
   /** Method for class instantiation. */
   itkFactorylessNewMacro(Self);
 
   /** Run-time type information (and related methods). */
-  itkTypeMacro(FFTWFFTImageFilterFactory, ObjectFactoryBase);
+  itkTypeMacro(VnlFFTImageFilterInitFactory, LightObject);
 
-  /** Register one factory of this type  */
+  /** Mimic factory interface for Python initialization  */
   static void
   RegisterOneFactory()
   {
-    auto factory = FFTWFFTImageFilterFactory::New();
-
-    ObjectFactoryBase::RegisterFactoryInternal(factory);
+    RegisterFactories();
   }
 
+  /** Register all Vnl FFT factories */
+  static void
+  RegisterFactories();
+
 protected:
-  FFTWFFTImageFilterFactory();
-  ~FFTWFFTImageFilterFactory() override;
+  VnlFFTImageFilterInitFactory();
+  ~VnlFFTImageFilterInitFactory() override;
 };
 } // end namespace itk
 

Modules/Filtering/FFT/itk-module.cmake

@@ -5,10 +5,10 @@ computations of Fast Fourier Transforms based on
 <a href=\"http://www.fftw.org\">FFTW</a>. Note that when using the FFTW
 implementation you must comply with the GPL license.")
 
-set(_fft_backends "FFTImageFilter::Vnl")
+set(_fft_backends "FFTImageFilterInit::Vnl")
 if(ITK_USE_FFTWF OR ITK_USE_FFTWD)
   # Prepend so that FFTW constructor is preferred
-  list(PREPEND _fft_backends "FFTImageFilter::FFTW")
+  list(PREPEND _fft_backends "FFTImageFilterInit::FFTW")
 endif()
 
 itk_module(ITKFFT

Modules/Filtering/FFT/src/CMakeLists.txt

@@ -1,10 +1,10 @@
 set(ITKFFT_SRCS
 itkComplexToComplexFFTImageFilter.cxx
-itkVnlFFTImageFilterFactory.cxx)
+itkVnlFFTImageFilterInitFactory.cxx)
 
 if( ITK_USE_FFTWF OR ITK_USE_FFTWD AND NOT ITK_USE_CUFFTW)
   list(APPEND ITKFFT_SRCS itkFFTWGlobalConfiguration.cxx )
-  list(APPEND ITKFFT_SRCS itkFFTWFFTImageFilterFactory.cxx )
+  list(APPEND ITKFFT_SRCS itkFFTWFFTImageFilterInitFactory.cxx )
 endif()
 
 itk_module_add_library(ITKFFT ${ITKFFT_SRCS})