STYLE: Remove backslash (continuation character) from string literals

Removed backspaces that were used as a continuation character at the end of a
line of code, from inside a string literal. Let Clang-Format take care of
splitting the literals over multiple lines properly.

Modules/Core/Common/include/itkImageSource.hxx

@@ -254,8 +254,8 @@ ImageSource<TOutputImage>::ThreadedGenerateData(const OutputImageRegionType &
 #if !defined(ITK_LEGACY_REMOVE)
   this->DynamicThreadedGenerateData(region);
 #else
-  itkExceptionMacro("With DynamicMultiThreadingOff subclass should override this method. \
-The signature of ThreadedGenerateData() has been changed in ITK v4 to use the new ThreadIdType.");
+  itkExceptionMacro("With DynamicMultiThreadingOff subclass should override this method. The signature of "
+                    "ThreadedGenerateData() has been changed in ITK v4 to use the new ThreadIdType.");
 #endif
 }
 
@@ -264,9 +264,9 @@ template <typename TOutputImage>
 void
 ImageSource<TOutputImage>::DynamicThreadedGenerateData(const OutputImageRegionType &)
 {
-  itkExceptionMacro("Subclass should override this method!!! \
-If old behavior is desired invoke this->DynamicMultiThreadingOff(); \
-before Update() is called. The best place is in class constructor.");
+  itkExceptionMacro(
+    "Subclass should override this method!!! If old behavior is desired invoke this->DynamicMultiThreadingOff(); "
+    "before Update() is called. The best place is in class constructor.");
 }
 
 // Callback routine used by the classic threading library. This routine just calls

Modules/Core/Common/include/itkPlatformMultiThreader.h

@@ -72,16 +72,14 @@ class ITKCommon_EXPORT PlatformMultiThreader : public MultiThreaderBase
    * of threads was accepted. Legacy: use MultiThreaderBase to invoke these. */
   itkLegacyMacro(static void SetGlobalMaximumNumberOfThreads(ThreadIdType val))
   {
-    itkGenericOutputMacro("Warning: SetGlobalMaximumNumberOfThreads \
-should now be called on itk::MultiThreaderBase. \
-It can affect all MultiThreaderBase's derived classes in ITK");
+    itkGenericOutputMacro("Warning: SetGlobalMaximumNumberOfThreads should now be called on itk::MultiThreaderBase. It "
+                          "can affect all MultiThreaderBase's derived classes in ITK");
     Superclass::SetGlobalMaximumNumberOfThreads(val);
   }
   itkLegacyMacro(static ThreadIdType GetGlobalMaximumNumberOfThreads())
   {
-    itkGenericOutputMacro("Warning: GetGlobalMaximumNumberOfThreads \
-should now be called on itk::MultiThreaderBase. \
-It can affect all MultiThreaderBase's derived classes in ITK");
+    itkGenericOutputMacro("Warning: GetGlobalMaximumNumberOfThreads should now be called on itk::MultiThreaderBase. It "
+                          "can affect all MultiThreaderBase's derived classes in ITK");
     return Superclass::GetGlobalMaximumNumberOfThreads();
   }
 
@@ -91,16 +89,14 @@ It can affect all MultiThreaderBase's derived classes in ITK");
    * of threads was accepted. Legacy: use MultiThreaderBase to invoke these. */
   itkLegacyMacro(static void SetGlobalDefaultNumberOfThreads(ThreadIdType val))
   {
-    itkGenericOutputMacro("Warning: SetGlobalDefaultNumberOfThreads \
-should now be called on itk::MultiThreaderBase. \
-It can affect all MultiThreaderBase's derived classes in ITK");
+    itkGenericOutputMacro("Warning: SetGlobalDefaultNumberOfThreads should now be called on itk::MultiThreaderBase. It "
+                          "can affect all MultiThreaderBase's derived classes in ITK");
     Superclass::SetGlobalDefaultNumberOfThreads(val);
   }
   itkLegacyMacro(static ThreadIdType GetGlobalDefaultNumberOfThreads())
   {
-    itkGenericOutputMacro("Warning: GetGlobalDefaultNumberOfThreads \
-should now be called on itk::MultiThreaderBase. \
-It can affect all MultiThreaderBase's derived classes in ITK");
+    itkGenericOutputMacro("Warning: GetGlobalDefaultNumberOfThreads should now be called on itk::MultiThreaderBase. It "
+                          "can affect all MultiThreaderBase's derived classes in ITK");
     return Superclass::GetGlobalDefaultNumberOfThreads();
   }
 #endif

Modules/Core/Common/src/itkMultiThreaderBase.cxx

@@ -152,10 +152,8 @@ MultiThreaderBase::GetGlobalDefaultThreaderPrivate()
              itksys::SystemTools::GetEnv("ITK_USE_THREADPOOL", envVar))
     {
       envVar = itksys::SystemTools::UpperCase(envVar);
-      itkGenericOutputMacro("Warning: ITK_USE_THREADPOOL \
-has been deprecated since ITK v5.0. \
-You should now use ITK_GLOBAL_DEFAULT_THREADER\
-\nFor example ITK_GLOBAL_DEFAULT_THREADER=Pool");
+      itkGenericOutputMacro("Warning: ITK_USE_THREADPOOL has been deprecated since ITK v5.0. You should now use "
+                            "ITK_GLOBAL_DEFAULT_THREADER\nFor example ITK_GLOBAL_DEFAULT_THREADER=Pool");
       if (envVar != "NO" && envVar != "OFF" && envVar != "FALSE")
       {
 #ifdef __EMSCRIPTEN__

Modules/Registration/Common/include/itkCompareHistogramImageToImageMetric.hxx

@@ -138,8 +138,7 @@ CompareHistogramImageToImageMetric<TFixedImage, TMovingImage>::FormTrainingHisto
 
   if (NumberOfPixelsCounted == 0)
   {
-    itkExceptionMacro(<< "All the points mapped to outside of the Training moving \
-age");
+    itkExceptionMacro(<< "All the points mapped to outside of the Training moving age");
   }
 }