ENH: Enhanced FindITK supporting use of ITK from an install tree or a build...

ENH: Enhanced FindITK supporting use of ITK from an install tree or a build tree.  Only one cache entry is brought into user's project, called "ITK_DIR".  This is the location of an ITKConfig.cmake file from which other settings are loaded.

Modules/FindITK.cmake

 #
-# Find the native ITK includes and library
+# Find an ITK installation or build tree.
 #
-# This module defines
+# When ITK is found, the ITKConfig.cmake file is sourced to setup the
+# location and configuration of ITK.  Please read this file, or
+# ITKConfig.cmake.in from the ITK source tree for the full list of
+# definitions.  Of particular interest is
 #
-# ITK_BINARY_PATH - where is the binary tree (only defined if SOURCE_PATH is defined)
-# USE_ITK_FILE - the full path and location of the UseITK.cmake file
+# ITK_USE_FILE          - A CMake source file that can be included
+#                         to set the include directories, library
+#                         directories, and preprocessor macros.
 #
-
+# In addition to the variables read from ITKConfig.cmake, this find
+# module also defines
+#
+# ITK_DIR      - The directory containing ITKConfig.cmake.  This is either
+#                the root of the build tree, or the lib/InsightToolkit
+#                directory.  This is the only cache entry.
+#
+# ITK_FOUND    - Whether ITK was found.  If this is true, ITK_DIR is okay.
 #
-# Look for a binary tree
-# 
-FIND_PATH(ITK_BINARY_PATH UseITK.cmake
+# USE_ITK_FILE - The full path to the UseITK.cmake file.  This is provided
+#                for backward compatability.  Use ITK_USE_FILE instead.
+#
+
+# Search only if the location is not already known.
+IF(NOT ITK_DIR)
+  # Get the system search path as a list.
+  IF(UNIX)
+    STRING(REGEX MATCHALL "[^:]+" ITK_DIR_SEARCH1 $ENV{PATH})
+  ELSE(UNIX)
+    STRING(REGEX REPLACE "\\\\" "/" ITK_DIR_SEARCH1 $ENV{PATH})
+  ENDIF(UNIX)
+  STRING(REGEX REPLACE "/;" ";" ITK_DIR_SEARCH2 ${ITK_DIR_SEARCH1})
+
+  # Construct a set of paths relative to the system search path.
+  SET(ITK_DIR_SEARCH "")
+  FOREACH(dir ${ITK_DIR_SEARCH2})
+    SET(ITK_DIR_SEARCH ${ITK_DIR_SEARCH} "${dir}/../lib/InsightToolkit")
+  ENDFOREACH(dir)
+
+  #
+  # Look for an installation or build tree.
+  #
+  FIND_PATH(ITK_DIR ITKConfig.cmake
+    # Look in places relative to the system executable search path.
+    ${ITK_DIR_SEARCH}
+
+    # Look in standard UNIX install locations.
+    /usr/local/lib/InsightToolkit
+    /usr/lib/InsightToolkit
+
+    # Read from the CMakeSetup registry entries.  It is likely that
+    # ITK will have been recently built.
     [HKEY_CURRENT_USER\\Software\\Kitware\\CMakeSetup\\Settings\\StartPath;WhereBuild1]
     [HKEY_CURRENT_USER\\Software\\Kitware\\CMakeSetup\\Settings\\StartPath;WhereBuild2]
     [HKEY_CURRENT_USER\\Software\\Kitware\\CMakeSetup\\Settings\\StartPath;WhereBuild3]
@@ -21,23 +62,20 @@ FIND_PATH(ITK_BINARY_PATH UseITK.cmake
     [HKEY_CURRENT_USER\\Software\\Kitware\\CMakeSetup\\Settings\\StartPath;WhereBuild8]
     [HKEY_CURRENT_USER\\Software\\Kitware\\CMakeSetup\\Settings\\StartPath;WhereBuild9]
     [HKEY_CURRENT_USER\\Software\\Kitware\\CMakeSetup\\Settings\\StartPath;WhereBuild10]
-    ../ITKBIN
-    ../itkbin
-    ../Insight-vc
-    ../InsightBin
-    ITKBIN
-    itkbin
-    $ENV{HOME}/ITKBIN
-    $ENV{HOME}/Insight
-    $ENV{HOME}/InsightBin
-    $ENV{HOME}/itkbin
-    )
-
-
-
-IF (ITK_BINARY_PATH)
-  SET (USE_ITK_FILE ${ITK_BINARY_PATH}/UseITK.cmake)
-ENDIF (ITK_BINARY_PATH)
 
+    # Help the user find it if we cannot.
+    DOC "The directory containing ITKConfig.cmake.  This is either the root of the build tree, or PREFIX/lib/InsightToolkit for an installation."
+  )
+ENDIF(NOT ITK_DIR)
 
+# If ITK was found, load the configuration file to get the rest of the
+# settings.
+IF(ITK_DIR)
+  SET(ITK_FOUND 1)
+  INCLUDE(${ITK_DIR}/ITKConfig.cmake)
 
+  # Set USE_ITK_FILE for backward-compatability.
+  SET(USE_ITK_FILE ${ITK_USE_FILE})
+ELSE(ITK_DIR)
+  SET(ITK_FOUND 0)
+ENDIF(ITK_DIR)