add pcl integration/todo notes

plugins/pcl/CMakeLists.txt

@@ -1,3 +1,41 @@
+#
+# PCL plugin CMake configuration
+#
+# The PCL integration still has a few warts that need to be resolved:
+# 
+#     1. PCL detection still occurs in the root CMakeLists.txt.
+#
+#        This is because it's presence must still be known to several
+#        downstream files (keep reading).
+#
+#     2. pdal_defines.h.in is configured to broadcast PDAL_HAVE_PCL and
+#        PDAL_HAVE_PCL_VISUALIZATION.
+#
+#        As with #1, these are used downstream.
+#
+#     3. src/pdal_config.cpp sets the PCL version in getVersionString(), which
+#        in turn requires pcl/pcl_config.h.
+#
+#        These are done conditionally if PDAL_HAVE_PCL is set.
+#
+#     4. src/kernel/Kernel.cpp requires PCL for invoking the PCLVisualizer with
+#        two point buffers.
+#
+#        This is currently disabled (commented out), and should be somehow
+#        fully integrated as a plugin behavior. When enabled, this is done
+#        conditionally if PDAL_HAVE_PCL_VISUALIZATION is set.
+#
+#     5. PCL is still linked into libpdalcpp via src/CMakeLists.txt.
+#
+#        Conditional on PDAL_HAVE_PCL.
+#
+#     6. PCL unit tests still live within main test directory. We should be
+#        able to move plugin tests to plugin directories without too much
+#        hassle.
+#
+#        Conditional on PDAL_HAVE_PCL.
+#
+
 include_directories(${PROJECT_SOURCE_DIR}/include)
 include_directories(${PROJECT_SOURCE_DIR}/plugin/pcl)