[JupyROOT] Install properly into CMAKE_INSTALL_PREFIX

The Jupyter config falls back to the CMAKE_INSTALL_PREFIX/js folder to
find JSROOT if ROOTSYS is not set. This ensures installations in prefix
directories to find the installed JSROOT libraries.

CMakeLists.txt

@@ -515,8 +515,14 @@ if(NOT CMAKE_SOURCE_DIR STREQUAL CMAKE_INSTALL_PREFIX)
     DESTINATION ${CMAKE_INSTALL_CMAKEDIR})
 endif()
 
-#---Make sure the Jupyter ROOT C++ kernel runs with the same Python version as ROOT-----
-set(root_kernel_dir  notebook/kernels/root)
+#---Add configuration files for kernel and jupyter----------------------------------------------
+# Make sure the Jupyter ROOT C++ kernel runs with the same Python version as ROOT
+set(root_jupyter_dir notebook)
+set(root_jupyter_config jupyter_notebook_config.py)
+configure_file(etc/${root_jupyter_dir}/${root_jupyter_config}.in etc/${root_jupyter_dir}/${root_jupyter_config})
+install(FILES ${CMAKE_BINARY_DIR}/etc/${root_jupyter_dir}/${root_jupyter_config} DESTINATION ${CMAKE_INSTALL_SYSCONFDIR}/${root_jupyter_dir})
+
+set(root_kernel_dir  ${root_jupyter_dir}/kernels/root)
 set(root_kernel_file kernel.json)
 configure_file(etc/${root_kernel_dir}/${root_kernel_file}.in etc/${root_kernel_dir}/${root_kernel_file})
 install(FILES ${CMAKE_BINARY_DIR}/etc/${root_kernel_dir}/${root_kernel_file} DESTINATION ${CMAKE_INSTALL_SYSCONFDIR}/${root_kernel_dir})

etc/notebook/jupyter_notebook_config.py.in

@@ -0,0 +1,7 @@
+import os
+if 'ROOTSYS' in os.environ:
+    # Prefer using JSROOT from ROOTSYS if defined
+    c.NotebookApp.extra_static_paths.append(os.path.join(os.environ['ROOTSYS'], 'js/'))
+else:
+    # Fall back to CMAKE_INSTALL_PREFIX to find JSROOT
+    c.NotebookApp.extra_static_paths.append(os.path.join("@CMAKE_INSTALL_PREFIX@", 'js/'))