diff --git a/cmake/Modules/BuildPython.cmake b/cmake/Modules/BuildPython.cmake
index 6cd9168a8..795303c4c 100644
--- a/cmake/Modules/BuildPython.cmake
+++ b/cmake/Modules/BuildPython.cmake
@@ -52,13 +52,20 @@ else()
     	set( platform Win32 )
     endif()
 
-    # @bug: This creates another .bat file and makes the original .bat file fail
-    # set( Python_ENV ${CMAKE_COMMAND} -E env "PATH=${Python_PATH}" -- )
-    string(CONCAT Python_ENV "cmd /c \"set PATH=\"${Python_PATH}\"")
-    string(CONCAT Python_BUILD ${Python_ENV} && PCbuild/build.bat -e -q -p ${platform} )
-
+    # @bug:
+    #    This creates another .bat file and makes the original .bat file fail
+    # set( Python_ENV ${CMAKE_COMMAND} -E env "PATH=${Python_PATH}" --)
+    
+    list(JOIN Python_PATH "|" Python_PATH_STR)
+    set(Python_SCRIPT "-DPATH=${Python_PATH_STR}" -DCMAKE_INSTALL_PREFIX=${CMAKE_INSTALL_PREFIX} -P ${PROJECT_SOURCE_DIR}/cmake/build_python_windows.cmake
+	)
+    
+    set(Python_BUILD ${CMAKE_COMMAND} -D Python_COMMAND=build
+	-D Python_PLATFORM=${platform})
+    set(Python_BUILD ${Python_BUILD} ${Python_SCRIPT})
     
-    set( Python_INSTALL ${Python_ENV} && python.bat PC/layout --precompile --preset-default  --copy "${CMAKE_INSTALL_PREFIX}/bin/" )
+    set(Python_INSTALL ${CMAKE_COMMAND} -D Python_COMMAND=install)
+    set(Python_INSTALL ${Python_INSTALL} ${Python_SCRIPT})
 endif()
 
 ExternalProject_Add(
diff --git a/cmake/Modules/BuildpyFLTK.cmake b/cmake/Modules/BuildpyFLTK.cmake
index a0f0f7fab..92fbb5f5b 100644
--- a/cmake/Modules/BuildpyFLTK.cmake
+++ b/cmake/Modules/BuildpyFLTK.cmake
@@ -30,6 +30,9 @@ set(pyFLTK_LD_LIBRARY_PATH $ENV{LD_LIBRARY_PATH})
 set(pyFLTK_DYLD_LIBRARY_PATH $ENV{DYLD_LIBRARY_PATH})
 
 set(pyFLTK_PATH $ENV{PATH})
+if(WIN32)
+    string(REPLACE ";" "|" pyFLTK_PATH "$ENV{PATH}")
+endif()
 
 #
 # Handle macOS min version.
@@ -68,16 +71,20 @@ set(pyFLTK_PATCH
     COMMAND
     ${CMAKE_COMMAND} -E copy_if_different
     "${PROJECT_SOURCE_DIR}/cmake/patches/pyFLTK-patch/swig/WindowShowTypemap.i"
-    "${CMAKE_BINARY_DIR}/pyFLTK-prefix/src/pyFLTK/swig/")
+    "${CMAKE_BINARY_DIR}/pyFLTK-prefix/src/pyFLTK/swig/"
+    COMMAND
+    ${CMAKE_COMMAND} -E copy_if_different
+    "${PROJECT_SOURCE_DIR}/cmake/patches/pyFLTK-patch/fltk14/test/exceptions.py"
+    "${CMAKE_BINARY_DIR}/pyFLTK-prefix/src/pyFLTK/fltk14/test")
 
 # Environment setup for configure, building and installing
 set(pyFLTK_ENV ${CMAKE_COMMAND} -E env CXXFLAGS=${pyFLTK_CXX_FLAGS} )
 if(WIN32)
-    set(pyFLTK_ENV ${pyFLTK_ENV} PATH=${pyFLTK_PATH} FLTK_HOME=${CMAKE_INSTALL_PREFIX} --) 
+    set(pyFLTK_ENV ${pyFLTK_ENV} "PATH=${pyFLTK_PATH}" FLTK_HOME=${CMAKE_INSTALL_PREFIX} --) 
 elseif(APPLE)
-    set(pyFLTK_ENV ${pyFLTK_ENV} PATH=${pyFLTK_PATH} DYLD_LIBRARY_PATH=${pyFLTK_DYLD_LIBRARY_PATH} -- )
+    set(pyFLTK_ENV ${pyFLTK_ENV} "PATH=${pyFLTK_PATH}" DYLD_LIBRARY_PATH=${pyFLTK_DYLD_LIBRARY_PATH} -- )
 else()
-    set(pyFLTK_ENV ${pyFLTK_ENV} PATH=${pyFLTK_PATH} LD_LIBRARY_PATH=${pyFLTK_LD_LIBRARY_PATH} -- )
+    set(pyFLTK_ENV ${pyFLTK_ENV} "PATH=${pyFLTK_PATH}" LD_LIBRARY_PATH=${pyFLTK_LD_LIBRARY_PATH} -- )
 endif()
 
 
@@ -86,7 +93,12 @@ set(pyFLTK_CONFIGURE ${pyFLTK_ENV} ${PYTHON_EXECUTABLE} setup.py swig --enable-s
 set(pyFLTK_BUILD     ${pyFLTK_ENV} ${PYTHON_EXECUTABLE} setup.py build --enable-shared)
 set(pyFLTK_INSTALL ${pyFLTK_ENV} ${PYTHON_EXECUTABLE} setup.py install --enable-shared)
 
-
+#
+# Output the commands
+#
+message(STATUS "pyFLTK_CONFIGURE=${pyFLTK_CONFIGURE}")
+message(STATUS "pyFLTK_BUIILD=${pyFLTK_BUILD}")
+message(STATUS "pyFLTK_INSTALL=${pyFLTK_INSTALL}")
 
 
 ExternalProject_Add(
@@ -101,6 +113,7 @@ ExternalProject_Add(
     CONFIGURE_COMMAND "${pyFLTK_CONFIGURE}"
     BUILD_COMMAND     "${pyFLTK_BUILD}"
     INSTALL_COMMAND   "${pyFLTK_INSTALL}"
+    LIST_SEPARATOR |
     BUILD_IN_SOURCE 1
 )
 
diff --git a/cmake/build_python_windows.cmake b/cmake/build_python_windows.cmake
new file mode 100644
index 000000000..25cf0a452
--- /dev/null
+++ b/cmake/build_python_windows.cmake
@@ -0,0 +1,30 @@
+
+
+message(STATUS "Python_COMMAND=${Python_COMMAND}")
+message(STATUS "CMAKE_INSTALL_PREFIX=${CMAKE_INSTALL_PREFIX}")
+message(STATUS "PATH ENV 1=$ENV{PATH}")
+message(STATUS "PATH     1=${PATH}")
+string(REPLACE "|" ";" $ENV{PATH} "${PATH}")
+message(STATUS "PATH ENV 2=$ENV{PATH}")
+
+set(ROOT_DIR ${CMAKE_INSTALL_PREFIX}/../Python-prefix/src/Python)
+
+if (Python_COMMAND STREQUAL "build")
+    set(CMD cmd /C PCbuild\\build.bat -e -q -p ${Python_PLATFORM})
+elseif(Python_COMMAND STREQUAL "install")
+    set(CMD cmd /C python.bat PC\\layout --precompile --preset-default  --copy "${CMAKE_INSTALL_PREFIX}/bin/")
+else()
+    message(FATAL_ERROR "Unknown Python_COMMAND ${Python_COMMAND}!")
+endif()
+
+message(STATUS "Running: ${CMD} in ${ROOT_DIR}...")
+
+execute_process(
+    COMMAND ${CMD}
+    WORKING_DIRECTORY ${ROOT_DIR}
+    ERROR_VARIABLE BAT_CMD_ERROR
+    OUTPUT_VARIABLE BAT_CMD_OUTPUT
+    ECHO_ERROR_VARIABLE 
+    ECHO_OUTPUT_VARIABLE 
+    COMMAND_ERROR_IS_FATAL ANY
+)
diff --git a/cmake/patches/pyFLTK-patch/fltk14/test/exceptions.py b/cmake/patches/pyFLTK-patch/fltk14/test/exceptions.py
new file mode 100644
index 000000000..b48b7cdd8
--- /dev/null
+++ b/cmake/patches/pyFLTK-patch/fltk14/test/exceptions.py
@@ -0,0 +1,67 @@
+# "$Id: demos.py 531 2019-12-27 12:15:45Z andreasheld $"
+#
+# Test program for pyFLTK the Python bindings
+# for the Fast Light Tool Kit (FLTK).
+#
+# FLTK copyright 1998-1999 by Bill Spitzak and others.
+# pyFLTK copyright 2003 by Andreas Held and others.
+#
+# This library is free software you can redistribute it and/or
+# modify it under the terms of the GNU Library General Public
+# License, version 2.0 as published by the Free Software Foundation.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Library General Public License for more details.
+#
+# You should have received a copy of the GNU Library General Public
+# License along with this library if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+# USA.
+#
+# Please report all bugs and problems to "pyfltk-user@lists.sourceforge.net".
+#
+
+
+from fltk14 import *
+
+class subwindow(Fl_Gl_Window):
+
+    def __init__(self, x,y,w,h):
+        super().__init__(x,y,w,h, "")
+
+    def handle(self, event):
+        if event == FL_PUSH:
+            raise Exception("exception in handle")
+        return super().handle(event)
+
+    def draw(self):
+        pass
+
+
+
+class MyButton(Fl_Button):
+   def __init__(self, x,y,w,h, l):
+       super().__init__(x,y,w,h, l)
+       self.callback(self.b_cb)
+
+   def b_cb(self, wid):
+       raise Exception("exception in callback")
+
+if __name__=='__main__':
+    window = Fl_Double_Window(0, 0, 500, 500, "tst")
+
+    widget = subwindow(0,0,500,400)
+    window.resizable(widget)
+
+    mb = MyButton(200,420,100,60, "Exit")
+
+
+    try:
+        window.end()
+        window.show()
+        Fl.run()
+    except Exception as e:
+        print("Exception: ", e)
+ 
diff --git a/tlRender b/tlRender
index 072c0012c..7a076e6af 160000
--- a/tlRender
+++ b/tlRender
@@ -1 +1 @@
-Subproject commit 072c0012c73f50377508d0ce81624a8edbf6494a
+Subproject commit 7a076e6af6910e15ee76228c07bd40aa9ff10dd1