do not attempt to download & install tkdnd or Tcl/Tk
--- cmake/external_projects/tcltk.cmake.orig	2026-05-10 13:04:45
+++ cmake/external_projects/tcltk.cmake	2026-05-10 13:11:40
@@ -69,60 +69,8 @@
 
 else(SKBUILD)
 if(APPLE)
-  set(tcl_prefix ${CMAKE_INSTALL_PREFIX})
-  # URL "http://sourceforge.net/projects/tcl/files/Tcl/8.6.9/tcl8.6.9-src.tar.gz"
-  # URL_MD5 aa0a121d95a0e7b73a036f26028538d4
-  ExternalProject_Add(project_tcl
-    URL "https://github.com/NGSolve/tcl/archive/7769161.zip"
-    URL_MD5 1131f188dd26944df557913c475d43b4
-    DOWNLOAD_DIR ${CMAKE_CURRENT_SOURCE_DIR}/external_dependencies
-    UPDATE_COMMAND ""
-    CONFIGURE_COMMAND ../project_tcl/macosx/configure --enable-threads --enable-framework --prefix=${tcl_prefix} --libdir=${tcl_prefix}/Contents/Frameworks --bindir=${tcl_prefix}/Contents/Frameworks/Tcl.framework/bin
-    BUILD_COMMAND make -j4 binaries libraries
-    INSTALL_COMMAND make install-binaries install-headers install-libraries install-private-headers
-    ${SUBPROJECT_ARGS}
-    )
+    find_package(TCL 8.5 REQUIRED)
 
-  # URL "http://sourceforge.net/projects/tcl/files/Tcl/8.6.9/tk8.6.9.1-src.tar.gz"
-  # URL_MD5 9efe3976468352dc894dae0c4e785a8e
-  ExternalProject_Add(project_tk
-    DEPENDS project_tcl
-    URL "https://github.com/NGSolve/tk/archive/e7c2bc7.zip"
-    URL_MD5 94044140d4826069c22f1c60cedb6e59
-    DOWNLOAD_DIR ${CMAKE_CURRENT_SOURCE_DIR}/external_dependencies
-    UPDATE_COMMAND ""
-    CONFIGURE_COMMAND ../project_tk/macosx/configure --enable-aqua=yes --enable-threads --enable-framework --prefix=${tcl_prefix} --libdir=${tcl_prefix}/Contents/Frameworks --bindir=${tcl_prefix}/Contents/Frameworks/Tcl.framework/bin --with-tcl=${tcl_prefix}/Contents/Frameworks/Tcl.framework
-    BUILD_COMMAND make -j4 binaries libraries
-    INSTALL_COMMAND make install-binaries install-headers install-libraries install-private-headers
-    ${SUBPROJECT_ARGS}
-    )
-
-  ExternalProject_Add(project_tkdnd
-    URL "https://src.fedoraproject.org/repo/pkgs/tkdnd/tkdnd2.8-src.tar.gz/a6d47a996ea957416469b12965d4db91/tkdnd2.8-src.tar.gz"
-    URL_MD5 a6d47a996ea957416469b12965d4db91
-    DEPENDS project_tcl project_tk
-    DOWNLOAD_DIR ${CMAKE_CURRENT_SOURCE_DIR}/external_dependencies
-    PATCH_COMMAND  patch < ${CMAKE_CURRENT_LIST_DIR}/tkdnd_macosx.patch
-    UPDATE_COMMAND "" # Disable update
-    BUILD_IN_SOURCE 1
-    CMAKE_ARGS
-           -DCMAKE_INSTALL_PREFIX=${CMAKE_INSTALL_PREFIX}/Contents/MacOS
-	   -DTCL_INCLUDE_PATH=${CMAKE_INSTALL_PREFIX}/Contents/Frameworks/Tcl.framework/Headers
-	   -DTK_INCLUDE_PATH=${CMAKE_INSTALL_PREFIX}/Contents/Frameworks/Tk.framework/Headers
-     -DCMAKE_POLICY_VERSION_MINIMUM=3.5
-    ${SUBPROJECT_ARGS}
-  )
-
-  list(APPEND NETGEN_DEPENDENCIES project_tcl project_tk project_tkdnd)
-  list(APPEND CMAKE_PREFIX_PATH ${CMAKE_INSTALL_PREFIX}/Contents/Frameworks)
-  set(TCL_INCLUDE_PATH ${CMAKE_INSTALL_PREFIX}/Contents/Frameworks/Tcl.framework/Headers)
-  set(TCL_LIBRARY ${CMAKE_INSTALL_PREFIX}/Contents/Frameworks/Tcl.framework)
-  set(TK_LIBRARY ${CMAKE_INSTALL_PREFIX}/Contents/Frameworks/Tk.framework)
-  set(TK_INCLUDE_PATH ${CMAKE_INSTALL_PREFIX}/Contents/Frameworks/Tk.framework/Headers)
-
-  set(TCL_STUB_LIBRARY ${CMAKE_INSTALL_PREFIX}/Contents/Frameworks/Tcl.framework/libtclstub8.6.a)
-  set(TK_STUB_LIBRARY ${CMAKE_INSTALL_PREFIX}/Contents/Frameworks/Tk.framework/libtkstub8.6.a)
-
 #   # use system tcl/tk
 #   if((${PYTHON_VERSION_STRING} VERSION_EQUAL "3.7") OR (${PYTHON_VERSION_STRING} VERSION_GREATER "3.7"))
 #     # fetch tcl/tk sources to match the one used in Python 3.7