From 5ed3e382cefef0148ff9d26d8b6a38f6fbd22574 Mon Sep 17 00:00:00 2001
From: Silvio <silvio.traversaro@iit.it>
Date: Wed, 25 Sep 2024 19:49:56 +0200
Subject: [PATCH] Ensure that wearables and hde Python bindings work on Windows
 when installed in arbitrary directories

---
 bindings/CMakeLists.txt                  | 25 ++++++++++++++++++++++++
 bindings/python-hde/CMakeLists.txt       |  4 +---
 bindings/python-wearables/CMakeLists.txt |  4 +---
 3 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/bindings/CMakeLists.txt b/bindings/CMakeLists.txt
index da48f355..a34237d8 100644
--- a/bindings/CMakeLists.txt
+++ b/bindings/CMakeLists.txt
@@ -35,6 +35,31 @@ if(HDE_COMPILE_PYTHON_BINDINGS)
     "Do you want HDE to detect and use the active site-package directory? (it could be a system dir)"
     FALSE)
 
+  # Function to generate __init__.py file for both hde and wearables
+  # It contains logic to ensure that it works fine on Windows when installing in arbitrary folders,
+  # See https://docs.python.org/3.8/library/os.html#os.add_dll_directory
+  function(hde_generate_init_py_file GENERATION_LOCATION_OF_INIT_PY_FILE INSTALLATION_LOCATION_OF_INIT_PY_FILE)
+    file(WRITE ${GENERATION_LOCATION_OF_INIT_PY_FILE}/__init__.py "")
+    if(WIN32 AND BUILD_SHARED_LIBS)
+        if(IS_ABSOLUTE ${INSTALLATION_LOCATION_OF_INIT_PY_FILE})
+            set(PYTHON_FULL_INSTDIR "${INSTALLATION_LOCATION_OF_INIT_PY_FILE}")
+        else()
+            set(PYTHON_FULL_INSTDIR "${CMAKE_INSTALL_PREFIX}/${INSTALLATION_LOCATION_OF_INIT_PY_FILE}")
+        endif()
+        file(RELATIVE_PATH RELATIVE_PATH_BETWEEN_INIT_PY_AND_DLL_DIRECTORY ${PYTHON_FULL_INSTDIR} ${CMAKE_INSTALL_FULL_BINDIR})
+        file(APPEND ${GENERATION_LOCATION_OF_INIT_PY_FILE}/__init__.py "import os\n")
+        file(APPEND ${GENERATION_LOCATION_OF_INIT_PY_FILE}/__init__.py "library_dll_path = os.path.join(os.path.dirname(__file__),'${RELATIVE_PATH_BETWEEN_INIT_PY_AND_DLL_DIRECTORY}')\n")
+        file(APPEND ${GENERATION_LOCATION_OF_INIT_PY_FILE}/__init__.py "# Avoid to call add_dll_directory if not necessary,\n")
+        file(APPEND ${GENERATION_LOCATION_OF_INIT_PY_FILE}/__init__.py "# for example if the library to find are already found in the proper location in a conda\n")
+        file(APPEND ${GENERATION_LOCATION_OF_INIT_PY_FILE}/__init__.py "if(library_dll_path != os.path.join(os.environ.get('CONDA_PREFIX', ''),'Library','bin') and library_dll_path != os.path.join(os.environ.get('CONDA_PREFIX', ''),'bin')):\n")
+        file(APPEND ${GENERATION_LOCATION_OF_INIT_PY_FILE}/__init__.py "    if(os.path.exists(library_dll_path)):\n")
+        file(APPEND ${GENERATION_LOCATION_OF_INIT_PY_FILE}/__init__.py "        os.add_dll_directory(library_dll_path)$\n")
+        file(APPEND ${GENERATION_LOCATION_OF_INIT_PY_FILE}/__init__.py "\n")
+    endif()
+
+    file(APPEND ${GENERATION_LOCATION_OF_INIT_PY_FILE}/__init__.py "from .bindings import *\n")
+  endfunction()
+
   # Install the resulting Python package for the active interpreter
   if(NOT DEFINED HDE_PYTHON_INSTALL_DIR)
     if(HDE_DETECT_ACTIVE_PYTHON_SITEPACKAGES)
diff --git a/bindings/python-hde/CMakeLists.txt b/bindings/python-hde/CMakeLists.txt
index 7b400d54..006ab8d6 100644
--- a/bindings/python-hde/CMakeLists.txt
+++ b/bindings/python-hde/CMakeLists.txt
@@ -43,9 +43,7 @@ set_target_properties(pybind11_hde PROPERTIES
 install(TARGETS pybind11_hde DESTINATION ${PYTHON_INSTDIR})
 
 # Create the __init__.py file
-file(GENERATE
-  OUTPUT "${HDE_PYTHON_PACKAGE}/__init__.py"
-  CONTENT "from .bindings import *\n")
+hde_generate_init_py_file("${HDE_PYTHON_PACKAGE}" "${PYTHON_INSTDIR}")
 # Install the __init__.py file
 install(FILES "${HDE_PYTHON_PACKAGE}/__init__.py"
   DESTINATION ${PYTHON_INSTDIR})
diff --git a/bindings/python-wearables/CMakeLists.txt b/bindings/python-wearables/CMakeLists.txt
index cd94f5e8..b5626247 100644
--- a/bindings/python-wearables/CMakeLists.txt
+++ b/bindings/python-wearables/CMakeLists.txt
@@ -42,9 +42,7 @@ set_target_properties(pybind11_wearables PROPERTIES
 
 install(TARGETS pybind11_wearables DESTINATION ${PYTHON_INSTDIR})
 
-file(GENERATE
-  OUTPUT "${WEARABLES_PYTHON_PACKAGE}/__init__.py"
-  CONTENT "from .bindings import *\n")
+hde_generate_init_py_file("${WEARABLES_PYTHON_PACKAGE}" "${PYTHON_INSTDIR}")
 # Install the __init__.py file
 install(FILES "${WEARABLES_PYTHON_PACKAGE}/__init__.py"
   DESTINATION ${PYTHON_INSTDIR})