Fix Windows DLL search for bundled Python in build tree

Author: akenmorris

Libs/Application/Job/PythonWorker.cpp

@@ -236,40 +236,32 @@ bool PythonWorker::init() {
   qputenv("PYTHONHOME", python_home.toUtf8());
 
 #ifdef _WIN32
-  // Python 3.8+ requires explicit DLL directory registration
-  // PATH environment variable is no longer used for DLL search
-  SetDefaultDllDirectories(LOAD_LIBRARY_SEARCH_DEFAULT_DIRS | LOAD_LIBRARY_SEARCH_USER_DIRS);
-
   if (using_bundled) {
-    // Register bundled Python DLL directories via AddDllDirectory
+    // Prepend Python DLL directories to PATH so the embedded interpreter can
+    // find .pyd extension dependencies (e.g. _ctypes.pyd -> libffi-8.dll).
+    // We use PATH instead of SetDefaultDllDirectories/AddDllDirectory because
+    // those restrict DLL search process-wide, which breaks the build tree
+    // where DLLs are spread across conda, deps, and build directories.
     QString dlls_dir = python_home + "/DLLs";
-    AddDllDirectory(dlls_dir.toStdWString().c_str());
-    AddDllDirectory(python_home.toStdWString().c_str());
-
-    // Also add the directory containing the executable (for dependency DLLs)
     QString app_dir = QCoreApplication::applicationDirPath();
-    AddDllDirectory(app_dir.toStdWString().c_str());
+    QString current_path = qgetenv("PATH");
+    QString new_path = dlls_dir + ";" + python_home + ";" + app_dir;
 
     // In the build tree, PYTHONHOME points to conda's prefix. Conda's .pyd
     // files need DLLs from conda's Library/bin/ (e.g. libexpat.dll for pyexpat).
     QString conda_library_bin = python_home + "/Library/bin";
-    if (QDir(conda_library_bin).exists()) {
-      AddDllDirectory(conda_library_bin.toStdWString().c_str());
-    }
-
-    // Prepend DLL directories to PATH as well. In the embedded interpreter,
-    // implicit DLL dependencies of .pyd files (e.g. _ctypes.pyd -> libffi-8.dll)
-    // are not always found via AddDllDirectory alone — PATH is still needed.
-    QString current_path = qgetenv("PATH");
-    QString new_path = dlls_dir + ";" + python_home + ";" + app_dir;
     if (QDir(conda_library_bin).exists()) {
       new_path += ";" + conda_library_bin;
     }
+
     new_path += ";" + current_path;
     qputenv("PATH", new_path.toUtf8());
 
     SW_LOG("Registered bundled Python DLL directories");
   } else {
+    // Legacy conda-based Python path
+    SetDefaultDllDirectories(LOAD_LIBRARY_SEARCH_DEFAULT_DIRS | LOAD_LIBRARY_SEARCH_USER_DIRS);
+
     QString home = qgetenv("USERPROFILE");
     if (python_home.isEmpty()) {
       SW_ERROR("Unable to initialize Python\nPlease run install_shapeworks.bat");