On Windows, use os.add_dll_directory to point to location of ThirdP…

…arty dlls. (#19258) (#19259)

To fix issues where Python 3.9 cannot import vtk modules due to change in how paths are searched for DLLs.
Added function to retrieve ThirdParty path for dev version of Windows (for non-dev, the dlls live with the executables).
Use that path in call to  `os.add_dll_directory`.

src/avt/PythonFilters/PythonInterpreter.C

@@ -207,6 +207,30 @@ PythonInterpreter::AddSystemPath(const std::string &path)
     return RunScript("sys.path.insert(1,r'" + path + "')\n");
 }
 
+#ifdef _WIN32
+// ****************************************************************************
+//  Method: PythonInterpreter::AddDLLPath
+//
+//  Purpose:
+//      Adds passed path to "os.add_dll_directory"
+//
+//  Arguments:
+//      path      Path to DLLs  (eg VisIt's third party dlls)
+//
+//  Programmer:   Kathleen Biagas 
+//  Creation:     January 24, 2024 
+//
+//  Modifications:
+//
+// ****************************************************************************
+
+bool
+PythonInterpreter::AddDLLPath(const std::string &path)
+{
+    return RunScript("os.add_dll_directory(r'" + path + "')\n");
+}
+#endif
+
 // ****************************************************************************
 //  Method: PythonInterpreter::RunScript
 //

src/avt/PythonFilters/PythonInterpreter.h

@@ -23,6 +23,10 @@ typedef _object PyObject;
 //  Programmer:  Cyrus Harrison
 //  Creation:    May 2, 2008
 //
+//  Modifications:
+//    Kathleen Biagas, Wed Jan 24, 2024
+//    Added new method 'AddDLLPath'.
+//
 // ****************************************************************************
 class AVTPYTHON_FILTERS_API PythonInterpreter
 {
@@ -36,6 +40,9 @@ class AVTPYTHON_FILTERS_API PythonInterpreter
     void         Shutdown();
 
     bool         AddSystemPath(const std::string &path);
+#ifdef _WIN32
+    bool         AddDLLPath(const std::string &path);
+#endif
     bool         RunScript(const std::string &script);
     bool         RunScriptFile(const std::string &fname);
 

src/avt/PythonFilters/avtPythonFilterEnvironment.C

@@ -95,6 +95,10 @@ avtPythonFilterEnvironment::~avtPythonFilterEnvironment()
 //    Cyrus Harrison, Tue Feb 23 17:04:32 PST 2021
 //    Use MPI_Comm_c2f handle to init mpicom module.
 //
+//    Kathleen Biagas, Wed Jan 24, 2024
+//    When running a dev version on Windows, add ThirdParty directory
+//    to dll directory.
+//
 // ****************************************************************************
 
 bool
@@ -113,6 +117,16 @@ avtPythonFilterEnvironment::Initialize()
     if(!pyi->AddSystemPath(vlibsp)) // vtk module is symlinked here
         return false;
 
+#ifdef _WIN32
+    // need to add ThirdParty dll directory to dll path if it is available
+    // (eg for development builds)
+    if(GetIsDevelopmentVersion())
+    {
+        string vdlldir = GetVisItThirdPartyDirectory();
+        if(!vdlldir.empty() && !pyi->AddDLLPath(vdlldir))
+            return false;
+    }
+#endif
     // import pyavt and vtk
     if(!pyi->RunScript("from pyavt.filters import *\n"))
         return false;

src/common/misc/InstallationFunctions.C

@@ -420,6 +420,40 @@ GetSystemVisItHostsDirectory()
     return retVal;
 }
 
+#ifdef _WIN32
+#include <filesystem>
+// ****************************************************************************
+// Method:  GetVisItThirdPartyDirectory
+//
+// Purpose:
+//   Returns the path to the ThirdParty directory for a dev build of VisIt.
+//   Returns an empty string if not running from a development build.
+//
+// Arguments:
+//   none
+//
+// Programmer:  Kathleen Biagas 
+// Creation:    January 24, 2024
+//
+// Modifications:
+//
+// ****************************************************************************
+
+std::string
+GetVisItThirdPartyDirectory()
+{
+    std::string retval;
+    if(GetIsDevelopmentVersion())
+    {
+        std::filesystem::path homeDir(GetVisItInstallationDirectory());
+        auto dllDir = homeDir.parent_path() / "ThirdParty";
+        retval = dllDir.string();
+    }
+    return retval;
+}
+
+#endif
+
 // ****************************************************************************
 // Method: GetVisItResourcesDirectory
 //

src/common/misc/InstallationFunctions.h

@@ -36,6 +36,10 @@ std::string MISC_API GetAndMakeUserVisItHostsDirectory();
 std::string MISC_API GetVisItHostsDirectory();
 std::string MISC_API GetSystemVisItHostsDirectory();
 
+#ifdef _WIN32
+std::string MISC_API GetVisItThirdPartyDirectory();
+#endif
+
 typedef enum {
     VISIT_RESOURCES,
     VISIT_RESOURCES_COLORTABLES,

src/visitpy/cli/cli.C

@@ -563,6 +563,18 @@ main(int argc, char *argv[])
         oss << "sys.path.append(pjoin(r'" << vlibdir  <<"','site-packages'))";
         PyRun_SimpleString(oss.str().c_str());
 
+#ifdef _WIN32
+        if(GetIsDevelopmentVersion())
+        {
+            // retrieve ThirdParty directory
+            std::string dlldir  = GetVisItThirdPartyDirectory(); 
+            // Add thirdparty DLL's directory
+            std::ostringstream ss;
+            ss << "os.add_dll_directory(r'" << dlldir  <<"')";
+            PyRun_SimpleString(ss.str().c_str());
+        }
+#endif
+
         // Initialize the VisIt module.
         cli_initvisit(bufferDebug ? -debugLevel : debugLevel,
                       verbose,