Fix help window for conda installs on Windows

docs/source/release/v6.14.0/Workbench/Bugfixes/34739.rst

@@ -0,0 +1 @@
+- Opening the help window will no longer cause a crash in Windows conda installs of mantidworkbench.

qt/applications/workbench/workbench/app/mantidworkbench_launch_wrapper.py

@@ -6,12 +6,42 @@
 # SPDX - License - Identifier: GPL - 3.0 +
 #  This file is part of the mantid workbench.
 import os
+from pathlib import Path
+import shutil
 import subprocess
 import sys
 
 from workbench.app.main import main
 
 
+def _patch_qtwebengine_files(prefix: str):
+    """
+    Copy Qt WebEngine executable, resources, locales, and ICU data into the environment
+    root so Qt can find them when launching from a conda environment on Windows.
+    """
+    env_root = Path(prefix)  # Python executable directory
+    library = env_root / "Library"
+
+    # Copy QtWebEngineProcess.exe
+    src_exe = library / "bin" / "QtWebEngineProcess.exe"
+    dst_exe = env_root / "QtWebEngineProcess.exe"
+    if src_exe.exists() and not dst_exe.exists():
+        shutil.copy2(src_exe, dst_exe)
+
+    # Copy the contents of the resources directory
+    src_resources = library / "resources"
+    for f in src_resources.glob("*"):
+        dst = env_root / f.name
+        if not dst.exists():
+            shutil.copy2(f, dst)
+
+    # Copy locales directory
+    src_locales = library / "translations" / "qtwebengine_locales"
+    dst_locales = env_root / "qtwebengine_locales"
+    if src_locales.exists() and not dst_locales.exists():
+        shutil.copytree(src_locales, dst_locales)
+
+
 def launch(args=None):
     if args is None:
         args = sys.argv
@@ -20,9 +50,12 @@ def launch(args=None):
         subprocess.run(command)
     else:
         if sys.platform.startswith("win"):
-            # Windows conda installs require us to set the QT_PLUGIN_PATH variable.
+            # Windows conda installs require us to set the QT_PLUGIN_PATH variable and copy QtWebEngine files
+            # to the root directory of the conda environment.
             if "CONDA_PREFIX" in os.environ:
-                os.environ["QT_PLUGIN_PATH"] = f"{os.environ.get('CONDA_PREFIX')}\\Library\\plugins"
+                prefix = os.environ.get("CONDA_PREFIX")
+                os.environ["QT_PLUGIN_PATH"] = f"{prefix}\\Library\\plugins"
+                _patch_qtwebengine_files(prefix)
         main(args[1:])