From e7d12e70ff73c9105d4f24da3791c80c6d02e520 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marvin=20N=C3=B6then?= <marvin.noethen@dlr.de>
Date: Thu, 7 May 2026 16:04:53 +0200
Subject: [PATCH] Fix Python ownership detection and stabilize GIL handling for
 binding mode

---
 src/module/utilities/gtpy_contextmanager.cpp | 48 ++++++++++++++++----
 src/module/utilities/gtpy_globals.h          |  8 ++++
 2 files changed, 48 insertions(+), 8 deletions(-)

diff --git a/src/module/utilities/gtpy_contextmanager.cpp b/src/module/utilities/gtpy_contextmanager.cpp
index 0627068..136aa9d 100644
--- a/src/module/utilities/gtpy_contextmanager.cpp
+++ b/src/module/utilities/gtpy_contextmanager.cpp
@@ -63,6 +63,38 @@
 namespace
 {
 
+void ensurePythonOwnerEnvVar()
+{
+    if (qEnvironmentVariableIsSet(gtpy::constants::env::PYTHON_OWNER_ENV_VAR))
+    {
+        return;
+    }
+
+    auto exeBaseName = QFileInfo(QCoreApplication::applicationFilePath())
+                           .completeBaseName()
+                           .toLower();
+
+    bool gtlabOwnsPython = (exeBaseName == QStringLiteral("gtlab") ||
+                            exeBaseName == QStringLiteral("gtlabconsole"));
+
+    qputenv(gtpy::constants::env::PYTHON_OWNER_ENV_VAR,
+            gtlabOwnsPython
+                ? gtpy::constants::env::PYTHON_OWNER_GTLAB
+                : gtpy::constants::env::PYTHON_OWNER_EXTERNAL);
+}
+
+bool isGtlabPythonOwner()
+{
+    ensurePythonOwnerEnvVar();
+
+    auto owner = qEnvironmentVariable(
+                     gtpy::constants::env::PYTHON_OWNER_ENV_VAR)
+                     .trimmed()
+                     .toLower();
+
+    return owner == QLatin1String(gtpy::constants::env::PYTHON_OWNER_GTLAB);
+}
+
 GtpyContext::ContextType contextTypeEnumConvert(
         GtpyContextManager::Context type)
 {
@@ -140,15 +172,15 @@ GtpyContextManager::GtpyContextManager(QObject* parent) :
     dlopen(PYTHON_LIBRARY, RTLD_LAZY | RTLD_GLOBAL);
 #endif
 
-    // In the embedded case, we are owning the python interpreter, so we
-    // need to create it first.
-    //
-    // When the python module is running from inside a normal python interpreter
-    // we are not allowed to reinit. Also, we don't want to redirect std out in this case
-    const bool pythonAlreadyInitialized = (Py_IsInitialized() != 0);
-    m_ownsPythonInterpreter = !pythonAlreadyInitialized;
+    // Determine interpreter ownership via GTLAB_PYTHON_INTERPRETER_OWNER.
+    // Ownership controls whether we initialize Python in embedded mode
+    // or attach to an externally hosted Python interpreter.
+    m_ownsPythonInterpreter = isGtlabPythonOwner();
 
-    int pythonQtFlags = m_ownsPythonInterpreter ? PythonQt::RedirectStdOut : PythonQt::PythonAlreadyInitialized;
+    const bool pythonAlreadyInitialized = (Py_IsInitialized() != 0);
+    int pythonQtFlags = pythonAlreadyInitialized
+                            ? PythonQt::PythonAlreadyInitialized
+                            : PythonQt::RedirectStdOut;
 
     PythonQt::init(pythonQtFlags);
 
diff --git a/src/module/utilities/gtpy_globals.h b/src/module/utilities/gtpy_globals.h
index 7705f5e..ea6d2a4 100644
--- a/src/module/utilities/gtpy_globals.h
+++ b/src/module/utilities/gtpy_globals.h
@@ -27,6 +27,14 @@ constexpr const char* COLLECTION_CAT = "category";
 constexpr const char* COLLECTION_SUBCAT = "subcategory";
 constexpr const char* PROJ_PY_SCRIPTS_DIR = "scripts/python";
 
+/// Environment
+namespace env
+{
+constexpr const char* PYTHON_OWNER_ENV_VAR = "GTLAB_PYTHON_INTERPRETER_OWNER";
+constexpr const char* PYTHON_OWNER_GTLAB = "gtlab";
+constexpr const char* PYTHON_OWNER_EXTERNAL = "external";
+}
+
 } // namespace constants
 
 } // namespace gtpy