From 5642b6fe7cd84d3fa39d7285e314777cd3c00a4f Mon Sep 17 00:00:00 2001
From: Allan Sandfeld Jensen <allan.jensen@qt.io>
Date: Mon, 18 Nov 2024 11:09:32 +0100
Subject: [PATCH] Facilitate disabling multi-threading in image manipulation
 and painting

On some platforms and setups, the multi-threaded implementation of this functionality is not desirable. Allow disabling it at runtime by setting the environment variable QT_NO_GUI_THREADPOOL.

Task-number: QTBUG-129650
Change-Id: If089ecb3b335defc06f14749841bf9f6041e6f5e
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>
(cherry picked from commit 7a8cefd6fb66e6bc6880aaf5a938194611278bed)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
---
 src/corelib/thread/qthreadpool.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/corelib/thread/qthreadpool.cpp b/src/corelib/thread/qthreadpool.cpp
index 18d4103fdfc..55f13a6b02a 100644
--- a/src/corelib/thread/qthreadpool.cpp
+++ b/src/corelib/thread/qthreadpool.cpp
@@ -481,7 +481,9 @@ QThreadPool *QThreadPoolPrivate::qtGuiInstance()
 {
     Q_CONSTINIT static QPointer<QThreadPool> guiInstance;
     Q_CONSTINIT static QBasicMutex theMutex;
-
+    const static bool runtime_disable = qEnvironmentVariableIsSet("QT_NO_GUI_THREADPOOL");
+    if (runtime_disable)
+        return nullptr;
     const QMutexLocker locker(&theMutex);
     if (guiInstance.isNull() && !QCoreApplication::closingDown()) {
         guiInstance = new QThreadPool();