From 50b4e988a4794be6fd526eb3e4b1626e17f19637 Mon Sep 17 00:00:00 2001
From: David Edmundson <kde@davidedmundson.co.uk>
Date: Tue, 27 Sep 2022 11:18:06 +0100
Subject: [PATCH] [windowthumbnails] Guard against software QtQuick backend

If we are using the software renderer
QQuickWindow::createTextureFromNativeObject returns null. We already
checking for kwin using GL compositing so we can expand to check
QtQuick's usage.
---
 src/scripting/windowthumbnailitem.cpp | 10 ++++++++--
 src/scripting/windowthumbnailitem.h   |  1 +
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/scripting/windowthumbnailitem.cpp b/src/scripting/windowthumbnailitem.cpp
index ba639f74d1..ba25ff202b 100644
--- a/src/scripting/windowthumbnailitem.cpp
+++ b/src/scripting/windowthumbnailitem.cpp
@@ -164,11 +164,17 @@ void WindowThumbnailItem::updateFrameRenderingConnection()
         return;
     }
 
-    if (Compositor::self()->backend()->compositingType() == OpenGLCompositing) {
+    if (useGlThumbnails()) {
         m_frameRenderingConnection = connect(Compositor::self()->scene(), &Scene::preFrameRender, this, &WindowThumbnailItem::updateOffscreenTexture);
     }
 }
 
+bool WindowThumbnailItem::useGlThumbnails()
+{
+    static bool qtQuickIsSoftware = QStringList({QStringLiteral("software"), QStringLiteral("softwarecontext")}).contains(QQuickWindow::sceneGraphBackend());
+    return Compositor::self()->backend()->compositingType() == OpenGLCompositing && !qtQuickIsSoftware;
+}
+
 QSize WindowThumbnailItem::sourceSize() const
 {
     return m_sourceSize;
@@ -188,7 +194,7 @@ void WindowThumbnailItem::destroyOffscreenTexture()
     if (!Compositor::compositing()) {
         return;
     }
-    if (Compositor::self()->backend()->compositingType() != OpenGLCompositing) {
+    if (!useGlThumbnails()) {
         return;
     }
 
diff --git a/src/scripting/windowthumbnailitem.h b/src/scripting/windowthumbnailitem.h
index 73bf7ee373..251fe03c8c 100644
--- a/src/scripting/windowthumbnailitem.h
+++ b/src/scripting/windowthumbnailitem.h
@@ -87,6 +87,7 @@ private:
     void destroyOffscreenTexture();
     void updateImplicitSize();
     void updateFrameRenderingConnection();
+    static bool useGlThumbnails();
 
     QSize m_sourceSize;
     QUuid m_wId;