From b708a93c1e7d87b6f39d0a6680d5d3ef3c999c41 Mon Sep 17 00:00:00 2001
From: Vlad Zahorodnii <vlad.zahorodnii@kde.org>
Date: Thu, 29 Aug 2024 17:07:29 +0300
Subject: [PATCH] scene: Add an assert to debug crash in
 BlurEffect::prePaintWindow()

This checks whether a WindowItem is destroyed in the middle of a painting
cycle.

This is meant as short-term means to debug the issue.
---
 src/scene/workspacescene.cpp | 11 +++++++++++
 src/scene/workspacescene.h   |  1 +
 2 files changed, 12 insertions(+)

diff --git a/src/scene/workspacescene.cpp b/src/scene/workspacescene.cpp
index aad9fa0e96..475b35a4ac 100644
--- a/src/scene/workspacescene.cpp
+++ b/src/scene/workspacescene.cpp
@@ -102,6 +102,14 @@ WorkspaceScene::WorkspaceScene(std::unique_ptr<ItemRenderer> renderer)
         connect(waylandServer()->seat(), &SeatInterface::dragStarted, this, &WorkspaceScene::createDndIconItem);
         connect(waylandServer()->seat(), &SeatInterface::dragEnded, this, &WorkspaceScene::destroyDndIconItem);
     }
+
+    connect(m_containerItem.get(), &Item::childAdded, this, [this](Item *item) {
+        connect(item, &Item::destroyed, this, [this]() {
+            if (m_painting) {
+                qFatal("Destroyed an item while painting");
+            }
+        });
+    });
 }
 
 WorkspaceScene::~WorkspaceScene()
@@ -255,6 +263,7 @@ void WorkspaceScene::frame(SceneDelegate *delegate, OutputFrame *frame)
 
 QRegion WorkspaceScene::prePaint(SceneDelegate *delegate)
 {
+    m_painting = true;
     createStackingOrder();
 
     painted_delegate = delegate;
@@ -384,6 +393,8 @@ void WorkspaceScene::preparePaintSimpleScreen()
 
 void WorkspaceScene::postPaint()
 {
+    m_painting = false;
+
     for (WindowItem *w : std::as_const(stacking_order)) {
         effects->postPaintWindow(w->effectWindow());
     }
diff --git a/src/scene/workspacescene.h b/src/scene/workspacescene.h
index 43a13630aa..7b195aa032 100644
--- a/src/scene/workspacescene.h
+++ b/src/scene/workspacescene.h
@@ -134,6 +134,7 @@ private:
     std::unique_ptr<Item> m_containerItem;
     std::unique_ptr<Item> m_overlayItem;
     std::unique_ptr<DragAndDropIconItem> m_dndIcon;
+    bool m_painting = false;
 };
 
 } // namespace