From fe8fc6f83d3a567b0774b433df011f899f7230d3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20Gr=C3=A4=C3=9Flin?= <mgraesslin@kde.org>
Date: Thu, 18 Aug 2016 16:03:26 +0200
Subject: [PATCH] Ensure to directly delete old Shadow on update

Summary:
So far when deleting a Shadow we used deleteLater which caused it
to be deleted in the next event cycle. This could in worst case result
in the Shadow being deleted after compositing got suspended. Thus the
Shadow not getting removed from the DecorationShadowCache which in
turn would mess up rendering on resume of compositing as the cache
returns a texture created for a different context.

BUG: 361154
FIXED-IN: 5.7.4

Reviewers: #kwin, #plasma

Subscribers: kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D2483
---
 scene.cpp  | 9 +++++++++
 scene.h    | 6 ------
 shadow.cpp | 7 ++++---
 3 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/scene.cpp b/scene.cpp
index 834a731e60..3415ed73e4 100644
--- a/scene.cpp
+++ b/scene.cpp
@@ -928,6 +928,15 @@ WindowQuadList Scene::Window::makeQuads(WindowQuadType type, const QRegion& reg,
     return ret;
 }
 
+void Scene::Window::updateShadow(Shadow* shadow)
+{
+    if (m_shadow == shadow) {
+        return;
+    }
+    delete m_shadow;
+    m_shadow = shadow;
+}
+
 //****************************************
 // WindowPixmap
 //****************************************
diff --git a/scene.h b/scene.h
index 3cdafc28f0..1ce7b18faa 100644
--- a/scene.h
+++ b/scene.h
@@ -537,12 +537,6 @@ void Scene::Window::suspendUnredirect(bool suspend)
     toplevel->suspendUnredirect(suspend);
 }
 
-inline
-void Scene::Window::updateShadow(Shadow* shadow)
-{
-    m_shadow = shadow;
-}
-
 inline
 const Shadow* Scene::Window::shadow() const
 {
diff --git a/shadow.cpp b/shadow.cpp
index 405ca064e7..0f647c7744 100644
--- a/shadow.cpp
+++ b/shadow.cpp
@@ -337,10 +337,11 @@ bool Shadow::updateShadow()
     auto clear = [this]() {
         if (m_topLevel && m_topLevel->effectWindow() && m_topLevel->effectWindow()->sceneWindow() &&
                                             m_topLevel->effectWindow()->sceneWindow()->shadow()) {
-            m_topLevel->effectWindow()->sceneWindow()->updateShadow(0);
-            m_topLevel->effectWindow()->buildQuads(true);
+            auto w = m_topLevel->effectWindow();
+            // this also deletes the shadow
+            w->sceneWindow()->updateShadow(nullptr);
+            w->buildQuads(true);
         }
-        deleteLater();
     };
     if (m_decorationShadow) {
         if (AbstractClient *c = qobject_cast<AbstractClient*>(m_topLevel)) {