From c890996a333c2cf3f961c0f8b2f0a522f8a6015f Mon Sep 17 00:00:00 2001
From: Vlad Zahorodnii <vlad.zahorodnii@kde.org>
Date: Wed, 10 Jun 2020 09:28:48 +0300
Subject: [PATCH] [scene] Setup scene window connections with correct receiver
 object

We need a couple of connections to ensure that the window pixmap, the
window quad cache, and the window shape get discarded when the geometry
of the toplevel has been changed. Currently, those connections are
created with the receiver object being the scene. The problem is that
the associated wayland surface may outlive the toplevel and we don't
cleanup the connections after the scene window has been destroyed.

The fact that the connections don't get destroyed can lead to accessing
dangling pointers, which may result in a crash.

In order to ensure that the connections are broken automatically when
the scene window is destroyed, we need to ensure that the received
object is the scene window. That way, the connections will be destroyed
automatically.
---
 scene.cpp | 43 ++++++++++++++++---------------------------
 scene.h   |  2 --
 2 files changed, 16 insertions(+), 29 deletions(-)

diff --git a/scene.cpp b/scene.cpp
index a094508557..93e5c1db2d 100644
--- a/scene.cpp
+++ b/scene.cpp
@@ -397,10 +397,6 @@ void Scene::addToplevel(Toplevel *c)
     Scene::Window *w = createWindow(c);
     m_windows[ c ] = w;
 
-    auto discardPixmap = [w]() { w->discardPixmap(); };
-    auto discardQuads = [w]() { w->discardQuads(); };
-
-    connect(c, SIGNAL(geometryShapeChanged(KWin::Toplevel*,QRect)), SLOT(windowGeometryShapeChanged(KWin::Toplevel*)));
     connect(c, SIGNAL(windowClosed(KWin::Toplevel*,KWin::Deleted*)), SLOT(windowClosed(KWin::Toplevel*,KWin::Deleted*)));
     if (c->surface()) {
         // We generate window quads for sub-surfaces so it's quite important to discard
@@ -408,25 +404,26 @@ void Scene::addToplevel(Toplevel *c)
         SubSurfaceMonitor *monitor = new SubSurfaceMonitor(c->surface(), this);
 
         // TODO(vlad): Is there a more efficient way to manage window pixmap trees?
-        connect(monitor, &SubSurfaceMonitor::subSurfaceAdded, this, discardPixmap);
-        connect(monitor, &SubSurfaceMonitor::subSurfaceRemoved, this, discardPixmap);
-        connect(monitor, &SubSurfaceMonitor::subSurfaceResized, this, discardPixmap);
-        connect(monitor, &SubSurfaceMonitor::subSurfaceMapped, this, discardPixmap);
-        connect(monitor, &SubSurfaceMonitor::subSurfaceUnmapped, this, discardPixmap);
+        connect(monitor, &SubSurfaceMonitor::subSurfaceAdded, w, &Window::discardPixmap);
+        connect(monitor, &SubSurfaceMonitor::subSurfaceRemoved, w, &Window::discardPixmap);
+        connect(monitor, &SubSurfaceMonitor::subSurfaceResized, w, &Window::discardPixmap);
+        connect(monitor, &SubSurfaceMonitor::subSurfaceMapped, w, &Window::discardPixmap);
+        connect(monitor, &SubSurfaceMonitor::subSurfaceUnmapped, w, &Window::discardPixmap);
 
-        connect(monitor, &SubSurfaceMonitor::subSurfaceAdded, this, discardQuads);
-        connect(monitor, &SubSurfaceMonitor::subSurfaceRemoved, this, discardQuads);
-        connect(monitor, &SubSurfaceMonitor::subSurfaceMoved, this, discardQuads);
-        connect(monitor, &SubSurfaceMonitor::subSurfaceResized, this, discardQuads);
-        connect(monitor, &SubSurfaceMonitor::subSurfaceMapped, this, discardQuads);
-        connect(monitor, &SubSurfaceMonitor::subSurfaceUnmapped, this, discardQuads);
+        connect(monitor, &SubSurfaceMonitor::subSurfaceAdded, w, &Window::discardQuads);
+        connect(monitor, &SubSurfaceMonitor::subSurfaceRemoved, w, &Window::discardQuads);
+        connect(monitor, &SubSurfaceMonitor::subSurfaceMoved, w, &Window::discardQuads);
+        connect(monitor, &SubSurfaceMonitor::subSurfaceResized, w, &Window::discardQuads);
+        connect(monitor, &SubSurfaceMonitor::subSurfaceMapped, w, &Window::discardQuads);
+        connect(monitor, &SubSurfaceMonitor::subSurfaceUnmapped, w, &Window::discardQuads);
 
-        connect(c->surface(), &KWaylandServer::SurfaceInterface::scaleChanged, this, discardQuads);
-        connect(c->surface(), &KWaylandServer::SurfaceInterface::viewportChanged, this, discardQuads);
+        connect(c->surface(), &KWaylandServer::SurfaceInterface::scaleChanged, w, &Window::discardQuads);
+        connect(c->surface(), &KWaylandServer::SurfaceInterface::viewportChanged, w, &Window::discardQuads);
     }
 
-    connect(c, &Toplevel::screenScaleChanged, this, discardQuads);
-    connect(c, &Toplevel::shadowChanged, this, discardQuads);
+    connect(c, &Toplevel::screenScaleChanged, w, &Window::discardQuads);
+    connect(c, &Toplevel::shadowChanged, w, &Window::discardQuads);
+    connect(c, &Toplevel::geometryShapeChanged, w, &Window::discardShape);
 
     c->effectWindow()->setSceneWindow(w);
     c->updateShadow();
@@ -456,14 +453,6 @@ void Scene::windowClosed(Toplevel *toplevel, Deleted *deleted)
     m_windows[deleted] = window;
 }
 
-void Scene::windowGeometryShapeChanged(Toplevel *c)
-{
-    if (!m_windows.contains(c))    // this is ok, shape is not valid by default
-        return;
-    Window *w = m_windows[ c ];
-    w->discardShape();
-}
-
 void Scene::createStackingOrder(const QList<Toplevel *> &toplevels)
 {
     // TODO: cache the stacking_order in case it has not changed
diff --git a/scene.h b/scene.h
index bb4d26425a..dda98097af 100644
--- a/scene.h
+++ b/scene.h
@@ -200,8 +200,6 @@ Q_SIGNALS:
     void resetCompositing();
 
 public Q_SLOTS:
-    // shape/size of a window changed
-    void windowGeometryShapeChanged(KWin::Toplevel* c);
     // a window has been closed
     void windowClosed(KWin::Toplevel* c, KWin::Deleted* deleted);
 protected: