From c05e2fea45da0f1692a5b1f07a8bd81a9924328b Mon Sep 17 00:00:00 2001
From: David Edmundson <kde@davidedmundson.co.uk>
Date: Wed, 30 Mar 2022 14:57:12 +0100
Subject: [PATCH] Guard subsurface parent access.

Whilst a subsurface must have a parent at the time of creation, the
lifespan is not guaranteed afterwards.

It's a weird thing for a client to do, but we need to not crash
afterwards.

If the parent surface is destroyed we should consider the surface
unmapped.

BUG: 452044
---
 src/wayland/surface_interface.cpp | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/wayland/surface_interface.cpp b/src/wayland/surface_interface.cpp
index f369fe4080..34538532c0 100644
--- a/src/wayland/surface_interface.cpp
+++ b/src/wayland/surface_interface.cpp
@@ -690,7 +690,13 @@ void SurfaceInterfacePrivate::commitFromCache()
 
 bool SurfaceInterfacePrivate::computeEffectiveMapped() const
 {
-    return bufferRef && (!subSurface || subSurface->parentSurface()->isMapped());
+    if (!bufferRef) {
+        return false;
+    }
+    if (subSurface) {
+        return subSurface->parentSurface() && subSurface->parentSurface()->isMapped();
+    }
+    return true;
 }
 
 void SurfaceInterfacePrivate::updateEffectiveMapped()