From afd525ced034b55ae1f89f6e899a79a58bc5e493 Mon Sep 17 00:00:00 2001
From: Aleix Pol <aleixpol@kde.org>
Date: Thu, 18 Nov 2021 17:12:37 +0100
Subject: [PATCH] Improve our reaction when primary changes

Ensure we sanitise the input so a client can't randomly crash KWin that
way.
---
 src/platform.cpp | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/platform.cpp b/src/platform.cpp
index 6d9494517a..0bc8c87d88 100644
--- a/src/platform.cpp
+++ b/src/platform.cpp
@@ -158,8 +158,15 @@ void Platform::requestOutputsChange(KWaylandServer::OutputConfigurationV2Interfa
     }
 
     if (applyOutputChanges(cfg)) {
-        if (config->primaryChanged()) {
-            setPrimaryOutput(findOutput(config->primary()->uuid()));
+        if (config->primaryChanged() || !primaryOutput()->isEnabled()) {
+            auto requestedPrimaryOutput = findOutput(config->primary()->uuid());
+            if (requestedPrimaryOutput && requestedPrimaryOutput->isEnabled()) {
+                setPrimaryOutput(requestedPrimaryOutput);
+            } else {
+                auto defaultPrimaryOutput = enabledOutputs().constFirst();
+                qCWarning(KWIN_CORE) << "Requested invalid primary screen, using" << defaultPrimaryOutput;
+                setPrimaryOutput(defaultPrimaryOutput);
+            }
         }
         Q_EMIT screens()->changed();
         config->setApplied();