From bc30ca64dc3b4d35c3bd7fb77749f949eb2f73bd Mon Sep 17 00:00:00 2001
From: Vlad Zahorodnii <vlad.zahorodnii@kde.org>
Date: Thu, 11 Jan 2024 14:44:40 +0200
Subject: [PATCH] Fix evaluating window rules for closed windows

gedit changes its caption from "Untitled document - gedit" to "gedit"
when it closes. This schedules Window::evaluateWindowRules() to be
called when the window is already marked as deleted. kwin then crashes.

In order to prevent that, a direct connection can be used instead. But
then the caption must be initialized extra carefully because if the
window rule changes the window type, "<N>" can be lost.
---
 src/rules.cpp     |  5 +----
 src/window.cpp    |  4 +++-
 src/x11window.cpp | 10 ++++------
 3 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/src/rules.cpp b/src/rules.cpp
index 6ddad43c97..4a91485ef9 100644
--- a/src/rules.cpp
+++ b/src/rules.cpp
@@ -408,10 +408,7 @@ bool Rules::match(const Window *c) const
         return false;
     }
     if (titlematch != UnimportantMatch) { // track title changes to rematch rules
-        QObject::connect(c, &Window::captionChanged, c, &Window::evaluateWindowRules,
-                         // QueuedConnection, because title may change before
-                         // the client is ready (could segfault!)
-                         static_cast<Qt::ConnectionType>(Qt::QueuedConnection | Qt::UniqueConnection));
+        QObject::connect(c, &Window::captionNormalChanged, c, &Window::evaluateWindowRules, Qt::UniqueConnection);
     }
     if (!matchTitle(c->captionNormal())) {
         return false;
diff --git a/src/window.cpp b/src/window.cpp
index e9f26e6c66..0982649be4 100644
--- a/src/window.cpp
+++ b/src/window.cpp
@@ -4084,7 +4084,7 @@ void Window::evaluateWindowRules()
 
 void Window::setupWindowRules()
 {
-    disconnect(this, &Window::captionChanged, this, &Window::evaluateWindowRules);
+    disconnect(this, &Window::captionNormalChanged, this, &Window::evaluateWindowRules);
     m_rules = workspace()->rulebook()->find(this);
     // check only after getting the rules, because there may be a rule forcing window type
 }
@@ -4099,6 +4099,7 @@ void Window::updateWindowRules(Rules::Types selection)
 
 void Window::finishWindowRules()
 {
+    disconnect(this, &Window::captionNormalChanged, this, &Window::evaluateWindowRules);
     updateWindowRules(Rules::All);
     m_rules = WindowRules();
 }
@@ -4107,6 +4108,7 @@ void Window::finishWindowRules()
 // Used e.g. after the rules have been modified using the kcm.
 void Window::applyWindowRules()
 {
+    Q_ASSERT(!isDeleted());
     // apply force rules
     // Placement - does need explicit update, just like some others below
     // Geometry : setGeometry() doesn't check rules
diff --git a/src/x11window.cpp b/src/x11window.cpp
index b782cd479d..f4c6e166bd 100644
--- a/src/x11window.cpp
+++ b/src/x11window.cpp
@@ -639,15 +639,13 @@ bool X11Window::manage(xcb_window_t w, bool isMapped)
     readWmClientLeader(wmClientLeaderCookie);
     getWmClientMachine();
     getSyncCounter();
-    // First only read the caption text, so that setupWindowRules() can use it for matching,
-    // and only then really set the caption using setCaption(), which checks for duplicates etc.
-    // and also relies on rules already existing
-    cap_normal = readName();
-    setupWindowRules();
-    setCaption(cap_normal, true);
+    setCaption(readName());
 
+    setupWindowRules();
     connect(this, &X11Window::windowClassChanged, this, &X11Window::evaluateWindowRules);
 
+    updateCaption(); // in case the window type has been changed by a window rule and <N> has been dropped
+
     if (Xcb::Extensions::self()->isShapeAvailable()) {
         xcb_shape_select_input(kwinApp()->x11Connection(), window(), true);
     }