From 14b495f933dadace7832fa6cbc809c3abdb7c682 Mon Sep 17 00:00:00 2001
From: Matt Whitlock <kde@mattwhitlock.name>
Date: Mon, 28 Jun 2021 18:01:14 -0400
Subject: [PATCH] don't make duplicate connections to
 ThemePrivate::onAppExitCleanup
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Plasma::Theme::Theme(…) and Plasma::Theme::setThemeName(…) were
unconditionally connecting the QCoreApplication::aboutToQuit signal to
the ThemePrivate::onAppExitCleanup slot, even though the ThemePrivate
instances are cached and shared across multiple Theme instances. In
long-running applications that make heavy use of the Svg class (such as
plasmashell), a single ThemePrivate instance can be reused by huge
numbers of Theme instances. If the reference count of that ThemePrivate
instance never reaches zero, then the connections just keep piling up,
contributing to excessive memory usage. This commit moves the relevant
connect(…) call so that it only happens in the case that a new
ThemePrivate instance is constructed. Thus, there will only ever be one
connection from QCoreApplication::aboutToQuit to
ThemePrivate::onAppExitCleanup per instance of ThemePrivate.
---
 src/plasma/theme.cpp | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/src/plasma/theme.cpp b/src/plasma/theme.cpp
index fabf98f4e..f403d393b 100644
--- a/src/plasma/theme.cpp
+++ b/src/plasma/theme.cpp
@@ -39,13 +39,13 @@ Theme::Theme(QObject *parent)
     if (!ThemePrivate::globalTheme) {
         ThemePrivate::globalTheme = new ThemePrivate;
         ThemePrivate::globalTheme->settingsChanged(false);
+        if (QCoreApplication::instance()) {
+            connect(QCoreApplication::instance(), &QCoreApplication::aboutToQuit, ThemePrivate::globalTheme, &ThemePrivate::onAppExitCleanup);
+        }
     }
     ThemePrivate::globalTheme->ref.ref();
     d = ThemePrivate::globalTheme;
 
-    if (QCoreApplication::instance()) {
-        connect(QCoreApplication::instance(), &QCoreApplication::aboutToQuit, d, &ThemePrivate::onAppExitCleanup);
-    }
     connect(d, &ThemePrivate::themeChanged, this, &Theme::themeChanged);
     connect(d, &ThemePrivate::defaultFontChanged, this, &Theme::defaultFontChanged);
     connect(d, &ThemePrivate::smallestFontChanged, this, &Theme::smallestFontChanged);
@@ -57,6 +57,9 @@ Theme::Theme(const QString &themeName, QObject *parent)
     auto &priv = ThemePrivate::themes[themeName];
     if (!priv) {
         priv = new ThemePrivate;
+        if (QCoreApplication::instance()) {
+            connect(QCoreApplication::instance(), &QCoreApplication::aboutToQuit, priv, &ThemePrivate::onAppExitCleanup);
+        }
     }
 
     priv->ref.ref();
@@ -68,9 +71,6 @@ Theme::Theme(const QString &themeName, QObject *parent)
     d->setThemeName(themeName, false, false);
     d->cacheTheme = useCache;
     d->fixedName = true;
-    if (QCoreApplication::instance()) {
-        connect(QCoreApplication::instance(), &QCoreApplication::aboutToQuit, d, &ThemePrivate::onAppExitCleanup);
-    }
     connect(d, &ThemePrivate::themeChanged, this, &Theme::themeChanged);
 }
 
@@ -105,12 +105,12 @@ void Theme::setThemeName(const QString &themeName)
         auto &priv = ThemePrivate::themes[themeName];
         if (!priv) {
             priv = new ThemePrivate;
+            if (QCoreApplication::instance()) {
+                connect(QCoreApplication::instance(), &QCoreApplication::aboutToQuit, priv, &ThemePrivate::onAppExitCleanup);
+            }
         }
         priv->ref.ref();
         d = priv;
-        if (QCoreApplication::instance()) {
-            connect(QCoreApplication::instance(), &QCoreApplication::aboutToQuit, d, &ThemePrivate::onAppExitCleanup);
-        }
         connect(d, &ThemePrivate::themeChanged, this, &Theme::themeChanged);
     }
 
-- 
GitLab