diff --git a/src/plasma/private/theme_p.h b/src/plasma/private/theme_p.h
--- a/src/plasma/private/theme_p.h
+++ b/src/plasma/private/theme_p.h
@@ -58,7 +58,7 @@
 Q_DECLARE_FLAGS(CacheTypes, CacheType)
 Q_DECLARE_OPERATORS_FOR_FLAGS(CacheTypes)
 
-class ThemePrivate : public QObject
+class ThemePrivate : public QObject, public QSharedData
 {
     Q_OBJECT
 
@@ -107,9 +107,7 @@
 #endif
 //Ref counting of ThemePrivate instances
     static ThemePrivate *globalTheme;
-    static QAtomicInt globalThemeRefCount;
     static QHash<QString, ThemePrivate *> themes;
-    static QHash<QString, QAtomicInt> themesRefCount;
 
     QString themeName;
     KPluginInfo pluginInfo;
diff --git a/src/plasma/private/theme_p.cpp b/src/plasma/private/theme_p.cpp
--- a/src/plasma/private/theme_p.cpp
+++ b/src/plasma/private/theme_p.cpp
@@ -47,9 +47,7 @@
 #endif
 
 ThemePrivate *ThemePrivate::globalTheme = nullptr;
-QAtomicInt ThemePrivate::globalThemeRefCount = QAtomicInt();
 QHash<QString, ThemePrivate *> ThemePrivate::themes = QHash<QString, ThemePrivate *>();
-QHash<QString, QAtomicInt> ThemePrivate::themesRefCount = QHash<QString, QAtomicInt>();
 
 ThemePrivate::ThemePrivate(QObject *parent)
     : QObject(parent),
diff --git a/src/plasma/svg.cpp b/src/plasma/svg.cpp
--- a/src/plasma/svg.cpp
+++ b/src/plasma/svg.cpp
@@ -310,13 +310,14 @@
     if (elementsWithSizeHints.isEmpty()) {
         // Fetch all size hinted element ids from the theme's rect cache
         // and store them locally.
-        QRegExp sizeHintedKeyExpr(CACHE_ID_NATURAL_SIZE(QStringLiteral("(\\d+)-(\\d+)-(.+)"), status, ratio));
+        static const QRegularExpression sizeHintedKeyExpr(CACHE_ID_NATURAL_SIZE(QStringLiteral("$(\\d+)-(\\d+)-(.+)^"), status, ratio));
 
         foreach (const QString &key, cacheAndColorsTheme()->listCachedRectKeys(path)) {
-            if (sizeHintedKeyExpr.exactMatch(key)) {
-                QString baseElementId = sizeHintedKeyExpr.cap(3);
-                QSize sizeHint(sizeHintedKeyExpr.cap(1).toInt(),
-                               sizeHintedKeyExpr.cap(2).toInt());
+            const auto match = sizeHintedKeyExpr.match(key);
+            if (match.hasMatch()) {
+                QString baseElementId = match.captured(3);
+                QSize sizeHint(match.capturedRef(1).toInt(),
+                               match.capturedRef(2).toInt());
 
                 if (sizeHint.isValid()) {
                     elementsWithSizeHints.insertMulti(baseElementId, sizeHint);
@@ -333,12 +334,12 @@
     // Look at the size hinted elements and try to find the smallest one with an
     // identical aspect ratio.
     if (s.isValid() && !elementId.isEmpty()) {
-        QList<QSize> elementSizeHints = elementsWithSizeHints.values(elementId);
+        const QList<QSize> elementSizeHints = elementsWithSizeHints.values(elementId);
 
         if (!elementSizeHints.isEmpty()) {
             QSize bestFit(-1, -1);
 
-            Q_FOREACH (QSize hint, elementSizeHints) {
+            for (const QSize &hint : elementSizeHints) {
 
                 if (hint.width() >= s.width() * ratio && hint.height() >= s.height() * ratio &&
                         (!bestFit.isValid() ||
@@ -368,11 +369,7 @@
         return QPixmap();
     }
 
-    QString id = cachePath(path, size);
-
-    if (!actualElementId.isEmpty()) {
-        id.append(actualElementId);
-    }
+    const QString id = cachePath(path, size) + actualElementId;
 
     //qCDebug(LOG_PLASMA) << "id is " << id;
 
diff --git a/src/plasma/theme.cpp b/src/plasma/theme.cpp
--- a/src/plasma/theme.cpp
+++ b/src/plasma/theme.cpp
@@ -54,7 +54,7 @@
     if (!ThemePrivate::globalTheme) {
         ThemePrivate::globalTheme = new ThemePrivate;
     }
-    ThemePrivate::globalThemeRefCount.ref();
+    ThemePrivate::globalTheme->ref.ref();
     d = ThemePrivate::globalTheme;
 
     d->settingsChanged(false);
@@ -70,13 +70,13 @@
 Theme::Theme(const QString &themeName, QObject *parent)
     : QObject(parent)
 {
-    if (!ThemePrivate::themes.contains(themeName)) {
-        ThemePrivate::themes[themeName] = new ThemePrivate;
-        ThemePrivate::themesRefCount[themeName] = QAtomicInt();
+    auto& priv = ThemePrivate::themes[themeName];
+    if (!priv) {
+        priv = new ThemePrivate;
     }
 
-    ThemePrivate::themesRefCount[themeName].ref();
-    d = ThemePrivate::themes[themeName];
+    priv->ref.ref();
+    d = priv;
 
     // turn off caching so we don't accidentally trigger unnecessary disk activity at this point
     bool useCache = d->cacheTheme;
@@ -94,18 +94,15 @@
 Theme::~Theme()
 {
     if (d == ThemePrivate::globalTheme) {
-        if (!ThemePrivate::globalThemeRefCount.deref()) {
+        if (!d->ref.deref()) {
             disconnect(ThemePrivate::globalTheme, nullptr, this, nullptr);
             delete ThemePrivate::globalTheme;
             ThemePrivate::globalTheme = nullptr;
             d = nullptr;
         }
     } else {
-        if (!ThemePrivate::themesRefCount[d->themeName].deref()) {
-            ThemePrivate *themePrivate = ThemePrivate::themes[d->themeName];
-            ThemePrivate::themes.remove(d->themeName);
-            ThemePrivate::themesRefCount.remove(d->themeName);
-            delete themePrivate;
+        if (!d->ref.deref()) {
+            delete ThemePrivate::themes.take(d->themeName);
         }
     }
 }
@@ -118,18 +115,16 @@
 
     if (d != ThemePrivate::globalTheme) {
         disconnect(QCoreApplication::instance(), nullptr, d, nullptr);
-        if (!ThemePrivate::themesRefCount[d->themeName].deref()) {
-            ThemePrivate *themePrivate = ThemePrivate::themes[d->themeName];
-            ThemePrivate::themes.remove(d->themeName);
-            ThemePrivate::themesRefCount.remove(d->themeName);
-            delete themePrivate;
+        if (!d->ref.deref()) {
+            delete ThemePrivate::themes.take(d->themeName);
         }
-        if (!ThemePrivate::themes.contains(themeName)) {
-            ThemePrivate::themes[themeName] = new ThemePrivate;
-            ThemePrivate::themesRefCount[themeName] = QAtomicInt();
+
+        auto& priv = ThemePrivate::themes[themeName];
+        if (!priv) {
+            priv = new ThemePrivate;
         }
-        ThemePrivate::themesRefCount[themeName].ref();
-        d = ThemePrivate::themes[themeName];
+        priv->ref.ref();
+        d = priv;
         if (QCoreApplication::instance()) {
             connect(QCoreApplication::instance(), &QCoreApplication::aboutToQuit,
                     d, &ThemePrivate::onAppExitCleanup);
@@ -300,8 +295,9 @@
 
     if (d->useCache()) {
         const QString id = d->keysToCache.value(key);
-        if (d->pixmapsToCache.contains(id)) {
-            pix = d->pixmapsToCache.value(id);
+        const auto it = d->pixmapsToCache.constFind(id);
+        if (it != d->pixmapsToCache.constEnd()) {
+            pix = *it;
             return !pix.isNull();
         }
 
@@ -325,14 +321,9 @@
 void Theme::insertIntoCache(const QString &key, const QPixmap &pix, const QString &id)
 {
     if (d->useCache()) {
-        d->pixmapsToCache.insert(id, pix);
-
-        if (d->idsToCache.contains(id)) {
-            d->keysToCache.remove(d->idsToCache[id]);
-        }
-
-        d->keysToCache.insert(key, id);
-        d->idsToCache.insert(id, key);
+        d->pixmapsToCache[id] = pix;
+        d->keysToCache[key] = id;
+        d->idsToCache[id] = key;
 
         //always start timer in d->pixmapSaveTimer's thread
         QMetaObject::invokeMethod(d->pixmapSaveTimer, "start", Qt::QueuedConnection);