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diff --git a/src/gui/image/qabstractfileiconengine.cpp b/src/gui/image/qabstractfileiconengine.cpp
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+++ b/src/gui/image/qabstractfileiconengine.cpp
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+// Copyright (C) 2016 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
+
+#include "qabstractfileiconengine_p.h"
+
+#include <qpixmapcache.h>
+
+QT_BEGIN_NAMESPACE
+
+using namespace Qt::StringLiterals;
+
+/*!
+    \class QAbstractFileIconEngine
+    \brief Helper base class for retrieving icons for files for usage by QFileIconProvider and related.
+
+    Reimplement availableSizes() and new virtual filePixmap() and return icons created
+    with this engine from QPlatformTheme::fileIcon().
+
+    Note: The class internally caches pixmaps for files by suffix (with the exception
+    of some files on Windows), but not for directories (since directory icons may have
+    overlay icons on Windows). You might want to cache pixmaps for directories
+    in your implementation.
+
+    \since 5.8
+    \internal
+    \sa QFileIconProvider::DontUseCustomDirectoryIcons, QPlatformTheme
+    \ingroup qpa
+*/
+QPixmap QAbstractFileIconEngine::pixmap(const QSize &size, QIcon::Mode mode,
+                                        QIcon::State state)
+{
+    Q_UNUSED(mode);
+    Q_UNUSED(state);
+
+    if (!size.isValid())
+        return QPixmap();
+
+    QString key = cacheKey();
+    if (key.isEmpty())
+        return filePixmap(size, mode, state);
+
+    key += u'_' + QString::number(size.width());
+
+    QPixmap result;
+    if (!QPixmapCache::find(key, &result)) {
+        result = filePixmap(size, mode, state);
+        if (!result.isNull())
+            QPixmapCache::insert(key, result);
+    }
+
+    return result;
+}
+
+QPixmap QAbstractFileIconEngine::scaledPixmap(const QSize &size, QIcon::Mode mode, QIcon::State state, qreal scale)
+{
+    Q_UNUSED(scale); // (size is pre-multiplied by scale)
+    return pixmap(size, mode, state);
+}
+
+QSize QAbstractFileIconEngine::actualSize(const QSize &size, QIcon::Mode mode,
+                                          QIcon::State state)
+{
+    const QList<QSize> &sizes = availableSizes(mode, state);
+    const int numberSizes = sizes.size();
+    if (numberSizes == 0)
+        return QSize();
+
+    // Find the smallest available size whose area is still larger than the input
+    // size. Otherwise, use the largest area available size. (We don't assume the
+    // platform theme sizes are sorted, hence the extra logic.)
+    const int sizeArea = size.width() * size.height();
+    QSize actualSize = sizes.first();
+    int actualArea = actualSize.width() * actualSize.height();
+    for (int i = 1; i < numberSizes; ++i) {
+        const QSize &s = sizes.at(i);
+        const int a = s.width() * s.height();
+        if ((sizeArea <= a && a < actualArea) || (actualArea < sizeArea && actualArea < a)) {
+            actualSize = s;
+            actualArea = a;
+        }
+    }
+
+    if (!actualSize.isNull() && (actualSize.width() > size.width() || actualSize.height() > size.height()))
+        actualSize.scale(size, Qt::KeepAspectRatio);
+
+    return actualSize;
+}
+
+/* Reimplement to return a cache key for the entry. An empty result indicates
+ * the icon should not be cached (for example, directory icons having custom icons). */
+QString QAbstractFileIconEngine::cacheKey() const
+{
+    if (!m_fileInfo.isFile() || m_fileInfo.isSymLink() || m_fileInfo.isExecutable())
+        return QString();
+
+    const QString &suffix = m_fileInfo.suffix();
+    return "qt_."_L1
+        + (suffix.isEmpty() ? m_fileInfo.fileName() : suffix); // handle "Makefile"                                    ;)
+}
+
+QT_END_NAMESPACE