QtPlatformSupport: Add QAbstractFileIconEngine

Move the code from QtWidgets/QFileIconEngine into a new class with
virtuals in QtPlatformSupport so that platforms can reuse it.

Prototypically use the class in the Windows and macOS QPA plugins.

Remove QPlatformTheme::fileIconPixmap() and change the type
of the hint QPlatformTheme::IconPixmapSizes from QList<int>
to QList<QSize> so that it fits better with the icon code.

Change-Id: I580e936f3507218757565ca099272cd575b3a779
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

3 files changed, 232 insertions, 0 deletions

diff --git a/src/platformsupport/themes/qabstractfileiconengine.cpp b/src/platformsupport/themes/qabstractfileiconengine.cpp
new file mode 100644
index 0000000000..19a8eee47b
--- /dev/null
+++ b/src/platformsupport/themes/qabstractfileiconengine.cpp
@@ -0,0 +1,130 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the plugins of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qabstractfileiconengine_p.h"
+
+#include <qpixmapcache.h>
+
+QT_BEGIN_NAMESPACE
+
+/*!
+    \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 += QLatin1Char('_');
+    key += 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;
+}
+
+QSize QAbstractFileIconEngine::actualSize(const QSize &size, QIcon::Mode mode,
+                                          QIcon::State state)
+{
+    const QList<QSize> &sizes = availableSizes(mode, state);
+    const int numberSizes = sizes.length();
+    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 QLatin1String("qt_.")
+        + (suffix.isEmpty() ? m_fileInfo.fileName() : suffix); // handle "Makefile"                                    ;)
+}
+
+QT_END_NAMESPACE
diff --git a/src/platformsupport/themes/qabstractfileiconengine_p.h b/src/platformsupport/themes/qabstractfileiconengine_p.h
new file mode 100644
index 0000000000..ce38cf262e
--- /dev/null
+++ b/src/platformsupport/themes/qabstractfileiconengine_p.h
@@ -0,0 +1,96 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the plugins of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QABSTRACTFILEICONENGINE_P_H
+#define QABSTRACTFILEICONENGINE_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include <QtCore/qfileinfo.h>
+#include <private/qicon_p.h>
+#include <qpa/qplatformtheme.h>
+
+QT_BEGIN_NAMESPACE
+
+class QAbstractFileIconEngine : public QPixmapIconEngine
+{
+public:
+    explicit QAbstractFileIconEngine(const QFileInfo &info, QPlatformTheme::IconOptions opts)
+        : QPixmapIconEngine(), m_fileInfo(info), m_options(opts) {}
+
+    QPixmap pixmap(const QSize &size, QIcon::Mode mode, QIcon::State) override;
+    QSize actualSize(const QSize &size, QIcon::Mode mode, QIcon::State state) override;
+
+    QFileInfo fileInfo() const { return m_fileInfo; }
+    QPlatformTheme::IconOptions options() const { return m_options; }
+
+    // Helper to convert a sequence of ints to a list of QSize
+    template <class It> static QList<QSize> toSizeList(It i1, It i2);
+
+protected:
+    virtual QPixmap filePixmap(const QSize &size, QIcon::Mode mode, QIcon::State) = 0;
+    virtual QString cacheKey() const;
+
+private:
+    const QFileInfo m_fileInfo;
+    const QPlatformTheme::IconOptions m_options;
+};
+
+template <class It>
+inline QList<QSize> QAbstractFileIconEngine::toSizeList(It i1, It i2)
+{
+    QList<QSize> result;
+    result.reserve(int(i2 - i1));
+    for ( ; i1 != i2; ++i1)
+        result.append(QSize(*i1, *i1));
+    return result;
+}
+
+QT_END_NAMESPACE
+
+#endif // QABSTRACTFILEICONENGINE_P_H
diff --git a/src/platformsupport/themes/themes.pri b/src/platformsupport/themes/themes.pri
index adee852626..552973431f 100644
--- a/src/platformsupport/themes/themes.pri
+++ b/src/platformsupport/themes/themes.pri
@@ -1,3 +1,9 @@
 unix:!mac {
     include($$PWD/genericunix/genericunix.pri)
 }
+
+HEADERS += \
+    $$PWD/qabstractfileiconengine_p.h
+
+SOURCES += \
+    $$PWD/qabstractfileiconengine.cpp