Implement support for Scale directory key according to Icon Theme spec

Qt already supports high DPI icons using the “@nx” approach, where the
device pixel ratio that the image was designed for is in the file
name. However, our implementation of the freedekstop.org Icon Theme
specification did not support the Scale directory key:

https://standards.freedesktop.org/icon-theme-spec/icon-theme-spec-latest.html#directory_layout

This meant that users creating icons via QIcon::fromTheme() did not
get high DPI support. This patch fixes that.

[ChangeLog][QtGui][QIcon] Implemented support for Scale directory key
according to Icon Theme Spec. Icons created via QIcon::fromTheme()
now have high DPI support by specifying the Scale in the appropriate
entry of the relevant index.theme file.

Task-number: QTBUG-49820
Change-Id: If442fbc551034166d88defe607109de1c6ca1d28
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>
Reviewed-by: Topi Reiniö <topi.reinio@qt.io>
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>

7 files changed, 232 insertions, 0 deletions

diff --git a/tests/auto/gui/image/qiconhighdpi/icons/testtheme/16x16/actions/appointment-new.png b/tests/auto/gui/image/qiconhighdpi/icons/testtheme/16x16/actions/appointment-new.png
new file mode 100644
index 0000000000..18b7c6781e
--- /dev/null
+++ b/tests/auto/gui/image/qiconhighdpi/icons/testtheme/16x16/actions/appointment-new.png
diff --git a/tests/auto/gui/image/qiconhighdpi/icons/testtheme/22x22/actions/appointment-new.png b/tests/auto/gui/image/qiconhighdpi/icons/testtheme/22x22/actions/appointment-new.png
new file mode 100644
index 0000000000..d676ffd463
--- /dev/null
+++ b/tests/auto/gui/image/qiconhighdpi/icons/testtheme/22x22/actions/appointment-new.png
diff --git a/tests/auto/gui/image/qiconhighdpi/icons/testtheme/22x22@2/actions/appointment-new.png b/tests/auto/gui/image/qiconhighdpi/icons/testtheme/22x22@2/actions/appointment-new.png
new file mode 100644
index 0000000000..6d094d7b54
--- /dev/null
+++ b/tests/auto/gui/image/qiconhighdpi/icons/testtheme/22x22@2/actions/appointment-new.png
diff --git a/tests/auto/gui/image/qiconhighdpi/icons/testtheme/index.theme b/tests/auto/gui/image/qiconhighdpi/icons/testtheme/index.theme
new file mode 100644
index 0000000000..6ab6c15c42
--- /dev/null
+++ b/tests/auto/gui/image/qiconhighdpi/icons/testtheme/index.theme
@@ -0,0 +1,21 @@
+[Icon Theme]
+Name=Test
+Comment=Test Theme
+
+Directories=16x16/actions,22x22/actions,22x22@2/actions
+
+[16x16/actions]
+Size=16
+Context=Actions
+Type=Fixed
+
+[22x22/actions]
+Size=22
+Context=Actions
+Type=Fixed
+
+[22x22@2/actions]
+Size=22
+Context=Actions
+Scale=2
+Type=Fixed
diff --git a/tests/auto/gui/image/qiconhighdpi/qiconhighdpi.pro b/tests/auto/gui/image/qiconhighdpi/qiconhighdpi.pro
new file mode 100644
index 0000000000..17553158bc
--- /dev/null
+++ b/tests/auto/gui/image/qiconhighdpi/qiconhighdpi.pro
@@ -0,0 +1,8 @@
+CONFIG += testcase
+TARGET = tst_qicon
+
+QT += testlib
+SOURCES += tst_qiconhighdpi.cpp
+RESOURCES = tst_qiconhighdpi.qrc
+
+TESTDATA += icons/*
diff --git a/tests/auto/gui/image/qiconhighdpi/tst_qiconhighdpi.cpp b/tests/auto/gui/image/qiconhighdpi/tst_qiconhighdpi.cpp
new file mode 100644
index 0000000000..ce7f68a0a6
--- /dev/null
+++ b/tests/auto/gui/image/qiconhighdpi/tst_qiconhighdpi.cpp
@@ -0,0 +1,195 @@
+/****************************************************************************
+**
+** Copyright (C) 2017 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:GPL-EXCEPT$
+** 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 General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** 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-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <QtTest/QtTest>
+#include <qicon.h>
+
+class tst_QIconHighDpi : public QObject
+{
+    Q_OBJECT
+public:
+    tst_QIconHighDpi();
+
+private slots:
+    void initTestCase();
+    void fromTheme_data();
+    void fromTheme();
+};
+
+tst_QIconHighDpi::tst_QIconHighDpi()
+{
+}
+
+void tst_QIconHighDpi::initTestCase()
+{
+}
+
+void tst_QIconHighDpi::fromTheme_data()
+{
+    QTest::addColumn<int>("requestedSize");
+    QTest::addColumn<int>("expectedSize");
+    QTest::addColumn<qreal>("expectedDpr");
+
+    // The pixmaps that we have available can be found in tst_qiconhighdpi.qrc.
+    // Currently we only have @1 and @2 icons available.
+    const int dpr = qCeil(qApp->devicePixelRatio());
+
+    // We have an @2 high DPI version of the 22x22 size of this icon.
+    switch (dpr) {
+    case 1: QTest::newRow("22x22,dpr=1") << 22 << 22 << 1.0; break;
+    case 2: QTest::newRow("22x22,dpr=2") << 22 << 44 << 2.0; break;
+    case 3: QTest::newRow("22x22,dpr=3") << 22 << 44 << 2.0; break;
+    }
+
+    // We don't have a high DPI version of the 16x16 size of this icon,
+    // so directoryMatchesSize() will return false for all directories.
+    // directorySizeDistance() is then called to find the best match.
+    // The table below illustrates the results for our available images at various DPRs:
+    // Available size | Available scale | Requested size | Requested scale | Distance
+    //        22      *        2        -       16       *        1        =    28
+    //        22      *        1        -       16       *        1        =     6
+    //        16      *        1        -       16       *        1        =     0 < (16x16)
+    // Available size | Available scale | Requested size | Requested scale | Distance
+    //        22      *        2        -       16       *        2        =    12
+    //        22      *        1        -       16       *        2        =    10 < (22x22)
+    //        16      *        1        -       16       *        2        =    16
+    // Available size | Available scale | Requested size | Requested scale | Distance
+    //        22      *        2        -       16       *        3        =     4 < (22x22@2)
+    //        22      *        1        -       16       *        3        =    26
+    //        16      *        1        -       16       *        3        =    32
+    // Both of these functions are implementations of the freedesktop icon theme spec,
+    // which dictates that if there is no matching scale, directorySizeDistance() determines
+    // the winner, regardless of whether or not the scale is too low for the requested scale.
+    switch (dpr) {
+    case 1: QTest::newRow("16x16,dpr=1") << 16 << 16 << 1.0; break;
+    // PixmapEntry::pixmap() will only downscale the pixmap if actualSize.width() > size.width().
+    // In this case, 22 > 32 is false, so a 22x22 pixmap is returned.
+    case 2: QTest::newRow("16x16,dpr=2") << 16 << 22 << 1.375; break;
+    case 3: QTest::newRow("16x16,dpr=3") << 16 << 44 << 2.75; break;
+    }
+
+    // We don't have an 8x8 size of this icon, so:
+    // Available size | Available scale | Requested size | Requested scale | Distance
+    //        22      *        2        -       8        *        1        =    36
+    //        22      *        1        -       8        *        1        =    14
+    //        16      *        1        -       8        *        1        =     8 < (16x16)
+    // Available size | Available scale | Requested size | Requested scale | Distance
+    //        22      *        2        -       8        *        2        =    28
+    //        22      *        1        -       8        *        2        =     6
+    //        16      *        1        -       8        *        2        =     0 < (16x16)
+    // Available size | Available scale | Requested size | Requested scale | Distance
+    //        22      *        2        -       8        *        3        =    20
+    //        22      *        1        -       8        *        3        =     2 < (22x22)
+    //        16      *        1        -       8        *        3        =     8
+    switch (dpr) {
+    case 1: QTest::newRow("8x8,dpr=1") << 8 << 8 << 1.0; break;
+    case 2: QTest::newRow("8x8,dpr=2") << 8 << 16 << 2.0; break;
+    case 3: QTest::newRow("8x8,dpr=3") << 8 << 22 << 2.75; break;
+    }
+
+    // We don't have a 44x44 size of this icon, so:
+    // Available size | Available scale | Requested size | Requested scale | Distance
+    //        22      *        2        -       44       *        1        =     0 < (22x22@2)
+    //        22      *        1        -       44       *        1        =    22
+    //        16      *        1        -       44       *        1        =    28
+    // Available size | Available scale | Requested size | Requested scale | Distance
+    //        22      *        2        -       44       *        2        =    44 < (22x22@2)
+    //        22      *        1        -       44       *        2        =    66
+    //        16      *        1        -       44       *        2        =    72
+    // Available size | Available scale | Requested size | Requested scale | Distance
+    //        22      *        2        -       44       *        3        =    88 < (22x22@2)
+    //        22      *        1        -       44       *        3        =   110
+    //        16      *        1        -       44       *        3        =   116
+    switch (dpr) {
+    case 1: QTest::newRow("44x44,dpr=1") << 44 << 44 << 1.0; break;
+    case 2: QTest::newRow("44x44,dpr=2") << 44 << 44 << 1.0; break;
+    case 3: QTest::newRow("44x44,dpr=3") << 44 << 44 << 1.0; break;
+    }
+
+    // We don't have a 20x20 size of this icon, so:
+    // Available size | Available scale | Requested size | Requested scale | Distance
+    //        22      *        2        -       20       *        1        =    24
+    //        22      *        1        -       20       *        1        =     2 < (22x22)
+    //        16      *        1        -       20       *        1        =     4
+    // Available size | Available scale | Requested size | Requested scale | Distance
+    //        22      *        2        -       20       *        2        =     4 < (22x22@2)
+    //        22      *        1        -       20       *        2        =    18
+    //        16      *        1        -       20       *        2        =    24
+    // Available size | Available scale | Requested size | Requested scale | Distance
+    //        22      *        2        -       20       *        3        =    16 < (22x22@2)
+    //        22      *        1        -       20       *        3        =    38
+    //        16      *        1        -       20       *        3        =    44
+    switch (dpr) {
+    case 1: QTest::newRow("20x20,dpr=1") << 20 << 20 << 1.0; break;
+    // PixmapEntry::pixmap() will only downscale the pixmap if actualSize.width() > size.width().
+    // In this case, 44 > 40 is true, so the 44x44 pixmap is downscaled to 40x40.
+    case 2: QTest::newRow("20x20,dpr=2") << 20 << 40 << 2.0; break;
+    case 3: QTest::newRow("20x20,dpr=3") << 20 << 44 << 2.2; break;
+    }
+}
+
+void tst_QIconHighDpi::fromTheme()
+{
+    QFETCH(int, requestedSize);
+    QFETCH(int, expectedSize);
+    QFETCH(qreal, expectedDpr);
+
+    QString searchPath = QLatin1String(":/icons");
+    QIcon::setThemeSearchPaths(QStringList() << searchPath);
+    QCOMPARE(QIcon::themeSearchPaths().size(), 1);
+    QCOMPARE(searchPath, QIcon::themeSearchPaths()[0]);
+
+    QString themeName("testtheme");
+    QIcon::setThemeName(themeName);
+    QCOMPARE(QIcon::themeName(), themeName);
+
+    QIcon appointmentIcon = QIcon::fromTheme("appointment-new");
+    QVERIFY(!appointmentIcon.isNull());
+    QVERIFY(!appointmentIcon.availableSizes(QIcon::Normal, QIcon::Off).isEmpty());
+    QVERIFY(appointmentIcon.availableSizes().contains(QSize(16, 16)));
+    QVERIFY(appointmentIcon.availableSizes().contains(QSize(22, 22)));
+
+    const QPixmap pixmap = appointmentIcon.pixmap(requestedSize);
+    QCOMPARE(pixmap.size(), QSize(expectedSize, expectedSize));
+    // We should get the high DPI version of an image if it exists in the correct directory.
+    // Note that we didn't pass the QWindow to QIcon::pixmap(),
+    // because QGuiApplication::devicePixelRatio() will be used if no window was given.
+    QCOMPARE(pixmap.devicePixelRatio(), expectedDpr);
+}
+
+int main(int argc, char *argv[])
+{
+    QGuiApplication::setAttribute(Qt::AA_UseHighDpiPixmaps);
+    QGuiApplication app(argc, argv);
+    Q_UNUSED(app);
+    tst_QIconHighDpi test;
+    QTEST_SET_MAIN_SOURCE_PATH
+    return QTest::qExec(&test, argc, argv);
+}
+
+#include "tst_qiconhighdpi.moc"
diff --git a/tests/auto/gui/image/qiconhighdpi/tst_qiconhighdpi.qrc b/tests/auto/gui/image/qiconhighdpi/tst_qiconhighdpi.qrc
new file mode 100644
index 0000000000..80b5e38ee6
--- /dev/null
+++ b/tests/auto/gui/image/qiconhighdpi/tst_qiconhighdpi.qrc
@@ -0,0 +1,8 @@
+<RCC>
+    <qresource prefix="/">
+        <file>icons/testtheme/16x16/actions/appointment-new.png</file>
+        <file>icons/testtheme/22x22/actions/appointment-new.png</file>
+        <file>icons/testtheme/index.theme</file>
+        <file>icons/testtheme/22x22@2/actions/appointment-new.png</file>
+    </qresource>
+</RCC>