QIconLoader: Use the GTK+ icon caches

Loading icons is quite slow because we need to stat many files in many directories.
That's why gtk adds a cache in the icon theme directory so it avoids stating lots
of files.

The cache file can be generated with gtk-update-icon-cache utility on a theme
directory. If the cache is not present, corrupted, or outdated, the normal slow lookup
is still run.

[ChangeLog][QtGui][QIcon] fromTheme gained the ability to use the GTK icon cache
to speed up lookups.

Change-Id: I3ab8a9910be67a34034556023be61a86789a7893
Reviewed-by: David Faure <david.faure@kdab.com>

3 files changed, 65 insertions, 0 deletions

diff --git a/tests/auto/gui/image/qicon/icons/themeparent/icon-theme.cache b/tests/auto/gui/image/qicon/icons/themeparent/icon-theme.cache
new file mode 100644
index 0000000000..a323875989
--- /dev/null
+++ b/tests/auto/gui/image/qicon/icons/themeparent/icon-theme.cache
diff --git a/tests/auto/gui/image/qicon/tst_qicon.cpp b/tests/auto/gui/image/qicon/tst_qicon.cpp
index 9ed3873682..afa72f6922 100644
--- a/tests/auto/gui/image/qicon/tst_qicon.cpp
+++ b/tests/auto/gui/image/qicon/tst_qicon.cpp
@@ -63,6 +63,7 @@ private slots:
     void streamAvailableSizes_data();
     void streamAvailableSizes();
     void fromTheme();
+    void fromThemeCache();
 
 #ifndef QT_NO_WIDGETS
     void task184901_badCache();
@@ -633,6 +634,69 @@ void tst_QIcon::fromTheme()
     QVERIFY(abIcon.isNull());
 }
 
+void tst_QIcon::fromThemeCache()
+{
+    QTemporaryDir dir;
+    QVERIFY(QDir().mkpath(dir.path() + QLatin1String("/testcache/16x16/actions")));
+    QVERIFY(QFile(QStringLiteral(":/styles/commonstyle/images/standardbutton-open-16.png"))
+        .copy( dir.path() + QLatin1String("/testcache/16x16/actions/button-open.png")));
+
+    {
+        QFile index(dir.path() + QLatin1String("/testcache/index.theme"));
+        QVERIFY(index.open(QFile::WriteOnly));
+        index.write("[Icon Theme]\nDirectories=16x16/actions\n[16x16/actions]\nSize=16\nContext=Actions\nType=Fixed\n");
+    }
+    QIcon::setThemeSearchPaths(QStringList() << dir.path());
+    QIcon::setThemeName("testcache");
+
+    // We just created a theme with that icon, it must exist
+    QVERIFY(!QIcon::fromTheme("button-open").isNull());
+
+    QString cacheName = dir.path() + QLatin1String("/testcache/icon-theme.cache");
+
+    // An invalid cache should not prevent lookup
+    {
+        QFile cacheFile(cacheName);
+        QVERIFY(cacheFile.open(QFile::WriteOnly));
+        QDataStream(&cacheFile) << quint16(1) << quint16(0) << "invalid corrupted stuff in there\n";
+    }
+    QIcon::setThemeSearchPaths(QStringList() << dir.path()); // reload themes
+    QVERIFY(!QIcon::fromTheme("button-open").isNull());
+
+    // An empty cache should prevent the lookup
+    {
+        QFile cacheFile(cacheName);
+        QVERIFY(cacheFile.open(QFile::WriteOnly));
+        QDataStream ds(&cacheFile);
+        ds << quint16(1) << quint16(0); // 0: version
+        ds << quint32(12) << quint32(20); // 4: hash offset / dir list offset
+        ds << quint32(1) << quint32(0xffffffff); // 12: one empty bucket
+        ds << quint32(1) << quint32(28); // 20: list with one element
+        ds.writeRawData("16x16/actions", sizeof("16x16/actions")); // 28
+    }
+    QIcon::setThemeSearchPaths(QStringList() << dir.path()); // reload themes
+    QVERIFY(QIcon::fromTheme("button-open").isNull()); // The icon was not in the cache, it should not be found
+
+    // Adding an icon should be changing the modification date of one sub directory which should make the cache ignored
+    QTest::qWait(1000); // wait enough to have a different modification time in seconds
+    QVERIFY(QFile(QStringLiteral(":/styles/commonstyle/images/standardbutton-save-16.png"))
+        .copy(dir.path() + QLatin1String("/testcache/16x16/actions/button-save.png")));
+    QVERIFY(QFileInfo(cacheName).lastModified() < QFileInfo(dir.path() + QLatin1String("/testcache/16x16/actions")).lastModified());
+    QIcon::setThemeSearchPaths(QStringList() << dir.path()); // reload themes
+    QVERIFY(!QIcon::fromTheme("button-open").isNull());
+
+    // Try to run the actual gtk-update-icon-cache and make sure that icons are still found
+    QProcess process;
+    process.start(QStringLiteral("gtk-update-icon-cache"),
+                  QStringList() << QStringLiteral("-f") << QStringLiteral("-t") << (dir.path() + QLatin1String("/testcache")));
+    if (!process.waitForFinished())
+        QSKIP("gtk-update-icon-cache not run");
+    QVERIFY(QFileInfo(cacheName).lastModified() >= QFileInfo(dir.path() + QLatin1String("/testcache/16x16/actions")).lastModified());
+    QIcon::setThemeSearchPaths(QStringList() << dir.path()); // reload themes
+    QVERIFY(!QIcon::fromTheme("button-open").isNull());
+    QVERIFY(!QIcon::fromTheme("button-open-fallback").isNull());
+    QVERIFY(QIcon::fromTheme("notexist-fallback").isNull());
+}
 
 void tst_QIcon::task223279_inconsistentAddFile()
 {
diff --git a/tests/auto/gui/image/qicon/tst_qicon.qrc b/tests/auto/gui/image/qicon/tst_qicon.qrc
index 1505ca925b..3c8fbba7c2 100644
--- a/tests/auto/gui/image/qicon/tst_qicon.qrc
+++ b/tests/auto/gui/image/qicon/tst_qicon.qrc
@@ -15,6 +15,7 @@
 <file>./icons/themeparent/32x32/actions/address-book-new.png</file>
 <file>./icons/themeparent/32x32/actions/appointment-new.png</file>
 <file>./icons/themeparent/index.theme</file>
+<file>./icons/themeparent/icon-theme.cache</file>
 <file>./icons/themeparent/scalable/actions/address-book-new.svg</file>
 <file>./icons/themeparent/scalable/actions/appointment-new.svg</file>
 <file>./styles/commonstyle/images/standardbutton-open-16.png</file>