feat: skip two-way copy for cuda devices when decoding video wallpapers + cache wallpapers as blobs in new database

Plugins/ZShell/Models/CMakeLists.txt

@@ -2,7 +2,12 @@ qml_module(ZShell-models
 	URI ZShell.Models
 	SOURCES
 		filesystemmodel.hpp filesystemmodel.cpp
+		wallpaperdb.hpp wallpaperdb.cpp
+		wallpaperutil.hpp
 	LIBRARIES
 		Qt::Gui
+		Qt::Quick
+		Qt::Qml
 		Qt::Concurrent
+		Qt::Sql
 )

Plugins/ZShell/Models/filesystemmodel.cpp

@@ -15,6 +15,7 @@
 #include <qtconcurrentrun.h>
 
 #include <algorithm>
+#include <mutex>
 
 namespace ZShell::models {
 
@@ -39,136 +40,43 @@ bool hasVideoExtension(const QString& path) {
 	return kVideoExtensions.contains(QFileInfo(path).suffix().toLower());
 }
 
-QString videoThumbnailPath(const QString& path) {
-	const QFileInfo info(path);
+const QStringList kHardwareCodecs = {
+	"av1",
+	"hevc",
+	"h264",
+	"vp9",
+	"vp8",
+	"vc1",
+	"mpeg2",
+	"mpeg2video",
+	"mpeg4",
+	"mjpeg",
+};
 
-	QString key = QStringLiteral("%1_%2_%3")
-					  .arg(info.baseName())
-					  .arg(info.size())
-					  .arg(info.lastModified().toMSecsSinceEpoch() / 1000);
-	key.replace(QRegularExpression("[^A-Za-z0-9._-]"), "_");
-
-	return QDir::homePath() + "/.cache/zshell/imagecache/video-previews/" +
-		   key + "_preview.jpg";
-}
-
-bool generateVideoThumbnail(const QString& src, const QString& cachePath) {
-	if (QFile::exists(cachePath)) {
-		return true;
-	}
-
-	const QString scale = QStringLiteral(
-		"scale=1920:1080:force_original_aspect_ratio=decrease,"
-		"scale=trunc(iw/2)*2:trunc(ih/2)*2");
-
-	auto runProcess = [](const QString& program, const QStringList& args) {
-		QProcess process;
-		process.start(program, args);
-		process.waitForFinished(15000);
-		return qMakePair(process.exitCode(), process.readAllStandardOutput());
-	};
-
-	double duration = 0.0;
-	const auto probe = runProcess(
+bool probeHardwareCodec(const QString& path) {
+	QProcess process;
+	process.start(
 		"ffprobe",
 		{
 			"-v",
 			"error",
+			"-select_streams",
+			"v:0",
 			"-show_entries",
-			"format=duration",
+			"stream=codec_name",
 			"-of",
 			"default=nw=1:nk=1",
-			src,
+			path,
 		});
-	if (probe.first == 0) {
-		duration = QString::fromUtf8(probe.second).trimmed().toDouble();
-	}
+	process.waitForFinished(5000);
 
-	const int samples = duration > 0 ? std::min(10, std::max(4, int(duration)))
-									 : 8;
-
-	QTemporaryDir tmpDir;
-	if (!tmpDir.isValid()) {
+	if (process.exitCode() != 0) {
 		return false;
 	}
 
-	int bestIndex = -1;
-	double bestChroma = -1.0;
-	double bestLuma = -1.0;
-
-	for (int i = 0; i < samples; ++i) {
-		const double frac = duration > 0 ? (i + 0.5) / samples : 0.0;
-		const QString seek = duration > 0
-								 ? QString::number(frac * duration, 'f', 3)
-								 : QStringLiteral("0");
-
-		const QString framePath =
-			tmpDir.filePath(QStringLiteral("frame_%1.jpg").arg(i));
-
-		runProcess(
-			"ffmpeg",
-			{
-				"-hide_banner",
-				"-loglevel",
-				"error",
-				"-ss",
-				seek,
-				"-i",
-				src,
-				"-frames:v",
-				"1",
-				"-vf",
-				scale,
-				"-pix_fmt",
-				"yuvj420p",
-				"-q:v",
-				"2",
-				"-y",
-				framePath,
-			});
-
-		QImage frame(framePath);
-		if (frame.isNull()) {
-			continue;
-		}
-
-		frame = frame.convertToFormat(QImage::Format_RGB888);
-
-		double chroma = 0.0;
-		double luma = 0.0;
-		int count = 0;
-		for (int y = 0; y < frame.height(); ++y) {
-			const auto* line = frame.constScanLine(y);
-			for (int x = 0; x < frame.width(); ++x) {
-				const int r = line[x * 3];
-				const int g = line[x * 3 + 1];
-				const int b = line[x * 3 + 2];
-				chroma += std::max({r, g, b}) - std::min({r, g, b});
-				luma += r + g + b;
-				++count;
-			}
-		}
-
-		const int n = std::max(1, count);
-		chroma /= n;
-		luma /= 3.0 * n;
-
-		if (chroma > bestChroma + 0.5 ||
-			(chroma > bestChroma - 0.5 && luma > bestLuma)) {
-			bestChroma = chroma;
-			bestLuma = luma;
-			bestIndex = i;
-		}
-	}
-
-	if (bestIndex < 0) {
-		return false;
-	}
-
-	QDir().mkpath(QFileInfo(cachePath).absolutePath());
-	return QFile::copy(
-		tmpDir.filePath(QStringLiteral("frame_%1.jpg").arg(bestIndex)),
-		cachePath);
+	const QString codec =
+		QString::fromUtf8(process.readAllStandardOutput()).trimmed().toLower();
+	return kHardwareCodecs.contains(codec);
 }
 
 FileSystemEntry::FileSystemEntry(
@@ -177,7 +85,6 @@ FileSystemEntry::FileSystemEntry(
 	, m_fileInfo(path)
 	, m_path(path)
 	, m_relativePath(relativePath)
-	, m_thumbnailPath(path)
 	, m_isImageInitialised(false)
 	, m_mimeTypeInitialised(false) {}
 
@@ -227,16 +134,7 @@ bool FileSystemEntry::isVideo() const {
 }
 
 QString FileSystemEntry::thumbnailPath() const {
-	return m_thumbnailPath;
-}
-
-void FileSystemEntry::setThumbnailPath(const QString& path) {
-	if (m_thumbnailPath == path) {
-		return;
-	}
-
-	m_thumbnailPath = path;
-	emit thumbnailPathChanged();
+	return m_path;
 }
 
 QString FileSystemEntry::mimeType() const {
@@ -404,6 +302,46 @@ void FileSystemModel::setNameFilters(const QStringList& nameFilters) {
 	update();
 }
 
+bool FileSystemModel::requireHardwareCodec() const {
+	return m_requireHardwareCodec;
+}
+
+void FileSystemModel::setRequireHardwareCodec(bool requireHardwareCodec) {
+	if (m_requireHardwareCodec == requireHardwareCodec) {
+		return;
+	}
+
+	m_requireHardwareCodec = requireHardwareCodec;
+	emit requireHardwareCodecChanged();
+
+	update();
+}
+
+bool FileSystemModel::isHardwareVideo(const QString& path) {
+	const QFileInfo info(path);
+	const QString key =
+		path + '|' + QByteArray::number(info.size()) + '|' +
+		QByteArray::number(info.lastModified().toMSecsSinceEpoch() / 1000);
+
+	{
+		std::lock_guard<QMutex> lock(m_codecMutex);
+
+		const auto it = m_codecCache.constFind(key);
+		if (it != m_codecCache.constEnd()) {
+			return it.value();
+		}
+	}
+
+	const bool hardware = probeHardwareCodec(path);
+
+	{
+		std::lock_guard<QMutex> lock(m_codecMutex);
+		m_codecCache.insert(key, hardware);
+	}
+
+	return hardware;
+}
+
 QQmlListProperty<FileSystemEntry> FileSystemModel::entries() {
 	return QQmlListProperty<FileSystemEntry>(this, &m_entries);
 }
@@ -434,14 +372,12 @@ void FileSystemModel::watchDirIfRecursive(const QString& path) {
 				const auto paths = watcher->result();
 				if (currentDir == m_dir && showHidden == m_showHidden &&
 					!paths.isEmpty()) {
-					// Ignore if dir or showHidden has changed
 					m_watcher.addPaths(paths);
 				}
 				watcher->deleteLater();
 			});
 		watcher->setFuture(future);
 	}
-	// NOLINTNEXTLINE(clang-analyzer-cplusplus.NewDeleteLeaks)
 }
 
 void FileSystemModel::update() {
@@ -488,6 +424,7 @@ void FileSystemModel::updateEntriesForDir(const QString& dir) {
 	const auto showHidden = m_showHidden;
 	const auto filter = m_filter;
 	const auto nameFilters = m_nameFilters;
+	const auto requireHardware = m_requireHardwareCodec;
 
 	QSet<QString> oldPaths;
 	for (const auto& entry : std::as_const(m_entries)) {
@@ -495,7 +432,7 @@ void FileSystemModel::updateEntriesForDir(const QString& dir) {
 	}
 
 	const auto future = QtConcurrent::run(
-		[=](QPromise<QPair<QSet<QString>, QSet<QString>>>& promise) {
+		[=, this](QPromise<QPair<QSet<QString>, QSet<QString>>>& promise) {
 			const auto flags = recursive ? QDirIterator::Subdirectories
 										 : QDirIterator::NoIteratorFlags;
 
@@ -553,18 +490,15 @@ void FileSystemModel::updateEntriesForDir(const QString& dir) {
 
 				QString path = iter->next();
 
-				if (filter == Images) {
+				if (hasVideoExtension(path)) {
+					if (requireHardware && !isHardwareVideo(path)) {
+						continue;
+					}
+				} else if (filter == Images || filter == Media) {
 					QImageReader reader(path);
 					if (!reader.canRead()) {
 						continue;
 					}
-				} else if (filter == Media) {
-					if (!hasVideoExtension(path)) {
-						QImageReader reader(path);
-						if (!reader.canRead()) {
-							continue;
-						}
-					}
 				}
 
 				newPaths.insert(path);
@@ -605,31 +539,6 @@ void FileSystemModel::updateEntriesForDir(const QString& dir) {
 		});
 
 	watcher->setFuture(future);
-	// NOLINTNEXTLINE(clang-analyzer-cplusplus.NewDeleteLeaks)
-}
-
-void FileSystemModel::startThumbnailGeneration(FileSystemEntry* entry) {
-	const QPointer<FileSystemEntry> guard(entry);
-	const QString source = entry->path();
-	const QString cachePath = videoThumbnailPath(source);
-
-	const auto future = QtConcurrent::run([source, cachePath]() {
-		return generateVideoThumbnail(source, cachePath);
-	});
-
-	const auto watcher = new QFutureWatcher<bool>(this);
-	connect(
-		watcher,
-		&QFutureWatcher<bool>::finished,
-		this,
-		[guard, cachePath, watcher]() {
-			if (guard && watcher->result()) {
-				guard->setThumbnailPath(cachePath);
-			}
-			watcher->deleteLater();
-		});
-	watcher->setFuture(future);
-	// NOLINTNEXTLINE(clang-analyzer-cplusplus.NewDeleteLeaks)
 }
 
 void FileSystemModel::applyChanges(
@@ -642,7 +551,6 @@ void FileSystemModel::applyChanges(
 	}
 	std::sort(removedIndices.begin(), removedIndices.end(), std::greater<int>());
 
-	// Batch remove old entries
 	int start = -1;
 	int end = -1;
 	for (int idx : std::as_const(removedIndices)) {
@@ -670,14 +578,10 @@ void FileSystemModel::applyChanges(
 		endRemoveRows();
 	}
 
-	// Create new entries
 	QList<FileSystemEntry*> newEntries;
 	for (const auto& path : addedPaths) {
 		auto* entry =
 			new FileSystemEntry(path, m_dir.relativeFilePath(path), this);
-		if (entry->isVideo()) {
-			startThumbnailGeneration(entry);
-		}
 		newEntries << entry;
 	}
 	std::sort(
@@ -687,7 +591,6 @@ void FileSystemModel::applyChanges(
 			return compareEntries(a, b);
 		});
 
-	// Batch insert new entries
 	int insertStart = -1;
 	QList<FileSystemEntry*> batchItems;
 	for (const auto& entry : std::as_const(newEntries)) {

Plugins/ZShell/Models/filesystemmodel.hpp

@@ -4,7 +4,9 @@
 #include <qdir.h>
 #include <qfilesystemwatcher.h>
 #include <qfuture.h>
+#include <qhash.h>
 #include <qimagereader.h>
+#include <qmutex.h>
 #include <qmimedatabase.h>
 #include <qobject.h>
 #include <qqmlintegration.h>
@@ -29,8 +31,7 @@ class FileSystemEntry : public QObject {
 	Q_PROPERTY(bool isDir READ isDir CONSTANT)
 	Q_PROPERTY(bool isImage READ isImage CONSTANT)
 	Q_PROPERTY(bool isVideo READ isVideo CONSTANT)
-	Q_PROPERTY(
-		QString thumbnailPath READ thumbnailPath NOTIFY thumbnailPathChanged)
+	Q_PROPERTY(QString thumbnailPath READ thumbnailPath CONSTANT)
 	Q_PROPERTY(QString mimeType READ mimeType CONSTANT)
 
 	public:
@@ -52,20 +53,16 @@ class FileSystemEntry : public QObject {
 	[[nodiscard]] QString thumbnailPath() const;
 	[[nodiscard]] QString mimeType() const;
 
-	void setThumbnailPath(const QString& path);
-
 	void updateRelativePath(const QDir& dir);
 
 	signals:
 	void relativePathChanged();
-	void thumbnailPathChanged();
 
 	private:
 	const QFileInfo m_fileInfo;
 
 	const QString m_path;
 	QString m_relativePath;
-	QString m_thumbnailPath;
 
 	mutable bool m_isImage;
 	mutable bool m_isImageInitialised;
@@ -94,6 +91,9 @@ class FileSystemModel : public QAbstractListModel {
 	Q_PROPERTY(
 		QStringList nameFilters READ nameFilters WRITE setNameFilters NOTIFY
 			nameFiltersChanged)
+	Q_PROPERTY(
+		bool requireHardwareCodec READ requireHardwareCodec WRITE
+			setRequireHardwareCodec NOTIFY requireHardwareCodecChanged)
 
 	Q_PROPERTY(
 		QQmlListProperty<ZShell::models::FileSystemEntry> entries READ entries
@@ -132,6 +132,9 @@ class FileSystemModel : public QAbstractListModel {
 	[[nodiscard]] QStringList nameFilters() const;
 	void setNameFilters(const QStringList& nameFilters);
 
+	[[nodiscard]] bool requireHardwareCodec() const;
+	void setRequireHardwareCodec(bool requireHardwareCodec);
+
 	[[nodiscard]] QQmlListProperty<FileSystemEntry> entries();
 
 	signals:
@@ -142,6 +145,7 @@ class FileSystemModel : public QAbstractListModel {
 	void sortReverseChanged();
 	void filterChanged();
 	void nameFiltersChanged();
+	void requireHardwareCodecChanged();
 	void entriesChanged();
 
 	private:
@@ -157,6 +161,10 @@ class FileSystemModel : public QAbstractListModel {
 	bool m_sortReverse;
 	Filter m_filter;
 	QStringList m_nameFilters;
+	bool m_requireHardwareCodec = false;
+
+	QHash<QString, bool> m_codecCache;
+	QMutex m_codecMutex;
 
 	void watchDirIfRecursive(const QString& path);
 	void update();
@@ -165,7 +173,7 @@ class FileSystemModel : public QAbstractListModel {
 	void updateEntriesForDir(const QString& dir);
 	void applyChanges(
 		const QSet<QString>& removedPaths, const QSet<QString>& addedPaths);
-	void startThumbnailGeneration(FileSystemEntry* entry);
+	[[nodiscard]] bool isHardwareVideo(const QString& path);
 	[[nodiscard]] bool compareEntries(
 		const FileSystemEntry* a, const FileSystemEntry* b) const;
 };

Plugins/ZShell/Models/wallpaperdb.cpp

@@ -0,0 +1,746 @@
+#include "wallpaperdb.hpp"
+#include "wallpaperutil.hpp"
+
+#include <QtQuick/qquickimageprovider.h>
+#include <qbytearray.h>
+#include <qdiriterator.h>
+#include <qelapsedtimer.h>
+#include <qfuturewatcher.h>
+#include <qimage.h>
+#include <qimagereader.h>
+#include <qlogging.h>
+#include <qqmlengine.h>
+#include <qsqldatabase.h>
+#include <qsqlerror.h>
+#include <qsqlquery.h>
+#include <qtconcurrentrun.h>
+#include <quuid.h>
+
+#include <algorithm>
+
+Q_LOGGING_CATEGORY(dbLog, "ZShell.Internal.wallpaper.db", QtWarningMsg)
+
+namespace ZShell::models {
+
+class WallpaperImageProvider : public QQuickImageProvider {
+	public:
+	explicit WallpaperImageProvider(const QString& dbPath)
+		: QQuickImageProvider(QQuickImageProvider::Image), m_dbPath(dbPath) {}
+
+	QImage requestImage(
+		const QString& id, QSize* size, const QSize& requestedSize) override {
+		const QString path =
+			QString::fromUtf8(QByteArray::fromHex(id.toUtf8()));
+		if (path.isEmpty() || !openThreadDb()) {
+			return {};
+		}
+
+		QSqlQuery query(QSqlDatabase::database(m_threadUuid));
+		query.prepare("SELECT cache FROM wallpapers WHERE path = ?");
+		query.addBindValue(path);
+
+		if (!query.exec() || !query.next()) {
+			return {};
+		}
+
+		const QByteArray bytes = query.value(0).toByteArray();
+		if (bytes.isEmpty()) {
+			return {};
+		}
+
+		QImage image = QImage::fromData(bytes, "JPEG");
+		if (image.isNull()) {
+			return {};
+		}
+
+		if (size) {
+			*size = image.size();
+		}
+
+		if (requestedSize.isValid() && !requestedSize.isEmpty() &&
+			(image.width() > requestedSize.width() ||
+			 image.height() > requestedSize.height())) {
+			image = image.scaled(
+				requestedSize, Qt::KeepAspectRatio, Qt::SmoothTransformation);
+		}
+
+		return image;
+	}
+
+	private:
+	bool openThreadDb() {
+		if (!m_threadUuid.isEmpty()) {
+			return true;
+		}
+
+		if (m_dbPath.isEmpty()) {
+			return false;
+		}
+
+		const QString uuid = QUuid::createUuid().toString(QUuid::WithoutBraces);
+
+		auto db = QSqlDatabase::addDatabase("QSQLITE", uuid);
+		db.setConnectOptions("QSQLITE_OPEN_READONLY");
+		db.setDatabaseName(m_dbPath);
+
+		if (!db.open()) {
+			return false;
+		}
+
+		QSqlQuery query(db);
+		query.exec("PRAGMA journal_mode=WAL");
+
+		m_threadUuid = uuid;
+		return true;
+	}
+
+	const QString m_dbPath;
+	thread_local static QString m_threadUuid;
+};
+
+thread_local QString WallpaperImageProvider::m_threadUuid;
+
+WallpaperEntry::WallpaperEntry(
+	const QString& path, const QString& relativePath, QObject* parent)
+	: QObject(parent)
+	, m_fileInfo(path)
+	, m_path(path)
+	, m_relativePath(relativePath) {}
+
+QString WallpaperEntry::path() const {
+	return m_path;
+}
+
+QString WallpaperEntry::relativePath() const {
+	return m_relativePath;
+}
+
+QString WallpaperEntry::name() const {
+	return m_fileInfo.fileName();
+}
+
+QString WallpaperEntry::baseName() const {
+	return m_fileInfo.baseName();
+}
+
+QString WallpaperEntry::parentDir() const {
+	return m_fileInfo.absolutePath();
+}
+
+QString WallpaperEntry::suffix() const {
+	return m_fileInfo.completeSuffix();
+}
+
+qint64 WallpaperEntry::size() const {
+	return m_fileInfo.size();
+}
+
+bool WallpaperEntry::isImage() const {
+	return !hasVideoExtension(m_path);
+}
+
+bool WallpaperEntry::isVideo() const {
+	return hasVideoExtension(m_path);
+}
+
+bool WallpaperEntry::hardware() const {
+	return m_hardware;
+}
+
+bool WallpaperEntry::cached() const {
+	return !m_thumbnailPath.isEmpty();
+}
+
+QString WallpaperEntry::thumbnailPath() const {
+	if (!m_thumbnailPath.isEmpty()) {
+		return m_thumbnailPath;
+	}
+
+	return isImage() ? m_path : QString();
+}
+
+void WallpaperEntry::setRelativePath(const QString& path) {
+	if (m_relativePath == path) {
+		return;
+	}
+
+	m_relativePath = path;
+	emit relativePathChanged();
+}
+
+void WallpaperEntry::setHardware(bool hardware) {
+	if (m_hardware == hardware) {
+		return;
+	}
+
+	m_hardware = hardware;
+	emit hardwareChanged();
+}
+
+void WallpaperEntry::setThumbnailPath(const QString& path) {
+	if (m_thumbnailPath == path) {
+		return;
+	}
+
+	m_thumbnailPath = path;
+	emit thumbnailPathChanged();
+}
+
+WallpaperDb::WallpaperDb(QObject* parent) : QObject(parent) {
+	m_uuid = QUuid::createUuid().toString(QUuid::WithoutBraces);
+	m_dbPath = QDir::homePath() + "/.local/state/zshell/wallpapers.sqlite";
+
+	m_queueTimer.setInterval(300);
+	m_queueTimer.setTimerType(Qt::CoarseTimer);
+	QObject::connect(
+		&m_queueTimer, &QTimer::timeout, this, &WallpaperDb::processQueue);
+
+	m_watchTimer.setInterval(400);
+	m_watchTimer.setSingleShot(true);
+	QObject::connect(
+		&m_watcher, &QFileSystemWatcher::directoryChanged, this, [this]() {
+			m_watchTimer.start();
+		});
+	QObject::connect(
+		&m_watchTimer, &QTimer::timeout, this, &WallpaperDb::scanDir);
+}
+
+WallpaperDb::~WallpaperDb() {
+	if (QSqlDatabase::contains(m_uuid)) {
+		{
+			auto db = QSqlDatabase::database(m_uuid, false);
+			if (db.isValid()) {
+				db.close();
+			}
+		}
+
+		QSqlDatabase::removeDatabase(m_uuid);
+	}
+}
+
+QString WallpaperDb::path() const {
+	return m_path;
+}
+
+void WallpaperDb::setPath(const QString& path) {
+	if (m_path == path) {
+		return;
+	}
+
+	m_path = path;
+	m_dir = QDir(path);
+	emit pathChanged();
+
+	for (const auto& dir : m_watcher.directories()) {
+		m_watcher.removePath(dir);
+	}
+
+	scanDir();
+}
+
+QString WallpaperDb::dbPath() const {
+	return m_dbPath;
+}
+
+void WallpaperDb::setDbPath(const QString& path) {
+	if (m_dbPath == path) {
+		return;
+	}
+
+	m_dbPath = path;
+	emit dbPathChanged();
+
+	if (!m_path.isEmpty()) {
+		scanDir();
+	}
+}
+
+bool WallpaperDb::requireHardwareCodec() const {
+	return m_requireHardwareCodec;
+}
+
+void WallpaperDb::setRequireHardwareCodec(bool requireHardwareCodec) {
+	if (m_requireHardwareCodec == requireHardwareCodec) {
+		return;
+	}
+
+	m_requireHardwareCodec = requireHardwareCodec;
+	emit requireHardwareCodecChanged();
+
+	rebuildEntries();
+}
+
+QQmlListProperty<WallpaperEntry> WallpaperDb::entries() {
+	return QQmlListProperty<WallpaperEntry>(this, &m_entries);
+}
+
+QString WallpaperDb::thumbnailUrl(const QString& path) {
+	return QStringLiteral("image:
+		   + QString::fromUtf8(path.toUtf8().toHex());
+}
+
+QSize WallpaperDb::cacheSize() const {
+	return m_cacheSize;
+}
+
+void WallpaperDb::setCacheSize(const QSize& cacheSize) {
+	if (m_cacheSize == cacheSize) {
+		return;
+	}
+
+	const QSize prev = m_cacheSize;
+	const bool hadPrevious = !prev.isEmpty();
+
+	m_cacheSize = cacheSize;
+	emit cacheSizeChanged();
+
+	if (hadPrevious && qint64(cacheSize.width()) * cacheSize.height() >
+						   qint64(prev.width()) * prev.height()) {
+		const auto db = QSqlDatabase::database(m_uuid, false);
+
+		for (auto* entry : std::as_const(m_byPath)) {
+			if (!entry->cached()) {
+				continue;
+			}
+
+			if (db.isOpen()) {
+				QSqlQuery query(db);
+				query.prepare(
+					"UPDATE wallpapers SET cache = NULL, scheme_thumb = NULL"
+					" WHERE path = ?");
+				query.addBindValue(entry->path());
+				query.exec();
+			}
+
+			entry->setThumbnailPath(QString());
+			queueMetadata(entry, entry->isVideo());
+		}
+
+		rebuildEntries();
+	}
+
+	if (!m_queue.isEmpty() && !m_queueTimer.isActive()) {
+		m_queueTimer.start();
+	}
+}
+
+void WallpaperDb::registerProvider() {
+	if (m_provider != nullptr) {
+		return;
+	}
+
+	auto* engine = qmlEngine(this);
+	if (engine == nullptr) {
+		return;
+	}
+
+	m_provider = new WallpaperImageProvider(m_dbPath);
+	engine->addImageProvider(QStringLiteral("wallpapers"), m_provider);
+}
+
+void WallpaperDb::openDb() {
+	if (m_dbPath.isEmpty()) {
+		return;
+	}
+
+	if (QSqlDatabase::contains(m_uuid)) {
+		{
+			auto db = QSqlDatabase::database(m_uuid, false);
+			if (db.isOpen() && db.databaseName() == m_dbPath) {
+				registerProvider();
+				return;
+			}
+
+			if (db.isValid()) {
+				db.close();
+			}
+		}
+
+		QSqlDatabase::removeDatabase(m_uuid);
+	}
+
+	QDir().mkpath(QFileInfo(m_dbPath).absolutePath());
+
+	auto db = QSqlDatabase::addDatabase("QSQLITE", m_uuid);
+	db.setDatabaseName(m_dbPath);
+
+	if (!db.open()) {
+		qWarning(dbLog) << "WallpaperDb: could not open database" << m_dbPath
+						<< db.lastError();
+		return;
+	}
+
+	QSqlQuery query(db);
+	query.exec("PRAGMA journal_mode=WAL");
+	query.exec(
+		"CREATE TABLE IF NOT EXISTS wallpapers("
+		"path TEXT PRIMARY KEY, kind TEXT, codec TEXT, hardware INTEGER,"
+		" size INTEGER, mtime INTEGER, cache BLOB, scheme_thumb BLOB)");
+
+	query.exec("SELECT cache FROM wallpapers LIMIT 1");
+	if (query.lastError().isValid()) {
+		query.exec("DROP TABLE IF EXISTS wallpapers");
+		query.exec(
+			"CREATE TABLE wallpapers("
+			"path TEXT PRIMARY KEY, kind TEXT, codec TEXT, hardware INTEGER,"
+			" size INTEGER, mtime INTEGER, cache BLOB, scheme_thumb BLOB)");
+	} else {
+		query.exec("ALTER TABLE wallpapers ADD COLUMN scheme_thumb BLOB");
+	}
+
+	registerProvider();
+}
+
+void WallpaperDb::scanDir() {
+	openDb();
+
+	watchDir(m_dir.absolutePath());
+
+	if (!m_dir.exists()) {
+		if (!m_entries.isEmpty()) {
+			m_entries.clear();
+			emit entriesChanged();
+		}
+
+		return;
+	}
+
+	auto* watcher = new QFutureWatcher<ScanResult>(this);
+	QObject::connect(
+		watcher, &QFutureWatcher<ScanResult>::finished, this, [this, watcher]() {
+			applyScan(watcher->result());
+			watcher->deleteLater();
+		});
+
+	const QDir dir = m_dir;
+
+	QHash<QString, QPair<qint64, bool>> knownCodecs;
+	for (const auto* entry : std::as_const(m_byPath)) {
+		if (entry->isVideo()) {
+			knownCodecs.insert(
+				entry->path(), qMakePair(entry->size(), entry->hardware()));
+		}
+	}
+
+	watcher->setFuture(QtConcurrent::run([dir, knownCodecs]() {
+		ScanResult result;
+		result.dir = dir;
+
+		QDirIterator it(dir.absolutePath(), QDirIterator::Subdirectories);
+		while (it.hasNext()) {
+			const QString path = it.next();
+			const QFileInfo info(path);
+
+			if (info.isDir()) {
+				continue;
+			}
+
+			if (hasVideoExtension(path)) {
+				FileEntry file;
+				file.info = info;
+
+				const auto known = knownCodecs.constFind(path);
+				if (known != knownCodecs.constEnd() &&
+					known.value().first == info.size()) {
+					file.hardware = known.value().second;
+				} else {
+					file.hardware = probeHardwareCodec(path);
+				}
+
+				result.files.append(file);
+			} else {
+				QImageReader reader(path);
+				if (reader.canRead()) {
+					FileEntry file;
+					file.info = info;
+					result.files.append(file);
+				}
+			}
+		}
+
+		return result;
+	}));
+}
+
+void WallpaperDb::watchDir(const QString& dir) {
+	if (dir.isEmpty() || m_watcher.directories().contains(dir)) {
+		return;
+	}
+
+	if (!QDir(dir).exists()) {
+		return;
+	}
+
+	m_watcher.addPath(dir);
+}
+
+void WallpaperDb::applyScan(const ScanResult& result) {
+	qCInfo(
+		dbLog,
+		"WallpaperDb: scan of %s found %d files (cache target %dx%d)",
+		m_dir.absolutePath().toUtf8().constData(),
+		int(result.files.size()),
+		m_cacheSize.width(),
+		m_cacheSize.height());
+
+	const auto db = QSqlDatabase::database(m_uuid, false);
+
+	QSet<QString> seen;
+	for (const auto& file : result.files) {
+		seen.insert(file.info.absoluteFilePath());
+	}
+
+	for (auto it = m_byPath.begin(); it != m_byPath.end();) {
+		if (!seen.contains(it.key())) {
+			if (db.isOpen()) {
+				QSqlQuery query(db);
+				query.prepare("DELETE FROM wallpapers WHERE path = ?");
+				query.addBindValue(it.key());
+				query.exec();
+			}
+
+			delete it.value();
+			it = m_byPath.erase(it);
+		} else {
+			++it;
+		}
+	}
+
+	for (const auto& file : result.files) {
+		const QFileInfo& info = file.info;
+		const QString path = info.absoluteFilePath();
+
+		const qint64 size = info.size();
+		const qint64 mtime = info.lastModified().toMSecsSinceEpoch() / 1000;
+		const bool isVideo = hasVideoExtension(path);
+
+		watchDir(info.absolutePath());
+
+		const auto existing = m_byPath.constFind(path);
+		if (existing != m_byPath.constEnd()) {
+			if (existing.value()->size() == size) {
+				existing.value()->setHardware(file.hardware);
+				continue;
+			}
+		}
+
+		WallpaperEntry* entry = m_byPath.value(path);
+		if (!entry) {
+			entry =
+				new WallpaperEntry(path, m_dir.relativeFilePath(path), this);
+			m_byPath.insert(path, entry);
+		}
+
+		entry->setHardware(file.hardware);
+
+		bool reused = false;
+		if (db.isOpen()) {
+			QSqlQuery query(db);
+			query.prepare(
+				"SELECT cache, scheme_thumb, size, mtime FROM wallpapers"
+				" WHERE path = ?");
+			query.addBindValue(path);
+			query.exec();
+
+			if (query.next()) {
+				const auto cache = query.value(0).toByteArray();
+				const auto scheme = query.value(1).toByteArray();
+				const auto storedSize = query.value(2).toLongLong();
+				const auto storedMtime = query.value(3).toLongLong();
+
+				if (storedSize == size && storedMtime == mtime &&
+					!cache.isEmpty()) {
+					reused = true;
+					entry->setThumbnailPath(thumbnailUrl(path));
+
+					if (scheme.isEmpty()) {
+						queueMetadata(entry, isVideo, cache);
+					}
+				}
+			}
+		}
+
+		if (!reused) {
+			if (db.isOpen()) {
+				QSqlQuery query(db);
+				query.prepare(
+					"INSERT OR REPLACE INTO wallpapers"
+					" (path, kind, hardware, size, mtime, cache)"
+					" VALUES (?, ?, ?, ?, ?, NULL)");
+				query.addBindValue(path);
+				query.addBindValue(isVideo ? "video" : "image");
+				query.addBindValue(
+					isVideo ? (file.hardware ? 1 : 0) : QVariant());
+				query.addBindValue(size);
+				query.addBindValue(mtime);
+				if (!query.exec()) {
+					qWarning(dbLog)
+						<< "WallpaperDb: could not store the row for" << path
+						<< query.lastError();
+				}
+			}
+
+			queueMetadata(entry, isVideo);
+		}
+	}
+
+	rebuildEntries();
+}
+
+void WallpaperDb::queueMetadata(
+	WallpaperEntry* entry, bool isVideo, const QByteArray& existingCache) {
+	qCInfo(
+		dbLog,
+		"WallpaperDb: queued cache job for %s (%s%s)",
+		entry->path().toUtf8().constData(),
+		isVideo ? "video" : "image",
+		existingCache.isEmpty() ? "" : ", existing blob");
+
+	m_queue.append(MetadataJob{entry, entry->path(), isVideo, existingCache});
+
+	if (!m_queueTimer.isActive()) {
+		m_queueTimer.start();
+	}
+}
+
+void WallpaperDb::processQueue() {
+	if (m_jobRunning) {
+		return;
+	}
+
+	if (m_queue.isEmpty()) {
+		m_queueTimer.stop();
+		return;
+	}
+
+	if (m_cacheSize.isEmpty()) {
+		return;
+	}
+
+	const MetadataJob job = m_queue.takeFirst();
+	m_jobRunning = true;
+
+	qCInfo(
+		dbLog,
+		"WallpaperDb: caching %s (%s, %d jobs left in queue)",
+		job.path.toUtf8().constData(),
+		job.isVideo ? "video" : "image",
+		int(m_queue.size()));
+
+	runMetadataJob(job);
+}
+
+void WallpaperDb::runMetadataJob(const MetadataJob& job) {
+	struct CacheResult {
+		QString path;
+		QByteArray cache;
+		QByteArray scheme;
+	};
+
+	const QSize cacheSize = m_cacheSize;
+
+	QElapsedTimer clock;
+	clock.start();
+
+	auto* watcher = new QFutureWatcher<CacheResult>(this);
+	QObject::connect(
+		watcher,
+		&QFutureWatcher<CacheResult>::finished,
+		this,
+		[this, watcher, clock]() {
+			const auto result = watcher->result();
+
+			qCInfo(
+				dbLog,
+				"WallpaperDb: %s produced %d bytes of cache in %dms",
+				result.path.toUtf8().constData(),
+				int(result.cache.size()),
+				int(clock.elapsed()));
+
+			if (QSqlDatabase::contains(m_uuid)) {
+				const auto db = QSqlDatabase::database(m_uuid, false);
+				if (db.isOpen()) {
+					QSqlQuery query(db);
+					query.prepare(
+						"UPDATE wallpapers SET cache = ?, scheme_thumb = ?"
+						" WHERE path = ?");
+					query.addBindValue(result.cache);
+					query.addBindValue(result.scheme);
+					query.addBindValue(result.path);
+					if (!query.exec()) {
+						qWarning(dbLog)
+							<< "WallpaperDb: could not store the cache for"
+							<< result.path << query.lastError();
+					}
+				}
+			}
+
+			if (!result.cache.isEmpty()) {
+				if (auto* entry = m_byPath.value(result.path)) {
+					entry->setThumbnailPath(thumbnailUrl(result.path));
+				}
+
+				emit cacheStored(result.path);
+			}
+
+			m_jobRunning = false;
+			rebuildEntries();
+			watcher->deleteLater();
+		});
+
+	watcher->setFuture(QtConcurrent::run([job, cacheSize]() {
+		CacheResult result;
+		result.path = job.path;
+
+		QByteArray cache = job.existingCache;
+		if (cache.isEmpty()) {
+			cache = job.isVideo ? videoCacheBytes(job.path, cacheSize)
+								: imageCacheBytes(job.path, cacheSize);
+		}
+
+		result.cache = cache;
+		result.scheme = cache.isEmpty() ? QByteArray()
+										: schemeThumbBytes(cache, 128);
+
+		return result;
+	}));
+}
+
+void WallpaperDb::rebuildEntries() {
+	QList<WallpaperEntry*> next;
+	next.reserve(m_byPath.size());
+
+	for (auto* entry : std::as_const(m_byPath)) {
+		if (entryAllowed(entry)) {
+			next.append(entry);
+		}
+	}
+
+	std::sort(
+		next.begin(),
+		next.end(),
+		[](const WallpaperEntry* a, const WallpaperEntry* b) {
+			return a->relativePath() < b->relativePath();
+		});
+
+	if (next == m_entries) {
+		return;
+	}
+
+	m_entries = next;
+	emit entriesChanged();
+}
+
+bool WallpaperDb::entryAllowed(const WallpaperEntry* entry) const {
+	if (!entry->isVideo()) {
+		return true;
+	}
+
+	if (!m_requireHardwareCodec) {
+		return true;
+	}
+
+	return entry->hardware();
+}
+
+} // namespace ZShell::models

Plugins/ZShell/Models/wallpaperdb.hpp

@@ -0,0 +1,174 @@
+#pragma once
+
+#include <qbytearray.h>
+#include <qdir.h>
+#include <qfileinfo.h>
+#include <qfilesystemwatcher.h>
+#include <qhash.h>
+#include <qlist.h>
+#include <qobject.h>
+#include <qqmlintegration.h>
+#include <qqmllist.h>
+#include <qsize.h>
+#include <qtimer.h>
+#include <qvector.h>
+
+namespace ZShell::models {
+
+class WallpaperImageProvider;
+
+class WallpaperEntry : public QObject {
+	Q_OBJECT
+	QML_ELEMENT
+	QML_UNCREATABLE(
+		"WallpaperEntry instances can only be retrieved from a WallpaperDb")
+
+	Q_PROPERTY(QString path READ path CONSTANT)
+	Q_PROPERTY(QString relativePath READ relativePath NOTIFY relativePathChanged)
+	Q_PROPERTY(QString name READ name CONSTANT)
+	Q_PROPERTY(QString baseName READ baseName CONSTANT)
+	Q_PROPERTY(QString parentDir READ parentDir CONSTANT)
+	Q_PROPERTY(QString suffix READ suffix CONSTANT)
+	Q_PROPERTY(qint64 size READ size CONSTANT)
+	Q_PROPERTY(bool isImage READ isImage CONSTANT)
+	Q_PROPERTY(bool isVideo READ isVideo CONSTANT)
+	Q_PROPERTY(bool hardware READ hardware NOTIFY hardwareChanged)
+	Q_PROPERTY(
+		QString thumbnailPath READ thumbnailPath NOTIFY thumbnailPathChanged)
+
+	public:
+	explicit WallpaperEntry(
+		const QString& path,
+		const QString& relativePath,
+		QObject* parent = nullptr);
+
+	[[nodiscard]] QString path() const;
+	[[nodiscard]] QString relativePath() const;
+	[[nodiscard]] QString name() const;
+	[[nodiscard]] QString baseName() const;
+	[[nodiscard]] QString parentDir() const;
+	[[nodiscard]] QString suffix() const;
+	[[nodiscard]] qint64 size() const;
+	[[nodiscard]] bool isImage() const;
+	[[nodiscard]] bool isVideo() const;
+	[[nodiscard]] bool hardware() const;
+	[[nodiscard]] bool cached() const;
+	[[nodiscard]] QString thumbnailPath() const;
+
+	void setRelativePath(const QString& path);
+	void setHardware(bool hardware);
+	void setThumbnailPath(const QString& path);
+
+	signals:
+	void relativePathChanged();
+	void hardwareChanged();
+	void thumbnailPathChanged();
+
+	private:
+	const QFileInfo m_fileInfo;
+
+	const QString m_path;
+	QString m_relativePath;
+	QString m_thumbnailPath;
+	bool m_hardware = false;
+};
+
+class WallpaperDb : public QObject {
+	Q_OBJECT
+	QML_ELEMENT
+
+	Q_PROPERTY(QString path READ path WRITE setPath NOTIFY pathChanged)
+	Q_PROPERTY(QString dbPath READ dbPath WRITE setDbPath NOTIFY dbPathChanged)
+	Q_PROPERTY(
+		bool requireHardwareCodec READ requireHardwareCodec WRITE
+			setRequireHardwareCodec NOTIFY requireHardwareCodecChanged)
+	Q_PROPERTY(
+		QQmlListProperty<ZShell::models::WallpaperEntry> entries READ entries
+			NOTIFY entriesChanged)
+	Q_PROPERTY(
+		QSize cacheSize READ cacheSize WRITE setCacheSize NOTIFY
+			cacheSizeChanged)
+
+	public:
+	explicit WallpaperDb(QObject* parent = nullptr);
+	~WallpaperDb() override;
+
+	[[nodiscard]] QString path() const;
+	void setPath(const QString& path);
+
+	[[nodiscard]] QString dbPath() const;
+	void setDbPath(const QString& path);
+
+	[[nodiscard]] bool requireHardwareCodec() const;
+	void setRequireHardwareCodec(bool requireHardwareCodec);
+
+	[[nodiscard]] QQmlListProperty<WallpaperEntry> entries();
+
+	[[nodiscard]] QSize cacheSize() const;
+	void setCacheSize(const QSize& cacheSize);
+
+	[[nodiscard]] static QString thumbnailUrl(const QString& path);
+
+	signals:
+	void pathChanged();
+	void dbPathChanged();
+	void requireHardwareCodecChanged();
+	void entriesChanged();
+	void cacheSizeChanged();
+
+	void cacheStored(const QString& path);
+
+	private:
+	struct FileEntry {
+		QFileInfo info;
+		bool hardware = false;
+	};
+
+	struct ScanResult {
+		QVector<FileEntry> files;
+		QDir dir;
+	};
+
+	struct MetadataJob {
+		WallpaperEntry* entry;
+		QString path;
+		bool isVideo;
+		QByteArray existingCache;
+	};
+
+	void openDb();
+	void registerProvider();
+	void scanDir();
+	void watchDir(const QString& dir);
+	void applyScan(const ScanResult& result);
+	void queueMetadata(
+		WallpaperEntry* entry,
+		bool isVideo,
+		const QByteArray& existingCache = {});
+	void processQueue();
+	void runMetadataJob(const MetadataJob& job);
+	void rebuildEntries();
+
+	[[nodiscard]] bool entryAllowed(const WallpaperEntry* entry) const;
+
+	QDir m_dir;
+	QString m_path;
+	QString m_dbPath;
+	QString m_uuid;
+	WallpaperImageProvider* m_provider = nullptr;
+
+	bool m_requireHardwareCodec = false;
+	QSize m_cacheSize;
+
+	QList<WallpaperEntry*> m_entries;
+	QHash<QString, WallpaperEntry*> m_byPath;
+
+	QVector<MetadataJob> m_queue;
+	QTimer m_queueTimer;
+	bool m_jobRunning = false;
+
+	QFileSystemWatcher m_watcher;
+	QTimer m_watchTimer;
+};
+
+} // namespace ZShell::models

Plugins/ZShell/Models/wallpaperutil.hpp

@@ -0,0 +1,313 @@
+#pragma once
+
+#include <qbuffer.h>
+#include <qfile.h>
+#include <qfileinfo.h>
+#include <qimage.h>
+#include <qimagereader.h>
+#include <qprocess.h>
+#include <qstring.h>
+#include <qstringlist.h>
+#include <qtemporarydir.h>
+
+#include <algorithm>
+#include <cstring>
+
+namespace ZShell::models {
+namespace {
+
+inline const QStringList kVideoExtensions = {
+	"mp4",
+	"mkv",
+	"webm",
+	"avi",
+	"mov",
+	"wmv",
+	"flv",
+	"m4v",
+	"mpg",
+	"mpeg",
+	"3gp",
+	"ogv",
+	"ts",
+	"vob",
+};
+
+inline bool hasVideoExtension(const QString& path) {
+	return kVideoExtensions.contains(QFileInfo(path).suffix().toLower());
+}
+
+inline const QStringList kHardwareCodecs = {
+	"av1",
+	"hevc",
+	"h264",
+	"vp9",
+	"vp8",
+	"vc1",
+	"mpeg2",
+	"mpeg2video",
+	"mpeg4",
+	"mjpeg",
+};
+
+inline bool probeHardwareCodec(const QString& path) {
+	QProcess process;
+	process.start(
+		"ffprobe",
+		{
+			"-v",
+			"error",
+			"-select_streams",
+			"v:0",
+			"-show_entries",
+			"stream=codec_name",
+			"-of",
+			"default=nw=1:nk=1",
+			path,
+		});
+	process.waitForFinished(5000);
+
+	if (process.exitCode() != 0) {
+		return false;
+	}
+
+	const QString codec =
+		QString::fromUtf8(process.readAllStandardOutput()).trimmed().toLower();
+	return kHardwareCodecs.contains(codec);
+}
+
+inline QSize coverSizeNoUpscale(const QSize& source, const QSize& fit) {
+	if (!source.isValid() || source.isEmpty() || !fit.isValid() ||
+		fit.isEmpty()) {
+		return source;
+	}
+
+	const QSize cover = source.scaled(fit, Qt::KeepAspectRatioByExpanding);
+	if (cover.width() <= source.width() && cover.height() <= source.height()) {
+		return cover;
+	}
+
+	return source;
+}
+
+inline QImage cleanImage(const QImage& src) {
+	QImage out(src.size(), QImage::Format_RGB888);
+	if (out.isNull()) {
+		return out;
+	}
+
+	const auto rowBytes =
+		static_cast<size_t>(std::min(src.bytesPerLine(), out.bytesPerLine()));
+	for (int y = 0; y < src.height(); ++y) {
+		std::memcpy(out.scanLine(y), src.constScanLine(y), rowBytes);
+	}
+
+	return out;
+}
+
+inline QByteArray imageCacheBytes(const QString& path, const QSize& fit) {
+	QImageReader reader(path);
+	reader.setAutoTransform(true);
+
+	const QSize source = reader.size();
+	const QSize target = coverSizeNoUpscale(source, fit);
+	if (target != source && !target.isEmpty()) {
+		reader.setScaledSize(target);
+	}
+
+	QImage image = reader.read();
+	if (image.isNull()) {
+		return {};
+	}
+
+	image = cleanImage(image.convertToFormat(QImage::Format_RGB888));
+
+	QByteArray bytes;
+	QBuffer buffer(&bytes);
+	if (!buffer.open(QIODevice::WriteOnly) ||
+		!image.save(&buffer, "JPEG", 90)) {
+		return {};
+	}
+
+	return bytes;
+}
+
+inline QByteArray videoCacheBytes(const QString& src, const QSize& fit) {
+	auto runProcess = [](const QString& program, const QStringList& args) {
+		QProcess process;
+		process.start(program, args);
+		if (!process.waitForFinished(15000)) {
+			process.kill();
+			process.waitForFinished(1000);
+		}
+		return qMakePair(process.exitCode(), process.readAllStandardOutput());
+	};
+
+	double duration = 0.0;
+	const auto probe = runProcess(
+		"ffprobe",
+		{
+			"-v",
+			"error",
+			"-show_entries",
+			"format=duration",
+			"-of",
+			"default=nw=1:nk=1",
+			src,
+		});
+	if (probe.first == 0) {
+		duration = QString::fromUtf8(probe.second).trimmed().toDouble();
+	}
+
+	QSize source;
+	const auto resProbe = runProcess(
+		"ffprobe",
+		{
+			"-v",
+			"error",
+			"-select_streams",
+			"v:0",
+			"-show_entries",
+			"stream=width,height",
+			"-of",
+			"csv=s=x:p=0",
+			src,
+		});
+	if (resProbe.first == 0) {
+		const auto parts =
+			QString::fromUtf8(resProbe.second).trimmed().split('x');
+		if (parts.size() == 2) {
+			source = QSize(parts[0].toInt(), parts[1].toInt());
+		}
+	}
+
+	const int samples = duration > 0 ? std::min(10, std::max(4, int(duration)))
+									 : 8;
+
+	QSize target = coverSizeNoUpscale(source, fit);
+	if (target.isEmpty()) {
+		target = fit;
+	}
+
+	target.setWidth(target.width() & ~1);
+	target.setHeight(target.height() & ~1);
+
+	const QString scale =
+		QStringLiteral(
+			"scale=%1:%2:force_original_aspect_ratio=decrease,"
+			"scale=trunc(iw/2)*2:trunc(ih/2)*2")
+			.arg(target.width())
+			.arg(target.height());
+
+	QTemporaryDir tmpDir;
+	if (!tmpDir.isValid()) {
+		return {};
+	}
+
+	int bestIndex = -1;
+	double bestChroma = -1.0;
+	double bestLuma = -1.0;
+
+	for (int i = 0; i < samples; ++i) {
+		const double frac = duration > 0 ? (i + 0.5) / samples : 0.0;
+		const QString seek = duration > 0
+								 ? QString::number(frac * duration, 'f', 3)
+								 : QStringLiteral("0");
+
+		const QString framePath =
+			tmpDir.filePath(QStringLiteral("frame_%1.jpg").arg(i));
+
+		runProcess(
+			"ffmpeg",
+			{
+				"-hide_banner",
+				"-loglevel",
+				"error",
+				"-ss",
+				seek,
+				"-i",
+				src,
+				"-frames:v",
+				"1",
+				"-vf",
+				scale,
+				"-pix_fmt",
+				"yuvj420p",
+				"-q:v",
+				"2",
+				"-y",
+				framePath,
+			});
+
+		QImage frame(framePath);
+		if (frame.isNull()) {
+			continue;
+		}
+
+		frame = frame.convertToFormat(QImage::Format_RGB888);
+
+		double chroma = 0.0;
+		double luma = 0.0;
+		int count = 0;
+		for (int y = 0; y < frame.height(); ++y) {
+			const auto* line = frame.constScanLine(y);
+			for (int x = 0; x < frame.width(); ++x) {
+				const int r = line[x * 3];
+				const int g = line[x * 3 + 1];
+				const int b = line[x * 3 + 2];
+				chroma += std::max({r, g, b}) - std::min({r, g, b});
+				luma += r + g + b;
+				++count;
+			}
+		}
+
+		const int n = std::max(1, count);
+		chroma /= n;
+		luma /= 3.0 * n;
+
+		if (chroma > bestChroma + 0.5 ||
+			(chroma > bestChroma - 0.5 && luma > bestLuma)) {
+			bestChroma = chroma;
+			bestLuma = luma;
+			bestIndex = i;
+		}
+	}
+
+	if (bestIndex < 0) {
+		return {};
+	}
+
+	QFile frame(tmpDir.filePath(QStringLiteral("frame_%1.jpg").arg(bestIndex)));
+	if (!frame.open(QIODevice::ReadOnly)) {
+		return {};
+	}
+
+	return frame.readAll();
+}
+
+inline QByteArray schemeThumbBytes(const QByteArray& source, int maxSide) {
+	QImage image = QImage::fromData(source, "JPEG");
+	if (image.isNull()) {
+		return {};
+	}
+
+	if (image.width() > maxSide || image.height() > maxSide) {
+		image = image.scaled(
+			maxSide, maxSide, Qt::KeepAspectRatio, Qt::SmoothTransformation);
+	}
+
+	image = cleanImage(image.convertToFormat(QImage::Format_RGB888));
+
+	QByteArray bytes;
+	QBuffer buffer(&bytes);
+	if (!buffer.open(QIODevice::WriteOnly) ||
+		!image.save(&buffer, "JPEG", 85)) {
+		return {};
+	}
+
+	return bytes;
+}
+
+} // namespace
+
+} // namespace ZShell::models