feat: split caching into separate service

Return original image if no cache hit instead of waiting for cache to
finish

plugin/src/Caelestia/Images/CMakeLists.txt

@@ -2,6 +2,7 @@ qml_module(caelestia-images
     URI Caelestia.Images
     SOURCES
         cachingimageprovider.cpp
+        imagecacher.cpp
         iutils.cpp
     LIBRARIES
         Qt::Gui

plugin/src/Caelestia/Images/cachingimageprovider.cpp

@@ -1,15 +1,12 @@
 #include "cachingimageprovider.hpp"
 
-#include <qcryptographichash.h>
-#include <qdir.h>
-#include <qfile.h>
+#include "imagecacher.hpp"
+
 #include <qfileinfo.h>
 #include <qimage.h>
 #include <qimagereader.h>
 #include <qloggingcategory.h>
-#include <qpainter.h>
 #include <qrunnable.h>
-#include <qsavefile.h>
 #include <qthreadpool.h>
 
 Q_LOGGING_CATEGORY(lcCProv, "caelestia.images.cacheprovider", QtInfoMsg)
@@ -18,44 +15,9 @@ namespace caelestia::images {
 
 namespace {
 
-const QString& cacheDir() {
-    static const QString s_dir = [] {
-        QString cache = qEnvironmentVariable("XDG_CACHE_HOME");
-        if (cache.isEmpty())
-            cache = QDir::homePath() + QStringLiteral("/.cache");
-        return cache + QStringLiteral("/caelestia/imagecache");
-    }();
-    return s_dir;
-}
-
-QString sha256sum(const QString& path) {
-    QFile file(path);
-    if (!file.open(QIODevice::ReadOnly)) {
-        qCWarning(lcCProv).noquote() << "sha256sum: failed to open" << path;
-        return {};
-    }
-
-    QCryptographicHash hash(QCryptographicHash::Sha256);
-    hash.addData(&file);
-    file.close();
-
-    return hash.result().toHex();
-}
-
-QString fillSuffix(CachingImageProvider::FillMode fillMode) {
-    switch (fillMode) {
-    case CachingImageProvider::FillMode::Crop:
-        return QStringLiteral("crop");
-    case CachingImageProvider::FillMode::Fit:
-        return QStringLiteral("fit");
-    default:
-        return QStringLiteral("stretch");
-    }
-}
-
 class CachingImageResponse final : public QQuickImageResponse, public QRunnable {
 public:
-    CachingImageResponse(const QString& id, const QSize& requestedSize, CachingImageProvider::FillMode fillMode)
+    CachingImageResponse(const QString& id, const QSize& requestedSize, ImageCacher::FillMode fillMode)
         : m_id(id)
         , m_requestedSize(requestedSize)
         , m_fillMode(fillMode) {
@@ -87,87 +49,39 @@ private:
 
         // Use original image if requested size is invalid
         if (m_requestedSize.width() <= 0 || m_requestedSize.height() <= 0) {
+            qCDebug(lcCProv).noquote() << "Given source size is invalid, returning original:" << path;
             m_image = QImage(path);
-            qCDebug(lcCProv) << "Given source size is invalid, not caching.";
+            if (m_image.isNull()) {
+                m_error = QStringLiteral("Failed to decode source: ") + path;
+                qCWarning(lcCProv).noquote() << m_error;
+            }
             return;
         }
 
-        const QString sha = sha256sum(path);
-        if (sha.isEmpty()) {
-            m_error = QStringLiteral("Failed to hash: ") + path;
-            return;
-        }
-
-        // clang-format off
-        const QString filename = QStringLiteral("%1@%2x%3-%4.png")
-            .arg(sha).arg(m_requestedSize.width()).arg(m_requestedSize.height()).arg(fillSuffix(m_fillMode));
-        // clang-format on
-        const QString cache = cacheDir() + QLatin1Char('/') + filename;
-
-        // Check cache, if it already exists, set and return
-        QImageReader cacheReader(cache);
+        // Try to use cached image
+        const auto cachePath = ImageCacher::cachePathFor(path, m_requestedSize, m_fillMode);
+        if (!cachePath.isEmpty()) {
+            QImageReader cacheReader(cachePath);
             if (cacheReader.canRead()) {
                 m_image = cacheReader.read();
                 if (!m_image.isNull())
                     return;
             }
+        }
 
-        QImage image(path);
-        if (image.isNull()) {
-            m_error = QStringLiteral("Failed to decode: ") + path;
+        // Schedule cache job (this call will return the original image, but later ones will use cache)
+        ImageCacher::instance()->schedule(path, cachePath, m_requestedSize, m_fillMode);
+
+        m_image = QImage(path);
+        if (m_image.isNull()) {
+            m_error = QStringLiteral("Failed to decode source: ") + path;
             qCWarning(lcCProv).noquote() << m_error;
-            return;
         }
-
-        image.convertTo(QImage::Format_ARGB32);
-
-        // Scale to requested size
-        switch (m_fillMode) {
-        case CachingImageProvider::FillMode::Crop:
-            image = image.scaled(m_requestedSize, Qt::KeepAspectRatioByExpanding, Qt::SmoothTransformation);
-            break;
-        case CachingImageProvider::FillMode::Fit:
-            image = image.scaled(m_requestedSize, Qt::KeepAspectRatio, Qt::SmoothTransformation);
-            break;
-        case CachingImageProvider::FillMode::Stretch:
-            image = image.scaled(m_requestedSize, Qt::IgnoreAspectRatio, Qt::SmoothTransformation);
-            break;
-        }
-
-        if (m_fillMode == CachingImageProvider::FillMode::Stretch) {
-            m_image = image;
-        } else {
-            // Crop or fit
-            QImage canvas(m_requestedSize, QImage::Format_ARGB32);
-            canvas.fill(Qt::transparent);
-
-            QPainter painter(&canvas);
-            painter.drawImage(
-                (m_requestedSize.width() - image.width()) / 2, (m_requestedSize.height() - image.height()) / 2, image);
-            painter.end();
-
-            m_image = canvas;
-        }
-
-        // Save to cache
-        const QString parent = QFileInfo(cache).absolutePath();
-        if (!QDir().mkpath(parent)) {
-            qCWarning(lcCProv).noquote() << "Failed to create cache dir" << parent;
-            return;
-        }
-
-        QSaveFile saveFile(cache);
-        if (!saveFile.open(QIODevice::WriteOnly) || !m_image.save(&saveFile, "PNG") || !saveFile.commit()) {
-            qCWarning(lcCProv).noquote() << "Failed to save to" << cache << ":" << saveFile.errorString();
-            return;
-        }
-
-        qCDebug(lcCProv).noquote() << "Saved to" << cache;
     }
 
     QString m_id;
     QSize m_requestedSize;
-    CachingImageProvider::FillMode m_fillMode;
+    ImageCacher::FillMode m_fillMode;
     QImage m_image;
     QString m_error;
 };

plugin/src/Caelestia/Images/cachingimageprovider.hpp

@@ -1,16 +1,14 @@
 #pragma once
 
+#include "imagecacher.hpp"
+
 #include <qquickimageprovider.h>
 
 namespace caelestia::images {
 
 class CachingImageProvider : public QQuickAsyncImageProvider {
 public:
-    enum class FillMode {
-        Crop,
-        Fit,
-        Stretch
-    };
+    using FillMode = ImageCacher::FillMode;
 
     explicit CachingImageProvider(FillMode fillMode);
 

plugin/src/Caelestia/Images/imagecacher.cpp

@@ -0,0 +1,159 @@
+#include "imagecacher.hpp"
+
+#include <qcryptographichash.h>
+#include <qdir.h>
+#include <qfile.h>
+#include <qfileinfo.h>
+#include <qimage.h>
+#include <qloggingcategory.h>
+#include <qmutex.h>
+#include <qpainter.h>
+#include <qsavefile.h>
+#include <qthreadpool.h>
+
+Q_LOGGING_CATEGORY(lcCacher, "caelestia.images.cacher", QtInfoMsg)
+
+namespace caelestia::images {
+
+namespace {
+
+QString sha256sum(const QString& path) {
+    QFile file(path);
+    if (!file.open(QIODevice::ReadOnly)) {
+        qCWarning(lcCacher).noquote() << "sha256sum: failed to open" << path;
+        return {};
+    }
+
+    QCryptographicHash hash(QCryptographicHash::Sha256);
+    hash.addData(&file);
+    file.close();
+
+    return hash.result().toHex();
+}
+
+QString fillSuffix(ImageCacher::FillMode fillMode) {
+    switch (fillMode) {
+    case ImageCacher::FillMode::Crop:
+        return QStringLiteral("crop");
+    case ImageCacher::FillMode::Fit:
+        return QStringLiteral("fit");
+    default:
+        return QStringLiteral("stretch");
+    }
+}
+
+} // namespace
+
+const QString& ImageCacher::cacheDir() {
+    static const QString s_dir = [] {
+        QString cache = qEnvironmentVariable("XDG_CACHE_HOME");
+        if (cache.isEmpty())
+            cache = QDir::homePath() + QStringLiteral("/.cache");
+        return cache + QStringLiteral("/caelestia/imagecache");
+    }();
+    return s_dir;
+}
+
+QString ImageCacher::cachePathFor(const QString& sourcePath, const QSize& size, FillMode fillMode) {
+    const QString sha = sha256sum(sourcePath);
+    if (sha.isEmpty())
+        return {};
+
+    const QString filename =
+        QStringLiteral("%1@%2x%3-%4.png")
+            .arg(sha, QString::number(size.width()), QString::number(size.height()), fillSuffix(fillMode));
+
+    return cacheDir() + QLatin1Char('/') + filename;
+}
+
+ImageCacher* ImageCacher::instance() {
+    static ImageCacher s_instance;
+    return &s_instance;
+}
+
+ImageCacher::ImageCacher(QObject* parent)
+    : QObject(parent) {}
+
+void ImageCacher::schedule(const QString& sourcePath, const QSize& size, FillMode fillMode) {
+    schedule(sourcePath, cachePathFor(sourcePath, size, fillMode), size, fillMode);
+}
+
+void ImageCacher::schedule(const QString& sourcePath, const QString& cachePath, const QSize& size, FillMode fillMode) {
+    if (cachePath.isEmpty())
+        return;
+
+    {
+        QMutexLocker locker(&m_mutex);
+        if (m_inflight.contains(cachePath))
+            return;
+        m_inflight.insert(cachePath);
+    }
+
+    QThreadPool::globalInstance()->start([this, sourcePath, cachePath, size, fillMode]() {
+        runJob(sourcePath, cachePath, size, fillMode);
+        QMutexLocker locker(&m_mutex);
+        m_inflight.remove(cachePath);
+    });
+}
+
+void ImageCacher::runJob(const QString& sourcePath, const QString& cachePath, const QSize& size, FillMode fillMode) {
+    if (QFile::exists(cachePath)) {
+        return;
+    }
+
+    QImage image(sourcePath);
+    if (image.isNull()) {
+        qCWarning(lcCacher).noquote() << "Failed to decode source" << sourcePath;
+        return;
+    }
+
+    Qt::AspectRatioMode scaleMode;
+    switch (fillMode) {
+    case FillMode::Crop:
+        scaleMode = Qt::KeepAspectRatioByExpanding;
+        break;
+    case FillMode::Fit:
+        scaleMode = Qt::KeepAspectRatio;
+        break;
+    case FillMode::Stretch:
+        scaleMode = Qt::IgnoreAspectRatio;
+        break;
+    }
+
+    image.convertTo(QImage::Format_ARGB32);
+    image = image.scaled(size, scaleMode, Qt::SmoothTransformation);
+
+    if (image.isNull()) {
+        qCWarning(lcCacher).noquote() << "Failed to scale" << sourcePath;
+        return;
+    }
+
+    QImage canvas;
+    if (fillMode == FillMode::Stretch) {
+        canvas = image;
+    } else {
+        canvas = QImage(size, QImage::Format_ARGB32);
+        canvas.fill(Qt::transparent);
+
+        QPainter painter(&canvas);
+        painter.drawImage((size.width() - image.width()) / 2, (size.height() - image.height()) / 2, image);
+        painter.end();
+    }
+
+    const QString parent = QFileInfo(cachePath).absolutePath();
+    if (!QDir().mkpath(parent)) {
+        qCWarning(lcCacher).noquote() << "Failed to create cache dir" << parent;
+        return;
+    }
+
+    QSaveFile saveFile(cachePath);
+    if (!saveFile.open(QIODevice::WriteOnly) || !canvas.save(&saveFile, "PNG") || !saveFile.commit()) {
+        qCWarning(
+            lcCacher, "Failed to save to %s: %s", qUtf8Printable(cachePath), qUtf8Printable(saveFile.errorString()));
+        return;
+    }
+
+    qCDebug(lcCacher).noquote() << "Saved to" << cachePath;
+}
+
+} // namespace caelestia::images

plugin/src/Caelestia/Images/imagecacher.hpp

@@ -0,0 +1,38 @@
+#pragma once
+
+#include <qmutex.h>
+#include <qobject.h>
+#include <qset.h>
+#include <qsize.h>
+#include <qstring.h>
+
+namespace caelestia::images {
+
+class ImageCacher : public QObject {
+    Q_OBJECT
+
+public:
+    enum class FillMode {
+        Crop,
+        Fit,
+        Stretch,
+    };
+
+    static ImageCacher* instance();
+
+    static const QString& cacheDir();
+    static QString cachePathFor(const QString& sourcePath, const QSize& size, FillMode fillMode);
+
+    void schedule(const QString& sourcePath, const QSize& size, FillMode fillMode);
+    void schedule(const QString& sourcePath, const QString& cachePath, const QSize& size, FillMode fillMode);
+
+private:
+    explicit ImageCacher(QObject* parent = nullptr);
+
+    static void runJob(const QString& sourcePath, const QString& cachePath, const QSize& size, FillMode fillMode);
+
+    QMutex m_mutex;
+    QSet<QString> m_inflight;
+};
+
+} // namespace caelestia::images