[Background Model] Use own QCache for thumbnails

Previously it would use an on-disk KImageCache which would never be invalidated.
Moreover, it just uses KIO::PreviewJob which does its own more clever (compares mtime and other properties) on-disk caching already.

It is using its own QCache rather than QPixmapCache to not jeopardize other caching for the potentially large wallpaper thumbnails
that are only relevant while the dialog is open.

BUG: 395447
FIXED-IN: 5.15.0

Differential Revision: https://phabricator.kde.org/D16095

wallpapers/image/CMakeLists.txt

@@ -24,7 +24,6 @@ target_link_libraries(plasma_wallpaper_imageplugin
          KF5::KIOCore
          KF5::KIOWidgets # KFileDialog
          KF5::NewStuff
-         KF5::GuiAddons
          )
 
 if(BUILD_TESTING)

wallpapers/image/backgroundlistmodel.cpp

@@ -39,7 +39,6 @@
 #include <QDebug>
 #include <KIO/PreviewJob>
 #include <KLocalizedString>
-#include <kimagecache.h>
 #include <kaboutdata.h>
 
 #include <KPackage/Package>
@@ -70,19 +69,16 @@ BackgroundListModel::BackgroundListModel(Image *wallpaper, QObject *parent)
     : QAbstractListModel(parent),
       m_wallpaper(wallpaper)
 {
+    m_imageCache.setMaxCost(10 * 1024 * 1024); // 10 MiB
+
     connect(&m_dirwatch, &KDirWatch::deleted, this, &BackgroundListModel::removeBackground);
 
     //TODO: on Qt 4.4 use the ui scale factor
     QFontMetrics fm(QGuiApplication::font());
     m_screenshotSize = fm.width('M') * 15;
-
-    m_imageCache = new KImageCache(QStringLiteral("plasma_wallpaper_preview"), 10485760);
 }
 
-BackgroundListModel::~BackgroundListModel()
-{
-    delete m_imageCache;
-}
+BackgroundListModel::~BackgroundListModel() = default;
 
 QHash<int, QByteArray> BackgroundListModel::BackgroundListModel::roleNames() const
 {
@@ -343,14 +339,14 @@ QVariant BackgroundListModel::data(const QModelIndex &index, int role) const
     }
 
     case ScreenshotRole: {
-        QPixmap preview = QPixmap(QSize(m_screenshotSize*1.6,
-                                                    m_screenshotSize));
-        if (m_imageCache->findPixmap(b.filePath("preferred"), &preview)) {
-            return preview;
+        const QString path = b.filePath("preferred");
+
+        QPixmap *cachedPreview = m_imageCache.object(path);
+        if (cachedPreview) {
+            return *cachedPreview;
         }
-//         qCDebug(IMAGEWALLPAPER) << "WP preferred: " << b.filePath("preferred");
-//         qCDebug(IMAGEWALLPAPER) << "WP screenshot: " << b.filePath("screenshot");
-        QUrl file = QUrl::fromLocalFile(b.filePath("preferred"));
+
+        const QUrl file = QUrl::fromLocalFile(path);
         if (!m_previewJobs.contains(file) && file.isValid()) {
 
             KFileItemList list;
@@ -451,7 +447,9 @@ void BackgroundListModel::showPreview(const KFileItem &item, const QPixmap &prev
         return;
     }
 
-    m_imageCache->insertPixmap(b.filePath("preferred"), preview);
+    const int cost = preview.width() * preview.height() * preview.depth() / 8;
+    m_imageCache.insert(b.filePath("preferred"), new QPixmap(preview), cost);
+
     //qCDebug(IMAGEWALLPAPER) << "WP preview size:" << preview.size();
     emit dataChanged(index, index);
 }

wallpapers/image/backgroundlistmodel.h

@@ -23,6 +23,7 @@
 #include "image.h"
 
 #include <QAbstractListModel>
+#include <QCache>
 #include <QPixmap>
 #include <QRunnable>
 #include <QThread>
@@ -32,8 +33,6 @@
 #include <KDirWatch>
 #include <KFileItem>
 
-#include <kimagecache.h>
-
 #include <KPackage/PackageStructure>
 
 class QEventLoop;
@@ -115,7 +114,7 @@ private:
     QHash<QString, QSize> m_sizeCache;
     QHash<QUrl, QPersistentModelIndex> m_previewJobs;
     KDirWatch m_dirwatch;
-    KImageCache* m_imageCache;
+    QCache<QString, QPixmap> m_imageCache;
 
     QString m_findToken;
     int m_screenshotSize;