Change wallpaper enums to be in namespaces rather than in gadgets

Qt 6 no longer allows exporting gadgets with an uppercase name. Namespaces
work just as well here, but we unfortunately have this problem also in
other places where the solution is less straightforward.

wallpapers/image/plugin/imagebackend.h

@@ -24,7 +24,7 @@ class ImageProxyModel;
 class SlideModel;
 class SlideFilterModel;
 
-class ImageBackend : public QObject, public QQmlParserStatus, public SortingMode
+class ImageBackend : public QObject, public QQmlParserStatus
 {
     Q_OBJECT
     Q_INTERFACES(QQmlParserStatus)

wallpapers/image/plugin/imageplugin.cpp

@@ -39,6 +39,6 @@ void ImagePlugin::registerTypes(const char *uri)
 
     qmlRegisterAnonymousType<QAbstractItemModel>("QAbstractItemModel", 1);
 
-    qmlRegisterUncreatableType<BackgroundType>(uri, 2, 0, "BackgroundType", QStringLiteral("error: only enums"));
-    qmlRegisterUncreatableType<SortingMode>(uri, 2, 0, "SortingMode", QStringLiteral("error: only enums"));
+    qmlRegisterUncreatableMetaObject(BackgroundType::staticMetaObject, uri, 2, 0, "BackgroundType", QStringLiteral("error: only enums"));
+    qmlRegisterUncreatableMetaObject(SortingMode::staticMetaObject, uri, 2, 0, "SortingMode", QStringLiteral("error: only enums"));
 }

wallpapers/image/plugin/sortingmode.h

@@ -7,19 +7,18 @@
 #ifndef SORTINGMODE_H
 #define SORTINGMODE_H
 
-class SortingMode
+namespace SortingMode
 {
-    Q_GADGET
+Q_NAMESPACE
 
-public:
-    enum Mode {
-        Random,
-        Alphabetical,
-        AlphabeticalReversed,
-        Modified,
-        ModifiedReversed,
-    };
-    Q_ENUM(Mode)
+enum Mode {
+    Random,
+    Alphabetical,
+    AlphabeticalReversed,
+    Modified,
+    ModifiedReversed,
 };
+Q_ENUM_NS(Mode)
+}
 
 #endif

wallpapers/image/plugin/utils/backgroundtype.h

@@ -6,15 +6,14 @@
 
 #pragma once
 
-class BackgroundType
+namespace BackgroundType
 {
-    Q_GADGET
+Q_NAMESPACE
 
-public:
-    enum class Type {
-        Unknown,
-        Image,
-        AnimatedImage, /**< AnimatedImage doesn't support \QQuickImageProvider , @see https://bugreports.qt.io/browse/QTBUG-30524 */
-    };
-    Q_ENUM(Type)
+enum class Type {
+    Unknown,
+    Image,
+    AnimatedImage, /**< AnimatedImage doesn't support \QQuickImageProvider , @see https://bugreports.qt.io/browse/QTBUG-30524 */
 };
+Q_ENUM_NS(Type)
+}