wallpaper selector: freedesktop spec-compliant thumbnail generation

.config/quickshell/ii/modules/wallpaperSelector/WallpaperDirectoryItem.qml

@@ -19,19 +19,19 @@ MouseArea {
     property alias colBackground: background.color
     property alias colText: wallpaperItemName.color
     property alias radius: background.radius
-    property alias padding: background.anchors.margins
+    property alias margins: background.anchors.margins
+    property alias padding: wallpaperItemColumnLayout.anchors.margins
+    margins: Appearance.sizes.wallpaperSelectorItemMargins
+    padding: Appearance.sizes.wallpaperSelectorItemPadding
 
-    signal activated
+    signal activated()
 
     hoverEnabled: true
     onClicked: root.activated()
 
     Rectangle {
         id: background
-        anchors {
-            fill: parent
-            margins: 8
-        }
+        anchors.fill: parent
         radius: Appearance.rounding.normal
         Behavior on color {
             animation: Appearance.animation.elementMoveFast.colorAnimation.createObject(this)
@@ -39,10 +39,7 @@ MouseArea {
 
         ColumnLayout {
             id: wallpaperItemColumnLayout
-            anchors {
-                fill: parent
-                margins: 6
-            }
+            anchors.fill: parent
             spacing: 4
 
             Item {
@@ -67,6 +64,7 @@ MouseArea {
                     active: root.useThumbnail
                     sourceComponent: ThumbnailImage {
                         id: thumbnailImage
+                        generateThumbnail: false
                         sourcePath: fileModelData.filePath
 
                         fillMode: Image.PreserveAspectCrop
@@ -74,6 +72,16 @@ MouseArea {
                         sourceSize.width: wallpaperItemColumnLayout.width
                         sourceSize.height: wallpaperItemColumnLayout.height - wallpaperItemColumnLayout.spacing - wallpaperItemName.height
 
+                        Connections {
+                            target: Wallpapers
+                            function onThumbnailGenerated(directory) {
+                                if (thumbnailImage.status !== Image.Error) return;
+                                if (FileUtils.parentDirectory(thumbnailImage.sourcePath) !== directory) return;
+                                thumbnailImage.source = "";
+                                thumbnailImage.source = thumbnailImage.thumbnailPath;
+                            }
+                        }
+
                         layer.enabled: true
                         layer.effect: OpacityMask {
                             maskSource: Rectangle {

.config/quickshell/ii/modules/wallpaperSelector/WallpaperSelectorContent.qml

@@ -16,6 +16,19 @@ Item {
     property real previewCellAspectRatio: 4 / 3
     property bool useDarkMode: Appearance.m3colors.darkmode
 
+    function updateThumbnails() {
+        const totalImageMargin = (Appearance.sizes.wallpaperSelectorItemMargins + Appearance.sizes.wallpaperSelectorItemPadding) * 2
+        const thumbnailSizeName = Images.thumbnailSizeNameForDimensions(grid.cellWidth - totalImageMargin, grid.cellHeight - totalImageMargin)
+        Wallpapers.generateThumbnail(thumbnailSizeName)
+    }
+
+    Connections {
+        target: Wallpapers
+        function onDirectoryChanged() {
+            root.updateThumbnails()
+        }
+    }
+
     Keys.onPressed: event => {
         if (event.key === Qt.Key_Escape) {
             GlobalStates.wallpaperSelectorOpen = false;
@@ -203,9 +216,12 @@ Item {
                         keyNavigationWraps: true
                         boundsBehavior: Flickable.StopAtBounds
                         bottomMargin: extraOptions.implicitHeight
-
                         ScrollBar.vertical: StyledScrollBar {}
 
+                        Component.onCompleted: {
+                            root.updateThumbnails()
+                        }
+
                         function moveSelection(delta) {
                             currentIndex = Math.max(0, Math.min(grid.model.count - 1, currentIndex + delta));
                             positionViewAtIndex(currentIndex, GridView.Contain);
@@ -219,7 +235,6 @@ Item {
 
                         model: Wallpapers.folderModel
                         onModelChanged: currentIndex = 0
-
                         delegate: WallpaperDirectoryItem {
                             required property var modelData
                             required property int index