SetupWallpaperStep: add scrollwheel support

Modules/SetupWizard/SetupWallpaperStep.qml

@@ -199,11 +199,34 @@ ColumnLayout {
     visible: filteredWallpapers.length > 0
 
     ScrollView {
+      id: galleryScroll
       anchors.fill: parent
       clip: true
       ScrollBar.horizontal.policy: ScrollBar.AsNeeded
       ScrollBar.vertical.policy: ScrollBar.AlwaysOff
 
+      // Enable vertical mouse wheel to scroll the horizontal strip by moving contentX
+      WheelHandler {
+        target: galleryScroll.contentItem
+        acceptedDevices: PointerDevice.Mouse | PointerDevice.TouchPad
+        onWheel: event => {
+                   const flick = galleryScroll.contentItem
+                   if (!flick)
+                   return
+                   const delta = event.pixelDelta.x !== 0 || event.pixelDelta.y !== 0 ? (event.pixelDelta.y !== 0 ? event.pixelDelta.y : event.pixelDelta.x) : (event.angleDelta.y !== 0 ? event.angleDelta.y : event.angleDelta.x)
+                   // Move opposite of wheel to scroll content to the right for wheel down
+                   const step = -delta
+                   const maxX = Math.max(0, flick.contentWidth - flick.width)
+                   let newX = flick.contentX + step
+                   if (newX < 0)
+                   newX = 0
+                   if (newX > maxX)
+                   newX = maxX
+                   flick.contentX = newX
+                   event.accepted = true
+                 }
+      }
+
       RowLayout {
         spacing: Style.marginM
         height: parent.height

Services/WallpaperService.qml

@@ -377,12 +377,12 @@ Singleton {
         var scanner = wallpaperScanners.objectAt(i)
         if (scanner) {
           // Capture scanner in closure
-          (function(s) {
+          (function (s) {
             var directory = root.getMonitorDirectory(s.screenName)
             // Trigger a change by setting to /tmp (always exists) then back to the actual directory
             // Note: This causes harmless Qt warnings (QTBUG-52262) but is necessary to force FolderListModel to re-scan
             s.currentDirectory = "/tmp"
-            Qt.callLater(function() {
+            Qt.callLater(function () {
               s.currentDirectory = directory
             })
           })(scanner)