feat(qt): queue rows slide into place instead of the list being rebuilt

The Listen list and the sidebar queue now reach their views through
QbzKeyedModel. In the Listen list a removed track fades out while the
rows below slide up, "play next" slides the queue open, a history row
trimmed above the window leaves the rows on screen where they are, and a
committed drag lands the row where it was dropped while its neighbours
slide (the chevrons keep the animated swap). Identity is the track
(source + id, repeats by occurrence); phase, section and phaseIndex are
data, so a track ending updates rows in place and moves nothing. The
follow-playing position and the cover window now run after the model
holds the new rows. A search is a different list and is replaced at once.

The sidebar's Up Next and Recently played are Repeaters in Columns, which
have no remove transition: a leaving row disappears and the rows below
slide up, a joining row fades in, and a page or search change is laid out
synchronously without animation. Drop slots count the Repeater's own
items.

tst_keyed_model gains the Repeater-in-a-Column case (silent first page and
page change, sliding rows that keep their items, fading insert).

cc

crates/qbz-qt/qml/shell/QueuePanel.qml

@@ -38,6 +38,24 @@ Rectangle {
     readonly property var currentRow: doc.current || null
     readonly property var upcoming: doc.upcoming || []
     readonly property var historyRows: doc.history || []
+    // Keyed models for both lists (2026-09-14): a track leaving Up Next (it
+    // started playing, it was removed) disappears and the rows below slide up;
+    // a track joining slides the list open; nothing is rebuilt. The rows are
+    // Repeaters in a Column, so the motion is the Column's own add / move
+    // transitions — a positioner has no remove transition. Identity is the
+    // track (source + id, repeats by occurrence); another page or search
+    // replaces the list at once.
+    QbzKeyedModel {
+        id: upcomingModel
+        rows: root.upcoming
+        keyOf: function (row) { return (row.source || "") + ":" + row.id }
+        scope: JSON.stringify([root.doc.searchQuery || "", root.doc.page || 0])
+    }
+    QbzKeyedModel {
+        id: historyModel
+        rows: root.historyRows
+        keyOf: function (row) { return (row.source || "") + ":" + row.id }
+    }
     readonly property var settingsDoc: {
         try { return JSON.parse(QbzBridge.settingsJson) }
         catch (e) { return ({}) }
@@ -138,7 +156,8 @@ Rectangle {
     // arithmetic model to keep in sync. Top half of row k -> slot k, bottom
     // half -> slot k+1, past the last row -> N (append). <=40 rows per page.
     function slotFromPointer(winY) {
-        var n = root.upcoming.length
+        // The Repeater's own count: its items are what the pointer is over.
+        var n = upcomingRepeater.count
         for (var i = 0; i < n; i++) {
             var d = upcomingRepeater.itemAt(i)
             if (d && winY < d.rowCenterY())
@@ -223,7 +242,13 @@ Rectangle {
             root.coverMap = Object.assign({}, m)
         }
     }
-    Component.onCompleted: dispatchCovers()
+    Component.onCompleted: {
+        // The lists' Columns, laid out synchronously around a reset so a new
+        // page or search appears at once (QbzKeyedModel).
+        upcomingModel.views = [upNextSection]
+        historyModel.views = [historyBody]
+        dispatchCovers()
+    }
     onDocChanged: dispatchCovers()
     onQueueTrackArtworkChanged: dispatchCovers()
     // Collect the covers of the document CURRENTLY on the property and ask the
@@ -1026,13 +1051,18 @@ Rectangle {
                             font.letterSpacing: 0.5
                         }
 
+                        add: QbzRowAdd { enabled: upcomingModel.animate }
+                        move: QbzRowDisplaced { enabled: upcomingModel.animate }
+
                         Repeater {
                             id: upcomingRepeater
-                            model: root.upcoming
+                            model: upcomingModel
                             delegate: Column {
                                 id: upDelegate
-                                required property var modelData
+                                required property string rowKey
+                                required property int rowRev
                                 required property int index
+                                readonly property var modelData: upcomingModel.row(rowKey, rowRev)
                                 width: parent ? parent.width : 0
                                 // Row center in window space — slotFromPointer()
                                 // reads it off the Repeater's items.
@@ -1167,9 +1197,16 @@ Rectangle {
                         font.weight: theme.weightSemibold
                         font.letterSpacing: 0.5
                     }
+                    add: QbzRowAdd { enabled: historyModel.animate }
+                    move: QbzRowDisplaced { enabled: historyModel.animate }
+
                     Repeater {
-                        model: root.historyRows
+                        model: historyModel
                         delegate: QueueRow {
+                            required property string rowKey
+                            required property int rowRev
+                            required property int index
+                            readonly property var modelData: historyModel.row(rowKey, rowRev)
                             width: parent.width
                             row: modelData
                             rowIndex: index

crates/qbz-qt/qml/views/QueueView.qml

@@ -40,6 +40,39 @@ Rectangle {
         && root.doc.currentIndex < root.rows.length
     readonly property int actionRailWidth: kioskHost ? 72 : 52
 
+    // The list's model (2026-09-14): queue changes reach the ListView as
+    // removes / inserts / moves instead of a new array, so removing a track
+    // fades that row out while the rest slide up, "play next" slides the
+    // queue open, a history row trimmed above the window leaves the rows on
+    // screen where they are, and nothing is rebuilt from the top.
+    //
+    // Identity is the track (source + id); a repeat of the same track is its
+    // next occurrence. Phase, section and phaseIndex are data, not identity:
+    // when a track ends, the chronological order does not change, only which
+    // row is current, so those rows update in place and nothing moves. A
+    // search is a different list (the scope), replaced at once.
+    QbzKeyedModel {
+        id: rowsModel
+        rows: root.rows
+        keyOf: function (row) { return (row.source || "") + ":" + row.id }
+        scope: root.doc.searchQuery || ""
+        onReconciled: {
+            // The follow and the covers read view indices: run them once the
+            // view holds the new rows.
+            root.scheduleVisibleCovers()
+            if (root.hasPlayingRow && root.followPlaying)
+                root.followPlayingRow()
+        }
+    }
+    // A committed drop lands the dragged row where the pointer left it; only
+    // its neighbours slide. The chevrons keep the move animation (a swap).
+    property bool dropSettling: false
+    Timer {
+        id: dropSettle
+        interval: 600
+        onTriggered: root.dropSettling = false
+    }
+
     // Timing for the chronological projection currently on screen. History is
     // fully elapsed, the current row contributes the player's live position,
     // and upcoming rows are fully remaining. A filtered listen list therefore
@@ -128,6 +161,7 @@ Rectangle {
     }
 
     Component.onCompleted: {
+        rowsModel.views = [queueList]
         QbzQueue.queueExtendedOpened()
         root.scheduleVisibleCovers()
     }
@@ -139,8 +173,6 @@ Rectangle {
         root.scheduleVisibleCovers()
         if (!root.hasPlayingRow)
             root.cancelPlayingFollow()
-        else if (root.followPlaying)
-            Qt.callLater(function () { root.followPlayingRow() })
     }
     onSearchActiveChanged: if (root.searchActive) root.cancelPlayingFollow()
 
@@ -170,20 +202,22 @@ Rectangle {
     }
 
     function requestVisibleCovers() {
-        if (root.rows.length === 0 || queueList.height <= 0)
+        // View indices index the rows the model holds, not a newer `rows`.
+        var shown = rowsModel.published
+        if (shown.length === 0 || queueList.height <= 0)
             return
         var first = queueList.indexAt(4, queueList.contentY + 2)
         if (first < 0)
             first = 0
         var last = queueList.indexAt(4, queueList.contentY + queueList.height - 2)
         if (last < first)
-            last = Math.min(root.rows.length - 1, first + 16)
+            last = Math.min(shown.length - 1, first + 16)
         first = Math.max(0, first - 3)
-        last = Math.min(root.rows.length - 1, last + 3)
+        last = Math.min(shown.length - 1, last + 3)
         var urls = []
         var wanted = ({})
         for (var i = first; i <= last; i++) {
-            var url = root.artUrl(root.rows[i])
+            var url = root.artUrl(shown[i])
             if (url !== "" && !root.coverMap[url] && wanted[url] !== true) {
                 wanted[url] = true
                 urls.push(url)
@@ -493,9 +527,12 @@ Rectangle {
         root.dropSlot = -1
         root.dropHot = false
         QbzShell.dragInlineVisual = false
-        if (shouldCommit)
+        if (shouldCommit) {
+            root.dropSettling = true
+            dropSettle.restart()
             QbzQueue.queueExtendedDrop(phase, phaseIndex, trackId,
                                        targetPhase, slot)
+        }
     }
 
     function dragProxyY() {
@@ -806,7 +843,11 @@ Rectangle {
                 spacing: 3
                 boundsBehavior: Flickable.StopAtBounds
                 reuseItems: true
-                model: root.rows
+                model: rowsModel
+                add: QbzRowAdd { enabled: rowsModel.animate }
+                remove: QbzRowRemove { enabled: rowsModel.animate }
+                move: QbzRowDisplaced { enabled: rowsModel.animate && !root.dropSettling }
+                displaced: QbzRowDisplaced { enabled: rowsModel.animate }
                 onContentYChanged: root.scheduleVisibleCovers()
                 onMovementStarted: {
                     if (!root.programmaticListPosition)
@@ -815,8 +856,10 @@ Rectangle {
 
                 delegate: Item {
                     id: rowHost
-                    required property var modelData
+                    required property string rowKey
+                    required property int rowRev
                     required property int index
+                    readonly property var modelData: rowsModel.row(rowKey, rowRev)
 
                     readonly property string heading: root.sectionText(index, modelData)
                     readonly property var displayItem: Object.assign({}, modelData, {
@@ -832,7 +875,12 @@ Rectangle {
                         trackRow.recycleActive = false
                         trackRow.releaseForReuse()
                     }
-                    ListView.onReused: trackRow.recycleActive = true
+                    ListView.onReused: {
+                        // A transition cut short can pool the row half faded.
+                        rowHost.opacity = 1
+                        rowHost.scale = 1
+                        trackRow.recycleActive = true
+                    }
 
                     Text {
                         visible: rowHost.heading !== ""

scripts/qml-tests/tst_keyed_model.qml

@@ -1,8 +1,9 @@
 // QbzKeyedModel: rows reconcile into removes / inserts / moves / updates
 // instead of a model swap. Guards the order and identity contract under
 // random edits, the minimal-move reorder, the silent reset, a removal that
-// keeps the viewport and the delegates, the fade that keeps its content, and
+// keeps the viewport and the delegates, the fade that keeps its content, the
-// the pooled delegate that must come back opaque (76 blank rows, 2026-09-14).
+// pooled delegate that must come back opaque (76 blank rows, 2026-09-14), and
+// the Repeater-in-a-Column shape the sidebar queue uses.
 import QtQuick
 import QtTest
 import "../../crates/qbz-qt/qml/controls"
@@ -83,6 +84,39 @@ Item {
     // --- no view: reconcile arithmetic -------------------------------------
     QbzKeyedModel { id: plain; rows: root.plainRows }
 
+    // --- a Repeater in a Column (the sidebar queue shape) -------------------
+    property var columnRows: []
+    property int columnAdds: 0
+    property int columnMoves: 0
+    QbzKeyedModel { id: columnModel; rows: root.columnRows; views: [column] }
+    Column {
+        id: column
+        x: 0; y: 0
+        width: 200
+        add: Transition {
+            enabled: columnModel.animate
+            ScriptAction { script: root.columnAdds++ }
+            NumberAnimation { property: "opacity"; from: 0; to: 1; duration: 60 }
+        }
+        move: Transition {
+            enabled: columnModel.animate
+            ScriptAction { script: root.columnMoves++ }
+            NumberAnimation { properties: "y"; duration: 120 }
+        }
+        Repeater {
+            id: columnRepeater
+            model: columnModel
+            delegate: Rectangle {
+                required property string rowKey
+                required property int rowRev
+                required property int index
+                readonly property var modelData: columnModel.row(rowKey, rowRev)
+                width: 200; height: 10
+                color: "transparent"
+            }
+        }
+    }
+
     TestCase {
         name: "KeyedModel"
         when: windowShown
@@ -326,6 +360,38 @@ Item {
             plain.ignoredKeys = []
         }
 
+        function test_j_column_repeater_resets_silently_and_slides_on_removal() {
+            columnModel.scope = "page-1"
+            root.columnRows = root.make(12, "c")
+            wait(0)
+            wait(150)
+            compare(columnRepeater.count, 12)
+            compare(root.columnAdds, 0, "the first page is not animated in")
+            var survivor = columnRepeater.itemAt(4)
+            // One row leaves: the rows below slide up, nothing is re-created.
+            root.columnRows = root.make(12, "c").filter(function (r) { return r.id !== "c2" })
+            columnModel.sync()
+            wait(30)
+            verify(root.columnMoves > 0, "the rows below slide")
+            wait(200)
+            compare(columnRepeater.itemAt(3), survivor, "the same row item, one slot up")
+            compare(survivor.y, 30)
+            // A row joins at the top: it fades in.
+            var adds = root.columnAdds
+            root.columnRows = [{ "id": "new", "title": "N" }].concat(root.columnRows)
+            columnModel.sync()
+            wait(150)
+            verify(root.columnAdds > adds, "the new row fades in")
+            // Another page replaces the list without animation.
+            adds = root.columnAdds
+            columnModel.scope = "page-2"
+            root.columnRows = root.make(8, "d")
+            wait(0)
+            wait(150)
+            compare(columnRepeater.count, 8)
+            compare(root.columnAdds, adds, "a page change is not animated")
+        }
+
         function test_i_repeated_entities_are_distinct_rows() {
             root.plainRows = [{ "id": "x" }, { "id": "y" }, { "id": "x" }]
             plain.scope = "dups"