From 8c719cd3e9d12840e54ab25741bc661ffc98e976 Mon Sep 17 00:00:00 2001
From: Erik <erik.nihlen@gmail.com>
Date: Mon, 22 Jun 2026 11:05:12 +0200
Subject: [PATCH] =?UTF-8?q?feat(ui):=20D.2b=20empty-slot=20art=20=E2=80=94?=
 =?UTF-8?q?=20InventoryController=20applies=20per-list=20empty=20sprites?=
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Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---
 .../UI/Layout/InventoryController.cs          | 19 ++++++++++++++++---
 .../UI/Layout/InventoryControllerTests.cs     | 13 +++++++++++++
 2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/src/AcDream.App/UI/Layout/InventoryController.cs b/src/AcDream.App/UI/Layout/InventoryController.cs
index a96537b3..81007e89 100644
--- a/src/AcDream.App/UI/Layout/InventoryController.cs
+++ b/src/AcDream.App/UI/Layout/InventoryController.cs
@@ -62,7 +62,10 @@ public sealed class InventoryController
         Func<uint> playerGuid,
         Func<ItemType, uint, uint, uint, uint, uint> iconIds,
         Func<int?> strength,
-        UiDatFont? datFont)
+        UiDatFont? datFont,
+        uint contentsEmptySprite,
+        uint sideBagEmptySprite,
+        uint mainPackEmptySprite)
     {
         _objects    = objects;
         _playerGuid = playerGuid;
@@ -101,6 +104,12 @@ public sealed class InventoryController
             _containerList.CellHeight = BackpackCellPx;
         }
 
+        // Per-list empty-slot art, resolved from the dat cell template (retail attr 0x1000000e
+        // -> catalog 0x21000037 prototype's ItemSlot_Empty). 0 = leave the UiItemSlot default.
+        if (_contentsGrid  is not null) _contentsGrid.CellEmptySprite  = contentsEmptySprite;
+        if (_containerList is not null) _containerList.CellEmptySprite = sideBagEmptySprite;
+        if (_topContainer  is not null) _topContainer.CellEmptySprite  = mainPackEmptySprite;
+
         // Burden meter: vertical 11×58 bar (gmBackpackUI m_burdenMeter, retail direction 4).
         _burdenMeter = layout.FindElement(BurdenMeterId) as UiMeter;
         if (_burdenMeter is not null)
@@ -132,8 +141,12 @@ public sealed class InventoryController
         Func<uint> playerGuid,
         Func<ItemType, uint, uint, uint, uint, uint> iconIds,
         Func<int?> strength,
-        UiDatFont? datFont)
-        => new InventoryController(layout, objects, playerGuid, iconIds, strength, datFont);
+        UiDatFont? datFont,
+        uint contentsEmptySprite = 0u,
+        uint sideBagEmptySprite  = 0u,
+        uint mainPackEmptySprite = 0u)
+        => new InventoryController(layout, objects, playerGuid, iconIds, strength, datFont,
+                                   contentsEmptySprite, sideBagEmptySprite, mainPackEmptySprite);
 
     private void OnObjectChanged(ClientObject o)        { if (Concerns(o)) Populate(); }
     private void OnObjectMoved(ClientObject o, uint from, uint to)
diff --git a/tests/AcDream.App.Tests/UI/Layout/InventoryControllerTests.cs b/tests/AcDream.App.Tests/UI/Layout/InventoryControllerTests.cs
index b44f0cd2..fc2a5de2 100644
--- a/tests/AcDream.App.Tests/UI/Layout/InventoryControllerTests.cs
+++ b/tests/AcDream.App.Tests/UI/Layout/InventoryControllerTests.cs
@@ -240,6 +240,19 @@ public class InventoryControllerTests
         Assert.Equal(0u,  containers.GetItem(2)!.ItemId);   // empty frame
     }
 
+    [Fact]
+    public void Empty_sprites_are_applied_to_the_three_lists()
+    {
+        var (layout, grid, containers, top, _, _, _, _) = BuildLayout();
+        InventoryController.Bind(layout, new ClientObjectTable(), () => Player,
+            iconIds: (_, _, _, _, _) => 0u, strength: () => 100, datFont: null,
+            contentsEmptySprite: 0x06004D20u, sideBagEmptySprite: 0x06005D9Cu, mainPackEmptySprite: 0x06005D9Cu);
+
+        Assert.Equal(0x06004D20u, grid.GetItem(0)!.EmptySprite);        // a padded empty contents cell
+        Assert.Equal(0x06005D9Cu, containers.GetItem(0)!.EmptySprite);  // a padded empty side-bag cell
+        Assert.Equal(0x06005D9Cu, top.GetItem(0)!.EmptySprite);         // the main-pack cell
+    }
+
     // Reads the text of the UiText caption child attached by the controller.
     private static string CaptionText(UiElement host)
     {