feat(D.2b): UiChannelMenu — channel selector popup (UIElement_Menu port)

Port of retail gmMainChatUI::InitTalkFocusMenu @0x4cdc50 + HandleSelection
@0x4cd540 → SetTalkFocus. Button shows active channel label; click opens a
12-item popup that extends UPWARD (chat sits at screen bottom); selecting an
entry calls OnChannelChanged and updates Selected. BitmapFont? Font uses the
fully-qualified type name to match UiChatInput convention. Includes 6 xunit
tests covering channel table shape, default selection, and popup-pick routing.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/AcDream.App/UI/UiChannelMenu.cs

@@ -0,0 +1,109 @@
+using System;
+using System.Numerics;
+using AcDream.UI.Abstractions;
+
+namespace AcDream.App.UI;
+
+/// <summary>
+/// Chat channel selector (the "Chat ▸" button). Port of retail
+/// <c>UIElement_Menu</c> as used by <c>gmMainChatUI::InitTalkFocusMenu @0x4cdc50</c>:
+/// a button whose label is the active channel; clicking opens a popup of channels;
+/// selecting one calls <c>SetTalkFocus</c> (here: <see cref="OnChannelChanged"/>).
+/// </summary>
+public sealed class UiChannelMenu : UiElement
+{
+    public readonly record struct Item(string Label, ChatChannelKind Channel);
+
+    /// <summary>Retail talk-focus channels (subset acdream's ChatInputParser routes).</summary>
+    public static readonly Item[] Channels =
+    {
+        new("Say", ChatChannelKind.Say),
+        new("General", ChatChannelKind.General),
+        new("Trade", ChatChannelKind.Trade),
+        new("LFG", ChatChannelKind.Lfg),
+        new("Fellowship", ChatChannelKind.Fellowship),
+        new("Allegiance", ChatChannelKind.Allegiance),
+        new("Patron", ChatChannelKind.Patron),
+        new("Vassals", ChatChannelKind.Vassals),
+        new("Monarch", ChatChannelKind.Monarch),
+        new("Roleplay", ChatChannelKind.Roleplay),
+        new("Society", ChatChannelKind.Society),
+        new("Olthoi", ChatChannelKind.Olthoi),
+    };
+
+    public ChatChannelKind Selected { get; private set; } = ChatChannelKind.Say;
+    public Action<ChatChannelKind>? OnChannelChanged { get; set; }
+
+    public UiDatFont? DatFont { get; set; }
+    public AcDream.App.Rendering.BitmapFont? Font { get; set; }
+    public Func<uint, (uint tex, int w, int h)>? SpriteResolve { get; set; }
+    public uint NormalSprite { get; set; }
+    public uint PressedSprite { get; set; }
+    public Vector4 TextColor { get; set; } = new(1f, 0.85f, 0.4f, 1f);
+
+    private bool _open;
+    private const float ItemH = 16f;
+    private const float PopupW = 90f;
+
+    public UiChannelMenu() { CapturesPointerDrag = true; }
+
+    private string Label => FindLabel(Selected);
+    private static string FindLabel(ChatChannelKind k)
+    {
+        foreach (var it in Channels) if (it.Channel == k) return it.Label;
+        return "Chat";
+    }
+
+    protected override void OnDraw(UiRenderContext ctx)
+    {
+        if (SpriteResolve is { } resolve)
+        {
+            var (tex, _, _) = resolve(_open ? PressedSprite : NormalSprite);
+            if (tex != 0) ctx.DrawSprite(tex, 0, 0, Width, Height, 0f, 0f, 1f, 1f, Vector4.One);
+        }
+        DrawLabel(ctx, Label + " >", 2f, (Height - LineH()) * 0.5f);
+
+        if (_open)
+        {
+            float h = Channels.Length * ItemH;
+            float top = -h;   // popup opens UPWARD (chat sits at screen bottom)
+            ctx.DrawRect(0, top, MathF.Max(Width, PopupW), h, new(0f, 0f, 0f, 0.85f));
+            for (int i = 0; i < Channels.Length; i++)
+                DrawLabel(ctx, Channels[i].Label, 2f, top + i * ItemH);
+        }
+    }
+
+    private float LineH() => DatFont?.LineHeight ?? Font?.LineHeight ?? 14f;
+    private void DrawLabel(UiRenderContext ctx, string s, float x, float y)
+    {
+        if (DatFont is { } df) ctx.DrawStringDat(df, s, x, y, TextColor);
+        else ctx.DrawString(s, x, y, TextColor, Font);
+    }
+
+    protected override bool OnHitTest(float lx, float ly)
+        => _open ? (lx >= 0 && lx < MathF.Max(Width, PopupW)
+                    && ly >= -Channels.Length * ItemH && ly < Height)
+                 : base.OnHitTest(lx, ly);
+
+    public override bool OnEvent(in UiEvent e)
+    {
+        if (e.Type == UiEventType.MouseDown)
+        {
+            float ly = e.Data2;
+            if (_open && ly < 0)
+            {
+                int idx = (int)((ly + Channels.Length * ItemH) / ItemH);
+                if (idx >= 0 && idx < Channels.Length)
+                {
+                    Selected = Channels[idx].Channel;
+                    OnChannelChanged?.Invoke(Selected);
+                }
+                _open = false;
+                return true;
+            }
+            _open = !_open;
+            return true;
+        }
+        return false;
+    }
+}

tests/AcDream.App.Tests/UI/UiChannelMenuTests.cs

@@ -0,0 +1,76 @@
+using AcDream.App.UI;
+using AcDream.UI.Abstractions;
+
+namespace AcDream.App.Tests.UI;
+
+public class UiChannelMenuTests
+{
+    [Fact]
+    public void Channels_HasExpected12Entries()
+    {
+        Assert.Equal(12, UiChannelMenu.Channels.Length);
+    }
+
+    [Fact]
+    public void Channels_FirstEntry_IsSay()
+    {
+        Assert.Equal(ChatChannelKind.Say, UiChannelMenu.Channels[0].Channel);
+        Assert.Equal("Say", UiChannelMenu.Channels[0].Label);
+    }
+
+    [Fact]
+    public void Channels_LastEntry_IsOlthoi()
+    {
+        var last = UiChannelMenu.Channels[^1];
+        Assert.Equal(ChatChannelKind.Olthoi, last.Channel);
+        Assert.Equal("Olthoi", last.Label);
+    }
+
+    [Fact]
+    public void Channels_ContainsAllExpectedKinds()
+    {
+        var kinds = new HashSet<ChatChannelKind>(UiChannelMenu.Channels.Select(c => c.Channel));
+        Assert.Contains(ChatChannelKind.Say, kinds);
+        Assert.Contains(ChatChannelKind.General, kinds);
+        Assert.Contains(ChatChannelKind.Trade, kinds);
+        Assert.Contains(ChatChannelKind.Lfg, kinds);
+        Assert.Contains(ChatChannelKind.Fellowship, kinds);
+        Assert.Contains(ChatChannelKind.Allegiance, kinds);
+        Assert.Contains(ChatChannelKind.Patron, kinds);
+        Assert.Contains(ChatChannelKind.Vassals, kinds);
+        Assert.Contains(ChatChannelKind.Monarch, kinds);
+        Assert.Contains(ChatChannelKind.Roleplay, kinds);
+        Assert.Contains(ChatChannelKind.Society, kinds);
+        Assert.Contains(ChatChannelKind.Olthoi, kinds);
+    }
+
+    [Fact]
+    public void DefaultSelected_IsSay()
+    {
+        var menu = new UiChannelMenu();
+        Assert.Equal(ChatChannelKind.Say, menu.Selected);
+    }
+
+    [Fact]
+    public void OnChannelChanged_FiredWhenSelectionMadeViaEvent()
+    {
+        var menu = new UiChannelMenu { Width = 80f, Height = 18f };
+
+        // Open the popup (click inside the button area — Data2 >= 0).
+        var openEvt = new UiEvent(0, menu, UiEventType.MouseDown, 0, 10, 5);
+        Assert.True(menu.OnEvent(openEvt));
+
+        // Click on the second item (General) in the upward popup.
+        // Popup renders UPWARD: top = -(12 * 16) = -192.
+        // Item i=1 (General) occupies y in [-192 + 16, -192 + 32) = [-176, -160).
+        // A click at ly = -176 + 8 = -168 hits item index = (int)((-168 + 192) / 16) = (int)(24/16) = 1.
+        ChatChannelKind? fired = null;
+        menu.OnChannelChanged = k => fired = k;
+
+        var selectEvt = new UiEvent(0, menu, UiEventType.MouseDown, 0, 10, -168);
+        Assert.True(menu.OnEvent(selectEvt));
+
+        Assert.Equal(ChatChannelKind.General, fired);
+        Assert.Equal(ChatChannelKind.General, menu.Selected);
+    }
+}