feat(D.2b): vital bars use retail dat sprites (back track + fill-cropped front)

UiMeter gains SpriteResolve/BackSpriteId/FrontSpriteId; when both are
set, OnDraw draws the empty-track sprite full-width then the colored-fill
sprite UV-cropped to the live fill fraction (left-to-right drain). Falls
back to solid rects when sprite ids are absent, keeping existing behavior
and tests intact.

MarkupDocument.Build() parses `back`/`front` hex attrs on <meter> and
passes `resolve` into every UiMeter.  vitals.xml wires the authoritative
LayoutDesc 0x21000014 sprites (Health 0x06005F3C/3D, Stamina 3E/3F,
Mana 40/41).  The bar prove-out block in GameWindow.cs was already gone.

If the sprites decode as 1x1 magenta at runtime they are paletted
(INDEX16/P8) — the solid-color fallback will display instead and can be
investigated separately.

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

src/AcDream.App/UI/MarkupDocument.cs

@@ -58,14 +58,17 @@ public static class MarkupDocument
                     var max = BindUint((string?)el.Attribute("max"), binding);
                     panel.AddChild(new UiMeter
                     {
-                        Left     = F(el, "x"),
+                        Left          = F(el, "x"),
-                        Top      = F(el, "y"),
+                        Top           = F(el, "y"),
-                        Width    = F(el, "w"),
+                        Width         = F(el, "w"),
-                        Height   = F(el, "h"),
+                        Height        = F(el, "h"),
-                        BarColor = Color((string?)el.Attribute("color")),
+                        BarColor      = Color((string?)el.Attribute("color")),
-                        Fill     = BindFloat((string?)el.Attribute("fill"), binding),
+                        Fill          = BindFloat((string?)el.Attribute("fill"), binding),
-                        Label    = () => (cur(), max()) is (uint c, uint m) ? $"{c}/{m}" : null,
+                        Label         = () => (cur(), max()) is (uint c, uint m) ? $"{c}/{m}" : null,
-                        Anchors  = Anchor((string?)el.Attribute("anchor")),
+                        Anchors       = Anchor((string?)el.Attribute("anchor")),
+                        SpriteResolve = resolve,
+                        BackSpriteId  = Hex((string?)el.Attribute("back")),
+                        FrontSpriteId = Hex((string?)el.Attribute("front")),
                     });
                     break;
                 // future element kinds (label, button, image) added here
@@ -125,6 +128,15 @@ public static class MarkupDocument
         return binding.GetType().GetProperty(expr[1..^1]);
     }
 
+    private static uint Hex(string? s)
+    {
+        if (string.IsNullOrWhiteSpace(s)) return 0;
+        var t = s.Trim();
+        if (t.StartsWith("0x", System.StringComparison.OrdinalIgnoreCase)) t = t[2..];
+        return uint.TryParse(t, System.Globalization.NumberStyles.HexNumber,
+            System.Globalization.CultureInfo.InvariantCulture, out var v) ? v : 0u;
+    }
+
     private static AnchorEdges Anchor(string? csv)
     {
         if (string.IsNullOrWhiteSpace(csv)) return AnchorEdges.Left | AnchorEdges.Top;

src/AcDream.App/UI/UiMeter.cs

@@ -24,6 +24,14 @@ public sealed class UiMeter : UiElement
     public Vector4 BgColor { get; set; } = new(0f, 0f, 0f, 0.5f);
     public Vector4 LabelColor { get; set; } = new(1f, 1f, 1f, 1f);
 
+    /// <summary>Resolver from a RenderSurface DataId to (GL handle, w, h). When set
+    /// with Back/Front sprite ids, the bar draws the retail sprites instead of solid color.</summary>
+    public Func<uint, (uint tex, int w, int h)>? SpriteResolve { get; set; }
+    /// <summary>Empty-track sprite (drawn full width). 0 = none.</summary>
+    public uint BackSpriteId { get; set; }
+    /// <summary>Colored-fill sprite (drawn cropped to the fill fraction). 0 = none.</summary>
+    public uint FrontSpriteId { get; set; }
+
     public UiMeter() { ClickThrough = true; }
 
     /// <summary>Clamp <paramref name="pct"/> to [0,1] and return the fill rect
@@ -38,13 +46,32 @@ public sealed class UiMeter : UiElement
 
     protected override void OnDraw(UiRenderContext ctx)
     {
-        ctx.DrawRect(0, 0, Width, Height, BgColor);
-
         float? pct = Fill();
-        if (pct is float p)
+        float p = pct is float pf ? (pf < 0f ? 0f : pf > 1f ? 1f : pf) : 0f;
+
+        if (SpriteResolve is { } resolve && (BackSpriteId != 0 || FrontSpriteId != 0))
         {
-            var (fx, fy, fw, fh) = ComputeFillRect(p, Width, Height);
+            // Retail bar: empty track full width, colored fill cropped to p (left→right).
-            if (fw > 0f) ctx.DrawRect(fx, fy, fw, fh, BarColor);
+            if (BackSpriteId != 0)
+            {
+                var (bt, _, _) = resolve(BackSpriteId);
+                if (bt != 0) ctx.DrawSprite(bt, 0, 0, Width, Height, 0, 0, 1, 1, Vector4.One);
+            }
+            if (FrontSpriteId != 0 && pct is not null && p > 0f)
+            {
+                var (ft, _, _) = resolve(FrontSpriteId);
+                if (ft != 0) ctx.DrawSprite(ft, 0, 0, Width * p, Height, 0, 0, p, 1, Vector4.One);
+            }
+        }
+        else
+        {
+            // Placeholder solid-color fallback.
+            ctx.DrawRect(0, 0, Width, Height, BgColor);
+            if (pct is not null && p > 0f)
+            {
+                var (fx, fy, fw, fh) = ComputeFillRect(p, Width, Height);
+                if (fw > 0f) ctx.DrawRect(fx, fy, fw, fh, BarColor);
+            }
         }
 
         string? label = Label();

src/AcDream.App/UI/assets/vitals.xml

@@ -1,5 +1,5 @@
 <panel id="acdream.vitals" x="10" y="30" w="220" h="96" resize="x">
-  <meter id="health"  x="8" y="24" w="200" h="14" fill="{HealthPercent}"  cur="{HealthCurrent}"  max="{HealthMax}"  color="#FFC70D0D" anchor="left,top,right"/>
+  <meter id="health"  x="8" y="24" w="200" h="14" fill="{HealthPercent}"  cur="{HealthCurrent}"  max="{HealthMax}"  color="#FFC70D0D" anchor="left,top,right" back="0x06005F3C" front="0x06005F3D"/>
-  <meter id="stamina" x="8" y="44" w="200" h="14" fill="{StaminaPercent}" cur="{StaminaCurrent}" max="{StaminaMax}" color="#FFD49E1F" anchor="left,top,right"/>
+  <meter id="stamina" x="8" y="44" w="200" h="14" fill="{StaminaPercent}" cur="{StaminaCurrent}" max="{StaminaMax}" color="#FFD49E1F" anchor="left,top,right" back="0x06005F3E" front="0x06005F3F"/>
-  <meter id="mana"    x="8" y="64" w="200" h="14" fill="{ManaPercent}"    cur="{ManaCurrent}"    max="{ManaMax}"    color="#FF1F33D9" anchor="left,top,right"/>
+  <meter id="mana"    x="8" y="64" w="200" h="14" fill="{ManaPercent}"    cur="{ManaCurrent}"    max="{ManaMax}"    color="#FF1F33D9" anchor="left,top,right" back="0x06005F40" front="0x06005F41"/>
 </panel>

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

@@ -56,4 +56,17 @@ public class MarkupDocumentTests
         Assert.True(panel.ResizeX);
         Assert.False(panel.ResizeY);
     }
+
+    [Fact]
+    public void Build_ParsesBackFrontSpriteIds()
+    {
+        const string xml = "<panel id=\"v\" x=\"0\" y=\"0\" w=\"100\" h=\"50\" title=\"V\">" +
+            "<meter id=\"h\" x=\"0\" y=\"0\" w=\"100\" h=\"14\" fill=\"{HealthPercent}\" back=\"0x06005F3C\" front=\"0x06005F3D\"/>" +
+            "</panel>";
+        var panel = MarkupDocument.Build(xml, new FakeBinding(), _ => ((uint)7, 32, 32));
+        var meter = Assert.IsType<UiMeter>(panel.Children[1]);
+        Assert.Equal(0x06005F3Cu, meter.BackSpriteId);
+        Assert.Equal(0x06005F3Du, meter.FrontSpriteId);
+        Assert.NotNull(meter.SpriteResolve);
+    }
 }