Decode color drag-pan cursor

engine/Age.Engine.Tests/CurDecoderTests.cs

@@ -22,7 +22,36 @@ public class CurDecoderTests
         Assert.Contains(cursor.Image.Pixels.Where((_, i) => i % 4 == 3), alpha => alpha == 255);
     }
 
+    [Fact]
+    public void HimegariPanCursor_DecodesFourBitPixelsAndHotspot()
+    {
+        var resources = ResourceMap.Load();
+        var entry = resources.ResolveCursor(0x32ce);
+
+        Assert.NotNull(entry);
+        Assert.Equal("CURSOR09.CUR", entry!.Name);
+        var cursor = resources.DecodeCursor(entry);
+
+        Assert.Equal(32, cursor.Image.Width);
+        Assert.Equal(32, cursor.Image.Height);
+        Assert.Equal(16, cursor.HotspotX);
+        Assert.Equal(14, cursor.HotspotY);
+        AssertPixel(cursor.Image, 0, 0, 0, 0, 0, 0);
+        AssertPixel(cursor.Image, 10, 10, 128, 128, 128, 255);
+        AssertPixel(cursor.Image, 12, 24, 0, 0, 128, 255);
+    }
+
     [Fact]
     public void TruncatedCursor_IsRejected()
         => Assert.Throws<InvalidDataException>(() => CurDecoder.Decode(new byte[21], "bad.cur"));
+
+    private static void AssertPixel(RgbaImage image, int x, int y,
+                                    byte r, byte g, byte b, byte a)
+    {
+        int offset = (y * image.Width + x) * 4;
+        Assert.Equal(r, image.Pixels[offset]);
+        Assert.Equal(g, image.Pixels[offset + 1]);
+        Assert.Equal(b, image.Pixels[offset + 2]);
+        Assert.Equal(a, image.Pixels[offset + 3]);
+    }
 }