增加Ring的radiusGradient参数设置渐变方向

Runtime/Serie/Ring/Ring.cs

@@ -9,7 +9,20 @@ namespace XCharts.Runtime
     [SerieDataExtraField()]
     public class Ring : Serie
     {
+        [SerializeField][Since("v3.12.0")] private bool m_RadiusGradient = false;
+
+        /// <summary>
+        /// Whether to use gradient color in pie chart.
+        /// || 是否开启半径方向的渐变效果。
+        /// </summary>
+        public bool radiusGradient
+        {
+            get { return m_RadiusGradient; }
+            set { if (PropertyUtil.SetStruct(ref m_RadiusGradient, value)) { SetVerticesDirty(); } }
+        }
+
         public override SerieColorBy defaultColorBy { get { return SerieColorBy.Data; } }
+
         public static Serie AddDefaultSerie(BaseChart chart, string serieName)
         {
             var serie = chart.AddSerie<Ring>(serieName);

Runtime/Serie/Ring/RingHandler.cs

@@ -162,7 +162,7 @@ namespace XCharts.Runtime
                 DrawBackground(vh, serie, serieData, j, insideRadius, outsideRadius);
                 UGL.DrawDoughnut(vh, serie.context.center, insideRadius, outsideRadius, itemColor, itemToColor,
                     Color.clear, startDegree, toDegree, borderWidth, borderColor, 0, chart.settings.cicleSmoothness,
-                    roundCap, serie.clockwise);
+                    roundCap, serie.clockwise, serie.radiusGradient);
                 DrawCenter(vh, serie, serieData, insideRadius, j == data.Count - 1);
             }