optimze GetVisbleTimelines_DesignMode()

OngekiFumenEditor/Modules/FumenVisualEditor/TGridCalculator.cs

@@ -234,15 +234,8 @@ public static double ConvertAudioTimeToY_PreviewMode(TimeSpan audioTime, FumenVi
 				?? ConvertYToTGrid_DesignMode(minVisibleCanvasY + judgeLineOffsetY, soflans, bpmList, 1);
 
 			var timeSignatures = meterList.GetCachedAllTimeSignatureUniformPositionList(bpmList);
-			var currentTimeSignatureIndex = 0;
 			//快速定位,尽量避免计算完全不用画的timesignature(
-			for (int i = 0; i < timeSignatures.Count; i++)
-			{
-				var cur = timeSignatures[i];
-				if (cur.startTGrid > minVisibleCanvasTGrid)
-					break;
-				currentTimeSignatureIndex = i;
-			}
+			var currentTimeSignatureIndex = timeSignatures.LastOrDefaultIndexByBinarySearch(minVisibleCanvasTGrid, x => x.startTGrid);
 
 			//钦定好要画的起始timeSignatrue
 			(TimeSpan audioTime, TGrid startTGrid, MeterChange meter, BPMChange bpm) currentTimeSignature = timeSignatures[currentTimeSignatureIndex];

OngekiFumenEditor/Utils/LinqExtensionMethod.cs

@@ -356,10 +356,16 @@ private static int BinarySearchBy<T, X>(this IReadOnlyList<T> insertable, X valu
 		/// <param name="keySelect"></param>
 		/// <returns></returns>
 		public static T LastOrDefaultByBinarySearch<T, X>(this IList<T> source, X value, Func<T, X> keySelect) where X : IComparable<X>
+		{
+			var idx = source.LastOrDefaultIndexByBinarySearch(value, keySelect);
+			return source[idx];
+		}
+
+		public static int LastOrDefaultIndexByBinarySearch<T, X>(this IList<T> source, X value, Func<T, X> keySelect) where X : IComparable<X>
 		{
 			var idx = source.BinarySearchBy(value, keySelect);
 			var i = Math.Max(0, idx < 0 ? ((~idx) - 1) : idx);
-			return source[i];
+			return i;
 		}
 
 		public static T LastOrDefaultByBinarySearch<T, X>(this IReadOnlyList<T> source, X value, Func<T, X> keySelect) where X : IComparable<X>