Offset start of distance snap grid drawing if reference object's start time doesn't align

Closes ppy#20938.

Author: peppy

osu.Game/Screens/Edit/Compose/Components/CircularDistanceSnapGrid.cs

@@ -53,9 +53,16 @@ protected override void CreateContent()
             float maxDistance = new Vector2(dx, dy).Length;
             int requiredCircles = Math.Min(MaxIntervals, (int)(maxDistance / DistanceBetweenTicks));
 
+            // We need to offset the drawn lines to the next valid snap for the currently selected divisor.
+            //
+            // Picture the scenario where the user has just placed an object on a 1/2 snap, then changes to
+            // 1/3 snap and expects to be able to place the next object on a valid 1/3 snap, regardless of the
+            // fact that the 1/2 snap reference object is not valid for 1/3 snapping.
+            float offset = SnapProvider.FindSnappedDistance(ReferenceObject, 0);
+
             for (int i = 0; i < requiredCircles; i++)
             {
-                float diameter = (i + 1) * DistanceBetweenTicks * 2;
+                float diameter = (offset + (i + 1) * DistanceBetweenTicks) * 2;
 
                 AddInternal(new Ring(ReferenceObject, GetColourForIndexFromPlacement(i))
                 {