fix(SV): snapping issues

- unable to snap to first/last item
- droid: invalid snap point calculation with uno impl

src/Uno.UI/UI/Xaml/Controls/ListViewBase/VirtualizingPanelLayout.Android.cs

@@ -2079,17 +2079,16 @@ private IEnumerable<float> GetSnapPointsInner(SnapPointsAlignment alignment)
 
 		private float GetSnapPoint(View view, SnapPointsAlignment alignment)
 		{
-			switch (alignment)
+			var snapPointInPhysical = alignment switch
 			{
-				case SnapPointsAlignment.Near:
-					return ContentOffset + GetChildStartWithMargin(view);
-				case SnapPointsAlignment.Center:
-					return ContentOffset + (GetChildStartWithMargin(view) + GetChildEndWithMargin(view)) / 2f;
-				case SnapPointsAlignment.Far:
-					return ContentOffset + GetChildEndWithMargin(view);
-				default:
-					throw new ArgumentOutOfRangeException(nameof(alignment));
-			}
+				SnapPointsAlignment.Near => ContentOffset + GetChildStartWithMargin(view),
+				SnapPointsAlignment.Center => ContentOffset + (GetChildStartWithMargin(view) + GetChildEndWithMargin(view)) / 2f,
+				SnapPointsAlignment.Far => ContentOffset + GetChildEndWithMargin(view),
+
+				_ => throw new ArgumentOutOfRangeException(nameof(alignment)),
+			};
+
+			return (float)ViewHelper.PhysicalToLogicalPixels(snapPointInPhysical);
 		}
 
 		/// <summary>

src/Uno.UI/UI/Xaml/Controls/ScrollViewer/ScrollViewer.SnapPoints.cs

@@ -385,32 +385,22 @@ private IReadOnlyList<float> CopyMotionSnapPoints(
 						// it doesn't matter so do it for consistency.
 						snapPoint *= zoomFactor;
 
-						var alignedSnapPoint = alignment switch
+						// Adjust snap point to relative(near/center/far) viewport offset, and then
+						// clamp it within valid scroll range.
+						var adjustedOffset = alignment switch
 						{
 							SnapPointsAlignment.Near => snapPoint,
 							SnapPointsAlignment.Center => (float)(snapPoint - viewportDimension / 2),
 							SnapPointsAlignment.Far => (float)(snapPoint - viewportDimension),
 							_ => throw new IndexOutOfRangeException("alignment")
 						};
+						var clampedOffset = (float)Math.Max(0, Math.Min(adjustedOffset, ScrollableWidth));
 
-						var distanceFromFarEdge = (float)(extentDimension - viewportDimension - alignedSnapPoint);
-
-						// With certain scale factors and resolutions the snap points sometimes get pushed out of bounds
-						// by rounding errors, in these cases we need to intervene and return them to the boundary.
-						if (distanceFromFarEdge < 0 &&
-						    distanceFromFarEdge >= (-1.0 * (ScrollViewerSnapPointLocationTolerance * Math.Max(1.0f, zoomFactor))))
-						{
-							alignedSnapPoint = (float)(extentDimension - viewportDimension);
-							distanceFromFarEdge = 0;
-						}
-						if (alignedSnapPoint >= 0 && distanceFromFarEdge >= 0)
+						if (staticZoomFactor == 1.0f)
 						{
-							if (staticZoomFactor == 1.0f)
-							{
-								alignedSnapPoint /= zoomFactor;
-							}
-							result.Add(alignedSnapPoint);
+							clampedOffset /= zoomFactor;
 						}
+						result.Add(clampedOffset);
 					}
 				}
 			}