We experiencing a atypical behavior in our application which is developed in Xamarin.Forms.macOS project.
We are using a custom NSView class which holds the ListViewItems and added a NSView as SubView for Selection (Changing the background color) in it (named as SelectionView) and to draw the border over the item, we have used a four CALayers (left, right, bottom and top) around the it and added it as SubLayers.
When the background color is defined to SelectionView, the color gets applied to view. But the border layers (i.e., CALayers) gets invisible nothing but the SelectionView gets overlapped with the borders. If the SelectionView background color is Transparent, the border layers are shown as expected.
This issue occurs only in macOS sierra version 10.13 and working fine in macOS sierra version 10.11 and 10.12.
On referencing the macOS sierra release notes, they have made a backing layer behavioral change but we could not able to understand it (not sufficient information is there) and no examples or code snippets are found.
Release Notes: https://developer.apple.com/library/archive/releasenotes/AppKit/RN-AppKit/index.html
Dinesh Babu Yadav