NSSegmentedControl in darkmode

Yes, I observe this as well when the segmented control overlaps the box (or anything behind in fact).

You could subclass segmentedControl to have a specific draw method where you would set the color (or just the alpha value ?) of unselected cell to what you need:

https://stackoverflow.com/questions/9952308/nssegmentedcontrol-colors

Here is the subclass I used to draw correctly in darkmode as well.

May be you'll have to tweak some constants for origin and size of outlineRect to match perfectly.

I changed NSSegmentedCell type in IB accordingly.

class coloredSegmentedCell: NSSegmentedCell {
  
    override func drawSegment(_ segment: Int, inFrame frame: NSRect, with controlView: NSView) {
      
        super.drawSegment(segment, inFrame: frame,  with:controlView)
        if !self.isSelected(forSegment: segment) {
            let color = NSColor.white
            color.setFill()
            frame.fill()
            var outlineRect = frame
            outlineRect.origin.x -= 0.5
            outlineRect.size.width += 0.5
            outlineRect.origin.y += 0.5
            outlineRect.size.height += 1.0

            let bPath: NSBezierPath = NSBezierPath(rect: outlineRect)
            let borderColor = NSColor.systemGray // lightGray
            borderColor.setStroke()
            bPath.lineWidth = 0.5
            bPath.stroke()
        }
    }
}

Thanks to report if that works for you and close the thread.

Thanks for the suggestion Claude31. I spent some time subclassing NSSegmentedCell and doing my own drawing similar to your example. However it didn't work very well. Unlike you, I just drew a background color and then called 'super' to get the text drawn and to get the same look as the default. After fiddling with modifications to the origin and size, you could still see elements of the horizontal line around the vertical line drawn between the segments. If I made it wider, then the vertical lines were gone. I also needed to draw in the selected segment as you could see the horizontal line when my App was not the "Active" App (the highlighting goes away). And since I used this method in a couple of different places, I found that the "fiddling" needed to be different in each case since the width of the segment and it's associated padding around the text was completely different each instance.

But as part of mucking around, I realized a much easier solution. I just put an NSView behind the NSSegmentedControl and in front of the NSBox. Made it the same width and height as the control (and alignment) and set it's colour to the same as the background around the NSBox. Viola! No more NSBox showing through.

Hope that helps someone else later.

Good trick.

Don't forget to close the thread.