NSRulerView's background color and transparency (macOS 26)

When I compiled my legacy project with Tahoe's macOS 26 SDK, NSRulerViews are showing a very different design:

Under prior macOS versions the horizontal and verrical ruler's background were blurring the content view, which was extending under the rulers, showing through their transparency.

With Tahoe the horizontal ruler is always reflecting the scrollview's background color, showing the blurred content view beneath.

And the vertical ruler is always completely transparent (without any blurring), showing the content together with the ruler's markers and ticks.

It's difficult to describe, I'll try to replicate this behavior with a minimal test project, and probably file a bug report / enhancement request.

But before I take next steps, can anyone confirm this observation? Maybe it is an intentional design decision by Apple?

Okay, let's try to sort this out a bit - I was confused facing a couple of different issues:

  • NSRulerViews are showing inconsistent Backgrounds: With macOS 26 NSRulerViews are showing a very different layout, not only in contrast to prior macOS versions, but also inconsistent between horizontal and vertical rulers. I filed a corresponding bug report (FB20342342)

    • The horizontal ruler view is showing with a solid color. I assume the color is selected based on the first line of the inner view, because with a transparent content view the scrollview's background color is used, otherwise the content view's background color.
    • The vertical ruler view is using a much lighter or transparent version of the content view's background, what I would consider the intended (and expected) behavior.
  • NSRulerView is obscuring content in full screen: Custom apps are facing an incorrect behavior of NSRulerViews when running in full screen: The height of the horizontal ruler is increased, obscuring the top of the clipview. I observed this issue with one of my apps, but was able to replicate it with a minimal sample app, using a scrollable text view with rulers, refer to the attached screenshots. Again, I files a bug report (FB20342122)

Window mode:

Full Screen:

NSRulerView's background color and transparency (macOS 26)
 
 
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