The cursor visibility and the state of relative mouse mode are not consistent on macOS.

Here is a minimal sample: https://github.com/rom1v/sample-relativemouse

Run the app from a console (keep the console visible to read the logs), and press Alt while the SDL window is focused to toggle "relative mouse mode".

It is expected that when relative mouse mode is enabled, the cursor is hidden.

With SDL 2.0.20, it works correctly on Linux.

But on macOS, relative mouse mode and cursor visibility are not consistent: sometimes relative mouse mode is enabled but the cursor is still visible.