gfx/accessibility.h

The vocabulary -- roles, names, values, ranges -- is in accessible_info.h, which Component includes so it can declare accessibleInfo(). This is the traversal, which needs Components and so cannot live there.

Everything here is testable against a component tree with no window at all. That is the reason for the split: the platform bridges are the part that cannot be tested on this machine, and they should be a mechanical mapping from this rather than a second source of truth about what a knob is called.

One table, every platform

What each role is called on each platform lives in ONE table below, read by both bridges: uia_win32.h for UI Automation's control type, and accessibility_mac.h for NSAccessibility's role, subrole and how the value is read. Two switch statements in two files are two answers to "what is a combo box", and the second platform would drift from the first without anything noticing; one row per role is a thing a test can walk.

The rest of what the macOS bridge decides -- which change to announce, which element survives a rebuild, where a rectangle is on a y-up screen -- is here too, in detail, because it is arithmetic and bookkeeping that runs on any machine. The bridge that cannot be run here is left holding only the calls into AppKit.