Click-through decides whether to swallow the mouse by hit-testing the document
under the cursor, and it learns where the cursor is from mousemove. Those keep
arriving while the window ignores the mouse only because of
`setIgnoreMouseEvents(true, { forward: true })`, and `forward` is
`@platform darwin,win32`. On Linux the moves stop the instant the HUD turns
click-through, so it never sees the pointer return to the bar: the bar is
visible, and clicking it hits whatever is behind.
Main can still see the cursor, so on Linux it polls and pushes the position to
the renderer, which runs its usual hit test on it. The decision and its rules
stay in one place — only the courier for that one input changes — and off-window
is sent as null, which is already how the renderer hands the mouse back.
Brooklyn Nicholson