>> So now here is the final patch:
>
> For 'window-point-context-set' I'd rather write something like:
>
>   Call function specified by `window-point-context-set-function' for every
>   live window on the selected frame with that window as sole argument and
>   that window's buffer current.  The function called is supposed to return
>   a context of the window's point that can be later used as argument for
>   `window-point-context-use'.  Remember the returned context in the window
>   parameter `context'.

Thanks for the suggestion, this is added in a new patch.

> I still don't get why you use 'with-current-buffer' here.  IIUC usually
> a buffer does not have 'window-point-context-set-function' set and so a
> simple
>
> (buffer-local-value 'window-point-context-set-function (window-buffer w))
>
> should suffice.

Ok, let's use buffer-local-value: