I don't see the hook called for each pixel.  What do you mean?


A second thing I wonder about: the docstring of
`window-scroll-functions' says:

| These functions are called whenever the `window-start' marker is modified,
| either to point into another buffer (e.g. via `set-window-buffer') or another
| place in the same buffer.

Is this correct and complete?  Is the window-start marker modified in
our scenario?  If it is, why do we have to call the hook explicitly?  If
it is not, should we update that marker?


TIA,

Michael.