Re: moving point over invisible and intangible text

[Richard Stallman]

    line1
    line2
    line3
    line4

    Put point at the end of line3.

    with line2 (including trailing newline) being either invisible or
    intangible, but _not both_, (line-move-to-column 0) takes point to the
    beginning of line3, but with line2 being _both_ invisible and
    intangible (line-move-to-column 0) takes point to the beginning of
    line2.  (Use C-x = if line2 is invisible.)  This seems to explain the
    behavior described by Klaus, given the call to `line-move-to-column'
    in `line-move-finish'.  However, is this behavior of
    `line-move-to-column' to be expected or a bug?

When line2 is both invisible and intangible, point cannot be
put after it.  In other words, point cannot be at the start
if line3.  So point goes to the start of line2.

That is the intended behavior.  In that case, line2 and line3
should be thought of as a single line; the newline after line2,
being invisible and intangible, does not count at all.  So the
bug is in some other part of the line-move code, whatever does
not consistently treat line2 and line3 as one line.

The idea of this is that it would be confusing to allow point to be at
two different positions that look the same on the screen.  So Emacs
allows point to be before the invisible-intangible text, but does
not allow point to be after it.