** Only one of the beginning or end of an invisible, intangible region is
considered an acceptable value for point; which one is determined by
examining how the invisible/intangible properties are inherited when new
-text is inserted adjacent to them. If text inserted at the beginning would
-inherit the invisible/intangible properties, then that position is
-considered unacceptable, and point is forced to the position following the
-invisible/intangible text. If text inserted at the end would inherit the
-properties, then the opposite happens.
+text is inserted adjacent to them. (The `front-sticky' and `rear-sticky'
+properties control this.)
+
+If the invisible/intangible would be inherited by any text inserted
+before this region, then the position before it is considered
+unacceptable, and point is forced to continue (if moving forwards, to
+the position following the invisible/intangible text; if moving
+backwards, to one position before). If the properties would be
+inherited by any text inserted after, then the position after is
+considered unacceptable, and point is forced to keep moving (if moving
+backwards, to the position preceding the invisible/intangible text; if
+moving forwards, to one position later).
Thus, point can only go to one end of an invisible, intangible region, but
not the other one. This prevents C-f and C-b from appearing to stand still
on the screen.
+You should not set it up so that both the position before and the position
+after are unacceptable.
+
** field-beginning and field-end now accept an additional optional
argument, LIMIT.