You can make characters invisible, so that they do not appear on
the screen, with the invisible
property. This can be either a
text property or a property of an overlay.
In the simplest case, any non-nil
invisible
property makes
a character invisible. This is the default case--if you don't alter
the default value of buffer-invisibility-spec
, this is how the
invisibility
property works. This feature is much like selective
display (see section Selective Display), but more general and cleaner.
More generally, you can use the variable buffer-invisibility-spec
to control which values of the invisible
property make text
invisible. This permits you to classify the text into different subsets
in advance, by giving them different invisible
values, and
subsequently make various subsets visible or invisible by changing the
value of buffer-invisibility-spec
.
Controlling visibility with buffer-invisibility-spec
is
especially useful in a program to display the list of entries in a data
base. It permits the implementation of convenient filtering commands to
view just a part of the entries in the data base. Setting this variable
is very fast, much faster than scanning all the text in the buffer
looking for properties to change.
invisible
properties
actually make a character invisible.
t
invisible
property is
non-nil
. This is the default.
atom
invisible
propery value
is atom or if it is a list with atom as a member.
(atom . t)
invisible
propery value
is atom or if it is a list with atom as a member.
Moreover, if this character is at the end of a line and is followed
by a visible newline, it displays an ellipsis.
Ordinarily, commands that operate on text or move point do not care
whether the text is invisible. The user-level line motion commands
explicitly ignore invisible newlines if
line-move-ignore-invisible
is non-nil
, but only because
they are explicitly programmed to do so.
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