@chapter Controlling the Display
Since only part of a large buffer fits in the window, Emacs tries to
-show a part that is likely to be interesting. Display-control commands
-allow you to specify which part of the text you want to see, and how to
-display it.
+show a part that is likely to be interesting. Display-control
+commands allow you to specify which part of the text you want to see,
+and how to display it. Many variables also affect the details of
+redisplay. Unless otherwise stated, the variables described in this
+chapter have their effect by customizing redisplay itself; therefore,
+their values only make a difference at the time of redisplay.
@menu
-* Scrolling:: Moving text up and down in a window.
+* Scrolling:: Commands to move text up and down in a window.
+* Auto Scrolling:: Redisplay scrolls text automatically when needed.
* Horizontal Scrolling:: Moving text left and right in a window.
* Follow Mode:: Follow mode lets two windows scroll as one.
* Faces:: How to change the display style using faces.
@kindex PAGEUP
@findex scroll-up
@findex scroll-down
-@vindex next-screen-context-lines
To read the buffer a windowful at a time, use @kbd{C-v}
(@code{scroll-up}) with no argument. This scrolls forward by nearly
the whole window height. The effect is to take the two lines at the
was in the text that scrolled off the top, it ends up at the new top
of the window.
+@vindex next-screen-context-lines
@kbd{M-v} (@code{scroll-down}) with no argument scrolls backward in
-a similar way, also with overlap. The number of lines of overlap
-across a @kbd{C-v} or @kbd{M-v} is controlled by the variable
-@code{next-screen-context-lines}; by default, it is 2. The function
-keys @key{NEXT} and @key{PRIOR}, or @key{PAGEDOWN} and @key{PAGEUP},
-are equivalent to @kbd{C-v} and @kbd{M-v}.
+a similar way, also with overlap. The number of lines of overlap that
+the @kbd{C-v} or @kbd{M-v} commands leave is controlled by the
+variable @code{next-screen-context-lines}; by default, it is 2. The
+function keys @key{NEXT} and @key{PRIOR}, or @key{PAGEDOWN} and
+@key{PAGEUP}, are equivalent to @kbd{C-v} and @kbd{M-v}.
The commands @kbd{C-v} and @kbd{M-v} with a numeric argument scroll
the text in the selected window up or down a few lines. @kbd{C-v}
Some users like the full-screen scroll commands to keep point at the
same screen line. To enable this behavior, set the variable
@code{scroll-preserve-screen-position} to a non-@code{nil} value. In
-this mode, when scrolling shifts point off the screen, or into the
-scrolling margins, Emacs moves point to keep the same vertical
-position within the window. This mode is convenient for browsing
-through a file by scrolling by screenfuls; if you come back to the
-screen where you started, point goes back to the line where it
-started. However, this mode is inconvenient when you move to the next
-screen in order to move point to the text there.
+this mode, when these commands would scroll the text around point off
+the screen, or within @code{scroll-margin} lines of the edge, they
+moves point to keep the same vertical position within the window.
+This mode is convenient for browsing through a file by scrolling by
+screenfuls; if you come back to the screen where you started, point
+goes back to the line where it started. However, this mode is
+inconvenient when you move to the next screen in order to move point
+to the text there.
Another way to do scrolling is with @kbd{C-l} with a numeric argument.
@kbd{C-l} does not clear the screen when given an argument; it only scrolls
the screen. For example, in a Lisp file, this command tries to get the
entire current defun onto the screen if possible.
+@node Auto Scrolling
+@section Automatic Scrolling
+
@vindex scroll-conservatively
- Scrolling happens automatically when point moves out of the visible
-portion of the text. Normally, automatic scrolling centers point
-vertically within the window. However, if you set
-@code{scroll-conservatively} to a small number @var{n}, then if you
-move point just a little off the screen---less than @var{n}
-lines---then Emacs scrolls the text just far enough to bring point
-back on screen. By default, @code{scroll-conservatively} is 0.
+ Redisplay scrolls the buffer automatically when point moves out of
+the visible portion of the text. The purpose of automatic scrolling
+is to make point visible, but you can customize many aspects of how
+this is done.
+
+ Normally, automatic scrolling centers point vertically within the
+window. However, if you set @code{scroll-conservatively} to a small
+number @var{n}, then if you move point just a little off the
+screen---less than @var{n} lines---then Emacs scrolls the text just
+far enough to bring point back on screen. By default,
+@code{scroll-conservatively} is 0.
@cindex aggressive scrolling
@vindex scroll-up-aggressively
This face is used for the prompt strings displayed in the minibuffer.
By default, Emacs automatically adds this face to the value of
@code{minibuffer-prompt-properties}, which is a list of text
-properties used to display the prompt text.
+properties used to display the prompt text. (This variable takes
+effect when you enter the minibuffer.)
@item fringe
@cindex @code{fringe} face
The face for the fringes to the left and right of windows on graphic
(global-font-lock-mode 0)
@end example
+@noindent
+This variable, like all the variables that control Font Lock mode,
+take effect whenever fontification is done; that is, potentially at
+any time.
+
@findex turn-on-font-lock
If you have disabled Global Font Lock mode, you can still enable Font
Lock for specific major modes by adding the function
(@code{hi-lock-write-interactive-patterns}) to have Hi Lock highlight
them.
-This command does nothing if the major mode is a member of the list
-@code{hi-lock-exclude-modes}.
+This command does nothing if the current major mode's symbol is a member
+of the list @code{hi-lock-exclude-modes}.
@end table
@node Fringes
@vindex visible-cursor
Some text terminals offer two different cursors: the normal cursor
and the very visible cursor, where the latter may be e.g. bigger or
-blinking. By default Emacs uses the very visible cursor. Setting the
-variable @code{visible-cursor} to @code{nil} makes it use the
-normal cursor.
+blinking. By default Emacs uses the very visible cursor, and switches
+to it when you start or resume Emacs. If the variable
+@code{visible-cursor} is @code{nil} when Emacs starts or resumes, it
+doesn't switch, so it uses the normal cursor.
@cindex cursor in non-selected windows
@vindex cursor-in-non-selected-windows
@vindex echo-keystrokes
The variable @code{echo-keystrokes} controls the echoing of multi-character
keys; its value is the number of seconds of pause required to cause echoing
-to start, or zero, meaning don't echo at all. @xref{Echo Area}.
+to start, or zero, meaning don't echo at all. The value takes effect when
+there is someting to echo. @xref{Echo Area}.
@cindex truncation
@cindex line truncation, and fringes
the termcap entry so that the @samp{ti} and @samp{te} strings (output
to the terminal when Emacs is entered and exited, respectively) switch
between pages of memory so as to use one page for Emacs and another
-page for other output. Then you might want to set the variable
+page for other output. On such terminals, you might want to set the variable
@code{no-redraw-on-reenter} non-@code{nil}; this tells Emacs to
assume, when resumed, that the screen page it is using still contains
what Emacs last wrote there.