emacs: Scrolling
14.1 Scrolling
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If a window is too small to display all the text in its buffer, it
displays only a portion of it. “Scrolling” commands change which
portion of the buffer is displayed.
Scrolling forward or up advances the portion of the buffer displayed
in the window; equivalently, it moves the buffer text upwards relative
to the window. Scrolling backward or down displays an earlier portion
of the buffer, and moves the text downwards relative to the window.
In Emacs, scrolling up or down refers to the direction that the text
moves in the window, _not_ the direction that the window moves relative
to the text. This terminology was adopted by Emacs before the modern
meaning of “scrolling up” and “scrolling down” became widespread.
Hence, the strange result that <PageDown> scrolls up in the Emacs sense.
The portion of a buffer displayed in a window always contains point.
If you move point past the bottom or top of the window, scrolling occurs
automatically to bring it back onscreen (
Auto Scrolling). You
can also scroll explicitly with these commands:
‘C-v’
‘<next>’
‘<PageDown>’
Scroll forward by nearly a full window (‘scroll-up-command’).
‘M-v’
‘<prior>’
‘<PageUp>’
Scroll backward (‘scroll-down-command’).
‘C-v’ (‘scroll-up-command’) scrolls forward by nearly the whole
window height. The effect is to take the two lines at the bottom of the
window and put them at the top, followed by lines that were not
previously visible. If point was in the text that scrolled off the top,
it ends up on the window’s new topmost line. The <next> (or <PageDown>)
key is equivalent to ‘C-v’.
‘M-v’ (‘scroll-down-command’) scrolls backward in a similar way. The
<prior> (or <PageUp>) key is equivalent to ‘M-v’.
The number of lines of overlap left by these scroll commands is
controlled by the variable ‘next-screen-context-lines’, whose default
value is 2. You can supply the commands with a numeric prefix argument,
N, to scroll by N lines; Emacs attempts to leave point unchanged, so
that the text and point move up or down together. ‘C-v’ with a negative
argument is like ‘M-v’ and vice versa.
By default, these commands signal an error (by beeping or flashing
the screen) if no more scrolling is possible, because the window has
reached the beginning or end of the buffer. If you change the variable
‘scroll-error-top-bottom’ to ‘t’, the command moves point to the
farthest possible position. If point is already there, the command
signals an error.
Some users like scroll commands to keep point at the same screen
position, so that scrolling back to the same screen conveniently returns
point to its original position. You can enable this behavior via the
variable ‘scroll-preserve-screen-position’. If the value is ‘t’, Emacs
adjusts point to keep the cursor at the same screen position whenever a
scroll command moves it off-window, rather than moving it to the topmost
or bottommost line. With any other non-‘nil’ value, Emacs adjusts point
this way even if the scroll command leaves point in the window. This
variable affects all the scroll commands documented in this section, as
well as scrolling with the mouse wheel (Mouse Commands); in
general, it affects any command that has a non-‘nil’ ‘scroll-command’
property. (elisp)Property Lists.
Sometimes, particularly when you hold down keys such as ‘C-v’ and
‘M-v’, activating keyboard auto-repeat, Emacs fails to keep up with the
rapid rate of scrolling requested; the display doesn’t update and Emacs
can become unresponsive to input for quite a long time. You can counter
this sluggishness by setting the variable ‘fast-but-imprecise-scrolling’
to a non-‘nil’ value. This instructs the scrolling commands not to
fontify (Font Lock) any unfontified text they scroll over,
instead to assume it has the default face. This can cause Emacs to
scroll to somewhat wrong buffer positions when the faces in use are not
all the same size, even with single (i.e., without auto-repeat)
scrolling operations.
The commands ‘M-x scroll-up’ and ‘M-x scroll-down’ behave similarly
to ‘scroll-up-command’ and ‘scroll-down-command’, except they do not
obey ‘scroll-error-top-bottom’. Prior to Emacs 24, these were the
default commands for scrolling up and down. The commands ‘M-x
scroll-up-line’ and ‘M-x scroll-down-line’ scroll the current window by
one line at a time. If you intend to use any of these commands, you
might want to give them key bindings (Init Rebinding).
Info Catalog
emacs: Display
emacs: Recentering