Textual scrolling means moving the text up or down through a
window. It works by changing the window’s display-start location. It
may also change the value of window-point to keep point on the
screen (see Windows and Point).
The basic textual scrolling functions are scroll-up (which
scrolls forward) and scroll-down (which scrolls backward). In
these function names, “up” and “down” refer to the direction of
motion of the buffer text relative to the window. Imagine that the
text is written on a long roll of paper and that the scrolling
commands move the paper up and down. Thus, if you are looking at the
middle of a buffer and repeatedly call scroll-down, you will
eventually see the beginning of the buffer.
Unfortunately, this sometimes causes confusion, because some people tend to think in terms of the opposite convention: they imagine the window moving over text that remains in place, so that “down” commands take you to the end of the buffer. This convention is consistent with fact that such a command is bound to a key named PageDown on modern keyboards.
Textual scrolling functions (aside from scroll-other-window)
have unpredictable results if the current buffer is not the one
displayed in the selected window. See The Current Buffer.
If the window contains a row taller than the height of the window
(for example in the presence of a large image), the scroll functions
will adjust the window’s vertical scroll position to scroll the
partially visible row. Lisp callers can disable this feature by
binding the variable auto-window-vscroll to nil
(see Vertical Fractional Scrolling).
This function scrolls forward by count lines in the selected window.
If count is negative, it scrolls backward instead. If
count is nil (or omitted), the distance scrolled is
next-screen-context-lines lines less than the height of the
window’s body.
If the selected window cannot be scrolled any further, this function
signals an error. Otherwise, it returns nil.
This function scrolls backward by count lines in the selected window.
If count is negative, it scrolls forward instead. In other
respects, it behaves the same way as scroll-up does.
This behaves like scroll-up, except that if the selected window
cannot be scrolled any further and the value of the variable
scroll-error-top-bottom is t, it tries to move to the
end of the buffer instead. If point is already there, it signals an
error.
This behaves like scroll-down, except that if the selected
window cannot be scrolled any further and the value of the variable
scroll-error-top-bottom is t, it tries to move to the
beginning of the buffer instead. If point is already there, it
signals an error.
This function scrolls the text in another window upward count
lines. Negative values of count, or nil, are handled
as in scroll-up.
You can specify which buffer to scroll by setting the variable
other-window-scroll-buffer to a buffer. If that buffer isn’t
already displayed, scroll-other-window displays it in some
window.
When the selected window is the minibuffer, the next window is normally
the leftmost one immediately above it. You can specify a different
window to scroll, when the minibuffer is selected, by setting the variable
minibuffer-scroll-window. This variable has no effect when any
other window is selected. When it is non-nil and the
minibuffer is selected, it takes precedence over
other-window-scroll-buffer. See Definition of minibuffer-scroll-window.
This function scrolls the text in another window downward count
lines. Negative values of count, or nil, are handled as
in scroll-down. In other respects, it behaves the same way as
scroll-other-window does.
If this variable is non-nil, it tells scroll-other-window
which buffer’s window to scroll.
This option specifies the size of the scroll margin—a minimum number of lines between point and the top or bottom of a window. Whenever point gets within this many lines of the top or bottom of the window, redisplay scrolls the text automatically (if possible) to move point out of the margin, closer to the center of the window.
This variable limits the effective value of scroll-margin to a
fraction of the current window line height. For example, if the
current window has 20 lines and maximum-scroll-margin is 0.1,
then the scroll margins will never be larger than 2 lines, no matter
how big scroll-margin is.
maximum-scroll-margin itself has a maximum value of 0.5, which
allows setting margins large to keep the cursor at the middle line of
the window (or two middle lines if the window has an even number of
lines). If it’s set to a larger value (or any value other than a
float between 0.0 and 0.5) then the default value of 0.25 will be used
instead.
This variable controls how scrolling is done automatically when point
moves off the screen (or into the scroll margin). If the value is a
positive integer n, then redisplay scrolls the text up to
n lines in either direction, if that will bring point back into
proper view. This behavior is called conservative scrolling.
Otherwise, scrolling happens in the usual way, under the control of
other variables such as scroll-up-aggressively and
scroll-down-aggressively.
The default value is zero, which means that conservative scrolling never happens.
The value of this variable should be either nil or a fraction
f between 0 and 1. If it is a fraction, that specifies where on
the screen to put point when scrolling down. More precisely, when a
window scrolls down because point is above the window start, the new
start position is chosen to put point f part of the window
height from the top. The larger f, the more aggressive the
scrolling.
A value of nil is equivalent to .5, since its effect is to center
point. This variable automatically becomes buffer-local when set in any
fashion.
Likewise, for scrolling up. The value, f, specifies how far
point should be placed from the bottom of the window; thus, as with
scroll-down-aggressively, a larger value scrolls more
aggressively.
This variable is an older variant of scroll-conservatively.
The difference is that if its value is n, that permits scrolling
only by precisely n lines, not a smaller number. This feature
does not work with scroll-margin. The default value is zero.
If this option is t, whenever a scrolling command moves point
off-window, Emacs tries to adjust point to keep the cursor at its old
vertical position in the window, rather than the window edge.
If the value is non-nil and not t, Emacs adjusts point
to keep the cursor at the same vertical position, even if the
scrolling command didn’t move point off-window.
This option affects all scroll commands that have a non-nil
scroll-command symbol property.
The value of this variable is the number of lines of continuity to
retain when scrolling by full screens. For example, scroll-up
with an argument of nil scrolls so that this many lines at the
bottom of the window appear instead at the top. The default value is
2.
If this option is nil (the default), scroll-up-command
and scroll-down-command simply signal an error when no more
scrolling is possible.
If the value is t, these commands instead move point to the
beginning or end of the buffer (depending on scrolling direction);
only if point is already on that position do they signal an error.
This function scrolls the text in the selected window so that point is displayed at a specified vertical position within the window. It does not move point with respect to the text.
If count is a non-negative number, that puts the line containing point count lines down from the top of the window. If count is a negative number, then it counts upward from the bottom of the window, so that −1 stands for the last usable line in the window.
If count is nil (or a non-nil list),
recenter puts the line containing point in the middle of the
window. If count is nil and redisplay is
non-nil, this function may redraw the frame, according to the
value of recenter-redisplay. Thus, omitting the second
argument can be used to countermand the effect of
recenter-redisplay being non-nil. Interactive calls
pass non-nil for redisplay.
When recenter is called interactively, count is the raw
prefix argument. Thus, typing C-u as the prefix sets the
count to a non-nil list, while typing C-u 4 sets
count to 4, which positions the current line four lines from the
top.
With an argument of zero, recenter positions the current line at
the top of the window. The command recenter-top-bottom offers
a more convenient way to achieve this.
This function is like recenter, except that when the selected
window is part of a group of windows (see Window Group),
recenter-window-group scrolls the entire group. This condition
holds when the buffer local variable
recenter-window-group-function is set to a function. In this
case, recenter-window-group calls the function with the
argument count, then returns its result. The argument
count has the same meaning as in recenter, but with
respect to the entire window group.
If this variable is non-nil, calling recenter with a
nil count argument and non-nil redisplay
argument redraws the frame. The default value is tty, which
means only redraw the frame if it is a tty frame.
This command, which is the default binding for C-l, acts like
recenter, except if called with no argument. In that case,
successive calls place point according to the cycling order defined
by the variable recenter-positions.
This variable controls how recenter-top-bottom behaves when
called with no argument. The default value is (middle top
bottom), which means that successive calls of
recenter-top-bottom with no argument cycle between placing
point at the middle, top, and bottom of the window.