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Since only part of a large buffer fits in the window, XEmacs tries to show the part that is likely to be interesting. The display control commands allow you to specify which part of the text you want to see.
Clear frame and redisplay, scrolling the selected window to center
point vertically within it (recenter
).
Scroll forward (a windowful or a specified number of lines) (scroll-up
).
On most X keyboards, you can get this functionality using the key
labelled ‘Page Down’, which generates either next or pgdn.
Scroll backward (scroll-down
). On most X keyboards, you can get
this functionality using the key labelled ‘Page Up’, which
generates either prior or pgup.
Scroll so point is on line arg (recenter
).
Scroll text in current window to the left (scroll-left
).
Scroll to the right (scroll-right
).
Make deeply indented lines invisible (set-selective-display
).
11.1 Scrolling | Moving text up and down in a window. | |
11.2 Horizontal Scrolling | Moving text left and right in a window. | |
11.3 Selective Display | Hiding lines with lots of indentation. | |
11.4 Variables Controlling Display | Information on variables for customizing display. |
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If a buffer contains text that is too large to fit entirely within the window that is displaying the buffer, XEmacs shows a contiguous section of the text. The section shown always contains point.
Scrolling means moving text up or down in the window so that different parts of the text are visible. Scrolling forward means that text moves up, and new text appears at the bottom. Scrolling backward moves text down and new text appears at the top.
Scrolling happens automatically if you move point past the bottom or top of the window. You can also explicitly request scrolling with the commands in this section.
The most basic scrolling command is C-l (recenter
) with no
argument. It clears the entire frame and redisplays all windows. In
addition, it scrolls the selected window so that point is halfway down
from the top of the window.
The scrolling commands C-v and M-v let you move all the text
in the window up or down a few lines. C-v (scroll-up
) with an
argument shows you that many more lines at the bottom of the window, moving
the text and point up together as C-l might. C-v with a
negative argument shows you more lines at the top of the window.
Meta-v (scroll-down
) is like C-v, but moves in the
opposite direction.
To read the buffer a windowful at a time, use C-v with no
argument. C-v takes the last two lines at the bottom of the
window and puts them at the top, followed by nearly a whole windowful of
lines not previously visible. Point moves to the new top of the window
if it was in the text scrolled off the top. M-v with no argument
moves backward with similar overlap. The number of lines of overlap
across a C-v or M-v is controlled by the variable
next-screen-context-lines
; by default, it is two.
Another way to scroll is using C-l with a numeric argument. C-l does not clear the frame when given an argument; it only scrolls the selected window. With a positive argument n, C-l repositions text to put point n lines down from the top. An argument of zero puts point on the very top line. Point does not move with respect to the text; rather, the text and point move rigidly on the frame. C-l with a negative argument puts point that many lines from the bottom of the window. For example, C-u - 1 C-l puts point on the bottom line, and C-u - 5 C-l puts it five lines from the bottom. Just C-u as argument, as in C-u C-l, scrolls point to the center of the frame.
Scrolling happens automatically if point has moved out of the visible
portion of the text when it is time to display. Usually scrolling is
done to put point vertically centered within the window. However, if
the variable scroll-step
has a non-zero value, an attempt is made to
scroll the buffer by that many lines; if that is enough to bring point back
into visibility, that is what happens.
Scrolling happens automatically if point has moved out of the visible
portion of the text when it is time to display. Usually scrolling is
done to put point vertically centered within the window. However, if
the variable scroll-step
has a non-zero value, an attempt is made to
scroll the buffer by that many lines; if that is enough to bring point back
into visibility, that is what happens.
If you set scroll-step
to a small value because you want to use
arrow keys to scroll the screen without recentering, the redisplay
preemption will likely make XEmacs keep recentering the screen when
scrolling fast, regardless of scroll-step
. To prevent this, set
scroll-conservatively
to a small value, which will have the
result of overriding the redisplay preemption.
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The text in a window can also be scrolled horizontally. This means that each line of text is shifted sideways in the window, and one or more characters at the beginning of each line are not displayed at all. When a window has been scrolled horizontally in this way, text lines are truncated rather than continued (see section Continuation Lines), with a ‘$’ appearing in the first column when there is text truncated to the left, and in the last column when there is text truncated to the right.
The command C-x < (scroll-left
) scrolls the selected
window to the left by n columns with argument n. With no
argument, it scrolls by almost the full width of the window (two columns
less, to be precise). C-x > (scroll-right
) scrolls
similarly to the right. The window cannot be scrolled any farther to
the right once it is displaying normally (with each line starting at the
window’s left margin); attempting to do so has no effect.
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XEmacs can hide lines indented more than a certain number of columns (you specify how many columns). This allows you to get an overview of a part of a program.
To hide lines, type C-x $ (set-selective-display
) with a
numeric argument n. (See section Numeric Arguments, for information on giving
the argument.) Lines with at least n columns of indentation
disappear from the screen. The only indication of their presence are
three dots (‘…’), which appear at the end of each visible
line that is followed by one or more invisible ones.
The invisible lines are still present in the buffer, and most editing commands see them as usual, so it is very easy to put point in the middle of invisible text. When this happens, the cursor appears at the end of the previous line, after the three dots. If point is at the end of the visible line, before the newline that ends it, the cursor appears before the three dots.
The commands C-n and C-p move across the invisible lines as if they were not there.
To make everything visible again, type C-x $ with no argument.
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This section contains information for customization only. Beginning users should skip it.
When you reenter XEmacs after suspending, XEmacs normally clears the
screen and redraws the entire display. On some terminals with more than
one page of memory, it is possible to arrange the termcap entry so that
the ‘ti’ and ‘te’ strings (output to the terminal when XEmacs
is entered and exited, respectively) switch between pages of memory so
as to use one page for XEmacs and another page for other output. In that
case, you might want to set the variable no-redraw-on-reenter
to
non-nil
so that XEmacs will assume, when resumed, that the screen
page it is using still contains what XEmacs last wrote there.
The variable 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. See section The Echo Area.
If the variable ctl-arrow
is nil
, control characters in the
buffer are displayed with octal escape sequences, all except newline and
tab. If its value is t
, then control characters will be printed
with an up-arrow, for example ^A.
If its value is not t
and not nil
, then characters whose
code is greater than 160 (that is, the space character (32) with its
high bit set) will be assumed to be printable, and will be displayed
without alteration. This is the default when running under X Windows,
since XEmacs assumes an ISO/8859-1 character set (also known as
“Latin1”). The ctl-arrow
variable may also be set to an
integer, in which case all characters whose codes are greater than or
equal to that value will be assumed to be printable.
Altering the value of ctl-arrow
makes it local to the current
buffer; until that time, the default value is in effect. See section Local Variables.
Normally, a tab character in the buffer is displayed as whitespace which
extends to the next display tab stop position, and display tab stops come
at intervals equal to eight spaces. The number of spaces per tab is
controlled by the variable tab-width
, which is made local by
changing it, just like ctl-arrow
. Note that how the tab character
in the buffer is displayed has nothing to do with the definition of
<TAB> as a command.
If you set the variable selective-display-ellipses
to nil
,
the three dots at the end of a line that precedes invisible
lines do not appear. There is no visible indication of the invisible lines.
This variable becomes local automatically when set.
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