diff options
Diffstat (limited to 'man/display.texi')
| -rw-r--r-- | man/display.texi | 397 |
1 files changed, 397 insertions, 0 deletions
diff --git a/man/display.texi b/man/display.texi new file mode 100644 index 00000000000..9c732014a8c --- /dev/null +++ b/man/display.texi @@ -0,0 +1,397 @@ +@c This is part of the Emacs manual. +@c Copyright (C) 1985, 86, 87, 93, 94, 95, 1997 Free Software Foundation, Inc. +@c See file emacs.texi for copying conditions. +@node Display, Search, Registers, Top +@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. + +@menu +* Scrolling:: Moving text up and down in a window. +* Horizontal Scrolling:: Moving text left and right in a window. +* Follow Mode:: Follow mode lets two windows scroll as one. +* Selective Display:: Hiding lines with lots of indentation. +* Optional Mode Line:: Optional mode line display features. +* Text Display:: How text characters are normally displayed. +* Display Vars:: Information on variables for customizing display. +@end menu + +@node Scrolling +@section Scrolling + + If a buffer contains text that is too large to fit entirely within a +window that is displaying the buffer, Emacs shows a contiguous portion of +the text. The portion shown always contains point. + +@cindex scrolling + @dfn{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. + +@table @kbd +@item C-l +Clear screen and redisplay, scrolling the selected window to center +point vertically within it (@code{recenter}). +@item C-v +Scroll forward (a windowful or a specified number of lines) (@code{scroll-up}). +@item @key{NEXT} +Likewise, scroll forward. +@item M-v +Scroll backward (@code{scroll-down}). +@item @key{PRIOR} +Likewise, scroll backward. +@item @var{arg} C-l +Scroll so point is on line @var{arg} (@code{recenter}). +@item C-M-l +Scroll heuristically to bring useful information onto the screen +(@code{reposition-window}). +@end table + +@kindex C-l +@findex recenter + The most basic scrolling command is @kbd{C-l} (@code{recenter}) with +no argument. It clears the entire screen and redisplays all windows. +In addition, it scrolls the selected window so that point is halfway +down from the top of the window. + +@kindex C-v +@kindex M-v +@kindex NEXT +@kindex PRIOR +@findex scroll-up +@findex scroll-down + The scrolling commands @kbd{C-v} and @kbd{M-v} let you move all the text +in the window up or down a few lines. @kbd{C-v} (@code{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 @kbd{C-l} might. @kbd{C-v} with a +negative argument shows you more lines at the top of the window. +@kbd{M-v} (@code{scroll-down}) is like @kbd{C-v}, but moves in the +opposite direction. The function keys @key{NEXT} and @key{PRIOR} are +equivalent to @kbd{C-v} and @kbd{M-v}. + + The names of scroll commands are based on the direction that the text +moves in the window. Thus, the command to scroll forward is called +@code{scroll-up} because it moves the text upward on the screen. + +@vindex next-screen-context-lines + To read the buffer a windowful at a time, use @kbd{C-v} with no argument. +It 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. If point was in the text scrolled off the top, it moves to the +new top of the window. @kbd{M-v} with no argument moves backward with +overlap similarly. 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. + +@vindex scroll-preserve-screen-position + 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. 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 selected window. With a positive argument @var{n}, it repositions text +to put point @var{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 screen. @kbd{C-l} with a +negative argument puts point that many lines from the bottom of the window. +For example, @kbd{C-u - 1 C-l} puts point on the bottom line, and @kbd{C-u +- 5 C-l} puts it five lines from the bottom. Just @kbd{C-u} as argument, +as in @kbd{C-u C-l}, scrolls point to the center of the selected window. + +@kindex C-M-l +@findex reposition-window + The @kbd{C-M-l} command (@code{reposition-window}) scrolls the current +window heuristically in a way designed to get useful information onto +the screen. For example, in a Lisp file, this command tries to get the +entire current defun onto the screen if possible. + +@vindex scroll-conservatively + Scrolling happens automatically if point has moved out of the visible +portion of the text when it is time to display. 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. + +@vindex scroll-margin + The variable @code{scroll-margin} restricts how close point can come +to the top or bottom of a window. Its value is a number of screen +lines; if point comes within that many lines of the top or bottom of the +window, Emacs recenters the window. By default, @code{scroll-margin} is +0. + +@node Horizontal Scrolling +@section Horizontal Scrolling +@cindex horizontal scrolling + + @dfn{Horizontal scrolling} means shifting all the lines sideways +within a window---so that some of the text near the left margin +is not displayed at all. + +@table @kbd +@item C-x < +Scroll text in current window to the left (@code{scroll-left}). +@item C-x > +Scroll to the right (@code{scroll-right}). +@end table + + When a window has been scrolled horizontally, text lines are truncated +rather than continued (@pxref{Continuation Lines}), with a @samp{$} +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. + +@kindex C-x < +@kindex C-x > +@findex scroll-left +@findex scroll-right + The command @kbd{C-x <} (@code{scroll-left}) scrolls the selected +window to the left by @var{n} columns with argument @var{n}. This moves +part of the beginning of each line off the left edge of the window. +With no argument, it scrolls by almost the full width of the window (two +columns less, to be precise). + + @kbd{C-x >} (@code{scroll-right}) scrolls similarly to the right. The +window cannot be scrolled any farther to the right once it is displayed +normally (with each line starting at the window's left margin); +attempting to do so has no effect. This means that you don't have to +calculate the argument precisely for @w{@kbd{C-x >}}; any sufficiently large +argument will restore the normal display. + +@cindex Hscroll mode +@cindex mode, Hscroll +@findex hscroll-mode + You can request automatic horizontal scrolling by enabling Hscroll +mode. When this mode is enabled, Emacs scrolls a window horizontally +whenever that is necessary to keep point visible and not too far from +the left or right edge. The command to enable or disable this mode is +@kbd{M-x hscroll-mode}. + +@node Follow Mode +@section Follow Mode +@cindex Follow mode +@cindex mode, Follow + + @dfn{Follow mode} is a minor mode that makes two windows showing the +same buffer scroll as one tall ``virtual window.'' To use Follow mode, +go to a frame with just one window, split it into two side-by-side +windows using @kbd{C-x 3}, and then type @kbd{M-x follow-mode}. From +then on, you can edit the buffer in either of the two windows, or scroll +either one; the other window follows it. + + To turn off Follow mode, type @kbd{M-x follow-mode} a second time. + +@node Selective Display +@section Selective Display +@findex set-selective-display +@kindex C-x $ + + Emacs has the ability to hide lines indented more than a certain number +of columns (you specify how many columns). You can use this to get an +overview of a part of a program. + + To hide lines, type @kbd{C-x $} (@code{set-selective-display}) with a +numeric argument @var{n}. Then lines with at least @var{n} columns of +indentation disappear from the screen. The only indication of their +presence is that three dots (@samp{@dots{}}) appear at the end of each +visible line that is followed by one or more hidden ones. + + The commands @kbd{C-n} and @kbd{C-p} move across the hidden lines as +if they were not there. + + The hidden lines are still present in the buffer, and most editing +commands see them as usual, so you may find point in the middle of the +hidden 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. + + To make all lines visible again, type @kbd{C-x $} with no argument. + +@vindex selective-display-ellipses + If you set the variable @code{selective-display-ellipses} to +@code{nil}, the three dots do not appear at the end of a line that +precedes hidden lines. Then there is no visible indication of the +hidden lines. This variable becomes local automatically when set. + +@node Optional Mode Line +@section Optional Mode Line Features + +@cindex Line Number mode +@cindex mode, Line Number +@findex line-number-mode + The current line number of point appears in the mode line when Line +Number mode is enabled. Use the command @kbd{M-x line-number-mode} to +turn this mode on and off; normally it is on. The line number appears +before the buffer percentage @var{pos}, with the letter @samp{L} to +indicate what it is. @xref{Minor Modes}, for more information about +minor modes and about how to use this command. + +@vindex line-number-display-limit + If the buffer is very large (larger than the value of +@code{line-number-display-limit}), then the line number doesn't appear. +Emacs doesn't compute the line number when the buffer is large, because +that would be too slow. If you have narrowed the buffer +(@pxref{Narrowing}), the displayed line number is relative to the +accessible portion of the buffer. + +@cindex Column Number mode +@cindex mode, Column Number +@findex column-number-mode + You can also display the current column number by turning on Column +Number mode. It displays the current column number preceded by the +letter @samp{C}. Type @kbd{M-x column-number-mode} to toggle this mode. + +@findex display-time +@cindex time (on mode line) + Emacs can optionally display the time and system load in all mode +lines. To enable this feature, type @kbd{M-x display-time}. The +information added to the mode line usually appears after the buffer +name, before the mode names and their parentheses. It looks like this: + +@example +@var{hh}:@var{mm}pm @var{l.ll} +@end example + +@noindent +@vindex display-time-24hr-format +Here @var{hh} and @var{mm} are the hour and minute, followed always by +@samp{am} or @samp{pm}. @var{l.ll} is the average number of running +processes in the whole system recently. (Some fields may be missing if +your operating system cannot support them.) If you prefer time display +in 24-hour format, set the variable @code{display-time-24hr-format} +to @code{t}. + +@cindex mail (on mode line) + The word @samp{Mail} appears after the load level if there is mail +for you that you have not read yet. + +@node Text Display +@section How Text Is Displayed +@cindex characters (in text) + + ASCII printing characters (octal codes 040 through 0176) in Emacs +buffers are displayed with their graphics. So are non-ASCII multibyte +printing characters (octal codes above 0400). + + Some ASCII control characters are displayed in special ways. The +newline character (octal code 012) is displayed by starting a new line. +The tab character (octal code 011) is displayed by moving to the next +tab stop column (normally every 8 columns). + + Other ASCII control characters are normally displayed as a caret +(@samp{^}) followed by the non-control version of the character; thus, +control-A is displayed as @samp{^A}. + + Non-ASCII characters 0200 through 0377 are displayed with octal escape +sequences; thus, character code 0243 (octal) is displayed as +@samp{\243}. However, if you enable European display, most of these +characters become non-ASCII printing characters, and are displayed using +their graphics (assuming your terminal supports them). +@xref{Single-Byte European Support}. + +@node Display Vars +@section Variables Controlling Display + + This section contains information for customization only. Beginning +users should skip it. + +@vindex mode-line-inverse-video + The variable @code{mode-line-inverse-video} controls whether the mode +line is displayed in inverse video (assuming the terminal supports it); +@code{nil} means don't do so. @xref{Mode Line}. If you specify the +foreground color for the @code{modeline} face, and +@code{mode-line-inverse-video} is non-@code{nil}, then the default +background color for that face is the usual foreground color. +@xref{Faces}. + +@vindex inverse-video + If the variable @code{inverse-video} is non-@code{nil}, Emacs attempts +to invert all the lines of the display from what they normally are. + +@vindex visible-bell + If the variable @code{visible-bell} is non-@code{nil}, Emacs attempts +to make the whole screen blink when it would normally make an audible bell +sound. This variable has no effect if your terminal does not have a way +to make the screen blink.@refill + +@vindex no-redraw-on-reenter + When you reenter Emacs after suspending, Emacs 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 @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 @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. + +@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}. + +@vindex ctl-arrow + If the variable @code{ctl-arrow} is @code{nil}, control characters in +the buffer are displayed with octal escape sequences, except for newline +and tab. Altering the value of @code{ctl-arrow} makes it local to the +current buffer; until that time, the default value is in effect. The +default is initially @code{t}. @xref{Display Tables,, Display Tables, +elisp, The Emacs Lisp Reference Manual}. + +@vindex tab-width + 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 @code{tab-width}, which is made local by +changing it, just like @code{ctl-arrow}. Note that how the tab character +in the buffer is displayed has nothing to do with the definition of +@key{TAB} as a command. The variable @code{tab-width} must have an +integer value between 1 and 1000, inclusive. + +@c @vindex truncate-lines @c No index entry here, because we have one +@c in the continuation section. + If the variable @code{truncate-lines} is non-@code{nil}, then each +line of text gets just one screen line for display; if the text line is +too long, display shows only the part that fits. If +@code{truncate-lines} is @code{nil}, then long text lines display as +more than one screen line, enough to show the whole text of the line. +@xref{Continuation Lines}. Altering the value of @code{truncate-lines} +makes it local to the current buffer; until that time, the default value +is in effect. The default is initially @code{nil}. + +@c @vindex truncate-partial-width-windows @c Idx entry is in Split Windows. + If the variable @code{truncate-partial-width-windows} is +non-@code{nil}, it forces truncation rather than continuation in any +window less than the full width of the screen or frame, regardless of +the value of @code{truncate-lines}. For information about side-by-side +windows, see @ref{Split Window}. See also @ref{Display,, Display, +elisp, The Emacs Lisp Reference Manual}. + +@vindex baud-rate + The variable @code{baud-rate} holds the output speed of the +terminal, as far as Emacs knows. Setting this variable does not change +the speed of actual data transmission, but the value is used for +calculations such as padding. It also affects decisions about whether +to scroll part of the screen or redraw it instead---even when using a +window system. (We designed it this way, despite the fact that a window +system has no true ``output speed,'' to give you a way to tune these +decisions.) + + You can customize the way any particular character code is displayed +by means of a display table. @xref{Display Tables,, Display Tables, +elisp, The Emacs Lisp Reference Manual}. |