+++ /dev/null
-This is Info file ../info/termcap.info, produced by Makeinfo version
-1.68 from the input file termcap.texi.
-
-START-INFO-DIR-ENTRY
-* Termcap: (termcap). Termcap library of the GNU system.
-END-INFO-DIR-ENTRY
-
- This file documents the termcap library of the GNU system.
-
- Copyright (C) 1988 Free Software Foundation, Inc.
-
- Permission is granted to make and distribute verbatim copies of this
-manual provided the copyright notice and this permission notice are
-preserved on all copies.
-
- Permission is granted to copy and distribute modified versions of
-this manual under the conditions for verbatim copying, provided that
-the entire resulting derived work is distributed under the terms of a
-permission notice identical to this one.
-
- Permission is granted to copy and distribute translations of this
-manual into another language, under the above conditions for modified
-versions, except that this permission notice may be stated in a
-translation approved by the Foundation.
-
-\1f
-File: termcap.info, Node: Capabilities, Next: Summary, Prev: Data Base, Up: Top
-
-Definitions of the Terminal Capabilities
-****************************************
-
- This section is divided into many subsections, each for one aspect of
-use of display terminals. For writing a display program, you usually
-need only check the subsections for the operations you want to use.
-For writing a terminal description, you must read each subsection and
-fill in the capabilities described there.
-
- String capabilities that are display commands may require numeric
-parameters (*note Parameters::.). Most such capabilities do not use
-parameters. When a capability requires parameters, this is explicitly
-stated at the beginning of its definition. In simple cases, the first
-or second sentence of the definition mentions all the parameters, in
-the order they should be given, using a name in upper case for each
-one. For example, the `rp' capability is a command that requires two
-parameters; its definition begins as follows:
-
- String of commands to output a graphic character C, repeated N
- times.
-
- In complex cases or when there are many parameters, they are
-described explicitly.
-
- When a capability is described as obsolete, this means that programs
-should not be written to look for it, but terminal descriptions should
-still be written to provide it.
-
- When a capability is described as very obsolete, this means that it
-should be omitted from terminal descriptions as well.
-
-* Menu:
-
-* Basic:: Basic characteristics.
-* Screen Size:: Screen size, and what happens when it changes.
-* Cursor Motion:: Various ways to move the cursor.
-* Scrolling:: Pushing text up and down on the screen.
-* Wrapping:: What happens if you write a character in the last column.
-* Windows:: Limiting the part of the window that output affects.
-* Clearing:: Erasing one or many lines.
-* Insdel Line:: Making new blank lines in mid-screen; deleting lines.
-* Insdel Char:: Inserting and deleting characters within a line.
-* Standout:: Highlighting some of the text.
-* Underlining:: Underlining some of the text.
-* Cursor Visibility:: Making the cursor more or less easy to spot.
-* Bell:: Attracts user's attention; not localized on the screen.
-* Keypad:: Recognizing when function keys or arrows are typed.
-* Meta Key:: <META> acts like an extra shift key.
-* Initialization:: Commands used to initialize or reset the terminal.
-* Pad Specs:: Info for the kernel on how much padding is needed.
-* Status Line:: A status line displays "background" information.
-* Half-Line:: Moving by half-lines, for superscripts and subscripts.
-* Printer:: Controlling auxiliary printers of display terminals.
-
-\1f
-File: termcap.info, Node: Basic, Next: Screen Size, Prev: Capabilities, Up: Capabilities
-
-Basic Characteristics
-=====================
-
- This section documents the capabilities that describe the basic and
-nature of the terminal, and also those that are relevant to the output
-of graphic characters.
-
-`os'
- Flag whose presence means that the terminal can overstrike. This
- means that outputting a graphic character does not erase whatever
- was present in the same character position before. The terminals
- that can overstrike include printing terminals, storage tubes (all
- obsolete nowadays), and many bit-map displays.
-
-`eo'
- Flag whose presence means that outputting a space can erase an
- overstrike. If this is not present and overstriking is supported,
- output of a space has no effect except to move the cursor.
-
-`gn'
- Flag whose presence means that this terminal type is a generic type
- which does not really describe any particular terminal. Generic
- types are intended for use as the default type assigned when the
- user connects to the system, with the intention that the user
- should specify what type he really has. One example of a generic
- type is the type `network'.
-
- Since the generic type cannot say how to do anything interesting
- with the terminal, termcap-using programs will always find that the
- terminal is too weak to be supported if the user has failed to
- specify a real terminal type in place of the generic one. The
- `gn' flag directs these programs to use a different error message:
- "You have not specified your real terminal type", rather than
- "Your terminal is not powerful enough to be used".
-
-`hc'
- Flag whose presence means this is a hardcopy terminal.
-
-`rp'
- String of commands to output a graphic character C, repeated N
- times. The first parameter value is the ASCII code for the desired
- character, and the second parameter is the number of times to
- repeat the character. Often this command requires padding
- proportional to the number of times the character is repeated.
- This effect can be had by using parameter arithmetic with
- `%'-sequences to compute the amount of padding, then generating
- the result as a number at the front of the string so that `tputs'
- will treat it as padding.
-
-`hz'
- Flag whose presence means that the ASCII character `~' cannot be
- output on this terminal because it is used for display commands.
-
- Programs handle this flag by checking all text to be output and
- replacing each `~' with some other character(s). If this is not
- done, the screen will be thoroughly garbled.
-
- The old Hazeltine terminals that required such treatment are
- probably very rare today, so you might as well not bother to
- support this flag.
-
-`CC'
- String whose presence means the terminal has a settable command
- character. The value of the string is the default command
- character (which is usually <ESC>).
-
- All the strings of commands in the terminal description should be
- written to use the default command character. If you are writing
- an application program that changes the command character, use the
- `CC' capability to figure out how to translate all the display
- commands to work with the new command character.
-
- Most programs have no reason to look at the `CC' capability.
-
-`xb'
- Flag whose presence identifies Superbee terminals which are unable
- to transmit the characters <ESC> and `Control-C'. Programs which
- support this flag are supposed to check the input for the code
- sequences sent by the <F1> and <F2> keys, and pretend that <ESC>
- or `Control-C' (respectively) had been read. But this flag is
- obsolete, and not worth supporting.
-
-\1f
-File: termcap.info, Node: Screen Size, Next: Cursor Motion, Prev: Basic, Up: Capabilities
-
-Screen Size
-===========
-
- A terminal description has two capabilities, `co' and `li', that
-describe the screen size in columns and lines. But there is more to
-the question of screen size than this.
-
- On some operating systems the "screen" is really a window and the
-effective width can vary. On some of these systems, `tgetnum' uses the
-actual width of the window to decide what value to return for the `co'
-capability, overriding what is actually written in the terminal
-description. On other systems, it is up to the application program to
-check the actual window width using a system call. For example, on BSD
-4.3 systems, the system call `ioctl' with code `TIOCGWINSZ' will tell
-you the current screen size.
-
- On all window systems, termcap is powerless to advise the application
-program if the user resizes the window. Application programs must deal
-with this possibility in a system-dependent fashion. On some systems
-the C shell handles part of the problem by detecting changes in window
-size and setting the `TERMCAP' environment variable appropriately.
-This takes care of application programs that are started subsequently.
-It does not help application programs already running.
-
- On some systems, including BSD 4.3, all programs using a terminal get
-a signal named `SIGWINCH' whenever the screen size changes. Programs
-that use termcap should handle this signal by using `ioctl TIOCGWINSZ'
-to learn the new screen size.
-
-`co'
- Numeric value, the width of the screen in character positions.
- Even hardcopy terminals normally have a `co' capability.
-
-`li'
- Numeric value, the height of the screen in lines.
-
-\1f
-File: termcap.info, Node: Cursor Motion, Next: Wrapping, Prev: Screen Size, Up: Capabilities
-
-Cursor Motion
-=============
-
- Termcap assumes that the terminal has a "cursor", a spot on the
-screen where a visible mark is displayed, and that most display
-commands take effect at the position of the cursor. It follows that
-moving the cursor to a specified location is very important.
-
- There are many terminal capabilities for different cursor motion
-operations. A terminal description should define as many as possible,
-but most programs do not need to use most of them. One capability,
-`cm', moves the cursor to an arbitrary place on the screen; this by
-itself is sufficient for any application as long as there is no need to
-support hardcopy terminals or certain old, weak displays that have only
-relative motion commands. Use of other cursor motion capabilities is an
-optimization, enabling the program to output fewer characters in some
-common cases.
-
- If you plan to use the relative cursor motion commands in an
-application program, you must know what the starting cursor position
-is. To do this, you must keep track of the cursor position and update
-the records each time anything is output to the terminal, including
-graphic characters. In addition, it is necessary to know whether the
-terminal wraps after writing in the rightmost column. *Note Wrapping::.
-
- One other motion capability needs special mention: `nw' moves the
-cursor to the beginning of the following line, perhaps clearing all the
-starting line after the cursor, or perhaps not clearing at all. This
-capability is a least common denominator that is probably supported
-even by terminals that cannot do most other things such as `cm' or `do'.
-Even hardcopy terminals can support `nw'.
-
-`cm'
- String of commands to position the cursor at line L, column C.
- Both parameters are origin-zero, and are defined relative to the
- screen, not relative to display memory.
-
- All display terminals except a few very obsolete ones support `cm',
- so it is acceptable for an application program to refuse to
- operate on terminals lacking `cm'.
-
-`ho'
- String of commands to move the cursor to the upper left corner of
- the screen (this position is called the "home position"). In
- terminals where the upper left corner of the screen is not the
- same as the beginning of display memory, this command must go to
- the upper left corner of the screen, not the beginning of display
- memory.
-
- Every display terminal supports this capability, and many
- application programs refuse to operate if the `ho' capability is
- missing.
-
-`ll'
- String of commands to move the cursor to the lower left corner of
- the screen. On some terminals, moving up from home position does
- this, but programs should never assume that will work. Just
- output the `ll' string (if it is provided); if moving to home
- position and then moving up is the best way to get there, the `ll'
- command will do that.
-
-`cr'
- String of commands to move the cursor to the beginning of the line
- it is on. If this capability is not specified, many programs
- assume they can use the ASCII carriage return character for this.
-
-`le'
- String of commands to move the cursor left one column. Unless the
- `bw' flag capability is specified, the effect is undefined if the
- cursor is at the left margin; do not use this command there. If
- `bw' is present, this command may be used at the left margin, and
- it wraps the cursor to the last column of the preceding line.
-
-`nd'
- String of commands to move the cursor right one column. The
- effect is undefined if the cursor is at the right margin; do not
- use this command there, not even if `am' is present.
-
-`up'
- String of commands to move the cursor vertically up one line. The
- effect of sending this string when on the top line is undefined;
- programs should never use it that way.
-
-`do'
- String of commands to move the cursor vertically down one line.
- The effect of sending this string when on the bottom line is
- undefined; programs should never use it that way.
-
- The original idea was that this string would not contain a newline
- character and therefore could be used without disabling the
- kernel's usual habit of converting of newline into a
- carriage-return newline sequence. But many terminal descriptions
- do use newline in the `do' string, so this is not possible; a
- program which sends the `do' string must disable output conversion
- in the kernel (*note Initialize::.).
-
-`bw'
- Flag whose presence says that `le' may be used in column zero to
- move to the last column of the preceding line. If this flag is
- not present, `le' should not be used in column zero.
-
-`nw'
- String of commands to move the cursor to start of next line,
- possibly clearing rest of line (following the cursor) before
- moving.
-
-`DO', `UP', `LE', `RI'
- Strings of commands to move the cursor N lines down vertically, up
- vertically, or N columns left or right. Do not attempt to move
- past any edge of the screen with these commands; the effect of
- trying that is undefined. Only a few terminal descriptions provide
- these commands, and most programs do not use them.
-
-`CM'
- String of commands to position the cursor at line L, column C,
- relative to display memory. Both parameters are origin-zero.
- This capability is present only in terminals where there is a
- difference between screen-relative and memory-relative addressing,
- and not even in all such terminals.
-
-`ch'
- String of commands to position the cursor at column C in the same
- line it is on. This is a special case of `cm' in which the
- vertical position is not changed. The `ch' capability is provided
- only when it is faster to output than `cm' would be in this
- special case. Programs should not assume most display terminals
- have `ch'.
-
-`cv'
- String of commands to position the cursor at line L in the same
- column. This is a special case of `cm' in which the horizontal
- position is not changed. The `cv' capability is provided only
- when it is faster to output than `cm' would be in this special
- case. Programs should not assume most display terminals have `cv'.
-
-`sc'
- String of commands to make the terminal save the current cursor
- position. Only the last saved position can be used. If this
- capability is present, `rc' should be provided also. Most
- terminals have neither.
-
-`rc'
- String of commands to make the terminal restore the last saved
- cursor position. If this capability is present, `sc' should be
- provided also. Most terminals have neither.
-
-`ff'
- String of commands to advance to the next page, for a hardcopy
- terminal.
-
-`ta'
- String of commands to move the cursor right to the next hardware
- tab stop column. Missing if the terminal does not have any kind of
- hardware tabs. Do not send this command if the kernel's terminal
- modes say that the kernel is expanding tabs into spaces.
-
-`bt'
- String of commands to move the cursor left to the previous hardware
- tab stop column. Missing if the terminal has no such ability; many
- terminals do not. Do not send this command if the kernel's
- terminal modes say that the kernel is expanding tabs into spaces.
-
- The following obsolete capabilities should be included in terminal
-descriptions when appropriate, but should not be looked at by new
-programs.
-
-`nc'
- Flag whose presence means the terminal does not support the ASCII
- carriage return character as `cr'. This flag is needed because
- old programs assume, when the `cr' capability is missing, that
- ASCII carriage return can be used for the purpose. We use `nc' to
- tell the old programs that carriage return may not be used.
-
- New programs should not assume any default for `cr', so they need
- not look at `nc'. However, descriptions should contain `nc'
- whenever they do not contain `cr'.
-
-`xt'
- Flag whose presence means that the ASCII tab character may not be
- used for cursor motion. This flag exists because old programs
- assume, when the `ta' capability is missing, that ASCII tab can be
- used for the purpose. We use `xt' to tell the old programs not to
- use tab.
-
- New programs should not assume any default for `ta', so they need
- not look at `xt' in connection with cursor motion. Note that `xt'
- also has implications for standout mode (*note Standout::.). It
- is obsolete in regard to cursor motion but not in regard to
- standout.
-
- In fact, `xt' means that the terminal is a Teleray 1061.
-
-`bc'
- Very obsolete alternative name for the `le' capability.
-
-`bs'
- Flag whose presence means that the ASCII character backspace may be
- used to move the cursor left. Obsolete; look at `le' instead.
-
-`nl'
- Obsolete capability which is a string that can either be used to
- move the cursor down or to scroll. The same string must scroll
- when used on the bottom line and move the cursor when used on any
- other line. New programs should use `do' or `sf', and ignore `nl'.
-
- If there is no `nl' capability, some old programs assume they can
- use the newline character for this purpose. These programs follow
- a bad practice, but because they exist, it is still desirable to
- define the `nl' capability in a terminal description if the best
- way to move down is *not* a newline.
-
-\1f
-File: termcap.info, Node: Wrapping, Next: Scrolling, Prev: Cursor Motion, Up: Capabilities
-
-Wrapping
-========
-
- "Wrapping" means moving the cursor from the right margin to the left
-margin of the following line. Some terminals wrap automatically when a
-graphic character is output in the last column, while others do not.
-Most application programs that use termcap need to know whether the
-terminal wraps. There are two special flag capabilities to describe
-what the terminal does when a graphic character is output in the last
-column.
-
-`am'
- Flag whose presence means that writing a character in the last
- column causes the cursor to wrap to the beginning of the next line.
-
- If `am' is not present, writing in the last column leaves the
- cursor at the place where the character was written.
-
- Writing in the last column of the last line should be avoided on
- terminals with `am', as it may or may not cause scrolling to occur
- (*note Scrolling::.). Scrolling is surely not what you would
- intend.
-
- If your program needs to check the `am' flag, then it also needs
- to check the `xn' flag which indicates that wrapping happens in a
- strange way. Many common terminals have the `xn' flag.
-
-`xn'
- Flag whose presence means that the cursor wraps in a strange way.
- At least two distinct kinds of strange behavior are known; the
- termcap data base does not contain anything to distinguish the two.
-
- On Concept-100 terminals, output in the last column wraps the
- cursor almost like an ordinary `am' terminal. But if the next
- thing output is a newline, it is ignored.
-
- DEC VT-100 terminals (when the wrap switch is on) do a different
- strange thing: the cursor wraps only if the next thing output is
- another graphic character. In fact, the wrap occurs when the
- following graphic character is received by the terminal, before the
- character is placed on the screen.
-
- On both of these terminals, after writing in the last column a
- following graphic character will be displayed in the first column
- of the following line. But the effect of relative cursor motion
- characters such as newline or backspace at such a time depends on
- the terminal. The effect of erase or scrolling commands also
- depends on the terminal. You can't assume anything about what
- they will do on a terminal that has `xn'. So, to be safe, you
- should never do these things at such a time on such a terminal.
-
- To be sure of reliable results on a terminal which has the `xn'
- flag, output a `cm' absolute positioning command after writing in
- the last column. Another safe thing to do is to output
- carriage-return newline, which will leave the cursor at the
- beginning of the following line.
-
-\1f
-File: termcap.info, Node: Scrolling, Next: Windows, Prev: Wrapping, Up: Capabilities
-
-Scrolling
-=========
-
- "Scrolling" means moving the contents of the screen up or down one or
-more lines. Moving the contents up is "forward scrolling"; moving them
-down is "reverse scrolling".
-
- Scrolling happens after each line of output during ordinary output
-on most display terminals. But in an application program that uses
-termcap for random-access output, scrolling happens only when
-explicitly requested with the commands in this section.
-
- Some terminals have a "scroll region" feature. This lets you limit
-the effect of scrolling to a specified range of lines. Lines outside
-the range are unaffected when scrolling happens. The scroll region
-feature is available if either `cs' or `cS' is present.
-
-`sf'
- String of commands to scroll the screen one line up, assuming it is
- output with the cursor at the beginning of the bottom line.
-
-`sr'
- String of commands to scroll the screen one line down, assuming it
- is output with the cursor at the beginning of the top line.
-
-`SF'
- String of commands to scroll the screen N lines up, assuming it is
- output with the cursor at the beginning of the bottom line.
-
-`SR'
- String of commands to scroll the screen N line down, assuming it
- is output with the cursor at the beginning of the top line.
-
-`cs'
- String of commands to set the scroll region. This command takes
- two parameters, START and END, which are the line numbers
- (origin-zero) of the first line to include in the scroll region
- and of the last line to include in it. When a scroll region is
- set, scrolling is limited to the specified range of lines; lines
- outside the range are not affected by scroll commands.
-
- Do not try to move the cursor outside the scroll region. The
- region remains set until explicitly removed. To remove the scroll
- region, use another `cs' command specifying the full height of the
- screen.
-
- The cursor position is undefined after the `cs' command is set, so
- position the cursor with `cm' immediately afterward.
-
-`cS'
- String of commands to set the scroll region using parameters in
- different form. The effect is the same as if `cs' were used.
- Four parameters are required:
-
- 1. Total number of lines on the screen.
-
- 2. Number of lines above desired scroll region.
-
- 3. Number of lines below (outside of) desired scroll region.
-
- 4. Total number of lines on the screen, the same as the first
- parameter.
-
- This capability is a GNU extension that was invented to allow the
- Ann Arbor Ambassador's scroll-region command to be described; it
- could also be done by putting non-Unix `%'-sequences into a `cs'
- string, but that would have confused Unix programs that used the
- `cs' capability with the Unix termcap. Currently only GNU Emacs
- uses the `cS' capability.
-
-`ns'
- Flag which means that the terminal does not normally scroll for
- ordinary sequential output. For modern terminals, this means that
- outputting a newline in ordinary sequential output with the cursor
- on the bottom line wraps to the top line. For some obsolete
- terminals, other things may happen.
-
- The terminal may be able to scroll even if it does not normally do
- so. If the `sf' capability is provided, it can be used for
- scrolling regardless of `ns'.
-
-`da'
- Flag whose presence means that lines scrolled up off the top of the
- screen may come back if scrolling down is done subsequently.
-
- The `da' and `db' flags do not, strictly speaking, affect how to
- scroll. But programs that scroll usually need to clear the lines
- scrolled onto the screen, if these flags are present.
-
-`db'
- Flag whose presence means that lines scrolled down off the bottom
- of the screen may come back if scrolling up is done subsequently.
-
-`lm'
- Numeric value, the number of lines of display memory that the
- terminal has. A value of zero means that the terminal has more
- display memory than can fit on the screen, but no fixed number of
- lines. (The number of lines may depend on the amount of text in
- each line.)
-
- Any terminal description that defines `SF' should also define `sf';
-likewise for `SR' and `sr'. However, many terminals can only scroll by
-one line at a time, so it is common to find `sf' and not `SF', or `sr'
-without `SR'.
-
- Therefore, all programs that use the scrolling facilities should be
-prepared to work with `sf' in the case that `SF' is absent, and
-likewise with `sr'. On the other hand, an application program that
-uses only `sf' and not `SF' is acceptable, though slow on some
-terminals.
-
- When outputting a scroll command with `tputs', the NLINES argument
-should be the total number of lines in the portion of the screen being
-scrolled. Very often these commands require padding proportional to
-this number of lines. *Note Padding::.
-
-\1f
-File: termcap.info, Node: Windows, Next: Clearing, Prev: Scrolling, Up: Capabilities
-
-Windows
-=======
-
- A "window", in termcap, is a rectangular portion of the screen to
-which all display operations are restricted. Wrapping, clearing,
-scrolling, insertion and deletion all operate as if the specified
-window were all the screen there was.
-
-`wi'
- String of commands to set the terminal output screen window. This
- string requires four parameters, all origin-zero:
- 1. The first line to include in the window.
-
- 2. The last line to include in the window.
-
- 3. The first column to include in the window.
-
- 4. The last column to include in the window.
-
- Most terminals do not support windows.
-
-\1f
-File: termcap.info, Node: Clearing, Next: Insdel Line, Prev: Windows, Up: Capabilities
-
-Clearing Parts of the Screen
-============================
-
- There are several terminal capabilities for clearing parts of the
-screen to blank. All display terminals support the `cl' string, and
-most display terminals support all of these capabilities.
-
-`cl'
- String of commands to clear the entire screen and position the
- cursor at the upper left corner.
-
-`cd'
- String of commands to clear the line the cursor is on, and all the
- lines below it, down to the bottom of the screen. This command
- string should be used only with the cursor in column zero; their
- effect is undefined if the cursor is elsewhere.
-
-`ce'
- String of commands to clear from the cursor to the end of the
- current line.
-
-`ec'
- String of commands to clear N characters, starting with the
- character that the cursor is on. This command string is expected
- to leave the cursor position unchanged. The parameter N should
- never be large enough to reach past the right margin; the effect
- of such a large parameter would be undefined.
-
- Clear to end of line (`ce') is extremely important in programs that
-maintain an updating display. Nearly all display terminals support this
-operation, so it is acceptable for a an application program to refuse to
-work if `ce' is not present. However, if you do not want this
-limitation, you can accomplish clearing to end of line by outputting
-spaces until you reach the right margin. In order to do this, you must
-know the current horizontal position. Also, this technique assumes
-that writing a space will erase. But this happens to be true on all
-the display terminals that fail to support `ce'.
-
-\1f
-File: termcap.info, Node: Insdel Line, Next: Insdel Char, Prev: Clearing, Up: Capabilities
-
-Insert/Delete Line
-==================
-
- "Inserting a line" means creating a blank line in the middle of the
-screen, and pushing the existing lines of text apart. In fact, the
-lines above the insertion point do not change, while the lines below
-move down, and one is normally lost at the bottom of the screen.
-
- "Deleting a line" means causing the line to disappear from the
-screen, closing up the gap by moving the lines below it upward. A new
-line appears at the bottom of the screen. Usually this line is blank,
-but on terminals with the `db' flag it may be a line previously moved
-off the screen bottom by scrolling or line insertion.
-
- Insertion and deletion of lines is useful in programs that maintain
-an updating display some parts of which may get longer or shorter.
-They are also useful in editors for scrolling parts of the screen, and
-for redisplaying after lines of text are killed or inserted.
-
- Many terminals provide commands to insert or delete a single line at
-the cursor position. Some provide the ability to insert or delete
-several lines with one command, using the number of lines to insert or
-delete as a parameter. Always move the cursor to column zero before
-using any of these commands.
-
-`al'
- String of commands to insert a blank line before the line the
- cursor is on. The existing line, and all lines below it, are
- moved down. The last line in the screen (or in the scroll region,
- if one is set) disappears and in most circumstances is discarded.
- It may not be discarded if the `db' is present (*note
- Scrolling::.).
-
- The cursor must be at the left margin before this command is used.
- This command does not move the cursor.
-
-`dl'
- String of commands to delete the line the cursor is on. The
- following lines move up, and a blank line appears at the bottom of
- the screen (or bottom of the scroll region). If the terminal has
- the `db' flag, a nonblank line previously pushed off the screen
- bottom may reappear at the bottom.
-
- The cursor must be at the left margin before this command is used.
- This command does not move the cursor.
-
-`AL'
- String of commands to insert N blank lines before the line that
- the cursor is on. It is like `al' repeated N times, except that
- it is as fast as one `al'.
-
-`DL'
- String of commands to delete N lines starting with the line that
- the cursor is on. It is like `dl' repeated N times, except that
- it is as fast as one `dl'.
-
- Any terminal description that defines `AL' should also define `al';
-likewise for `DL' and `dl'. However, many terminals can only insert or
-delete one line at a time, so it is common to find `al' and not `AL',
-or `dl' without `DL'.
-
- Therefore, all programs that use the insert and delete facilities
-should be prepared to work with `al' in the case that `AL' is absent,
-and likewise with `dl'. On the other hand, it is acceptable to write
-an application that uses only `al' and `dl' and does not look for `AL'
-or `DL' at all.
-
- If a terminal does not support line insertion and deletion directly,
-but does support a scroll region, the effect of insertion and deletion
-can be obtained with scrolling. However, it is up to the individual
-user program to check for this possibility and use the scrolling
-commands to get the desired result. It is fairly important to implement
-this alternate strategy, since it is the only way to get the effect of
-line insertion and deletion on the popular VT100 terminal.
-
- Insertion and deletion of lines is affected by the scroll region on
-terminals that have a settable scroll region. This is useful when it is
-desirable to move any few consecutive lines up or down by a few lines.
-*Note Scrolling::.
-
- The line pushed off the bottom of the screen is not lost if the
-terminal has the `db' flag capability; instead, it is pushed into
-display memory that does not appear on the screen. This is the same
-thing that happens when scrolling pushes a line off the bottom of the
-screen. Either reverse scrolling or deletion of a line can bring the
-apparently lost line back onto the bottom of the screen. If the
-terminal has the scroll region feature as well as `db', the pushed-out
-line really is lost if a scroll region is in effect.
-
- When outputting an insert or delete command with `tputs', the NLINES
-argument should be the total number of lines from the cursor to the
-bottom of the screen (or scroll region). Very often these commands
-require padding proportional to this number of lines. *Note Padding::.
-
- For `AL' and `DL' the NLINES argument should *not* depend on the
-number of lines inserted or deleted; only the total number of lines
-affected. This is because it is just as fast to insert two or N lines
-with `AL' as to insert one line with `al'.
-
-\1f
-File: termcap.info, Node: Insdel Char, Next: Standout, Prev: Insdel Line, Up: Capabilities
-
-Insert/Delete Character
-=======================
-
- "Inserting a character" means creating a blank space in the middle
-of a line, and pushing the rest of the line rightward. The character
-in the rightmost column is lost.
-
- "Deleting a character" means causing the character to disappear from
-the screen, closing up the gap by moving the rest of the line leftward.
-A blank space appears in the rightmost column.
-
- Insertion and deletion of characters is useful in programs that
-maintain an updating display some parts of which may get longer or
-shorter. It is also useful in editors for redisplaying the results of
-editing within a line.
-
- Many terminals provide commands to insert or delete a single
-character at the cursor position. Some provide the ability to insert
-or delete several characters with one command, using the number of
-characters to insert or delete as a parameter.
-
- Many terminals provide an insert mode in which outputting a graphic
-character has the added effect of inserting a position for that
-character. A special command string is used to enter insert mode and
-another is used to exit it. The reason for designing a terminal with
-an insert mode rather than an insert command is that inserting
-character positions is usually followed by writing characters into
-them. With insert mode, this is as fast as simply writing the
-characters, except for the fixed overhead of entering and leaving
-insert mode. However, when the line speed is great enough, padding may
-be required for the graphic characters output in insert mode.
-
- Some terminals require you to enter insert mode and then output a
-special command for each position to be inserted. Or they may require
-special commands to be output before or after each graphic character to
-be inserted.
-
- Deletion of characters is usually accomplished by a straightforward
-command to delete one or several positions; but on some terminals, it
-is necessary to enter a special delete mode before using the delete
-command, and leave delete mode afterward. Sometimes delete mode and
-insert mode are the same mode.
-
- Some terminals make a distinction between character positions in
-which a space character has been output and positions which have been
-cleared. On these terminals, the effect of insert or delete character
-runs to the first cleared position rather than to the end of the line.
-In fact, the effect may run to more than one line if there is no
-cleared position to stop the shift on the first line. These terminals
-are identified by the `in' flag capability.
-
- On terminals with the `in' flag, the technique of skipping over
-characters that you know were cleared, and then outputting text later
-on in the same line, causes later insert and delete character
-operations on that line to do nonstandard things. A program that has
-any chance of doing this must check for the `in' flag and must be
-careful to write explicit space characters into the intermediate
-columns when `in' is present.
-
- A plethora of terminal capabilities are needed to describe all of
-this complexity. Here is a list of them all. Following the list, we
-present an algorithm for programs to use to take proper account of all
-of these capabilities.
-
-`im'
- String of commands to enter insert mode.
-
- If the terminal has no special insert mode, but it can insert
- characters with a special command, `im' should be defined with a
- null value, because the `vi' editor assumes that insertion of a
- character is impossible if `im' is not provided.
-
- New programs should not act like `vi'. They should pay attention
- to `im' only if it is defined.
-
-`ei'
- String of commands to leave insert mode. This capability must be
- present if `im' is.
-
- On a few old terminals the same string is used to enter and exit
- insert mode. This string turns insert mode on if it was off, and
- off if it was on. You can tell these terminals because the `ei'
- string equals the `im' string. If you want to support these
- terminals, you must always remember accurately whether insert mode
- is in effect. However, these terminals are obsolete, and it is
- reasonable to refuse to support them. On all modern terminals, you
- can safely output `ei' at any time to ensure that insert mode is
- turned off.
-
-`ic'
- String of commands to insert one character position at the cursor.
- The cursor does not move.
-
- If outputting a graphic character while in insert mode is
- sufficient to insert the character, then the `ic' capability
- should be defined with a null value.
-
- If your terminal offers a choice of ways to insert--either use
- insert mode or use a special command--then define `im' and do not
- define `ic', since this gives the most efficient operation when
- several characters are to be inserted. *Do not* define both
- strings, for that means that *both* must be used each time
- insertion is done.
-
-`ip'
- String of commands to output following an inserted graphic
- character in insert mode. Often it is used just for a padding
- spec, when padding is needed after an inserted character (*note
- Padding::.).
-
-`IC'
- String of commands to insert N character positions at and after
- the cursor. It has the same effect as repeating the `ic' string
- and a space, N times.
-
- If `IC' is provided, application programs may use it without first
- entering insert mode.
-
-`mi'
- Flag whose presence means it is safe to move the cursor while in
- insert mode and assume the terminal remains in insert mode.
-
-`in'
- Flag whose presence means that the terminal distinguishes between
- character positions in which space characters have been output and
- positions which have been cleared.
-
- An application program can assume that the terminal can do character
-insertion if *any one of* the capabilities `IC', `im', `ic' or `ip' is
-provided.
-
- To insert N blank character positions, move the cursor to the place
-to insert them and follow this algorithm:
-
- 1. If an `IC' string is provided, output it with parameter N and you
- are finished. Otherwise (or if you don't want to bother to look
- for an `IC' string) follow the remaining steps.
-
- 2. Output the `im' string, if there is one, unless the terminal is
- already in insert mode.
-
- 3. Repeat steps 4 through 6, N times.
-
- 4. Output the `ic' string if any.
-
- 5. Output a space.
-
- 6. Output the `ip' string if any.
-
- 7. Output the `ei' string, eventually, to exit insert mode. There is
- no need to do this right away. If the `mi' flag is present, you
- can move the cursor and the cursor will remain in insert mode;
- then you can do more insertion elsewhere without reentering insert
- mode.
-
- To insert N graphic characters, position the cursor and follow this
-algorithm:
-
- 1. If an `IC' string is provided, output it with parameter N, then
- output the graphic characters, and you are finished. Otherwise
- (or if you don't want to bother to look for an `IC' string) follow
- the remaining steps.
-
- 2. Output the `im' string, if there is one, unless the terminal is
- already in insert mode.
-
- 3. For each character to be output, repeat steps 4 through 6.
-
- 4. Output the `ic' string if any.
-
- 5. Output the next graphic character.
-
- 6. Output the `ip' string if any.
-
- 7. Output the `ei' string, eventually, to exit insert mode. There is
- no need to do this right away. If the `mi' flag is present, you
- can move the cursor and the cursor will remain in insert mode;
- then you can do more insertion elsewhere without reentering insert
- mode.
-
- Note that this is not the same as the original Unix termcap
-specifications in one respect: it assumes that the `IC' string can be
-used without entering insert mode. This is true as far as I know, and
-it allows you be able to avoid entering and leaving insert mode, and
-also to be able to avoid the inserted-character padding after the
-characters that go into the inserted positions.
-
- Deletion of characters is less complicated; deleting one column is
-done by outputting the `dc' string. However, there may be a delete
-mode that must be entered with `dm' in order to make `dc' work.
-
-`dc'
- String of commands to delete one character position at the cursor.
- If `dc' is not present, the terminal cannot delete characters.
-
-`DC'
- String of commands to delete N characters starting at the cursor.
- It has the same effect as repeating the `dc' string N times. Any
- terminal description that has `DC' also has `dc'.
-
-`dm'
- String of commands to enter delete mode. If not present, there is
- no delete mode, and `dc' can be used at any time (assuming there is
- a `dc').
-
-`ed'
- String of commands to exit delete mode. This must be present if
- `dm' is.
-
- To delete N character positions, position the cursor and follow these
-steps:
-
- 1. If the `DC' string is present, output it with parameter N and you
- are finished. Otherwise, follow the remaining steps.
-
- 2. Output the `dm' string, unless you know the terminal is already in
- delete mode.
-
- 3. Output the `dc' string N times.
-
- 4. Output the `ed' string eventually. If the flag capability `mi' is
- present, you can move the cursor and do more deletion without
- leaving and reentering delete mode.
-
- As with the `IC' string, we have departed from the original termcap
-specifications by assuming that `DC' works without entering delete mode
-even though `dc' would not.
-
- If the `dm' and `im' capabilities are both present and have the same
-value, it means that the terminal has one mode for both insertion and
-deletion. It is useful for a program to know this, because then it can
-do insertions after deletions, or vice versa, without leaving
-insert/delete mode and reentering it.
-
projects / chise / xemacs-chise.git.1 / blobdiff