NAME
Curses - terminal screen handling and optimization
SYNOPSIS
use Curses;
initscr;
...
endwin;DESCRIPTION
Curses is the interface between Perl and your system's curses(3) library. For descriptions on the usage of a given function, variable, or constant, consult your system's documentation, as such information invariably varies (:-) between different curses(3) libraries and operating systems. This document describes the interface itself, and assumes that you already know how your system's curses(3) library works.
Unified Functions
Many curses(3) functions have variants starting with the prefixes w-, mv-, and/or wmv-. These variants differ only in the explicit addition of a window, or by the addition of two coordinates that are used to move the cursor first. For example, addch() has three other variants: waddch(), mvaddch(), and mvwaddch(). The variants aren't very interesting; in fact, we could roll all of the variants into original function by allowing a variable number of arguments and analyzing the argument list for which variant the user wanted to call.
Unfortunately, curses(3) predates varargs(3), so in C we were stuck with all the variants. However, Curses is a Perl interface, so we are free to "unify" these variants into one function. The section "Available Functions" below lists all curses(3) functions Curses makes available as Perl equivalents, along with a column listing if it is unified. If so, it takes a varying number of arguments as follows:
function( [win], [y, x], args );
win is an optional window argument, defaulting to stdscr if not specified.
y, x is an optional coordinate pair used to move the cursor, defaulting to no move if not specified.
args are the required arguments of the function. These are the arguments you would specify if you were just calling the base function and not any of the variants.
This makes the variants obsolete, since their functionality has been merged into a single function, so Curses does not define them by default. You can still get them if you want, by setting the variable $Curses::OldCurses to a non-zero value before using the Curses package. See "Perl 4.X cursperl Compatibility" for an example of this.
Wide-Character-Aware Functions
The following are the preferred functions for working with strings, though they don't follow the normal unified function naming convention (based on the names in the Curses library) described above. Despite the naming, each corresponds to a Curses library function. For example, a getchar call performs a Curses library function in the getch family.
In addition to these functions, The Curses module contains corresponding functions with the conventional naming (e.g. getch); the duplication is for historical reasons. The preferred functions were new in Curses 1.29 (April 2014). They use the wide character functions in the Curses library if available (falling back to using the traditional non-wide-character versions). They also have a more Perl-like interface, taking care of some gory details under the hood about which a Perl programmer shouldn't have to worry.
The reason for two sets of string-handling functions is historical. The original Curses Perl module predates Curses libraries that understand multiple byte character encodings. Moreover, the module was designed to have a Perl interface that closely resembles the C interface syntactically and directly passes the internal byte representation of Perl strings to C code. This was probably fine before Perl got Unicode function, but today, Perl stores strings internally in either Latin-1 or Unicode UTF-8 and the original module was not sensitive to which encoding was used.
While most of the problems could be worked around in Perl code using the traditional interface, it's hard to get right and you need a wide-character-aware curses library (e.g. ncursesw) anyway to make it work properly. Because existing consumers of the Curses module may be relying on the traditional behavior, Curses module designers couldn't simply modify the existing functions to understand wide characters and convert from and to Perl strings.
None of these functions exist if Perl is older than 5.6.
getchar
This calls wget_wch(). It returns a character -- more precisely, a one-character (not necessarily one-byte!) string holding the character -- for a normal key and a two-element list (undef, key-number) for a function key. It returns undef on error.
If you don't expect function keys (i.e. with keypad(0)), you can simply do
my $ch = getchar;
die "getchar failed" unless defined $ch;If you do expect function keys (i.e. with keypad(1)), you can still assign the result to a scalar variable as above. Because of of the way the comma operator works, that variable will receive either undef or the string or the number, and you can decode it yourself.
my $ch = getchar;
die "getchar failed" unless defined $ch;
if (<$ch looks like a number >= 0x100>) {
<handle function key>
} else {
<handle normal key>
}or do
my ($ch, $key) = getchar;
if (defined $key) {
<handle function key $key>
} else if (defined $ch) {
<handle normal key $ch>
} else {
die "getchar failed";
}If wget_wch() is not available (i.e. The Curses library does not understand wide characters), this calls wgetch(), but returns the values described above nonetheless. This can be a problem because with a multibyte character encoding like UTF-8, you will receive two one-character strings for a two-byte-character (e.g. "õ€‚‚" and "â–½" for "∽"). If you append these characters to a Perl string, that string may internally contain a valid UTF-8 encoding of a character, but Perl will not interpret it that way. Perl may even try to convert what it believes to be two characters to UTF-8, giving you four bytes.
getstring
This calls wgetn_wstr and returns a string or undef. It cannot return a function key value; the Curses library will itself interpret KEY_LEFT and KEY_BACKSPACE.
If wgett_wstr() is unavailable, this calls wgetstr().
In both cases, the function allocates a buffer of fixed size to hold the result of the Curses library call.
my $s = getstring();
die "getstring failed" unless defined $s;addstring/insstring
This adds/inserts the Perl string passed as an argument to the Curses window using waddnwstr()/wins_nwstr() or, if unavailable, waddnstr()/winsnstr(). It returns a true value on success, false on failure.
addstring("H∽ll‡, W‡rld") || die "addstring failed";instring
This returns a Perl string (or undef on failure) holding the characters from the current cursor position up to the end of the line. It uses winnwstr() if available, and otherwise innstr().
my $s = instring();
die "instring failed" unless defined $s;ungetchar
This pushes one character (passed as a one-character Perl string) back to the input queue. It uses unget_wch() or ungetch(). It returns a true value on success, false on failure. It cannot push back a function key; the Curses library provides no way to push back function keys, only characters.
ungetchar("X") || die "ungetchar failed";The Curses module provides no interface to the complex-character routines (wadd_wch(), wadd_wchnstr(), wecho_wchar(), win_wch(), win_wchnstr(), wins_wch()) because there is no sensible way of converting from Perl to a C cchar_t or back.
Objects
Objects work. Example:
$win = new Curses;
$win->addstr(10, 10, 'foo');
$win->refresh;
...Any function that has been marked as unified (see "Available Functions" below and "Unified Functions" above) can be called as a method for a Curses object.
Do not use initscr() if using objects, as the first call to get a new Curses will do it for you.
Security Concerns
It has always been the case with the curses functions, but please note that the following functions:
getstr() (and optional wgetstr(), mvgetstr(), and mvwgetstr())
inchstr() (and optional winchstr(), mvinchstr(), and mvwinchstr())
instr() (and optional winstr(), mvinstr(), and mvwinstr())are subject to buffer overflow attack. This is because you pass in the buffer to be filled in, which has to be of finite length, but there is no way to stop a bad guy from typing.
In order to avoid this problem, use the alternate functions:
getnstr()
inchnstr()
innstr()which take an extra "size of buffer" argument or the wide-character-aware getstring() and instring() versions.
COMPATIBILITY
Perl 4.X cursperl Compatibility
Curses was written to take advantage of features of Perl 5 and later. The author thought it was better to provide an improved curses programming environment than to be 100% compatible. However, many old curseperl applications will probably still work by starting the script with:
BEGIN { $Curses::OldCurses = 1; }
use Curses;Any old application that still does not work should print an understandable error message explaining the problem.
Some functions and variables are not available through Curses, even with the BEGIN line. They are listed under "Curses items not available through Perl Curses".
The variables $stdscr and $curscr are also available as functions stdscr and curscr. This is because of a Perl bug. See the LIMITATIONS section for details.
Incompatibilities with previous versions of Curses
In previous versions of this software, some Perl functions took a different set of parameters than their C counterparts. This is not true in the current version. You should now use getstr($str) and getyx($y, $x) instead of $str = getstr() and ($y, $x) = getyx().
DIAGNOSTICS
Curses function '%s' called with too %s arguments at ...
You have called a
Cursesfunction with a wrong number of arguments.argument %d to Curses function '%s' is not a Curses %s at ...
argument is not a Curses %s at ...
The argument you gave to the function wasn't of a valid type for the place you used it.
This probably means that you didn't give the right arguments to a unified function. See the DESCRIPTION section on "Unified Functions" for more information.
Curses function '%s' is not defined in your Curses library at ...
Your code has a call to a Perl
Cursesfunction that your system's Curses library doesn't provide.Curses variable '%s' is not defined in your Curses library at ...
Your code has a Perl
Cursesvariable that your system's Curses library doesn't provide.Curses constant '%s' is not defined in your Curses library at ...
Your code references the specified
Cursesconstant, and your system's Curses library doesn't provide it.Curses::Vars::FETCH called with bad index at ...
Curses::Vars::STORE called with bad index at ...
You've been playing with the
tieinterface to theCursesvariables. Don't do that. :-)Anything else
Check out the perldiag man page to see if the error is in there.
LIMITATIONS
If you use the variables $stdscr and $curscr instead of their functional counterparts (stdscr and curscr), you might run into a bug in Perl where the "magic" isn't called early enough. This is manifested by the Curses package telling you $stdscr isn't a window. One workaround is to put a line like $stdscr = $stdscr near the front of your program.
AUTHOR
William Setzer <William_Setzer@ncsu.edu>
SYNOPSIS OF PERL CURSES AVAILABILITY
Available Functions
Available Function Unified? Available via $OldCurses[*]
------------------ -------- ------------------------
addch Yes waddch mvaddch mvwaddch
echochar Yes wechochar
addchstr Yes waddchstr mvaddchstr mvwaddchstr
addchnstr Yes waddchnstr mvaddchnstr mvwaddchnstr
addstr Yes waddstr mvaddstr mvwaddstr
addnstr Yes waddnstr mvaddnstr mvwaddnstr
attroff Yes wattroff
attron Yes wattron
attrset Yes wattrset
standend Yes wstandend
standout Yes wstandout
attr_get Yes wattr_get
attr_off Yes wattr_off
attr_on Yes wattr_on
attr_set Yes wattr_set
chgat Yes wchgat mvchgat mvwchgat
COLOR_PAIR No
PAIR_NUMBER No
beep No
flash No
bkgd Yes wbkgd
bkgdset Yes wbkgdset
getbkgd Yes
border Yes wborder
box Yes
hline Yes whline mvhline mvwhline
vline Yes wvline mvvline mvwvline
erase Yes werase
clear Yes wclear
clrtobot Yes wclrtobot
clrtoeol Yes wclrtoeol
start_color No
init_pair No
init_color No
has_colors No
can_change_color No
color_content No
pair_content No
delch Yes wdelch mvdelch mvwdelch
deleteln Yes wdeleteln
insdelln Yes winsdelln
insertln Yes winsertln
getch Yes wgetch mvgetch mvwgetch
ungetch No
has_key No
KEY_F No
getstr Yes wgetstr mvgetstr mvwgetstr
getnstr Yes wgetnstr mvgetnstr mvwgetnstr
getyx Yes
getparyx Yes
getbegyx Yes
getmaxyx Yes
inch Yes winch mvinch mvwinch
inchstr Yes winchstr mvinchstr mvwinchstr
inchnstr Yes winchnstr mvinchnstr mvwinchnstr
initscr No
endwin No
isendwin No
newterm No
set_term No
delscreen No
cbreak No
nocbreak No
echo No
noecho No
halfdelay No
intrflush Yes
keypad Yes
meta Yes
nodelay Yes
notimeout Yes
raw No
noraw No
qiflush No
noqiflush No
timeout Yes wtimeout
typeahead No
insch Yes winsch mvinsch mvwinsch
insstr Yes winsstr mvinsstr mvwinsstr
insnstr Yes winsnstr mvinsnstr mvwinsnstr
instr Yes winstr mvinstr mvwinstr
innstr Yes winnstr mvinnstr mvwinnstr
def_prog_mode No
def_shell_mode No
reset_prog_mode No
reset_shell_mode No
resetty No
savetty No
getsyx No
setsyx No
curs_set No
napms No
move Yes wmove
clearok Yes
idlok Yes
idcok Yes
immedok Yes
leaveok Yes
setscrreg Yes wsetscrreg
scrollok Yes
nl No
nonl No
overlay No
overwrite No
copywin No
newpad No
subpad No
prefresh No
pnoutrefresh No
pechochar No
refresh Yes wrefresh
noutrefresh Yes wnoutrefresh
doupdate No
redrawwin Yes
redrawln Yes wredrawln
scr_dump No
scr_restore No
scr_init No
scr_set No
scroll Yes
scrl Yes wscrl
slk_init No
slk_set No
slk_refresh No
slk_noutrefresh No
slk_label No
slk_clear No
slk_restore No
slk_touch No
slk_attron No
slk_attrset No
slk_attr No
slk_attroff No
slk_color No
baudrate No
erasechar No
has_ic No
has_il No
killchar No
longname No
termattrs No
termname No
touchwin Yes
touchline Yes
untouchwin Yes
touchln Yes wtouchln
is_linetouched Yes
is_wintouched Yes
unctrl No
keyname No
filter No
use_env No
putwin No
getwin No
delay_output No
flushinp No
newwin No
delwin Yes
mvwin Yes
subwin Yes
derwin Yes
mvderwin Yes
dupwin Yes
syncup Yes wsyncup
syncok Yes
cursyncup Yes wcursyncup
syncdown Yes wsyncdown
getmouse No
ungetmouse No
mousemask No
enclose Yes wenclose
mouse_trafo Yes wmouse_trafo
mouseinterval No
BUTTON_RELEASE No
BUTTON_PRESS No
BUTTON_CLICK No
BUTTON_DOUBLE_CLICK No
BUTTON_TRIPLE_CLICK No
BUTTON_RESERVED_EVENT No
use_default_colors No
assume_default_colors No
define_key No
keybound No
keyok No
resizeterm No
resize Yes wresize
getmaxy Yes
getmaxx Yes
flusok Yes
getcap No
touchoverlap No
new_panel No
bottom_panel No
top_panel No
show_panel No
update_panels No
hide_panel No
panel_window No
replace_panel No
move_panel No
panel_hidden No
panel_above No
panel_below No
set_panel_userptr No
panel_userptr No
del_panel No
set_menu_fore No
menu_fore No
set_menu_back No
menu_back No
set_menu_grey No
menu_grey No
set_menu_pad No
menu_pad No
pos_menu_cursor No
menu_driver No
set_menu_format No
menu_format No
set_menu_items No
menu_items No
item_count No
set_menu_mark No
menu_mark No
new_menu No
free_menu No
menu_opts No
set_menu_opts No
menu_opts_on No
menu_opts_off No
set_menu_pattern No
menu_pattern No
post_menu No
unpost_menu No
set_menu_userptr No
menu_userptr No
set_menu_win No
menu_win No
set_menu_sub No
menu_sub No
scale_menu No
set_current_item No
current_item No
set_top_row No
top_row No
item_index No
item_name No
item_description No
new_item No
free_item No
set_item_opts No
item_opts_on No
item_opts_off No
item_opts No
item_userptr No
set_item_userptr No
set_item_value No
item_value No
item_visible No
menu_request_name No
menu_request_by_name No
set_menu_spacing No
menu_spacing No
pos_form_cursor No
data_ahead No
data_behind No
form_driver No
set_form_fields No
form_fields No
field_count No
move_field No
new_form No
free_form No
set_new_page No
new_page No
set_form_opts No
form_opts_on No
form_opts_off No
form_opts No
set_current_field No
current_field No
set_form_page No
form_page No
field_index No
post_form No
unpost_form No
set_form_userptr No
form_userptr No
set_form_win No
form_win No
set_form_sub No
form_sub No
scale_form No
set_field_fore No
field_fore No
set_field_back No
field_back No
set_field_pad No
field_pad No
set_field_buffer No
field_buffer No
set_field_status No
field_status No
set_max_field No
field_info No
dynamic_field_info No
set_field_just No
field_just No
new_field No
dup_field No
link_field No
free_field No
set_field_opts No
field_opts_on No
field_opts_off No
field_opts No
set_field_userptr No
field_userptr No
field_arg No
form_request_name No
form_request_by_name No[*] To use any functions in this column, the program must set the variable $Curses::OldCurses variable to a non-zero value before using the Curses package. See "Perl 4.X cursperl Compatibility" for an example of this.
Available Wide-Character-Aware Functions
Function Uses wide-character call Reverts to legacy call
-------- ------------------------ ----------------------
getchar wget_wch wgetch
getstring wgetn_wstr wgetnstr
ungetchar unget_wch ungetch
instring winnwtr winnstr
addstring waddnwstr waddnstr
insstring wins_nwstr winsnstrAvailable Variables
LINES COLS stdscr
curscr COLORS COLOR_PAIRSAvailable Constants
ERR OK ACS_BLOCK
ACS_BOARD ACS_BTEE ACS_BULLET
ACS_CKBOARD ACS_DARROW ACS_DEGREE
ACS_DIAMOND ACS_HLINE ACS_LANTERN
ACS_LARROW ACS_LLCORNER ACS_LRCORNER
ACS_LTEE ACS_PLMINUS ACS_PLUS
ACS_RARROW ACS_RTEE ACS_S1
ACS_S9 ACS_TTEE ACS_UARROW
ACS_ULCORNER ACS_URCORNER ACS_VLINE
A_ALTCHARSET A_ATTRIBUTES A_BLINK
A_BOLD A_CHARTEXT A_COLOR
A_DIM A_INVIS A_NORMAL
A_PROTECT A_REVERSE A_STANDOUT
A_UNDERLINE COLOR_BLACK COLOR_BLUE
COLOR_CYAN COLOR_GREEN COLOR_MAGENTA
COLOR_RED COLOR_WHITE COLOR_YELLOW
KEY_A1 KEY_A3 KEY_B2
KEY_BACKSPACE KEY_BEG KEY_BREAK
KEY_BTAB KEY_C1 KEY_C3
KEY_CANCEL KEY_CATAB KEY_CLEAR
KEY_CLOSE KEY_COMMAND KEY_COPY
KEY_CREATE KEY_CTAB KEY_DC
KEY_DL KEY_DOWN KEY_EIC
KEY_END KEY_ENTER KEY_EOL
KEY_EOS KEY_EVENT KEY_EXIT
KEY_F0
KEY_FIND KEY_HELP KEY_HOME
KEY_IC KEY_IL KEY_LEFT
KEY_LL KEY_MARK KEY_MAX
KEY_MESSAGE KEY_MIN KEY_MOVE
KEY_NEXT KEY_NPAGE KEY_OPEN
KEY_OPTIONS KEY_PPAGE KEY_PREVIOUS
KEY_PRINT KEY_REDO KEY_REFERENCE
KEY_REFRESH KEY_REPLACE KEY_RESET
KEY_RESIZE KEY_RESTART KEY_RESUME
KEY_RIGHT
KEY_SAVE KEY_SBEG KEY_SCANCEL
KEY_SCOMMAND KEY_SCOPY KEY_SCREATE
KEY_SDC KEY_SDL KEY_SELECT
KEY_SEND KEY_SEOL KEY_SEXIT
KEY_SF KEY_SFIND KEY_SHELP
KEY_SHOME KEY_SIC KEY_SLEFT
KEY_SMESSAGE KEY_SMOVE KEY_SNEXT
KEY_SOPTIONS KEY_SPREVIOUS KEY_SPRINT
KEY_SR KEY_SREDO KEY_SREPLACE
KEY_SRESET KEY_SRIGHT KEY_SRSUME
KEY_SSAVE KEY_SSUSPEND KEY_STAB
KEY_SUNDO KEY_SUSPEND KEY_UNDO
KEY_UP KEY_MOUSE BUTTON1_RELEASED
BUTTON1_PRESSED BUTTON1_CLICKED BUTTON1_DOUBLE_CLICKED
BUTTON1_TRIPLE_CLICKED BUTTON1_RESERVED_EVENT BUTTON2_RELEASED
BUTTON2_PRESSED BUTTON2_CLICKED BUTTON2_DOUBLE_CLICKED
BUTTON2_TRIPLE_CLICKED BUTTON2_RESERVED_EVENT BUTTON3_RELEASED
BUTTON3_PRESSED BUTTON3_CLICKED BUTTON3_DOUBLE_CLICKED
BUTTON3_TRIPLE_CLICKED BUTTON3_RESERVED_EVENT BUTTON4_RELEASED
BUTTON4_PRESSED BUTTON4_CLICKED BUTTON4_DOUBLE_CLICKED
BUTTON4_TRIPLE_CLICKED BUTTON4_RESERVED_EVENT BUTTON_CTRL
BUTTON_SHIFT BUTTON_ALT ALL_MOUSE_EVENTS
REPORT_MOUSE_POSITION NCURSES_MOUSE_VERSION E_OK
E_SYSTEM_ERROR E_BAD_ARGUMENT E_POSTED
E_CONNECTED E_BAD_STATE E_NO_ROOM
E_NOT_POSTED E_UNKNOWN_COMMAND E_NO_MATCH
E_NOT_SELECTABLE E_NOT_CONNECTED E_REQUEST_DENIED
E_INVALID_FIELD E_CURRENT REQ_LEFT_ITEM
REQ_RIGHT_ITEM REQ_UP_ITEM REQ_DOWN_ITEM
REQ_SCR_ULINE REQ_SCR_DLINE REQ_SCR_DPAGE
REQ_SCR_UPAGE REQ_FIRST_ITEM REQ_LAST_ITEM
REQ_NEXT_ITEM REQ_PREV_ITEM REQ_TOGGLE_ITEM
REQ_CLEAR_PATTERN REQ_BACK_PATTERN REQ_NEXT_MATCH
REQ_PREV_MATCH MIN_MENU_COMMAND MAX_MENU_COMMAND
O_ONEVALUE O_SHOWDESC O_ROWMAJOR
O_IGNORECASE O_SHOWMATCH O_NONCYCLIC
O_SELECTABLE REQ_NEXT_PAGE REQ_PREV_PAGE
REQ_FIRST_PAGE REQ_LAST_PAGE REQ_NEXT_FIELD
REQ_PREV_FIELD REQ_FIRST_FIELD REQ_LAST_FIELD
REQ_SNEXT_FIELD REQ_SPREV_FIELD REQ_SFIRST_FIELD
REQ_SLAST_FIELD REQ_LEFT_FIELD REQ_RIGHT_FIELD
REQ_UP_FIELD REQ_DOWN_FIELD REQ_NEXT_CHAR
REQ_PREV_CHAR REQ_NEXT_LINE REQ_PREV_LINE
REQ_NEXT_WORD REQ_PREV_WORD REQ_BEG_FIELD
REQ_END_FIELD REQ_BEG_LINE REQ_END_LINE
REQ_LEFT_CHAR REQ_RIGHT_CHAR REQ_UP_CHAR
REQ_DOWN_CHAR REQ_NEW_LINE REQ_INS_CHAR
REQ_INS_LINE REQ_DEL_CHAR REQ_DEL_PREV
REQ_DEL_LINE REQ_DEL_WORD REQ_CLR_EOL
REQ_CLR_EOF REQ_CLR_FIELD REQ_OVL_MODE
REQ_INS_MODE REQ_SCR_FLINE REQ_SCR_BLINE
REQ_SCR_FPAGE REQ_SCR_BPAGE REQ_SCR_FHPAGE
REQ_SCR_BHPAGE REQ_SCR_FCHAR REQ_SCR_BCHAR
REQ_SCR_HFLINE REQ_SCR_HBLINE REQ_SCR_HFHALF
REQ_SCR_HBHALF REQ_VALIDATION REQ_NEXT_CHOICE
REQ_PREV_CHOICE MIN_FORM_COMMAND MAX_FORM_COMMAND
NO_JUSTIFICATION JUSTIFY_LEFT JUSTIFY_CENTER
JUSTIFY_RIGHT O_VISIBLE O_ACTIVE
O_PUBLIC O_EDIT O_WRAP
O_BLANK O_AUTOSKIP O_NULLOK
O_PASSOK O_STATIC O_NL_OVERLOAD
O_BS_OVERLOAD Curses functions not available through Perl Curses
tstp _putchar fullname scanw wscanw mvscanw mvwscanw ripoffline
setupterm setterm set_curterm del_curterm restartterm tparm tputs
putp vidputs vidattr mvcur tigetflag tigetnum tigetstr tgetent
tgetflag tgetnum tgetstr tgoto tputsCurses menu functions not available through Perl Curses
set_item_init item_init set_item_term item_term set_menu_init
menu_init set_menu_term menu_termCurses form functions not available through Perl Curses
new_fieldtype free_fieldtype set_fieldtype_arg
set_fieldtype_choice link_fieldtype set_form_init form_init
set_form_term form_term set_field_init field_init set_field_term
field_term set_field_type field_type