The X/Open Curses Interface Definition describes a set of C-Language functions that provide screen-handling and updating, which are collectively known as the curses library.
The curses library permits manipulation of data structures called windows which may be thought of as two-dimensional arrays of characters representing all or part of a terminal’s screen. The windows are manipulated using a procedural interface described elsewhere. The curses package maintains a record of what characters are on the screen. At the most basic level, manipulation is done with the routines move() and addch() which are used to “move” the curses around and add characters to the default window, stdscr, which represents the whole screen.
An application may use these routines to add data to the window in any convenient order. Once all data have been added, the routine refresh() is called. The package then determines what changes have been made which affect the screen. The screen contents are then changed to reflect those characters now in the window, using a sequence of operations optimized for the type of terminal in use.
At a higher level routines combining the actions of move() and addch() are defined, as are routines to add whole strings and to perform format conversions in the manner of printf().
Interfaces are also defined to erase the entire window and to specify the attributes of individual characters in the window. Attributes such as inverse video, underline and blink can be used on a per-character basis.
New windows can be created by allowing the application to build several images of the screen and display the appropriate one very quickly. New windows are created using the routine newwin(). For each routine that manipulates the default window, stdscr, there is a corresponding routine prefixed with w to manipulate the contents of a specified window; for example, move() and wmove(). In fact, move(…) is functionally equivalent to wmove( stdscr, …). This is similar to the interface offered by printf(…) and fprintf(stdout, …).
Windows do not have to correspond to the entire screen. It is possible to create smaller windows, and also to indicate that the window is only partially visible on the screen. Furthermore, large windows or pads, which are bigger than the actual screen size, may be created.
Interfaces are also defined to allow input character manipulation and to disable and enable many input attributes: character echo, single character input with or without signal processing (cbreak or raw modes), carriage returns mapping to newlines, screen scrolling, etc.
The data types supported by curses are described in this section.
As the library supports a procedural interface to the data types, actual structure contents are not described. All curses data are manipulated using the routines provided.
The <curses.h> header defines various constants and declares the data types that are available to the application.
The following data types are declared:
WINDOW * pointer to screen representation SCREEN * pointer to terminal descriptor bool boolean data type chtype representation of a character in a window cchar_t the wide-character equivalent of chtype attr_t for WA_-style attributes
The actual WINDOW and SCREEN objects used to store information are created by the corresponding routines and a pointer to them is provided. All manipulation is through that pointer.
The following variables are defined:
LINES number of lines on terminal screen COLS number of columns on terminal screen stdscr pointer to the default screen window curscr pointer to the current screen image SP pointer to the current SCREEN struct Mouse_status status of the mouse COLORS number of colors available COLOR_PAIRS number of color pairs available TABSIZE size of one TAB block acs_map alternate character set map ttytype terminal name/description
The following constants are defined:
FALSE boolean false value TRUE boolean true value NULL zero pointer value ERR value returned on error condition OK value returned on successful completion
Normally, attributes are a property of the character.
A_ALTCHARSET use the alternate character set A_BLINK bright background or blinking A_BOLD bright foreground or bold A_DIM half bright -- no effect in PDCurses A_INVIS invisible -- no effect in PDCurses A_ITALIC italic A_LEFT line along the left edge A_PROTECT protected -- no effect in PDCurses A_REVERSE reverse video A_RIGHT line along the right edge A_STANDOUT terminal's best highlighting mode A_UNDERLINE underline A_ATTRIBUTES bit-mask to extract attributes A_CHARTEXT bit-mask to extract a character A_COLOR bit-mask to extract a color-pair
Not all attributes will work on all terminals. A_ITALIC is not standard, but is shared with ncurses.
WA_ALTCHARSET same as A_ALTCHARSET WA_BLINK same as A_BLINK WA_BOLD same as A_BOLD WA_DIM same as A_DIM WA_INVIS same as A_INVIS WA_ITALIC same as A_ITALIC WA_LEFT same as A_LEFT WA_PROTECT same as A_PROTECT WA_REVERSE same as A_REVERSE WA_RIGHT same as A_RIGHT WA_STANDOUT same as A_STANDOUT WA_UNDERLINE same as A_UNDERLINE
The following are also defined, for compatibility, but currently have no effect in PDCurses: A_HORIZONTAL, A_LOW, A_TOP, A_VERTICAL and their WA_* equivalents.
For use in chtypes and with related functions. These are a portable way to represent graphics characters on different terminals.
VT100-compatible symbols – box characters:
ACS_ULCORNER upper left box corner ACS_LLCORNER lower left box corner ACS_URCORNER upper right box corner ACS_LRCORNER lower right box corner ACS_RTEE right "T" ACS_LTEE left "T" ACS_BTEE bottom "T" ACS_TTEE top "T" ACS_HLINE horizontal line ACS_VLINE vertical line ACS_PLUS plus sign, cross, or four-corner piece
VT100-compatible symbols – other:
ACS_S1 scan line 1 ACS_S9 scan line 9 ACS_DIAMOND diamond ACS_CKBOARD checkerboard -- 50% grey ACS_DEGREE degree symbol ACS_PLMINUS plus/minus sign ACS_BULLET bullet
Teletype 5410v1 symbols – these are defined in SysV curses, but are not well-supported by most terminals. Stick to VT100 characters for optimum portability:
ACS_LARROW left arrow ACS_RARROW right arrow ACS_DARROW down arrow ACS_UARROW up arrow ACS_BOARD checkerboard -- lighter (less dense) than ACS_CKBOARD ACS_LANTERN lantern symbol ACS_BLOCK solid block
That goes double for these – undocumented SysV symbols. Don’t use them:
ACS_S3 scan line 3 ACS_S7 scan line 7 ACS_LEQUAL less than or equal ACS_GEQUAL greater than or equal ACS_PI pi ACS_NEQUAL not equal ACS_STERLING pounds sterling symbol
Box character aliases:
ACS_BSSB same as ACS_ULCORNER ACS_SSBB same as ACS_LLCORNER ACS_BBSS same as ACS_URCORNER ACS_SBBS same as ACS_LRCORNER ACS_SBSS same as ACS_RTEE ACS_SSSB same as ACS_LTEE ACS_SSBS same as ACS_BTEE ACS_BSSS same as ACS_TTEE ACS_BSBS same as ACS_HLINE ACS_SBSB same as ACS_VLINE ACS_SSSS same as ACS_PLUS
For cchar_t and wide-character functions, WACS_ equivalents are also defined.
For use with init_pair(), color_set(), etc.:
COLOR_BLACK COLOR_BLUE COLOR_GREEN COLOR_CYAN COLOR_RED COLOR_MAGENTA COLOR_YELLOW COLOR_WHITE
Use these instead of numeric values. The definition of the colors depends on the implementation of curses.
The following constants might be returned by getch() if keypad() has been enabled. Note that not all of these may be supported on a particular terminal:
KEY_BREAK break key KEY_DOWN the four arrow keys KEY_UP KEY_LEFT KEY_RIGHT KEY_HOME home key (upward+left arrow) KEY_BACKSPACE backspace KEY_F0 function keys; space for 64 keys is reserved KEY_F(n) (KEY_F0+(n)) KEY_DL delete line KEY_IL insert line KEY_DC delete character KEY_IC insert character KEY_EIC exit insert character mode KEY_CLEAR clear screen KEY_EOS clear to end of screen KEY_EOL clear to end of line KEY_SF scroll 1 line forwards KEY_SR scroll 1 line backwards (reverse) KEY_NPAGE next page KEY_PPAGE previous page KEY_STAB set tab KEY_CTAB clear tab KEY_CATAB clear all tabs KEY_ENTER enter or send KEY_SRESET soft (partial) reset KEY_RESET reset or hard reset KEY_PRINT print or copy KEY_LL home down or bottom (lower left) KEY_A1 upper left of virtual keypad KEY_A3 upper right of virtual keypad KEY_B2 center of virtual keypad KEY_C1 lower left of virtual keypad KEY_C3 lower right of virtual keypad KEY_BTAB Back tab key KEY_BEG Beginning key KEY_CANCEL Cancel key KEY_CLOSE Close key KEY_COMMAND Cmd (command) key KEY_COPY Copy key KEY_CREATE Create key KEY_END End key KEY_EXIT Exit key KEY_FIND Find key KEY_HELP Help key KEY_MARK Mark key KEY_MESSAGE Message key KEY_MOVE Move key KEY_NEXT Next object key KEY_OPEN Open key KEY_OPTIONS Options key KEY_PREVIOUS Previous object key KEY_REDO Redo key KEY_REFERENCE Reference key KEY_REFRESH Refresh key KEY_REPLACE Replace key KEY_RESTART Restart key KEY_RESUME Resume key KEY_SAVE Save key KEY_SBEG Shifted beginning key KEY_SCANCEL Shifted cancel key KEY_SCOMMAND Shifted command key KEY_SCOPY Shifted copy key KEY_SCREATE Shifted create key KEY_SDC Shifted delete char key KEY_SDL Shifted delete line key KEY_SELECT Select key KEY_SEND Shifted end key KEY_SEOL Shifted clear line key KEY_SEXIT Shifted exit key KEY_SFIND Shifted find key KEY_SHELP Shifted help key KEY_SHOME Shifted home key KEY_SIC Shifted input key KEY_SLEFT Shifted left arrow key KEY_SMESSAGE Shifted message key KEY_SMOVE Shifted move key KEY_SNEXT Shifted next key KEY_SOPTIONS Shifted options key KEY_SPREVIOUS Shifted prev key KEY_SPRINT Shifted print key KEY_SREDO Shifted redo key KEY_SREPLACE Shifted replace key KEY_SRIGHT Shifted right arrow KEY_SRSUME Shifted resume key KEY_SSAVE Shifted save key KEY_SSUSPEND Shifted suspend key KEY_SUNDO Shifted undo key KEY_SUSPEND Suspend key KEY_UNDO Undo key
The virtual keypad is arranged like this:
A1 up A3 left B2 right C1 down C3
This list is incomplete – see curses.h for the full list, and use the testcurs demo to see what values are actually returned. The above are just the keys required by X/Open. In particular, PDCurses defines many CTL_ and ALT_ combinations; these are not portable.