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NAME |SYNOPSIS |DESCRIPTION |RETURN VALUE |NOTES |PORTABILITY |SEE ALSO |COLOPHON | |
curs_bkgd(3X)curs_bkgd(3X)bkgdset,wbkgdset,bkgd,wbkgd,getbkgd-curseswindow background manipulation routines
#include <curses.h>void bkgdset(chtypech);void wbkgdset(WINDOW *win, chtype ch);int bkgd(chtypech);int wbkgd(WINDOW *win, chtypech);chtype getbkgd(WINDOW *win);
bkgdset Thebkgdsetandwbkgdsetroutines set thebackground for a window. A window's background is achtypeconsisting of any combination of attributes (i.e., rendition) and a character: • The attribute part of the background is combined (OR'ed) with all non-blank characters that are written into the window withwaddch. • Both the character and attribute parts of the background are combined with blank characters that are written into the window. The background becomes a property of each character and moves with the character through any scrolling and insert/delete line/character operations. To the extent possible on a particular terminal, the attribute part of the background is displayed as the graphic rendition of the character put on the screen.bkgd Thebkgdandwbkgdfunctions set the background property of the current or specified window and then apply this setting to every character position in that window. According to X/Open Curses, it should do this: • The rendition of every character on the screen is changed to the new background rendition. • Wherever the former background character appears, it is changed to the new background character. Neither X/Open Curses nor the SVr4 manual pages give details about the way the rendition of characters on the screen is updated whenbkgdorwbkgdis used to change the background character. This implementation, like SVr4 curses, does not store the background and window attribute contributions to each cell separately. It updates the rendition by comparing the character, non-color attributes and colors contained in the background. For each cell in the window, whether or not it is blank: • The library first compares thecharacter, and if it matches the current character part of the background, it replaces that with the new background character. Whenbkgdsetis used to set the background character, that does not update each cell in the window. A subsequent call tobkgdwill only modify thecharacter in cells which match the current background character. • The library then checks if the cell uses color, i.e., its color pair value is nonzero. If not, it simply replaces the attributes and color pair in the cell with those from the new background character. • If the cell uses color, and that matches the color in the current background, the library removes attributes which may have come from the current background and adds attributes from the new background. It finishes by setting the cell to use the color from the new background. • If the cell uses color, and that does not match the color in the current background, the library updates only the non-color attributes, first removing those which may have come from the current background, and then adding attributes from the new background. If the background's character value is zero (0), a space is assumed. If the terminal does not support color, or if color has not been started withstart_color, the new background character's color attribute will be ignored.getbkgd Thegetbkgdfunction returns the given window's current background character/attribute pair.
These functions are described in the XSI Curses standard, Issue 4. It specifies thatbkgdandwbkgdreturnERRon failure, but gives no failure conditions. The routinesbkgdandwbkgdreturn the integerOK, unless the library has not been initialized. In contrast, the SVr4.0 manual saysbkgdandwbkgdmay returnOK "or a non-negative integer ifimmedokis set", which refers to the return value fromwrefresh(used to implement the immediate repainting). The SVr4 curseswrefreshreturns the number of characters written to the screen during the refresh. This implementation does not do that.
Note thatbkgdsetandbkgdmay be macros. X/Open Curses mentions that the character part of the background must be a single-byte value. This implementation, like SVr4, checks to ensure that, and will reuse the old background character if the check fails.
These functions are described in the XSI Curses standard, Issue 4 (X/Open Curses).
curses(3X),curs_addch(3X),curs_attr(3X),curs_outopts(3X)
This page is part of thencurses (new curses) project. Information about the project can be found at ⟨https://www.gnu.org/software/ncurses/ncurses.html⟩. If you have a bug report for this manual page, send it to bug-ncurses-request@gnu.org. This page was obtained from the project's upstream Git mirror of the CVS repository ⟨https://github.com/mirror/ncurses.git⟩ on 2025-08-11. (At that time, the date of the most recent commit that was found in the repository was 2023-03-12.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which isnot part of the original manual page), send a mail to man-pages@man7.orgcurs_bkgd(3X)HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH. | |