OVERLAY(3XCURSES) X/Open Curses Library Functions OVERLAY(3XCURSES)


overlay, overwrite - copy overlapped windows


cc [ flag... ] file... -I /usr/xpg4/include -L /usr/xpg4/lib \
-R /usr/xpg4/lib -lcurses [ library... ]

c89 [ flag... ] file... -lcurses [ library... ]

#include <curses.h>

int overlay(const WINDOW *srcwin, WINDOW *dstwin);

int overwrite(const WINDOW *srcwin, WINDOW *dstwin);


Is a pointer to the source window to be copied.

Is a pointer to the destination window to be overlayed or


The overwrite() and overlay() functions overlay srcwin on top of destwin.
The srcwin and dstwin arguments do not have to be the same size; only
text where the two windows overlap is copied.

The overwrite() function copies characters as though a sequence of
win_wch(3XCURSES) and wadd_wch(3XCURSES) were performed with the
destination window's attributes and background attributes cleared.

The overlay() function does the same thing, except that, whenever a
character to be copied is the background character of the source window,
overlay() does not copy the character but merely moves the destination
cursor the width of the source background character.

If any portion of the overlaying window border is not the first column of
a multi-column character, then all the column positions will be replaced
with the background character and rendition before the overlay is done.
If the default background character is a multi-column character when this
occurs, then these functions fail.


Upon successful completion, these functions return OK. Otherwise, they
return ERR.


No errors are defined.


Example 1: Implement a pop-up dialog

The following example demonstrates the use of overwrite() to implement a
pop-up dialog box.

#include <curses.h>
* Pop-up a window on top of curscr. If row and/or col
* are -1 then that dimension will be centered within
* curscr. Return 0 for success or -1 if malloc() failed.
* Pass back the working window and the saved window for the
* pop-up. The saved window should not be modified.
popup(work, save, nrows, ncols, row, col)
WINDOW **work, **save;
int nrows, ncols, row, col;
int mr, mc;
getmaxyx(curscr, mr, mc);
/* Windows are limited to the size of curscr. */
if (mr < nrows)
nrows = mr;
if (mc < ncols)
ncols = mc;
/* Center dimensions. */
if (row == -1)
row = (mr-nrows)/2;
if (col == -1)
col = (mc-ncols)/2;
/* The window must fit entirely in curscr. */
if (mr < row+nrows)
row = 0;
if (mc < col+ncols)
col = 0;
*work = newwin(nrows, ncols, row, col);
if (*work == NULL)
return (-1);
if ((*save = dupwin(*work)) == NULL) {
return (-1);
overwrite(curscr, *save);
return (0);
* Restore the region covered by a pop-up window.
* Delete the working window and the saved window.
* This function is the complement to popup(). Return
* 0 for success or -1 for an error.
popdown(work, save)
WINDOW *work, *save;
(void) wnoutrefresh(save);
(void) delwin(save);
(void) delwin(work);
return (0);
* Compute the size of a dialog box that would fit around
* the string.
dialsize(str, nrows, ncols)
char *str;
int *nrows, *ncols;
int rows, cols, col;
for (rows = 1, cols = col = 0; *str != '\0'; ++str) {
if (*str == '\n') {
if (cols < col)
cols = col;
col = 0;
} else {
if (cols < col)
cols = col;
*nrows = rows;
*ncols = cols;
* Write a string into a dialog box.
dialfill(w, s)
char *s;
int row;
(void) wmove(w, 1, 1);
for (row = 1; *s != '\0'; ++s) {
(void) waddch(w, *((unsigned char*) s));
if (*s == '\n')
wmove(w, ++row, 1);
box(w, 0, 0);
char *str;
WINDOW *work, *save;
int nrows, ncols, row, col;
/* Figure out size of window. */
dialsize(str, &nrows, &ncols);
/* Create a centered working window with extra */
/* room for a border. */
(void) popup(&work, &save, nrows+2, ncols+2, -1, -1);
/* Write text into the working window. */
dialfill(work, str);
/* Pause. Remember that wgetch() will do a wrefresh() */
/* for us. */
(void) wgetch(work);
/* Restore curscr and free windows. */
(void) popdown(work, save);
/* Redraw curscr to remove window from physical screen. */
(void) doupdate();


See attributes(7) for descriptions of the following attributes:

|Interface Stability | Standard |
|MT-Level | Unsafe |


copywin(3XCURSES), libcurses(3XCURSES), wadd_wch(3XCURSES),
win_wch(3XCURSES), attributes(7), standards(7)

June 5, 2002 OVERLAY(3XCURSES)