curses (ncurses) library question Post: 2853

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Top Forums Programming curses (ncurses) library question Post 2853 by TelePlayer on Thursday 7th of June 2001 03:28:38 PM

06-07-2001

Registered User

curses (ncurses) library question

Hi again. I'm using the curses functions simply to output data to
the screen in certain areas. Very simple, just using the full
screen, no windows.

The problem is that I'm calling mvprintw from within several child
processes in the same session, and the output is going
bananas. ie, no matter what x and y values I put in the
mvprintw, the output appears at the last cursor position of
another child process.

I found some info about a buffering problem, but I followed all
their suggestions and came up with the same result.

The code should output this:
0 2 4 6 8
1 3 5 7 9

but instead outputs this:
0 3 2 5 4 7 6 9 8
1

Here's the code: OH, and thanks to the kind person who replied
to my post about IPC...that helped me immensely. The ipc_
functions below are wrappers for the mutexes and shared
memory functions:

<pre>
int Print(int, int, char *);

struct shared_memory
{
int sem;
// void *pPrint;
WINDOW *win;
// SCREEN *scr;
};

struct shared_memory *sm = NULL;

int main(int argc, char** argv)
{
pid_t p;
int ch;
char temp[5];

sm = ipc_sram_alloc(1, sizeof(struct shared_memory));
if (sm == (void *)NULL)
exit(0);

// sm->pPrint = (void *)Print;

ipc_mutex_alloc(&sm->sem, 0);

if (sm->sem < 0)
printf("BAD mutex\r\n");

sm->win = initscr();
wclear(sm->win);
wrefresh(sm->win);

p = fork();
if (p == 0) // If we are a child process
{
for (ch = 0; ch < 10; ch += 2)
{
usleep(500000);
sprintf(temp, "%d", ch);
Print(9, ch + 1, temp);
usleep(500000);
}
exit(0);
}
else // otherwise we're in the parent
{
for (ch = 1; ch < 10; ch += 2)
{
usleep(500000);
sprintf(temp, "%d", ch);
Print(10, ch + 1, temp);
usleep(500000);
}
}

wait(NULL); // wait for child to die
endwin();
ipc_mutex_free(sm->sem);
ipc_sram_free(sm);
}

int Print(int row, int col, char *psz)
{
ipc_mutex_acquire(sm->sem);
mvwprintw(sm->win, row, col, psz);
wrefresh(sm->win);
// mvprintw(row, col, psz);
// refresh();
ipc_mutex_release(sm->sem);
return 0;
}
</pre>

Last edited by TelePlayer; 06-07-2001 at 05:27 PM..

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LEARN ABOUT CENTOS

is_term_resized

resizeterm(3X)															    resizeterm(3X)

NAME

       is_term_resized, resize_term, resizeterm - change the curses terminal size

SYNOPSIS

       #include <curses.h>

       bool is_term_resized(int lines, int columns);
       int resize_term(int lines, int columns);
       int resizeterm(int lines, int columns);

DESCRIPTION

       This  is an extension to the curses library.  It provides callers with a hook into the ncurses data to resize windows, primarily for use by
       programs running in an X Window terminal (e.g., xterm).	The function resizeterm resizes the standard and current windows to the  specified
       dimensions, and adjusts other bookkeeping data used by the ncurses library that record the window dimensions.

       Most of the work is done by the inner function resize_term.  The outer function resizeterm adds bookkeeping for the SIGWINCH handler.  When
       resizing the windows, resize_term blank-fills the areas that are extended.  The calling application should fill in these areas with  appro-
       priate  data.  The resize_term function attempts to resize all windows.	However, due to the calling convention of pads, it is not possible
       to resize these without additional interaction with the application.

       A support function is_term_resized is provided so that applications can check if the resize_term function would modify  the  window  struc-
       tures.  It returns TRUE if the windows would be modified, and FALSE otherwise.

RETURN VALUE

       Except as notes, these function return the integer ERR upon failure and OK on success.  They will fail if either of the dimensions are less
       than or equal to zero, or if an error occurs while (re)allocating memory for the windows.

NOTES

       While these functions are intended to be used to support a signal handler (i.e., for SIGWINCH), care should be taken to avoid invoking them
       in a context where malloc or realloc may have been interrupted, since it uses those functions.

       If  ncurses is configured to supply its own SIGWINCH handler, the resizeterm function ungetch's a KEY_RESIZE which will be read on the next
       call to getch.  This is used to alert an application that the screen size has changed, and that it should repaint special features such	as
       pads that cannot be done automatically.

       If the environment variables LINES or COLUMNS are set, this overrides the library's use of the window size obtained from the operating sys-
       tem.  Thus, even if a SIGWINCH is received, no screen size change may be recorded.

SEE ALSO

       curs_variables(3X), wresize(3X).

AUTHOR

       Thomas Dickey (from an equivalent function written in 1988 for BSD curses).

																    resizeterm(3X)