Ncurses wrefresh not showing window borders - c++

Question

I am experimenting with some C++ using ncurses and am having trouble showing the window borders, but am having trouble with the following programs.
#include <cstdio>
#include <cstdlib>
#include <ncurses.h>
int main(int argc, char **argv)
{
if(argc != 5)
{
printf("not enough arguments\n");
exit(1);
}
int height = atoi(argv[1]);
int width = atoi(argv[2]);
int y = atoi(argv[3]);
int x = atoi(argv[4]);
initscr();
WINDOW *win = newwin(height, width, y, x);
box(win, 0, 0);
wrefresh(win);
int py, px;
getparyx(win, py, px);
mvprintw(LINES-2, 0, "getparyx: (%d, %d)", py, px);
int by, bx;
getbegyx(win, by, bx);
mvprintw(LINES-1, 0, "getbegyx: (%d, %d)", by, bx);
getch();
delwin(win);
endwin();
}
In the program above I draw the border using box and refresh using wrefresh, but it doesn't show anything. The other stuff that I print to stdscr, however, does show.
In another program however I was able to get the border working.
#include <ncurses.h>
int main()
{
const int height = 6, width = 8;
WINDOW *win;
int starty, startx;
int ch;
initscr();
cbreak();
noecho();
keypad(stdscr, TRUE);
starty = (LINES - height) / 2;
startx = (COLS - width) / 2;
win = newwin(height, width, starty, startx);
box(win, 0, 0);
wrefresh(win);
while((ch = getch()) != KEY_F(1))
{
wborder(win, ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ');
wrefresh(win);
delwin(win);
switch(ch)
{
case KEY_UP:
win = newwin(height, width, --starty, startx);
break;
case KEY_DOWN:
win = newwin(height, width, ++starty, startx);
break;
case KEY_LEFT:
win = newwin(height, width, starty, --startx);
break;
case KEY_RIGHT:
win = newwin(height, width, starty, ++startx);
break;
}
move(starty + (height / 2) - 1, startx + (width / 2) - 1);
box(win, 0, 0);
wrefresh(win);
}
delwin(win);
endwin();
}
The thing is that the border only appears in the loop. In other words the border does not start to show until I press buttons, meaning the initial wrefresh did not work.
After doing some research I this thread which suggested to call refresh after initscr (or at least before wrefresh()) but that did not work. So what am I missing that the border does not show in the first program?

Answer 1

For my tests, that initial refresh() is certainly what is missing. I checked some old code I wrote, and it indeed calls refresh() as part of the ncurses initialisation. Adding this to your code made it work for me. A lot of the curses documentation is still constrained to books, it never really made it onto the web.
initscr();
refresh(); // <-- HERE
WINDOW *win = newwin( height, width, y, x );
box( win, 0, 0 );
wrefresh(win);
I don't think the windowing model is fully initialised until after that first refresh() is called. But I could not find any documentation on exactly why that would be the case.
So not much detail in this answer, sorry... but I hope it helps.

Answer 2

The manual pages answer the question:
initscr
initscr also causes the first call to refresh(3x)
to clear the screen.
getch
If the window is not a pad, and it has been moved or modified since the
last call to wrefresh, wrefresh will be called before another character
is read.
The initscr (clear) and the mvprintw calls update stdscr, which is finally refreshed when you call getch. stdscr is a window, and as noted in the discussion of wrefresh, the physical screen is updated in the order that refreshes are applied (that is, it overlaps with the other window, and if you want the other window to appear, you should refresh stdscr first, to handle the clearing operation).