Ncurses: printw(); prints to screen even if refresh(); is not called

violagirl23 · 03-08-2008, 06:23 PM

All the tutorials I have read say that the changes you make in output will not actually display unless you call refresh();. I liked that idea because I could make several changes before displaying them. However, it doesn't seem to make a difference whether I use it or not-- printw() prints to the screen. How can I change this?
(The language is C++).

zensunni · 03-09-2008, 02:14 PM

I had this exact same question when I was using ncurses. I basically shrugged it off and didn't worry about refreshing, but I'm still curious why this is the case. Anyone?

orgcandman · 03-10-2008, 07:37 AM

Not an ncurses guy myself, however my guess after reading some google would be that printw() behaves in a similar fashion to printf(). Namely, if you use '\n' at the end of the text, it will auto flush the stream to which you're writing. My guess (again from reading code) is that refresh() is a flush() analog.

I could be wrong. Experiment :P

Guttorm · 03-10-2008, 08:12 AM

Hi

I don't know ncurses either. But it could be it's because standard output is line buffered. Maybe add this somewhere in the beginning to make it fully buffered:

setvbuf(stdout,NULL,_IOFBF,8192);

This changes stdout so the output is buffered, and sets the buffer size to 8k. Then no output will be visible until the buffer is full or fflush(stdout) is called. The refresh() probably does an fflush on stdout.