ncurses: filling window with background

[Schmidt]

I have some ideas about writing a small game in terminal ( just for fun ) using ncurses library. I want to use some kind of menus (in Midnight Commander's style), but there are some problems with rendering windows, that I don't understand. I create a window with newwin(), assign a color pair to it calling wattron() (for example, I want to fill a window with blue background), and then I call my own function wnd_fill() :

void wnd_fill (WINDOW* wnd)
{
  int i;
  int maxy = wnd->_maxy;       // retrieve the window's Y and X sizes
  int maxx = wnd->_maxx;
  int area = maxy * maxx;        // calc the window's area
  char *buf = (char *) malloc (area);
  for(i=0; i < area; i++) {
    buf[i] = ' ';               // generate an "empty" string
  }
  buf[area] = '\0';
  waddstr (wnd, buf);           // fill the window
  wrefresh (wnd);
}

But the result is not the same as I expect. The window is filled entirely, except the last (bottom) line - only its lesser part is filled. No matter how huge I make the string in 'buf' - it always left the window's lower right part unfilled. If I highlight the window's borders with the box() function, it looks like on the image in attachment.

Can anyone tell me what's the matter of such broken window fill and how I can fix it?

[Rubberman]

First, allocate one byte more than the 'area' for your buffer. You are overriting the end of the buffer since the position of buf[area] is actually beyond the end of the buffer you allocated. As a result, it has munged your stack. You are lucky it didn't segfault on you. This may be related to your problem. Try it at least to be sure that this isn't causing the effect you are seeing.

[Schmidt]

Oh my God... That's thing I've just forgot :) of course, you are right, cause of this function is called also from other code parts, a segfault appears randomly with some trash on the screen. Thanks, it seems that all other problems are also could be fixed in that way :)

[Rubberman]

Happy to help. This is one of the most common software bugs out there - mis-sized buffers and buffer overruns. If you are developing software for commercial or corporate use, it is helpful to utilize some memory checking tools that will detect these sort of problems. If $$ is no issue, then you can't go wrong with IBM/Rational Purify. If it is, then are are some open source tools that will help detect these sort of problems. In fact, I think that the GNU debugger (GDB) can do bounds-checking if you compile your software properly and run it in the debugger for testing. I haven't done this, personally, so I only THINK it can be done, from some things I have read in the past...

[Schmidt]

Thanks, I think I should try some of them ) at now it's only my own interest, not $$ yet
And the window-filling problem at last appeared to be a quite more interesting...) the window's X size (width) in fact doesn't match with summary width of filling chars ) I had to add 11 spaces to reach the correct result

[Rubberman]

Probably due to line-wrapping? It's been a LONG time since I last did much ncurses programming (almost 20 years). Never had this particular problem, but the environment is different. In fact, at one time, I implemented my own curses library for realtime systems. One resource I have been very productive with was Unix Curses Explained from Prentice-Hall by Berny Goodheart. I don't know if it is still in print (Copyright 1991), but it was very useful to me.

[Rubberman]

Also I had a lot of use from O'Reilly & Associates' book Programming with Curses, published in 1986 originally. I'm sure there are newer books on the subject, but these two, the O'Reilly and Prentice-Hall books, enabled me to implement a completely compatible and efficient curses library suitable for realtime applications.

[Schmidt]

Probably due to line-wrapping? It's been a LONG time since I last did much ncurses programming (almost 20 years). Never had this particular problem, but the environment is different. In fact, at one time, I implemented my own curses library for realtime systems. One resource I have been very productive with was Unix Curses Explained from Prentice-Hall by Berny Goodheart. I don't know if it is still in print (Copyright 1991), but it was very useful to me.

Maybe so, I can't imagine a reason yet - just a few days earlier I decided to dig into subject of curses library) thanks for the books, I found "Unix Curses Explained" on Amazon, I think it will be useful in any way)

[Schmidt]

I heard that some people compile ncurses from the source code, so can I find it anywhere?.. Does ncurses library has its own website, or source repository?..

[unlimitedscolobb]

Does ncurses library has its own website, or source repository?..

Try this: ftp.gnu.org/pub/gnu/ncurses/ . Sorry, no links -- Linux Forums doesn't trust me yet