Drawing to a Window in C++

[Dan Again]

StackOverflow post relating to this question can be found here (http://stackoverflow.com/questions/16214987/c-linux-drawing-to-a-window).

I am trying to alter a Conway's Game of Life (http://www.conwaylife.com/wiki/Main_Page) program that I wrote for an object oriented programming class I am taking. As it stands, the program outputs successive lines of text to the terminal. Instead, I would like to have a window that dynamically displays the state of my cells. I feel like I'm on the right path, but for some reason the line breaks that I've coded into my Life's "toString" method do not appear when I print my Life object to the X11 window. I feel like this problem is probably related to the way that I'm using the X11 window, since I'm a total n00b at that. Can anyone spot what's going wrong?


#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <X11/Xlib.h>
#include <sstream>

#include "Cell.h"
#include "Life.h"

int main (int argc, char *argv[])
{
Display *display;
Visual *visual;
int depth;
int text_x;
int text_y;
XSetWindowAttributes frame_attributes;
Window frame_window;
XFontStruct *fontinfo;
XGCValues gr_values;
GC graphical_context;
XEvent event;
char hello_string[] = "Hello World";
int hello_string_length = strlen(hello_string);

display = XOpenDisplay(NULL);
visual = DefaultVisual(display, 0);
depth = DefaultDepth(display, 0);

frame_attributes.background_pixel = XWhitePixel(display, 0);
/* create the application window */
frame_window = XCreateWindow(display, XRootWindow(display, 0),
0, 0, 400, 400, 5, depth,
InputOutput, visual, CWBackPixel,
&frame_attributes);
XStoreName(display, frame_window, "The Game of Life");
XSelectInput(display, frame_window, ExposureMask | StructureNotifyMask);

fontinfo = XLoadQueryFont(display, "10x20");
gr_values.font = fontinfo->fid;
gr_values.foreground = XBlackPixel(display, 0);
graphical_context = XCreateGC(display, frame_window,
GCFont+GCForeground, &gr_values);
XMapWindow(display, frame_window);

Life <ConwayCell> aLife (21, 21);

aLife.animate (10, 5, '*');
aLife.animate (10, 6, '*');
aLife.animate (10, 7, '*');
aLife.animate (10, 8, '*');
aLife.animate (10, 9, '*');
aLife.animate (10, 10, '*');
aLife.animate (10, 11, '*');
aLife.animate (10, 12, '*');
aLife.animate (10, 13, '*');
aLife.animate (10, 14, '*');

std::ostringstream outStream;
outStream << aLife;
string aString = outStream.str ();
const char* aChar = aString.c_str ();
int len = outStream.str ().size ();

while ( 1 ) {
XNextEvent(display, (XEvent *)&event);
switch ( event.type ) {
case Expose:
{
XWindowAttributes window_attributes;
int font_direction, font_ascent, font_descent;
XCharStruct text_structure;
XTextExtents(fontinfo, aChar, len,
&font_direction, &font_ascent, &font_descent,
&text_structure);
XGetWindowAttributes(display, frame_window, &window_attributes);
text_x = (window_attributes.width - text_structure.width)/2;
text_y = (window_attributes.height -
(text_structure.ascent+text_structure.descent))/2;

outStream << aLife;

XDrawString(display, frame_window, graphical_context,
text_x, text_y, aChar, len);
break;
}
default:
break;
}
}
return(0);
}