[Fallen Angel]

Did anyone work with programs in C that use X? I would really appreciate it if you could tell me how to compile this:

 *
 * simple-text.c - demonstrate drawing of text strings on a window. All
 *		   drawings are done in black color over a white background.
 */

#include <X11/Xlib.h>

#include <stdio.h>
#include <stdlib.h>		/* getenv(), etc. */
#include <unistd.h>		/* sleep(), etc.  */

/*
 * function: create_simple_window. Creates a window with a white background
 *           in the given size.
 * input:    display, size of the window (in pixels), and location of the window
 *           (in pixels).
 * output:   the window's ID.
 * notes:    window is created with a black border, 2 pixels wide.
 *           the window is automatically mapped after its creation.
 */
Window
create_simple_window(Display* display, int width, int height, int x, int y)
{
  int screen_num = DefaultScreen(display);
  int win_border_width = 2;
  Window win;

  /* create a simple window, as a direct child of the screen's */
  /* root window. Use the screen's black and white colors as   */
  /* the foreground and background colors of the window,       */
  /* respectively. Place the new window's top-left corner at   */
  /* the given 'x,y' coordinates.                              */
  win = XCreateSimpleWindow(display, RootWindow(display, screen_num),
                            x, y, width, height, win_border_width,
                            BlackPixel(display, screen_num),
                            WhitePixel(display, screen_num));

  /* make the window actually appear on the screen. */
  XMapWindow(display, win);

  /* flush all pending requests to the X server. */
  XFlush(display);

  return win;
}

GC
create_gc(Display* display, Window win, int reverse_video)
{
  GC gc;				/* handle of newly created GC.  */
  unsigned long valuemask = 0;		/* which values in 'values' to  */
					/* check when creating the GC.  */
  XGCValues values;			/* initial values for the GC.   */
  unsigned int line_width = 2;		/* line width for the GC.       */
  int line_style = LineSolid;		/* style for lines drawing and  */
  int cap_style = CapButt;		/* style of the line's edje and */
  int join_style = JoinBevel;		/*  joined lines.		*/
  int screen_num = DefaultScreen(display);

  gc = XCreateGC(display, win, valuemask, &values);
  if (gc < 0) {
	fprintf(stderr, "XCreateGC: \n");
  }

  /* allocate foreground and background colors for this GC. */
  if (reverse_video) {
    XSetForeground(display, gc, WhitePixel(display, screen_num));
    XSetBackground(display, gc, BlackPixel(display, screen_num));
  }
  else {
    XSetForeground(display, gc, BlackPixel(display, screen_num));
    XSetBackground(display, gc, WhitePixel(display, screen_num));
  }

  /* define the style of lines that will be drawn using this GC. */
  XSetLineAttributes(display, gc,
                     line_width, line_style, cap_style, join_style);

  /* define the fill style for the GC. to be 'solid filling'. */
  XSetFillStyle(display, gc, FillSolid);

  return gc;
}

void
main(int argc, char* argv[])
{
  Display* display;		/* pointer to X Display structure.           */
  int screen_num;		/* number of screen to place the window on.  */
  Window win;			/* pointer to the newly created window.      */
  unsigned int display_width,
               display_height;	/* height and width of the X display.        */
  unsigned int win_width,
	       win_height;	/* height and width for the new window.      */
  char *display_name = getenv("DISPLAY");  /* address of the X display.      */
  GC gc;			/* GC (graphics context) used for drawing    */
				/*  in our window.			     */
  XFontStruct* font_info;       /* Font structure, used for drawing text.    */
  char* font_name = "*-helvetica-*-12-*"; /* font to use for drawing text.   */

  /* open connection with the X server. */
  display = XOpenDisplay(display_name);
  if (display == NULL) {
    fprintf(stderr, "%s: cannot connect to X server '%s'\n",
            argv[0], display_name);
    exit(1);
  }

  /* get the geometry of the default screen for our display. */
  screen_num = DefaultScreen(display);
  display_width = DisplayWidth(display, screen_num);
  display_height = DisplayHeight(display, screen_num);

  /* make the new window occupy 1/9 of the screen's size. */
  win_width = (display_width / 3);
  win_height = (display_height / 3);
  printf("window width - '%d'; height - '%d'\n", win_width, win_height);

  /* create a simple window, as a direct child of the screen's   */
  /* root window. Use the screen's white color as the background */
  /* color of the window. Place the new window's top-left corner */
  /* at the given 'x,y' coordinates.                             */
  win = create_simple_window(display, win_width, win_height, 0, 0);

  /* allocate a new GC (graphics context) for drawing in the window. */
  gc = create_gc(display, win, 0);
  XSync(display, False);

  /* try to load the given font. */
  font_info = XLoadQueryFont(display, font_name);
  if (!font_info) {
      fprintf(stderr, "XLoadQueryFont: failed loading font '%s'\n", font_name);
      exit(-1);
  }

  /* assign the given font to our GC. */
  XSetFont(display, gc, font_info->fid);

  {
    /* variables used for drawing the text strings. */
    int x, y;
    char* text_string;
    int string_width;
    int font_height;

    /* find the height of the characters drawn using this font.        */
    font_height = font_info->ascent + font_info->descent;

    /* draw a "hello world" string on the top-left side of our window. */
    text_string = "hello world";
    x = 0;
    y = font_height;
    XDrawString(display, win, gc, x, y, text_string, strlen(text_string));

    /* draw a "middle of the road" string in the middle of our window. */
    text_string = "middle of the road";
    /* find the width, in pixels, of the text that will be drawn using */
    /* the given font.                                                 */
    string_width = XTextWidth(font_info, text_string, strlen(text_string));
    x = (win_width - string_width) / 2;
    y = (win_height + font_height) / 2;
    XDrawString(display, win, gc, x, y, text_string, strlen(text_string));
  }

  /* flush all pending requests to the X server. */
  XFlush(display);

  /* make a delay for a short period. */
  sleep(4);

  /* close the connection to the X server. */
  XCloseDisplay(display);
}

[Santa's little helper]

I think cc <file> -lX11
By the way on line 56 I get a warning for the gc < 0
part.

[kyku]

This is better

gcc -Wall -o simple-text simple-text.c -lX11 -L/usr/X11R6/lib

[Fallen Angel]

I tried but it didn't work. It gives a bunch of mistakes about size_t in library.Do you know some other way?

Anyway, thanks.

[Santa's little helper]

Try putting #include <malloc.h> along with the other includes.

[kyku]

Originally Posted by Fallen Angel

I tried but it didn't work. It gives a bunch of mistakes about size_t in library.Do you know some other way?

Anyway, thanks.

Do you have a complete environment? I was able to compile you program without any mistakes after removing the incorrect comment at the top, adding #include <string.h> and changing main's return type from void to int. I'm using gcc 3.3.5. It could be helpful if you pasted compiler output so that we could see what exactly went wrong.

[Fallen Angel]

I changed things you said kyku and there are less mistakes. Here is what I get now:

/usr/lib/gcc-lib/i486-slackware-linux/3.3.4/../../../../i486-slackware-linux/bin/ld: cannot find -lX11
collect2: ld returned 1 exit status

[kyku]

This should vanish if you add -L/usr/X11R6/lib flag to commandline as I suggested in my previous post.

[Fallen Angel]

Thanks kyku, it worked now.

[Lebowski]

Originally Posted by kyku

This is better

gcc -Wall -o simple-text simple-text.c -lX11 -L/usr/X11R6/lib

That suggestion solved a bunch of 'undefined reference' errors. But there is still one left:

[simon@localhost test]$ gcc -o test hello1.c -lX11 -L/usr/X11R6/lib
/home/simon/tmp/ccaKofH8.o(.text+0x2ad): In function `main':
: undefined reference to `sin'
collect2: ld returned 1 exit status
[simon@localhost test]$

Any idea how to solve this one? And is there a way to somehow include those switches automatically so I don't have to type them every time?