graphics problem

Roman Goldov <[email protected]> Tue, 13 Oct 2015 15:54:34 +0300

Newsgroups	gmane.comp.lib.cairo
Message-ID	<[email protected]>

Hello, i installed CentOS 7 and gtk-devel libaries. I learn GTK+ and Cairo. I downloaded (copied) from Internet an exmple of cairo file (file9.c that is attached) where i tried to draw lines (graphics) on the window. However, the window is opened and it is empty, and also theer is warning message in the terminal:

[...@localhost ~]$ gcc -Wall -g file9.c -o file9.exe `pkg-config --cflags gtk+-2.0` `pkg-config --libs gtk+-2.0`
[...@localhost ~]$ ./file9.exe 

(file9.exe:9678): GLib-GObject-WARNING **: gsignal.c:2462: signal 'draw' is invalid for instance '0x968440' of type 'GtkDrawingArea'

I would appreciate help in solving the problem. A detailed answer would be appreciated because i am a new user of Linux.
Thank you.
Roman Goldov

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file9.c (text/x-c, 1.8 KB)

#include <cairo.h>
#include <gtk/gtk.h>

static void do_drawing(cairo_t *);

struct {
  int count;
  double coordx[100];
  double coordy[100];
} glob;

static gboolean on_draw_event(GtkWidget *widget, cairo_t *cr, 
    gpointer user_data)
{
  do_drawing(cr);

  return FALSE;
}

static void do_drawing(cairo_t *cr)
{
  cairo_set_source_rgb(cr, 0, 0, 0);
  cairo_set_line_width(cr, 0.5);

  int i, j;
  for (i = 0; i <= glob.count - 1; i++ ) {
      for (j = 0; j <= glob.count - 1; j++ ) {
          cairo_move_to(cr, glob.coordx[i], glob.coordy[i]);
          cairo_line_to(cr, glob.coordx[j], glob.coordy[j]);
      }
  }

  glob.count = 0;
  cairo_stroke(cr);    
}

static gboolean clicked(GtkWidget *widget, GdkEventButton *event,
    gpointer user_data)
{
    if (event->button == 1) {
        glob.coordx[glob.count] = event->x;
        glob.coordy[glob.count++] = event->y;
    }

    if (event->button == 3) {
        gtk_widget_queue_draw(widget);
    }

    return TRUE;
}


int main(int argc, char *argv[])
{
  GtkWidget *window;
  GtkWidget *darea;
  
  glob.count = 0;

  gtk_init(&argc, &argv);

  window = gtk_window_new(GTK_WINDOW_TOPLEVEL);

  darea = gtk_drawing_area_new();
  gtk_container_add(GTK_CONTAINER(window), darea);
 
  gtk_widget_add_events(window, GDK_BUTTON_PRESS_MASK);

  g_signal_connect(G_OBJECT(darea), "draw", 
      G_CALLBACK(on_draw_event), NULL); 
  g_signal_connect(window, "destroy",
      G_CALLBACK(gtk_main_quit), NULL);  
    
  g_signal_connect(window, "button-press-event", 
      G_CALLBACK(clicked), NULL);
 
  gtk_window_set_position(GTK_WINDOW(window), GTK_WIN_POS_CENTER);
  gtk_window_set_default_size(GTK_WINDOW(window), 400, 300); 
  gtk_window_set_title(GTK_WINDOW(window), "Lines");

  gtk_widget_show_all(window);

  gtk_main();

  return 0;
}