Temperature.c

#include <gtk/gtk.h>
#include <stdio.h>
#include <math.h> 
#include <stdlib.h>
#define W_WIDTH  500
#define W_HEIGHT 500
#define N W_WIDTH

const double k=1.0;
const double dt=0.002,dx=0.1;
int stop=0;
double T[N];
double t=0;

void InitTemperature(int init_condition);
void Calc();

gboolean cb_key_press(GtkWidget *widget,GdkEventKey *event,gpointer user_data){
  int i;

  for(i=0;i<4;i++){
    if(event->keyval == '1'+i)
      InitTemperature(i);
  }

  if(event->keyval == 's')
    stop^=1;
  if(event->keyval == 'n')
    Calc();
  return FALSE;
}

gboolean cb_expose_event(GtkWidget *widget,GdkEventExpose *event,gpointer data){
  int i;
  char time[64];
  cairo_t *cr;
  cr = gdk_cairo_create(widget->window);

  for(i=0;i<N;i++){
    cairo_move_to (cr, i%N, W_HEIGHT/2-T[i]);
    cairo_line_to (cr, (i+1)%N, W_HEIGHT/2-T[i+1]);
    cairo_stroke (cr);
  }

  cairo_select_font_face(cr, "VL ゴシック",CAIRO_FONT_SLANT_NORMAL,CAIRO_FONT_WEIGHT_BOLD);
  cairo_set_font_size(cr, 13);
  cairo_move_to(cr, 15, 15);
  sprintf(time,"time:%f",t); 
  cairo_show_text(cr,time);  

  cairo_destroy(cr);
  return FALSE;
}
 
gboolean ivent_loop(GtkWidget *widget){
  if (widget->window == NULL){  
    return FALSE;
  }
 
  if(!stop) Calc();
  gtk_widget_queue_draw(widget);
 
  return (TRUE);
}
 
int main(int argc, char *argv[]){
  GtkWidget *window;
 
  gtk_init(&argc, &argv);
 
  window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
  gtk_window_set_title(GTK_WINDOW(window), "Temperature");
  gtk_widget_set_size_request(window, W_WIDTH, W_HEIGHT);
  gtk_widget_set_app_paintable(window, TRUE);
  g_signal_connect (G_OBJECT(window), "key-press-event",
            G_CALLBACK(cb_key_press), NULL);
  g_signal_connect(G_OBJECT(window), "expose-event",
           G_CALLBACK(cb_expose_event), NULL);
  g_signal_connect(window, "destroy",
           G_CALLBACK(gtk_main_quit), NULL);
 
  g_timeout_add(10, (GSourceFunc)ivent_loop, window);
 
  gtk_widget_show_all(window);
 
  InitTemperature(1);
  gtk_main();
 
  return 0;
}


void InitTemperature(int init_condition){
  int i;
  t=0;
      
  for(i=0;i<N;i++){  
    T[i]=0;
    switch(init_condition){  
      case 0:
        if( 200<i&&i<W_WIDTH-200 )
          T[i]=200;
        break;
      case 1:
        T[i]=300*exp(-(double)(i-N/2)*(i-N/2)/100);
        break;
      case 2:
        T[i]=100*sin(M_PI*i/(N-1));
        break;
      case 3:
        if( (100<i&&i<W_WIDTH/2-100)||(W_WIDTH/2+100<i&&i<W_WIDTH-100))
          T[i]=100;
        break;
      default:
        break;
    }
  }
}

void Calc(){
  int i;
  for(i=1;i<N-1;i++)
    T[i]=T[i]+dt*k*(T[i+1]-2*T[i]+T[i-1])/(dx*dx);

  t+=dt;
}