example of Bresenham's line algorithm

it depends on gtk+-2.0,using function gdk_draw_point to draw points.I wrote this little program because the stupid Chinese education:they are still writing c programs compiled by turbo c and with a "graphic.h" to draw graphics.

#include <gdk/gdk.h>//in fact,I do not know whether I need this

#include <gtk/gtk.h>



void linebres(int xa, int ya, int xb, int yb,GtkWidget *widget,GdkDrawable *drawable)

{

 int dx = abs(xa-xb), dy = abs(ya-yb);

 int p;

 int twody, twodx;

 int x,y,xend,yend;

 float k=dy/dx;

 int temp;

 if(k > 1|| k < -1){

  temp = xa;

  xa = ya;

  ya = temp;

  temp = xb;

  xb = yb;

  yb = temp;

 }



 p = 2 * dy - dx;

 twody = 2 * dy;

 twodx = 2 * dx;



 if(xa - xb > 0){

  x = xb;

  y = yb;

  xend=xa;

 }

 else{

  x = xa;

  y = ya;

  xend = xb;

 }



 gdk_draw_point (drawable,widget->style->black_gc,x,y);

 

 while(x < xend){

  x++;

  if(p < 0)

   p += twody;

  else{

   y++;

   p += (twody-twodx);

  }

  gdk_draw_point (drawable,widget->style->black_gc,x,y);

 }

}





static void on_destroy (GtkWidget * widget, gpointer data)

{

 gtk_main_quit ();

}



gint expose_callback(GtkWidget *widget, GdkEventAny *event, gpointer data)

{

 GdkDrawable *drawable;

 int i;

 drawable=widget->window;

 linebres (10,5,180,60,widget,drawable);

 return 0;

}



int main(int argc, char **argv)

{

 gtk_init ( &argc, &argv);



 GdkWindowAttr attr;

 

 GtkWidget *window;



 GtkWidget *widget = gtk_drawing_area_new ();

 gtk_drawing_area_size (GTK_DRAWING_AREA (widget),200,200);

 

 window = gtk_window_new (GTK_WINDOW_TOPLEVEL);

 gtk_container_add (GTK_CONTAINER (window),widget);

 

 g_signal_connect (G_OBJECT (window), "destroy",G_CALLBACK (on_destroy), NULL);



 g_signal_connect (G_OBJECT(widget), "expose_event",GTK_SIGNAL_FUNC(expose_callback), NULL);

 

 gtk_widget_show_all (window);



 gtk_main ();

 

 return 0;

 

}