/** canvasdrag.c **/
#include <gnome.h>

gint eventDelete(GtkWidget *widget,
        GdkEvent *event,gpointer data);
gint eventDestroy(GtkWidget *widget,
        GdkEvent *event,gpointer data);
static gint dragEvent(GnomeCanvasItem *item,
        GdkEvent *event,gpointer data);

#define HORIZ 100
#define VERT 60
#define WIDTH (HORIZ * 6)
#define HEIGHT (VERT * 6)

int main(int argc,char *argv[])
{
    GtkWidget *app;
    GtkWidget *canvas;
    GnomeCanvasGroup *rootGroup;
    GnomeCanvasItem *item;

    gnome_init("canvasdrag","1.0",argc,argv);
    app = gnome_app_new("canvasdrag",
            "Gnome Canvas Dragging");
    gtk_signal_connect(GTK_OBJECT(app),"delete_event",
            GTK_SIGNAL_FUNC(eventDelete),NULL);
    gtk_signal_connect(GTK_OBJECT(app),"destroy",
            GTK_SIGNAL_FUNC(eventDestroy),NULL);

    canvas = gnome_canvas_new();
    gtk_widget_set_usize(canvas,WIDTH,HEIGHT);
    gnome_canvas_set_scroll_region(GNOME_CANVAS(canvas),
            0.0,0.0,WIDTH,HEIGHT);
    rootGroup = gnome_canvas_root(GNOME_CANVAS(canvas));
    gnome_app_set_contents(GNOME_APP(app),canvas);

    item = gnome_canvas_item_new(rootGroup,
                      gnome_canvas_rect_get_type(),
                      "x1",(double)(HORIZ * 1),
                      "y1",(double)(VERT * 1),
                      "x2",(double)(HORIZ * 3),
                      "y2",(double)(VERT * 3),
                      "fill_color","white",
                      "outline_color","black",
                      NULL);
    gtk_signal_connect(GTK_OBJECT(item),"event",
                (GtkSignalFunc)dragEvent,NULL);

    item = gnome_canvas_item_new(rootGroup,
                      gnome_canvas_ellipse_get_type(),
                      "x1",(double)(HORIZ * 2),
                      "y1",(double)(VERT * 2),
                      "x2",(double)(HORIZ * 4),
                      "y2",(double)(VERT * 4),
                      "fill_color","blue",
                      "outline_color","black",
                      NULL);
    gtk_signal_connect(GTK_OBJECT(item),"event",
                (GtkSignalFunc)dragEvent,NULL);

    item = gnome_canvas_item_new(rootGroup,
                      gnome_canvas_rect_get_type(),
                      "x1",(double)(HORIZ * 3),
                      "y1",(double)(VERT * 3),
                      "x2",(double)(HORIZ * 5),
                      "y2",(double)(VERT * 5),
                      "fill_color","black",
                      "outline_color","white",
                      NULL);
    gtk_signal_connect(GTK_OBJECT(item),"event",
                (GtkSignalFunc)dragEvent,NULL);

    gtk_widget_show_all(app);
    gtk_main();
    exit(0);
}
static gint dragEvent(GnomeCanvasItem *item,
        GdkEvent *event,gpointer data) {
    static gint x;
    static gint y;
    gint new_x;
    gint new_y;

    switch(event->type) {
    case GDK_MOTION_NOTIFY:
        if(event->button.state & 0x00000400) {
            new_x = event->button.x;
            new_y = event->button.y;
            gnome_canvas_item_move(item,
                (double)(new_x - x),
                (double)(new_y - y));
            x = new_x;
            y = new_y;
        }
        break;
    case GDK_BUTTON_PRESS:
        if(event->button.button == 1)
            gnome_canvas_item_raise_to_top(item);
        x = event->button.x;
        y = event->button.y;
        break;
    default:
        break;
    }
    return(0);
}
gint eventDelete(GtkWidget *widget,
        GdkEvent *event,gpointer data) {
    return(FALSE);
}
gint eventDestroy(GtkWidget *widget,
        GdkEvent *event,gpointer data) {
    gtk_main_quit();
    return(0);
}