/* * * Sample Code for Gtk+ Programming in C, 1st Edition, Prentice Hall * * Copyright 2000 - 2002 Syd Logan, All Rights Reserved * * This code is distributed without warranty. You are free to use this * code for any purpose, however, if this code is republished or * redistributed in its original form, as hardcopy or electronically, * then you must include this copyright notice along with the code. * * Questions or comments regarding this code or any bugs it contains can * be directed to the author via e-mail at slogan@cts.com **/#include <gtk/gtk.h>#include <stdlib.h>/* number of GtkLabel widgets */#define NUM_LABELS 10/* width, height of window. used to determine if we need to change direction   of movement */#define WIN_WIDTH 300#define WIN_HEIGHT 200/* what we know about a label: its widget, its current position, and direction   of movement */typedef struct _labels{	GtkWidget *w;	gint x;	gint y;	gint x_trend;	gint y_trend;} Labels;static Labels labels[NUM_LABELS];static GtkWidget *fixed;/* called 10 times a second to compute new positions for all of the labels,    and adjust directions of movement if necessary */ gintfixed_timeout (gpointer data){	gint x_inc, y_inc;	int i;	for ( i = 0; i < NUM_LABELS; i++ ) {		/* compute new movement in range of 0 to 10 pixels */		x_inc = ((float) rand() / RAND_MAX) * 10;		y_inc = ((float) rand() / RAND_MAX) * 10;		/* add (or subtract) increment to (from)  both x and y 		   positions of widget */		labels[i].x += x_inc * labels[i].x_trend;		labels[i].y += y_inc * labels[i].y_trend;		/* 		   if label has gone offscreen, flip the direction of 		   movement for the label (only flip the component that 	     went offscreen)		*/		if ( labels[i].x > WIN_WIDTH ) 			labels[i].x_trend = -1; 		else if ( labels[i].x < 0 )			labels[i].x_trend = 1; 		if ( labels[i].y > WIN_HEIGHT ) 			labels[i].y_trend = -1; 		else if ( labels[i].y < 0 )			labels[i].y_trend = 1; 		/* clear the previous position. GtkFixed doesn't do this 		   very cleanly */		gtk_widget_queue_clear (labels[i].w);		/* reposition the widget */		gtk_fixed_move( GTK_FIXED( fixed ), labels[i].w,       labels[i].x, labels[i].y );	}		}int main( int argc, char *argv[] ){ 	GtkWidget *window;	int i, timer;  	gtk_init (&argc, &argv); 	/* create a window, sets its size and title */  	window = gtk_window_new (GTK_WINDOW_TOPLEVEL); 	gtk_signal_connect (GTK_OBJECT(window), "destroy", 		GTK_SIGNAL_FUNC (gtk_main_quit), "WM destroy"); 	gtk_window_set_title (GTK_WINDOW(window), "Fixed"); 	gtk_widget_set_usize (GTK_WIDGET(window), WIN_WIDTH, WIN_HEIGHT);	/* create an instance of GtkFixed, add it to the window */ 	fixed = gtk_fixed_new(); 	gtk_container_add( GTK_CONTAINER( window ), fixed ); 	gtk_widget_show (fixed);	/* create the labels, placing them in the middle of the window      using gtk_fixed_put(). Set the direction trends to random values */ 	for ( i = 0; i < NUM_LABELS; i++ ) { 		labels[i].w = gtk_label_new ("Gtk+ Rules!");		labels[i].x = WIN_WIDTH / 2; labels[i].y = WIN_HEIGHT / 2;		labels[i].x_trend = (rand() > RAND_MAX / 2 ? 1 : -1 ); 		labels[i].y_trend = (rand() > RAND_MAX / 2 ? 1 : -1 ); 		gtk_widget_show( labels[i].w );		gtk_fixed_put( GTK_FIXED( fixed ), labels[i].w, 			labels[i].x, labels[i].y ); 	} 	gtk_widget_show (window);	/* register a timeout callback with Gtk+ to fire every 100ms */ 	timer = gtk_timeout_add (100, fixed_timeout, NULL); 	gtk_main ();  	return(0);}