DisplayLib.java

package prefuse.util.display;

import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;
import java.util.Iterator;

import prefuse.Display;
import prefuse.visual.VisualItem;


/**
 * Library routines pertaining to a prefuse Display.
 *
 * @author <a href="http://jheer.org">jeffrey heer</a>
 */
public class DisplayLib {

    private DisplayLib() {
        // don't instantiate
    }
    
    /**
     * Get a bounding rectangle of the VisualItems in the input iterator.
     * @param iter an iterator of VisualItems
     * @param margin a margin to add on to the bounding rectangle
     * @param b the Rectangle instance in which to store the result
     * @return the bounding rectangle. This is the same object as the
     * parameter <code>b</code>.
     */
    public static Rectangle2D getBounds(
        Iterator iter, double margin, Rectangle2D b)
    {
        b.setFrame(Double.NaN,Double.NaN,Double.NaN,Double.NaN);
        // TODO: synchronization?
        if ( iter.hasNext() ) {
            VisualItem item = (VisualItem)iter.next();
            Rectangle2D nb = item.getBounds();
            b.setFrame(nb);
        }
        while ( iter.hasNext() ) {   
            VisualItem item = (VisualItem)iter.next();
            Rectangle2D nb = item.getBounds();
            double x1 = (nb.getMinX()<b.getMinX() ? nb.getMinX() : b.getMinX());
            double x2 = (nb.getMaxX()>b.getMaxX() ? nb.getMaxX() : b.getMaxX());
            double y1 = (nb.getMinY()<b.getMinY() ? nb.getMinY() : b.getMinY());
            double y2 = (nb.getMaxY()>b.getMaxY() ? nb.getMaxY() : b.getMaxY());
            b.setFrame(x1,y1,x2-x1,y2-y1);
        }
        b.setFrame(b.getMinX() - margin,
                   b.getMinY() - margin,
                   b.getWidth() + 2*margin,
                   b.getHeight() + 2*margin);
        return b;
    }
    
    /**
     * Get a bounding rectangle of the VisualItems in the input iterator.
     * @param iter an iterator of VisualItems
     * @param margin a margin to add on to the bounding rectangle
     * @return the bounding rectangle. A new Rectangle2D instance is
     * allocated and returned.
     */
    public static Rectangle2D getBounds(Iterator iter, double margin)
    {
        Rectangle2D b = new Rectangle2D.Double();
        return getBounds(iter, margin, b);
    }
    
    /**
     * Return the centroid (averaged location) of a group of items.
     * @param iter an iterator of VisualItems
     * @param p a Point2D instance in which to store the result
     * @return the centroid point. This is the same object as the
     * parameter <code>p</code>.
     */
    public static Point2D getCentroid(Iterator iter, Point2D p) {
        double cx = 0, cy = 0;
        int count = 0;
        
        while ( iter.hasNext() ) {
            VisualItem item = (VisualItem)iter.next();
            double x = item.getX(), y = item.getY();
            if ( !(Double.isInfinite(x) || Double.isNaN(x)) &&
                 !(Double.isInfinite(y) || Double.isNaN(y)) )
            {
                cx += x;
                cy += y;
                count++;
            }
        }
        if ( count > 0 ) {
            cx /= count;
            cy /= count;
        }
        p.setLocation(cx, cy);
        return p;
    }
    
    /**
     * Return the centroid (averaged location) of a group of items.
     * @param iter an iterator of VisualItems
     * @return the centroid point. A new Point2D instance is allocated
     * and returned.
     */
    public static Point2D getCentroid(Iterator iter)
    {
        return getCentroid(iter, new Point2D.Double());
    }
    
    /**
     * Set the display view such that the given bounds are within view.
     * @param display the Display instance
     * @param bounds the bounds that should be visible in the Display view
     * @param duration the duration of an animated transition. A value of
     * zero will result in an instantaneous change.
     */
    public static void fitViewToBounds(Display display, Rectangle2D bounds,
            long duration)
    {
        fitViewToBounds(display, bounds, null, duration);
    }

    /**
     * Set the display view such that the given bounds are within view, subject
     * to a given center point being maintained.
     * @param display the Display instance
     * @param bounds the bounds that should be visible in the Display view
     * @param center the point that should be the center of the Display
     * @param duration the duration of an animated transition. A value of
     * zero will result in an instantaneous change.
     */
    public static void fitViewToBounds(Display display, Rectangle2D bounds,
            Point2D center, long duration)
    {
        // init variables
        double w = display.getWidth(), h = display.getHeight();
        double cx = (center==null? bounds.getCenterX() : center.getX());
        double cy = (center==null? bounds.getCenterY() : center.getY());
        
        // compute half-widths of final bounding box around
        // the desired center point
        double wb = Math.max(cx-bounds.getMinX(),
                             bounds.getMaxX()-cx);
        double hb = Math.max(cy-bounds.getMinY(),
                             bounds.getMaxY()-cy);
        
        // compute scale factor
        //  - figure out if z or y dimension takes priority
        //  - then balance against the current scale factor
        double scale = Math.min(w/(2*wb),h/(2*hb)) / display.getScale();

        // animate to new display settings
        if ( center == null )
            center = new Point2D.Double(cx,cy);
        if ( duration > 0 ) {
            display.animatePanAndZoomToAbs(center,scale,duration);
        } else {
            display.panToAbs(center);
            display.zoomAbs(center, scale);
        }
    }
    
} // end of class DisplayLib