InitialShellPosition.java

package com.mkalugin.corchy.internal.ui.location;

import org.eclipse.jface.util.Geometry;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Monitor;
import org.eclipse.swt.widgets.Shell;

public enum InitialShellPosition {
    
    SYSTEM_DEFAULT {

        @Override
        public Point calculatePosition(Display display, Shell parent, Point initialSize) {
            return null;
        }
    },
    
    CENTERED {
        
        @Override
        public Point calculatePosition(Display display, Shell parent, Point initialSize) {
            return calculateCenteredPosition(display, parent, initialSize, 1, 2);
        }
        
    },
    
    SHIFTED_CENTERED {

        @Override
        public Point calculatePosition(Display display, Shell parent, Point initialSize) {
            return calculateCenteredPosition(display, parent, initialSize, 2, 3);
        }
   
    };
    
    public abstract Point calculatePosition(Display display, Shell parent, Point initialSize);

    static Point calculateCenteredPosition(Display display, Shell parent, Point initialSize, int factorA, int factorB) {
        Monitor monitor = display.getPrimaryMonitor();
        if (parent != null) {
            monitor = parent.getMonitor();
        }

        Rectangle monitorBounds = monitor.getClientArea();
        Point centerPoint;
        if (parent != null) {
            centerPoint = Geometry.centerPoint(parent.getBounds());
        } else {
            centerPoint = Geometry.centerPoint(monitorBounds);
        }

        return new Point(centerPoint.x - (initialSize.x / 2), Math.max(
                monitorBounds.y, Math.min(centerPoint.y
                        - (initialSize.y * factorA / factorB), monitorBounds.y
                        + monitorBounds.height - initialSize.y)));
    }
    
}