package horstmann.ch05_layout;
import java.awt.Component;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.Insets;
import java.awt.LayoutManager;

/**
   A layout manager that lays out components along a central axis
 */
public class FormLayout implements LayoutManager
{
  public Dimension preferredLayoutSize(Container parent)
  {
    Component[] components = parent.getComponents();
    left = 0;
    right = 0;
    height = 0;
    for (int i = 0; i < components.length; i += 2)
    {
      Component cleft = components[i];
      Component cright = components[i + 1];

      Dimension dleft = cleft.getPreferredSize();
      Dimension dright = cright.getPreferredSize();
      left = Math.max(left, dleft.width);
      right = Math.max(right, dright.width);
      height = height + Math.max(dleft.height,
          dright.height);
    }
    return new Dimension(left + GAP + right, height);
  }

  public Dimension minimumLayoutSize(Container parent)
  {
    return preferredLayoutSize(parent);
  }

  public void layoutContainer(Container parent)
  {
    preferredLayoutSize(parent); // Sets left, right

    Component[] components = parent.getComponents();

    Insets insets = parent.getInsets();
    int xcenter = insets.left + left;
    int y = insets.top;

    for (int i = 0; i < components.length; i += 2)
    {
      Component cleft = components[i];
      Component cright = components[i + 1];

      Dimension dleft = cleft.getPreferredSize();
      Dimension dright = cright.getPreferredSize();

      int height = Math.max(dleft.height, dright.height);

      cleft.setBounds(xcenter - dleft.width, y + (height
          - dleft.height) / 2, dleft.width, dleft.height);

      cright.setBounds(xcenter + GAP, y + (height
          - dright.height) / 2, dright.width, dright.height);
      y += height;
    }
  }

  public void addLayoutComponent(String name, Component comp)
  {}

  public void removeLayoutComponent(Component comp)
  {}

  private int left;
  private int right;
  private int height;
  private static final int GAP = 6;
}