content: package tim.prune.gui;
  
  import java.awt.Dimension;
  import java.awt.GridBagConstraints;
  import java.awt.GridBagLayout;
  import java.awt.Insets;
  
  import javax.swing.JComponent;
  import javax.swing.JLabel;
  import javax.swing.JPanel;
  
  /**
   * Class to make it easier to use GridBagLayout for a non-equal-width layout
   * Default is two columns but can handle more
   */
  public class GuiGridLayout
  {
  	private final GridBagLayout _layout;
  	private final GridBagConstraints _constraints;
  	private final JPanel _panel;
  	private final int _numColumns;
  	private double[] _colWeights = null;
  	private boolean[] _rightAligns = null;
  	private int _x = 0;
  	private int _y = 0;
  
  	/**
  	 * Constructor
  	 * @param inPanel panel using layout
  	 */
  	public GuiGridLayout(JPanel inPanel)
  	{
  		// Default is two columns, with more weight to the right-hand one; first column is right-aligned
  		this(inPanel, null, null);
  	}
  
  	/**
  	 * Constructor
  	 * @param inPanel panel using layout
  	 * @param inColumnWeights array of column weights
  	 * @param inAlignRights array of booleans, true for right alignment, false for left
  	 */
  	public GuiGridLayout(JPanel inPanel, double[] inColumnWeights, boolean[] inAlignRights)
  	{
  		_panel = inPanel;
  		_layout = new GridBagLayout();
  		_constraints = new GridBagConstraints();
  		_colWeights = inColumnWeights;
  		_rightAligns = inAlignRights;
  		if (_colWeights == null || _rightAligns == null || _colWeights.length != _rightAligns.length
  			|| _colWeights.length < 2)
  		{
  			_colWeights = new double[] {0.5, 1.0};
  			_rightAligns = new boolean[] {true, false};
  		}
  		_numColumns = _colWeights.length;
  		_constraints.weightx = 1.0;
  		_constraints.weighty = 0.0;
  		_constraints.ipadx = 10;
  		_constraints.ipady = 1;
  		_constraints.insets = new Insets(1, 5, 1, 5);
  		// Apply layout to panel
  		_panel.setLayout(_layout);
  	}
  
  	/**
  	 * @param inPadding y padding of grid cells (default 1)
  	 */
  	public void setYPadding(int inPadding) {
  		_constraints.ipady = inPadding;
  	}
  
  	/**
  	 * Add the given component to the grid
  	 * @param inComponent component to add
  	 */
  	public void add(JComponent inComponent) {
  		add(inComponent, 1, false);
  	}
  
  	/**
  	 * Add the given component to the grid
  	 * @param inComponent component to add
  	 * @param inFillWidth true to fill width of column, default false
  	 */
  	public void add(JComponent inComponent, boolean inFillWidth) {
  		add(inComponent, 1, inFillWidth);
  	}
  
  	/**
  	 * Add the given component to the grid
  	 * @param inComponent component to add
  	 * @param inColspan number of columns to span (normally 1)
  	 * @param inFillWidth true to fill width of column, default false
  	 */
  	public void add(JComponent inComponent, int inColspan, boolean inFillWidth)
  	{
  		_constraints.gridx = _x;
  		_constraints.gridy = _y;
  		_constraints.weightx = _colWeights[_x];
  		_constraints.gridwidth = inColspan;
  		// set anchor
  		_constraints.anchor = (_rightAligns[_x]?GridBagConstraints.LINE_END:GridBagConstraints.LINE_START);
  		_constraints.fill = (inFillWidth ? GridBagConstraints.HORIZONTAL: GridBagConstraints.NONE);
  		_layout.setConstraints(inComponent, _constraints);
  		// add to panel
  		_panel.add(inComponent);
  		// work out next position
  		_x += inColspan;
  		if (_x >= _numColumns) {
  			nextRow();
  		}
  	}
  
  	/**
  	 * Go to the next row of the grid
  	 */
  	public void nextRow()
  	{
  		_x = 0;
  		_y++;
  	}
  
  	public void addVerticalGap(int inPixels)
  	{
  		JLabel invisibleLabel = new JLabel();
  		invisibleLabel.setPreferredSize(new Dimension(10, inPixels));
  		add(invisibleLabel);
  		nextRow();
  	}
  }
  