source: trunk/gcc/libjava/java/awt/GridLayout.java

// GridLayout.java - Grid-based layout engine

/* Copyright (C) 1999, 2000, 2002  Free Software Foundation

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package java.awt;

import java.io.Serializable;

/** This class implements a grid-based layout scheme.  Components are
 * all given the same size and are laid out from left to right and top
 * to bottom.  A GridLayout is configured with a number of rows and a
 * number of columns.  If both are specified, then the number of
 * columns is ignored and is derived from the number of rows and the
 * total number of components.  If either is zero then that dimension
 * is computed based on the actual size of the container.  An
 * exception is thrown if an attempt is made to set both the number of
 * rows and the number of columns to 0.  This class also supports
 * horizontal and vertical gaps; these are used as spacing between
 * cells.
 *
 * @author Tom Tromey <tromey@redhat.com>
 * @author Aaron M. Renn (arenn@urbanophile.com)
 */
public class GridLayout implements LayoutManager, Serializable
{
  static final long serialVersionUID = -7411804673224730901L;
  
  /** Add a new component to the layout.  This particular implementation
   * does nothing.
   * @param name The name of the component to add.
   * @param component The component to add.
   */
  public void addLayoutComponent (String name, Component comp)
  {
    // Nothing.
  }

  /** Return the number of columns in this layout.  */
  public int getColumns ()
  {
    return cols;
  }

  /** Return the horizontal gap.  */
  public int getHgap ()
  {
    return hgap;
  }

  /** Return the number of rows in this layout.  */
  public int getRows ()
  {
    return rows;
  }

  /** Return the vertical gap.  */
  public int getVgap ()
  {
    return vgap;
  }

  /** Create a new <code>GridLayout</code> with one row and any number
   * of columns.  Both gaps are set to 0.
   */
  public GridLayout ()
  {
    this (1, 0, 0, 0);
  }

  /** Create a new <code>GridLayout</code> with the specified number
   * of rows and columns.  Both gaps are set to 0.  Note that the row
   * and column settings cannot both be zero.  If both the row and
   * column values are non-zero, the rows value takes precedence.
   * @param rows Number of rows
   * @param cols Number of columns
   * @exception IllegalArgumentException If rows and columns are both
   *        0, or if either are negative
   */
  public GridLayout (int rows, int cols)
  {
    this (rows, cols, 0, 0);
  }

  /** Create a new GridLayout with the specified number of rows and
   * columns and the specified gaps.
   * Note that the row and column settings cannot both be
   * zero.  If both the row and column values are non-zero, the rows value
   * takes precedence.
   * @param rows Number of rows
   * @param cols Number of columns
   * @param hgap The horizontal gap
   * @param vgap The vertical gap
   * @exception IllegalArgumentException If rows and columns are both
   *        0, if either are negative, or if either gap is negative
   */
  public GridLayout (int rows, int cols, int hgap, int vgap)
  {
    if (rows < 0)
      throw new IllegalArgumentException ("number of rows cannot be negative");
    if (cols < 0)
      throw new IllegalArgumentException ("number of columns cannot be negative");
    if (rows == 0 && cols == 0)
      throw new IllegalArgumentException ("both rows and columns cannot be 0");
    if (hgap < 0)
      throw new IllegalArgumentException ("horizontal gap must be nonnegative");
    if (vgap < 0)
      throw new IllegalArgumentException ("vertical gap must be nonnegative");
    this.rows = rows;
    this.cols = cols;
    this.hgap = hgap;
    this.vgap = vgap;
  }

  /** Lay out the container's components based on current settings.
   * The free space in the container is divided evenly into the specified
   * number of rows and columns in this object.
   * @param parent The container to lay out
   */
  public void layoutContainer (Container parent)
  {
    synchronized (parent.getTreeLock ())
      {
        int num = parent.ncomponents;

        // There's no point, and handling this would mean adding special
        // cases.
        if (num == 0)
          return;

        // This is more efficient than calling getComponents().
        Component[] comps = parent.component;

        int real_rows = rows;
        int real_cols = cols;
        if (real_rows == 0)
          real_rows = (num + real_cols - 1) / real_cols;
        else
          real_cols = (num + real_rows - 1) / real_rows;

        // We might have less than a single row.  In this case we expand
        // to fill.
        if (num < real_cols)
          real_cols = num;

        Dimension d = parent.getSize ();
        Insets ins = parent.getInsets ();

        // Compute width and height of each cell in the grid.
        int tw = d.width - ins.left - ins.right;
        tw = (tw - (real_cols - 1) * hgap) / real_cols;
        int th = d.height - ins.top - ins.bottom;
        th = (th - (real_rows - 1) * vgap) / real_rows;

        // If the cells are too small, still try to do something.
        if (tw < 0)
          tw = 1;
        if (th < 0)
          th = 1;

        int x = ins.left;
        int y = ins.top;
        int i = 0;
        int recount = 0;

        while (i < num)
          {
            comps[i].setBounds (x, y, tw, th);

            ++i;
            ++recount;
            if (recount == real_cols)
              {
                recount = 0;
                y += vgap + th;
                x = ins.left;
              }
            else
              x += hgap + tw;
          }
      }
  }

  /** Get the minimum layout size of the container.
   * @param cont The parent container
   */
  public Dimension minimumLayoutSize (Container cont)
  {
    return getSize (cont, true);
  }

  /** Get the preferred layout size of the container.
   * @param cont The parent container
   */
  public Dimension preferredLayoutSize (Container cont)
  {
    return getSize (cont, false);
  }

  /** Remove the indicated component from this layout manager.
   * This particular implementation does nothing.
   * @param comp The component to remove
   */
  public void removeLayoutComponent (Component comp)
  {
    // Nothing.
  }

  /** Set the number of columns.
   * @param newCols
   * @exception IllegalArgumentException If the number of columns is
   *     negative, or if the number of columns is zero and the number
   *     of rows is already 0.
   */
  public void setColumns (int newCols)
  {
    if (newCols < 0)
      throw new IllegalArgumentException ("number of columns cannot be negative");
    if (newCols == 0 && rows == 0)
      throw new IllegalArgumentException ("number of rows is already 0");
    this.cols = newCols;
  }

  /** Set the horizontal gap
   * @param hgap The horizontal gap
   * @exception IllegalArgumentException If the hgap value is less than zero.
   */
  public void setHgap (int hgap)
  {
    if (hgap < 0)
      throw new IllegalArgumentException ("horizontal gap must be nonnegative");
    this.hgap = hgap;
  }

  /** Set the number of rows
   * @param newRows
   * @exception IllegalArgumentException If the number of rows is
   *     negative, or if the number of rows is zero and the number
   *     of columns is already 0.
   */
  public void setRows (int newRows)
  {
    if (newRows < 0)
      throw new IllegalArgumentException ("number of rows cannot be negative");
    if (newRows == 0 && cols == 0)
      throw new IllegalArgumentException ("number of columns is already 0");
    this.rows = newRows;
  }

  /** Set the vertical gap.
   * @param vgap The vertical gap
   * @exception IllegalArgumentException If the vgap value is less than zero.
   */
  public void setVgap (int vgap)
  {
    if (vgap < 0)
      throw new IllegalArgumentException ("vertical gap must be nonnegative");
    this.vgap = vgap;
  }

  /** Return String description of this object.  */
  public String toString ()
  {
    return ("[" + getClass ().getName ()
            + ",hgap=" + hgap + ",vgap=" + vgap
            + ",rows=" + rows + ",cols=" + cols
            + "]");
  }

  // This method is used to compute the various sizes.
  private Dimension getSize (Container parent, boolean is_min)
  {
    synchronized (parent.getTreeLock ())
      {
        int w = 0, h = 0, num = parent.ncomponents;
        // This is more efficient than calling getComponents().
        Component[] comps = parent.component;

        for (int i = 0; i < num; ++i)
          {
            Dimension d;

            if (is_min)
              d = comps[i].getMinimumSize ();
            else
              d = comps[i].getPreferredSize ();

            w = Math.max (d.width, w);
            h = Math.max (d.height, h);
          }

        int real_rows = rows;
        int real_cols = cols;
        if (real_rows == 0)
          real_rows = (num + real_cols - 1) / real_cols;
        else
          real_cols = (num + real_rows - 1) / real_rows;

        Insets ins = parent.getInsets ();
        // We subtract out an extra gap here because the gaps are only
        // between cells.
        w = ins.left + ins.right + real_cols * (w + hgap) - hgap;
        h = ins.top + ins.bottom + real_rows * (h + vgap) - vgap;
        return new Dimension (w, h);
      }
  }

  /**
   * @serial The number of columns in the grid.
   */
  private int cols;

  /**
   * @serial The number of rows in the grid.
   */
  private int rows;

  /**
   * @serial The horizontal gap between columns
   */
  private int hgap;

  /**
   * @serial The vertical gap between rows
   */
  private int vgap;
}