riverlayout.java

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package com.component.pagination;

import java.awt.Component;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Insets;
import java.awt.LayoutManager;
import java.util.HashMap;
import java.util.Map;
import java.util.StringTokenizer;
import java.util.Vector;

/**
 * <p>RiverLayout makes it very simple to construct user interfaces as components
 * are laid out similar to how text is added to a word processor (Components flow
 * like a "river". RiverLayout is however much more powerful than FlowLayout:
 * Components added with the add() method generally gets laid out horizontally,
 * but one may add a string before the component being added to specify "constraints"
 * like this:
 * add("br hfill", new JTextField("Your name here");
 * The code above forces a "line break" and extends the added component horizontally.
 * Without the "hfill" constraint, the component would take on its preferred size.
 *</p>
 * <p>
 * List of constraints:<ul>
 * <li>br - Add a line break
 * <li>p - Add a paragraph break
 * <li>tab - Add a tab stop (handy for constructing forms with labels followed by fields)
 * <li>hfill - Extend component horizontally
 * <li>vfill - Extent component vertically (currently only one allowed)
 * <li>left - Align following components to the left (default)
 * <li>center - Align following components horizontally centered
 * <li>right - Align following components to the right
 * <li>vtop - Align following components vertically top aligned
 * <li>vcenter - Align following components vertically centered (default)
 * </ul>
 * </p>
 * RiverLayout is LGPL licenced - use it freely in free and commercial programs
 *
 * @author David Ekholm
 * @version 1.1 (2005-05-23) -Bugfix: JScrollPanes were oversized (sized to their containing component)
 *  if the container containing the JScrollPane was resized.
 */
public class RiverLayout
    extends FlowLayout
    implements LayoutManager, java.io.Serializable {

	private static final long serialVersionUID = 1L;
	public static final String LINE_BREAK = "br";
   public static final String PARAGRAPH_BREAK = "p";
   public static final String TAB_STOP = "tab";
   public static final String HFILL = "hfill";
   public static final String VFILL = "vfill";
   public static final String LEFT = "left";
   public static final String RIGHT = "right";
   public static final String CENTER = "center";
   public static final String VTOP = "vtop";
   public static final String VCENTER = "vcenter";

   Map constraints = new HashMap();
   String valign = VCENTER;
   int hgap;
   int vgap;
   Insets extraInsets;
   Insets totalInsets = new Insets(0, 0, 0, 0);// Dummy values. Set by getInsets()


   public RiverLayout() {
      this(10, 5);
   }

   public RiverLayout(int hgap, int vgap) {
      this.hgap = hgap;
      this.vgap = vgap;
      setExtraInsets(new Insets(0, hgap, hgap, hgap));
   }

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

   /**
    * Sets the horizontal gap between components.
    */
   public void setHgap(int hgap) {
       this.hgap = hgap;
   }

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

   public Insets getExtraInsets() {
      return extraInsets;
   }

   public void setExtraInsets(Insets newExtraInsets) {
     extraInsets = newExtraInsets;
   }

   protected Insets getInsets(Container target) {
      Insets insets = target.getInsets();
      totalInsets.top = insets.top + extraInsets.top;
      totalInsets.left = insets.left + extraInsets.left;
      totalInsets.bottom = insets.bottom + extraInsets.bottom;
      totalInsets.right = insets.right + extraInsets.right;
      return totalInsets;
   }

   /**
    * Sets the vertical gap between components.
    */
   public void setVgap(int vgap) {
       this.vgap = vgap;
   }


   /**
    * @param name the name of the component
    * @param comp the component to be added
    */
   public void addLayoutComponent(String name, Component comp) {
      constraints.put(comp, name);
   }

   /**
    * Removes the specified component from the layout. Not used by
    * this class.
    * @param comp the component to remove
    * @see       java.awt.Container#removeAll
    */
   public void removeLayoutComponent(Component comp) {
      constraints.remove(comp);
   }

   boolean isFirstInRow(Component comp) {
      String cons = (String) constraints.get(comp);
      return cons != null && (cons.indexOf(RiverLayout.LINE_BREAK) != -1 ||
                              cons.indexOf(RiverLayout.PARAGRAPH_BREAK) != -1);
   }

   boolean hasHfill(Component comp) {
      return hasConstraint(comp, RiverLayout.HFILL);
   }

   boolean hasVfill(Component comp) {
      return hasConstraint(comp, RiverLayout.VFILL);
   }

   boolean hasConstraint(Component comp, String test) {
      String cons = (String) constraints.get(comp);
      if (cons == null) return false;
      StringTokenizer tokens = new StringTokenizer(cons);
      while (tokens.hasMoreTokens())
         if (tokens.nextToken().equals(test)) return true;
      return false;
   }

   /**
    * Figure out tab stop x-positions
    */
   protected Ruler calcTabs(Container target) {
      Ruler ruler = new Ruler();
      int nmembers = target.getComponentCount();

      int x = 0;
      int tabIndex = 0; // First tab stop
      for (int i = 0; i < nmembers; i++) {
         Component m = target.getComponent(i);
//         if (m.isVisible()) {
            if (isFirstInRow(m) || i == 0) {
               x = 0;
               tabIndex = 0;
            }
            else x+= hgap;
            if (hasConstraint(m, TAB_STOP)) {
               ruler.setTab(tabIndex, x); // Will only increase
               x = ruler.getTab(tabIndex++); // Jump forward if neccesary
            }
            Dimension d = m.getPreferredSize();
            x += d.width;
         }
//      }
      return ruler;
   }

   /**
    * Returns the preferred dimensions for this layout given the
    * <i>visible</i> components in the specified target container.
    * @param target the component which needs to be laid out
    * @return    the preferred dimensions to lay out the
    *            subcomponents of the specified container
    * @see Container
    * @see #minimumLayoutSize
    * @see       java.awt.Container#getPreferredSize
    */
   public Dimension preferredLayoutSize(Container target) {
      synchronized (target.getTreeLock()) {
         Dimension dim = new Dimension(0, 0);
         Dimension rowDim = new Dimension(0, 0);
         int nmembers = target.getComponentCount();
         boolean firstVisibleComponent = true;
         int tabIndex = 0;
         Ruler ruler = calcTabs(target);

         for (int i = 0; i < nmembers; i++) {
            Component m = target.getComponent(i);
//            if (m.isVisible()) {
               if (isFirstInRow(m)) {
                  tabIndex = 0;
                  dim.width = Math.max(dim.width, rowDim.width);
                  dim.height += rowDim.height + vgap;
                  if (hasConstraint(m, PARAGRAPH_BREAK)) dim.height += 2*vgap;
                  rowDim = new Dimension(0, 0);
               }
               if (hasConstraint(m, TAB_STOP)) rowDim.width = ruler.getTab(tabIndex++);
               Dimension d = m.getPreferredSize();
               rowDim.height = Math.max(rowDim.height, d.height);
               if (firstVisibleComponent) {
                  firstVisibleComponent = false;
               }
               else {
                  rowDim.width += hgap;
               }
               rowDim.width += d.width;
  //          }
         }
         dim.width = Math.max(dim.width, rowDim.width);
         dim.height += rowDim.height;

         Insets insets = getInsets(target);
         dim.width += insets.left + insets.right;// + hgap * 2;
         dim.height += insets.top + insets.bottom;// + vgap * 2;
         return dim;
      }
   }

   /**
    * Returns the minimum dimensions needed to layout the <i>visible</i>
    * components contained in the specified target container.
    * @param target the component which needs to be laid out
    * @return    the minimum dimensions to lay out the
    *            subcomponents of the specified container
    * @see #preferredLayoutSize