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    1   /*
    2    * Copyright (c) 2000, 2003, Oracle and/or its affiliates. All rights reserved.
    3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
    4    *
    5    * This code is free software; you can redistribute it and/or modify it
    6    * under the terms of the GNU General Public License version 2 only, as
    7    * published by the Free Software Foundation.  Oracle designates this
    8    * particular file as subject to the "Classpath" exception as provided
    9    * by Oracle in the LICENSE file that accompanied this code.
   10    *
   11    * This code is distributed in the hope that it will be useful, but WITHOUT
   12    * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   13    * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   14    * version 2 for more details (a copy is included in the LICENSE file that
   15    * accompanied this code).
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   17    * You should have received a copy of the GNU General Public License version
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   19    * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   20    *
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   23    * questions.
   24    */
   25   package java.awt;
   26   
   27   import java.util.List;
   28   import java.util.ArrayList;
   29   import sun.util.logging.PlatformLogger;
   30   
   31   /**
   32    * A FocusTraversalPolicy that determines traversal order based on the order
   33    * of child Components in a Container. From a particular focus cycle root, the
   34    * policy makes a pre-order traversal of the Component hierarchy, and traverses
   35    * a Container's children according to the ordering of the array returned by
   36    * <code>Container.getComponents()</code>. Portions of the hierarchy that are
   37    * not visible and displayable will not be searched.
   38    * <p>
   39    * By default, ContainerOrderFocusTraversalPolicy implicitly transfers focus
   40    * down-cycle. That is, during normal forward focus traversal, the Component
   41    * traversed after a focus cycle root will be the focus-cycle-root's default
   42    * Component to focus. This behavior can be disabled using the
   43    * <code>setImplicitDownCycleTraversal</code> method.
   44    * <p>
   45    * By default, methods of this class with return a Component only if it is
   46    * visible, displayable, enabled, and focusable. Subclasses can modify this
   47    * behavior by overriding the <code>accept</code> method.
   48    * <p>
   49    * This policy takes into account <a
   50    * href="doc-files/FocusSpec.html#FocusTraversalPolicyProviders">focus traversal
   51    * policy providers</a>.  When searching for first/last/next/previous Component,
   52    * if a focus traversal policy provider is encountered, its focus traversal
   53    * policy is used to perform the search operation.
   54    *
   55    * @author David Mendenhall
   56    *
   57    * @see Container#getComponents
   58    * @since 1.4
   59    */
   60   public class ContainerOrderFocusTraversalPolicy extends FocusTraversalPolicy
   61       implements java.io.Serializable
   62   {
   63       private static final PlatformLogger log = PlatformLogger.getLogger("java.awt.ContainerOrderFocusTraversalPolicy");
   64   
   65       final private int FORWARD_TRAVERSAL = 0;
   66       final private int BACKWARD_TRAVERSAL = 1;
   67   
   68       /*
   69        * JDK 1.4 serialVersionUID
   70        */
   71       private static final long serialVersionUID = 486933713763926351L;
   72   
   73       private boolean implicitDownCycleTraversal = true;
   74   
   75       /**
   76        * Used by getComponentAfter and getComponentBefore for efficiency. In
   77        * order to maintain compliance with the specification of
   78        * FocusTraversalPolicy, if traversal wraps, we should invoke
   79        * getFirstComponent or getLastComponent. These methods may be overriden in
   80        * subclasses to behave in a non-generic way. However, in the generic case,
   81        * these methods will simply return the first or last Components of the
   82        * sorted list, respectively. Since getComponentAfter and
   83        * getComponentBefore have already built the list before determining
   84        * that they need to invoke getFirstComponent or getLastComponent, the
   85        * list should be reused if possible.
   86        */
   87       transient private Container cachedRoot;
   88       transient private List cachedCycle;
   89   
   90       /*
   91        * We suppose to use getFocusTraversalCycle & getComponentIndex methods in order
   92        * to divide the policy into two parts:
   93        * 1) Making the focus traversal cycle.
   94        * 2) Traversing the cycle.
   95        * The 1st point assumes producing a list of components representing the focus
   96        * traversal cycle. The two methods mentioned above should implement this logic.
   97        * The 2nd point assumes implementing the common concepts of operating on the
   98        * cycle: traversing back and forth, retrieving the initial/default/first/last
   99        * component. These concepts are described in the AWT Focus Spec and they are
  100        * applied to the FocusTraversalPolicy in general.
  101        * Thus, a descendant of this policy may wish to not reimplement the logic of
  102        * the 2nd point but just override the implementation of the 1st one.
  103        * A striking example of such a descendant is the javax.swing.SortingFocusTraversalPolicy.
  104        */
  105       /*protected*/ private List<Component> getFocusTraversalCycle(Container aContainer) {
  106           List<Component> cycle = new ArrayList<Component>();
  107           enumerateCycle(aContainer, cycle);
  108           return cycle;
  109       }
  110       /*protected*/ private int getComponentIndex(List<Component> cycle, Component aComponent) {
  111           return cycle.indexOf(aComponent);
  112       }
  113   
  114       private void enumerateCycle(Container container, List cycle) {
  115           if (!(container.isVisible() && container.isDisplayable())) {
  116               return;
  117           }
  118   
  119           cycle.add(container);
  120   
  121           Component[] components = container.getComponents();
  122           for (int i = 0; i < components.length; i++) {
  123               Component comp = components[i];
  124               if (comp instanceof Container) {
  125                   Container cont = (Container)comp;
  126   
  127                   if (!cont.isFocusCycleRoot() && !cont.isFocusTraversalPolicyProvider()) {
  128                       enumerateCycle(cont, cycle);
  129                       continue;
  130                   }
  131               }
  132               cycle.add(comp);
  133           }
  134       }
  135   
  136       private Container getTopmostProvider(Container focusCycleRoot, Component aComponent) {
  137           Container aCont = aComponent.getParent();
  138           Container ftp = null;
  139           while (aCont  != focusCycleRoot && aCont != null) {
  140               if (aCont.isFocusTraversalPolicyProvider()) {
  141                   ftp = aCont;
  142               }
  143               aCont = aCont.getParent();
  144           }
  145           if (aCont == null) {
  146               return null;
  147           }
  148           return ftp;
  149       }
  150   
  151       /*
  152        * Checks if a new focus cycle takes place and returns a Component to traverse focus to.
  153        * @param comp a possible focus cycle root or policy provider
  154        * @param traversalDirection the direction of the traversal
  155        * @return a Component to traverse focus to if {@code comp} is a root or provider
  156        *         and implicit down-cycle is set, otherwise {@code null}
  157        */
  158       private Component getComponentDownCycle(Component comp, int traversalDirection) {
  159           Component retComp = null;
  160   
  161           if (comp instanceof Container) {
  162               Container cont = (Container)comp;
  163   
  164               if (cont.isFocusCycleRoot()) {
  165                   if (getImplicitDownCycleTraversal()) {
  166                       retComp = cont.getFocusTraversalPolicy().getDefaultComponent(cont);
  167   
  168                       if (retComp != null && log.isLoggable(PlatformLogger.FINE)) {
  169                           log.fine("### Transfered focus down-cycle to " + retComp +
  170                                    " in the focus cycle root " + cont);
  171                       }
  172                   } else {
  173                       return null;
  174                   }
  175               } else if (cont.isFocusTraversalPolicyProvider()) {
  176                   retComp = (traversalDirection == FORWARD_TRAVERSAL ?
  177                              cont.getFocusTraversalPolicy().getDefaultComponent(cont) :
  178                              cont.getFocusTraversalPolicy().getLastComponent(cont));
  179   
  180                   if (retComp != null && log.isLoggable(PlatformLogger.FINE)) {
  181                       log.fine("### Transfered focus to " + retComp + " in the FTP provider " + cont);
  182                   }
  183               }
  184           }
  185           return retComp;
  186       }
  187   
  188       /**
  189        * Returns the Component that should receive the focus after aComponent.
  190        * aContainer must be a focus cycle root of aComponent or a focus traversal policy provider.
  191        * <p>
  192        * By default, ContainerOrderFocusTraversalPolicy implicitly transfers
  193        * focus down-cycle. That is, during normal forward focus traversal, the
  194        * Component traversed after a focus cycle root will be the focus-cycle-
  195        * root's default Component to focus. This behavior can be disabled using
  196        * the <code>setImplicitDownCycleTraversal</code> method.
  197        * <p>
  198        * If aContainer is <a href="doc-files/FocusSpec.html#FocusTraversalPolicyProviders">focus
  199        * traversal policy provider</a>, the focus is always transferred down-cycle.
  200        *
  201        * @param aContainer a focus cycle root of aComponent or a focus traversal policy provider
  202        * @param aComponent a (possibly indirect) child of aContainer, or
  203        *        aContainer itself
  204        * @return the Component that should receive the focus after aComponent, or
  205        *         null if no suitable Component can be found
  206        * @throws IllegalArgumentException if aContainer is not a focus cycle
  207        *         root of aComponent or focus traversal policy provider, or if either aContainer or
  208        *         aComponent is null
  209        */
  210       public Component getComponentAfter(Container aContainer, Component aComponent) {
  211           if (log.isLoggable(PlatformLogger.FINE)) log.fine("### Searching in " + aContainer + " for component after " + aComponent);
  212   
  213           if (aContainer == null || aComponent == null) {
  214               throw new IllegalArgumentException("aContainer and aComponent cannot be null");
  215           }
  216           if (!aContainer.isFocusTraversalPolicyProvider() && !aContainer.isFocusCycleRoot()) {
  217               throw new IllegalArgumentException("aContainer should be focus cycle root or focus traversal policy provider");
  218   
  219           } else if (aContainer.isFocusCycleRoot() && !aComponent.isFocusCycleRoot(aContainer)) {
  220               throw new IllegalArgumentException("aContainer is not a focus cycle root of aComponent");
  221           }
  222   
  223           synchronized(aContainer.getTreeLock()) {
  224   
  225               if (!(aContainer.isVisible() && aContainer.isDisplayable())) {
  226                   return null;
  227               }
  228   
  229               // Before all the ckecks below we first see if it's an FTP provider or a focus cycle root.
  230               // If it's the case just go down cycle (if it's set to "implicit").
  231               Component comp = getComponentDownCycle(aComponent, FORWARD_TRAVERSAL);
  232               if (comp != null) {
  233                   return comp;
  234               }
  235   
  236               // See if the component is inside of policy provider.
  237               Container provider = getTopmostProvider(aContainer, aComponent);
  238               if (provider != null) {
  239                   if (log.isLoggable(PlatformLogger.FINE)) {
  240                       log.fine("### Asking FTP " + provider + " for component after " + aComponent);
  241                   }
  242   
  243                   // FTP knows how to find component after the given. We don't.
  244                   FocusTraversalPolicy policy = provider.getFocusTraversalPolicy();
  245                   Component afterComp = policy.getComponentAfter(provider, aComponent);
  246   
  247                   // Null result means that we overstepped the limit of the FTP's cycle.
  248                   // In that case we must quit the cycle, otherwise return the component found.
  249                   if (afterComp != null) {
  250                       if (log.isLoggable(PlatformLogger.FINE)) log.fine("### FTP returned " + afterComp);
  251                       return afterComp;
  252                   }
  253                   aComponent = provider;
  254               }
  255   
  256               List<Component> cycle = getFocusTraversalCycle(aContainer);
  257   
  258               if (log.isLoggable(PlatformLogger.FINE)) log.fine("### Cycle is " + cycle + ", component is " + aComponent);
  259   
  260               int index = getComponentIndex(cycle, aComponent);
  261   
  262               if (index < 0) {
  263                   if (log.isLoggable(PlatformLogger.FINE)) {
  264                       log.fine("### Didn't find component " + aComponent + " in a cycle " + aContainer);
  265                   }
  266                   return getFirstComponent(aContainer);
  267               }
  268   
  269               for (index++; index < cycle.size(); index++) {
  270                   comp = cycle.get(index);
  271                   if (accept(comp)) {
  272                       return comp;
  273                   } else if ((comp = getComponentDownCycle(comp, FORWARD_TRAVERSAL)) != null) {
  274                       return comp;
  275                   }
  276               }
  277   
  278               if (aContainer.isFocusCycleRoot()) {
  279                   this.cachedRoot = aContainer;
  280                   this.cachedCycle = cycle;
  281   
  282                   comp = getFirstComponent(aContainer);
  283   
  284                   this.cachedRoot = null;
  285                   this.cachedCycle = null;
  286   
  287                   return comp;
  288               }
  289           }
  290           return null;
  291       }
  292   
  293       /**
  294        * Returns the Component that should receive the focus before aComponent.
  295        * aContainer must be a focus cycle root of aComponent or a <a
  296        * href="doc-files/FocusSpec.html#FocusTraversalPolicyProviders">focus traversal policy
  297        * provider</a>.
  298        *
  299        * @param aContainer a focus cycle root of aComponent or focus traversal policy provider
  300        * @param aComponent a (possibly indirect) child of aContainer, or
  301        *        aContainer itself
  302        * @return the Component that should receive the focus before aComponent,
  303        *         or null if no suitable Component can be found
  304        * @throws IllegalArgumentException if aContainer is not a focus cycle
  305        *         root of aComponent or focus traversal policy provider, or if either aContainer or
  306        *         aComponent is null
  307        */
  308       public Component getComponentBefore(Container aContainer, Component aComponent) {
  309           if (aContainer == null || aComponent == null) {
  310               throw new IllegalArgumentException("aContainer and aComponent cannot be null");
  311           }
  312           if (!aContainer.isFocusTraversalPolicyProvider() && !aContainer.isFocusCycleRoot()) {
  313               throw new IllegalArgumentException("aContainer should be focus cycle root or focus traversal policy provider");
  314   
  315           } else if (aContainer.isFocusCycleRoot() && !aComponent.isFocusCycleRoot(aContainer)) {
  316               throw new IllegalArgumentException("aContainer is not a focus cycle root of aComponent");
  317           }
  318   
  319           synchronized(aContainer.getTreeLock()) {
  320   
  321               if (!(aContainer.isVisible() && aContainer.isDisplayable())) {
  322                   return null;
  323               }
  324   
  325               // See if the component is inside of policy provider.
  326               Container provider = getTopmostProvider(aContainer, aComponent);
  327               if (provider != null) {
  328                   if (log.isLoggable(PlatformLogger.FINE)) {
  329                       log.fine("### Asking FTP " + provider + " for component after " + aComponent);
  330                   }
  331   
  332                   // FTP knows how to find component after the given. We don't.
  333                   FocusTraversalPolicy policy = provider.getFocusTraversalPolicy();
  334                   Component beforeComp = policy.getComponentBefore(provider, aComponent);
  335   
  336                   // Null result means that we overstepped the limit of the FTP's cycle.
  337                   // In that case we must quit the cycle, otherwise return the component found.
  338                   if (beforeComp != null) {
  339                       if (log.isLoggable(PlatformLogger.FINE)) log.fine("### FTP returned " + beforeComp);
  340                       return beforeComp;
  341                   }
  342                   aComponent = provider;
  343   
  344                   // If the provider is traversable it's returned.
  345                   if (accept(aComponent)) {
  346                       return aComponent;
  347                   }
  348               }
  349   
  350               List<Component> cycle = getFocusTraversalCycle(aContainer);
  351   
  352               if (log.isLoggable(PlatformLogger.FINE)) log.fine("### Cycle is " + cycle + ", component is " + aComponent);
  353   
  354               int index = getComponentIndex(cycle, aComponent);
  355   
  356               if (index < 0) {
  357                   if (log.isLoggable(PlatformLogger.FINE)) {
  358                       log.fine("### Didn't find component " + aComponent + " in a cycle " + aContainer);
  359                   }
  360                   return getLastComponent(aContainer);
  361               }
  362   
  363               Component comp = null;
  364               Component tryComp = null;
  365   
  366               for (index--; index>=0; index--) {
  367                   comp = cycle.get(index);
  368                   if (comp != aContainer && (tryComp = getComponentDownCycle(comp, BACKWARD_TRAVERSAL)) != null) {
  369                       return tryComp;
  370                   } else if (accept(comp)) {
  371                       return comp;
  372                   }
  373               }
  374   
  375               if (aContainer.isFocusCycleRoot()) {
  376                   this.cachedRoot = aContainer;
  377                   this.cachedCycle = cycle;
  378   
  379                   comp = getLastComponent(aContainer);
  380   
  381                   this.cachedRoot = null;
  382                   this.cachedCycle = null;
  383   
  384                   return comp;
  385               }
  386           }
  387           return null;
  388       }
  389   
  390       /**
  391        * Returns the first Component in the traversal cycle. This method is used
  392        * to determine the next Component to focus when traversal wraps in the
  393        * forward direction.
  394        *
  395        * @param aContainer the focus cycle root or focus traversal policy provider whose first
  396        *        Component is to be returned
  397        * @return the first Component in the traversal cycle of aContainer,
  398        *         or null if no suitable Component can be found
  399        * @throws IllegalArgumentException if aContainer is null
  400        */
  401       public Component getFirstComponent(Container aContainer) {
  402           List<Component> cycle;
  403   
  404           if (log.isLoggable(PlatformLogger.FINE)) log.fine("### Getting first component in " + aContainer);
  405           if (aContainer == null) {
  406               throw new IllegalArgumentException("aContainer cannot be null");
  407   
  408           }
  409   
  410           synchronized(aContainer.getTreeLock()) {
  411   
  412               if (!(aContainer.isVisible() && aContainer.isDisplayable())) {
  413                   return null;
  414               }
  415   
  416               if (this.cachedRoot == aContainer) {
  417                   cycle = this.cachedCycle;
  418               } else {
  419                   cycle = getFocusTraversalCycle(aContainer);
  420               }
  421   
  422               if (cycle.size() == 0) {
  423                   if (log.isLoggable(PlatformLogger.FINE)) log.fine("### Cycle is empty");
  424                   return null;
  425               }
  426               if (log.isLoggable(PlatformLogger.FINE)) log.fine("### Cycle is " + cycle);
  427   
  428               for (Component comp : cycle) {
  429                   if (accept(comp)) {
  430                       return comp;
  431                   } else if (comp != aContainer &&
  432                              (comp = getComponentDownCycle(comp, FORWARD_TRAVERSAL)) != null)
  433                   {
  434                       return comp;
  435                   }
  436               }
  437           }
  438           return null;
  439       }
  440   
  441       /**
  442        * Returns the last Component in the traversal cycle. This method is used
  443        * to determine the next Component to focus when traversal wraps in the
  444        * reverse direction.
  445        *
  446        * @param aContainer the focus cycle root or focus traversal policy provider whose last
  447        *        Component is to be returned
  448        * @return the last Component in the traversal cycle of aContainer,
  449        *         or null if no suitable Component can be found
  450        * @throws IllegalArgumentException if aContainer is null
  451        */
  452       public Component getLastComponent(Container aContainer) {
  453           List<Component> cycle;
  454           if (log.isLoggable(PlatformLogger.FINE)) log.fine("### Getting last component in " + aContainer);
  455   
  456           if (aContainer == null) {
  457               throw new IllegalArgumentException("aContainer cannot be null");
  458           }
  459   
  460           synchronized(aContainer.getTreeLock()) {
  461   
  462               if (!(aContainer.isVisible() && aContainer.isDisplayable())) {
  463                   return null;
  464               }
  465   
  466               if (this.cachedRoot == aContainer) {
  467                   cycle = this.cachedCycle;
  468               } else {
  469                   cycle = getFocusTraversalCycle(aContainer);
  470               }
  471   
  472               if (cycle.size() == 0) {
  473                   if (log.isLoggable(PlatformLogger.FINE)) log.fine("### Cycle is empty");
  474                   return null;
  475               }
  476               if (log.isLoggable(PlatformLogger.FINE)) log.fine("### Cycle is " + cycle);
  477   
  478               for (int i= cycle.size() - 1; i >= 0; i--) {
  479                   Component comp = cycle.get(i);
  480                   if (accept(comp)) {
  481                       return comp;
  482                   } else if (comp instanceof Container && comp != aContainer) {
  483                       Container cont = (Container)comp;
  484                       if (cont.isFocusTraversalPolicyProvider()) {
  485                           return cont.getFocusTraversalPolicy().getLastComponent(cont);
  486                       }
  487                   }
  488               }
  489           }
  490           return null;
  491       }
  492   
  493       /**
  494        * Returns the default Component to focus. This Component will be the first
  495        * to receive focus when traversing down into a new focus traversal cycle
  496        * rooted at aContainer. The default implementation of this method
  497        * returns the same Component as <code>getFirstComponent</code>.
  498        *
  499        * @param aContainer the focus cycle root or focus traversal policy provider whose default
  500        *        Component is to be returned
  501        * @return the default Component in the traversal cycle of aContainer,
  502        *         or null if no suitable Component can be found
  503        * @see #getFirstComponent
  504        * @throws IllegalArgumentException if aContainer is null
  505        */
  506       public Component getDefaultComponent(Container aContainer) {
  507           return getFirstComponent(aContainer);
  508       }
  509   
  510       /**
  511        * Sets whether this ContainerOrderFocusTraversalPolicy transfers focus
  512        * down-cycle implicitly. If <code>true</code>, during normal forward focus
  513        * traversal, the Component traversed after a focus cycle root will be the
  514        * focus-cycle-root's default Component to focus. If <code>false</code>,
  515        * the next Component in the focus traversal cycle rooted at the specified
  516        * focus cycle root will be traversed instead. The default value for this
  517        * property is <code>true</code>.
  518        *
  519        * @param implicitDownCycleTraversal whether this
  520        *        ContainerOrderFocusTraversalPolicy transfers focus down-cycle
  521        *        implicitly
  522        * @see #getImplicitDownCycleTraversal
  523        * @see #getFirstComponent
  524        */
  525       public void setImplicitDownCycleTraversal(boolean implicitDownCycleTraversal) {
  526           this.implicitDownCycleTraversal = implicitDownCycleTraversal;
  527       }
  528   
  529       /**
  530        * Returns whether this ContainerOrderFocusTraversalPolicy transfers focus
  531        * down-cycle implicitly. If <code>true</code>, during normal forward focus
  532        * traversal, the Component traversed after a focus cycle root will be the
  533        * focus-cycle-root's default Component to focus. If <code>false</code>,
  534        * the next Component in the focus traversal cycle rooted at the specified
  535        * focus cycle root will be traversed instead.
  536        *
  537        * @return whether this ContainerOrderFocusTraversalPolicy transfers focus
  538        *         down-cycle implicitly
  539        * @see #setImplicitDownCycleTraversal
  540        * @see #getFirstComponent
  541        */
  542       public boolean getImplicitDownCycleTraversal() {
  543           return implicitDownCycleTraversal;
  544       }
  545   
  546       /**
  547        * Determines whether a Component is an acceptable choice as the new
  548        * focus owner. By default, this method will accept a Component if and
  549        * only if it is visible, displayable, enabled, and focusable.
  550        *
  551        * @param aComponent the Component whose fitness as a focus owner is to
  552        *        be tested
  553        * @return <code>true</code> if aComponent is visible, displayable,
  554        *         enabled, and focusable; <code>false</code> otherwise
  555        */
  556       protected boolean accept(Component aComponent) {
  557           if (!aComponent.canBeFocusOwner()) {
  558               return false;
  559           }
  560   
  561           // Verify that the Component is recursively enabled. Disabling a
  562           // heavyweight Container disables its children, whereas disabling
  563           // a lightweight Container does not.
  564           if (!(aComponent instanceof Window)) {
  565               for (Container enableTest = aComponent.getParent();
  566                    enableTest != null;
  567                    enableTest = enableTest.getParent())
  568               {
  569                   if (!(enableTest.isEnabled() || enableTest.isLightweight())) {
  570                       return false;
  571                   }
  572                   if (enableTest instanceof Window) {
  573                       break;
  574                   }
  575               }
  576           }
  577   
  578           return true;
  579       }
  580   }

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