user/src/com/google/gwt/view/client/DefaultSelectionEventManager.java - gwt - Git at Google

 /*
  * Copyright 2010 Google Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not
  * use this file except in compliance with the License. You may obtain a copy of
  * the License at
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
  * License for the specific language governing permissions and limitations under
  * the License.
  */
 package com.google.gwt.view.client;

 import com.google.gwt.dom.client.BrowserEvents;
 import com.google.gwt.dom.client.Element;
 import com.google.gwt.dom.client.InputElement;
 import com.google.gwt.dom.client.NativeEvent;

 import java.util.ArrayList;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;

 /**
  * An implementation of {@link CellPreviewEvent.Handler} that adds selection
  * support via the spacebar and mouse clicks and handles the control key.
  *
  * <p>
  * If the {@link HasData} source of the selection event uses a
  * {@link MultiSelectionModel}, this manager additionally provides support for
  * shift key to select a range of values. For all other {@link SelectionModel}s,
  * only the control key is supported.
  * </p>
  *
  * @param <T> the data type of records in the list
  */
 public class DefaultSelectionEventManager<T> implements
     CellPreviewEvent.Handler<T> {

   /**
    * An event translator that disables selection for the specified blacklisted
    * columns.
    *
    * @param <T> the data type
    */
   public static class BlacklistEventTranslator<T> implements EventTranslator<T> {
     private final Set<Integer> blacklist = new HashSet<Integer>();

     /**
      * Construct a new {@link BlacklistEventTranslator}.
      *
      * @param blacklistedColumns the columns to blacklist
      */
     public BlacklistEventTranslator(int... blacklistedColumns) {
       if (blacklistedColumns != null) {
         for (int i : blacklistedColumns) {
           setColumnBlacklisted(i, true);
         }
       }
     }

     /**
      * Clear all columns from the blacklist.
      */
     public void clearBlacklist() {
       blacklist.clear();
     }

     public boolean clearCurrentSelection(CellPreviewEvent<T> event) {
       return false;
     }

     /**
      * Check if the specified column is blacklisted.
      *
      * @param index the column index
      * @return true if blacklisted, false if not
      */
     public boolean isColumnBlacklisted(int index) {
       return blacklist.contains(index);
     }

     /**
      * Set whether or not the specified column in blacklisted.
      *
      * @param index the column index
      * @param isBlacklisted true to blacklist, false to allow selection
      */
     public void setColumnBlacklisted(int index, boolean isBlacklisted) {
       if (isBlacklisted) {
         blacklist.add(index);
       } else {
         blacklist.remove(index);
       }
     }

     public SelectAction translateSelectionEvent(CellPreviewEvent<T> event) {
       return isColumnBlacklisted(event.getColumn()) ? SelectAction.IGNORE
           : SelectAction.DEFAULT;
     }
   }

   /**
    * Implementation of {@link EventTranslator} that only triggers selection when
    * any checkbox is selected.
    *
    * @param <T> the data type
    */
   public static class CheckboxEventTranslator<T> implements EventTranslator<T> {

     /**
      * The column index of the checkbox. Other columns are ignored.
      */
     private final int column;

     /**
      * Construct a new {@link CheckboxEventTranslator} that will trigger
      * selection when any checkbox in any column is selected.
      */
     public CheckboxEventTranslator() {
       this(-1);
     }

     /**
      * Construct a new {@link CheckboxEventTranslator} that will trigger
      * selection when a checkbox in the specified column is selected.
      *
      * @param column the column index, or -1 for all columns
      */
     public CheckboxEventTranslator(int column) {
       this.column = column;
     }

     public boolean clearCurrentSelection(CellPreviewEvent<T> event) {
       return false;
     }

     public SelectAction translateSelectionEvent(CellPreviewEvent<T> event) {
       // Handle the event.
       NativeEvent nativeEvent = event.getNativeEvent();
       if (BrowserEvents.CLICK.equals(nativeEvent.getType())) {
         // Ignore if the event didn't occur in the correct column.
         if (column > -1 && column != event.getColumn()) {
           return SelectAction.IGNORE;
         }

         // Determine if we clicked on a checkbox.
         Element target = nativeEvent.getEventTarget().cast();
         if ("input".equals(target.getTagName().toLowerCase())) {
           final InputElement input = target.cast();
           if ("checkbox".equals(input.getType().toLowerCase())) {
             // Synchronize the checkbox with the current selection state.
             input.setChecked(event.getDisplay().getSelectionModel().isSelected(
                 event.getValue()));
             return SelectAction.TOGGLE;
           }
         }
         return SelectAction.IGNORE;
       }

       // For keyboard events, do the default action.
       return SelectAction.DEFAULT;
     }
   }

   /**
    * Translates {@link CellPreviewEvent}s into {@link SelectAction}s.
    */
   public static interface EventTranslator<T> {
     /**
      * Check whether a user selection event should clear all currently selected
      * values.
      *
      * @param event the {@link CellPreviewEvent} to translate
      */
     boolean clearCurrentSelection(CellPreviewEvent<T> event);

     /**
      * Translate the user selection event into a {@link SelectAction}.
      *
      * @param event the {@link CellPreviewEvent} to translate
      */
     SelectAction translateSelectionEvent(CellPreviewEvent<T> event);
   }

   /**
    * The action that controls how selection is handled.
    */
   public static enum SelectAction {
     DEFAULT, // Perform the default action.
     SELECT, // Select the value.
     DESELECT, // Deselect the value.
     TOGGLE, // Toggle the selected state of the value.
     IGNORE; // Ignore the event.
   }

   /**
    * An event translator that allows selection only for the specified
    * whitelisted columns.
    *
    * @param <T> the data type
    */
   public static class WhitelistEventTranslator<T> implements EventTranslator<T> {
     private final Set<Integer> whitelist = new HashSet<Integer>();

     /**
      * Construct a new {@link WhitelistEventTranslator}.
      *
      * @param whitelistedColumns the columns to whitelist
      */
     public WhitelistEventTranslator(int... whitelistedColumns) {
       if (whitelistedColumns != null) {
         for (int i : whitelistedColumns) {
           setColumnWhitelisted(i, true);
         }
       }
     }

     public boolean clearCurrentSelection(CellPreviewEvent<T> event) {
       return false;
     }

     /**
      * Clear all columns from the whitelist.
      */
     public void clearWhitelist() {
       whitelist.clear();
     }

     /**
      * Check if the specified column is whitelisted.
      *
      * @param index the column index
      * @return true if whitelisted, false if not
      */
     public boolean isColumnWhitelisted(int index) {
       return whitelist.contains(index);
     }

     /**
      * Set whether or not the specified column in whitelisted.
      *
      * @param index the column index
      * @param isWhitelisted true to whitelist, false to allow disallow selection
      */
     public void setColumnWhitelisted(int index, boolean isWhitelisted) {
       if (isWhitelisted) {
         whitelist.add(index);
       } else {
         whitelist.remove(index);
       }
     }

     public SelectAction translateSelectionEvent(CellPreviewEvent<T> event) {
       return isColumnWhitelisted(event.getColumn()) ? SelectAction.DEFAULT
           : SelectAction.IGNORE;
     }
   }

   /**
    * Construct a new {@link DefaultSelectionEventManager} that ignores selection
    * for the columns in the specified blacklist.
    *
    * @param <T> the data type of the display
    * @param blacklistedColumns the columns to include in the blacklist
    * @return a {@link DefaultSelectionEventManager} instance
    */
   public static <T> DefaultSelectionEventManager<T> createBlacklistManager(
       int... blacklistedColumns) {
     return new DefaultSelectionEventManager<T>(new BlacklistEventTranslator<T>(
         blacklistedColumns));
   }

   /**
    * Construct a new {@link DefaultSelectionEventManager} that triggers
    * selection when any checkbox in any column is clicked.
    *
    * @param <T> the data type of the display
    * @return a {@link DefaultSelectionEventManager} instance
    */
   public static <T> DefaultSelectionEventManager<T> createCheckboxManager() {
     return new DefaultSelectionEventManager<T>(new CheckboxEventTranslator<T>());
   }

   /**
    * Construct a new {@link DefaultSelectionEventManager} that triggers
    * selection when a checkbox in the specified column is clicked.
    *
    * @param <T> the data type of the display
    * @param column the column to handle
    * @return a {@link DefaultSelectionEventManager} instance
    */
   public static <T> DefaultSelectionEventManager<T> createCheckboxManager(
       int column) {
     return new DefaultSelectionEventManager<T>(new CheckboxEventTranslator<T>(
         column));
   }

   /**
    * Create a new {@link DefaultSelectionEventManager} using the specified
    * {@link EventTranslator} to control which {@link SelectAction} to take for
    * each event.
    *
    * @param <T> the data type of the display
    * @param translator the {@link EventTranslator} to use
    * @return a {@link DefaultSelectionEventManager} instance
    */
   public static <T> DefaultSelectionEventManager<T> createCustomManager(
       EventTranslator<T> translator) {
     return new DefaultSelectionEventManager<T>(translator);
   }

   /**
    * Create a new {@link DefaultSelectionEventManager} that handles selection
    * via user interactions.
    *
    * @param <T> the data type of the display
    * @return a new {@link DefaultSelectionEventManager} instance
    */
   public static <T> DefaultSelectionEventManager<T> createDefaultManager() {
     return new DefaultSelectionEventManager<T>(null);
   }

   /**
    * Construct a new {@link DefaultSelectionEventManager} that allows selection
    * only for the columns in the specified whitelist.
    *
    * @param <T> the data type of the display
    * @param whitelistedColumns the columns to include in the whitelist
    * @return a {@link DefaultSelectionEventManager} instance
    */
   public static <T> DefaultSelectionEventManager<T> createWhitelistManager(
       int... whitelistedColumns) {
     return new DefaultSelectionEventManager<T>(new WhitelistEventTranslator<T>(
         whitelistedColumns));
   }

   /**
    * The last {@link HasData} that was handled.
    */
   private HasData<T> lastDisplay;

   /**
    * The last page start.
    */
   private int lastPageStart;

   /**
    * The last selected row index.
    */
   private int lastSelectedIndex = -1;

   /**
    * A boolean indicating that the last shift selection was additive.
    */
   private boolean shiftAdditive;

   /**
    * The last place where the user clicked without holding shift. Multi
    * selections that use the shift key are rooted at the anchor.
    */
   private int shiftAnchor = -1;

   /**
    * The {@link EventTranslator} that controls how selection is handled.
    */
   private final EventTranslator<T> translator;

   /**
    * Construct a new {@link DefaultSelectionEventManager} using the specified
    * {@link EventTranslator} to control which {@link SelectAction} to take for
    * each event.
    *
    * @param translator the {@link EventTranslator} to use
    */
   protected DefaultSelectionEventManager(EventTranslator<T> translator) {
     this.translator = translator;
   }

   /**
    * Update the selection model based on a user selection event.
    *
    * @param selectionModel the selection model to update
    * @param row the absolute index of the selected row
    * @param rowValue the selected row value
    * @param action the {@link SelectAction} to apply
    * @param selectRange true to select the range from the last selected row
    * @param clearOthers true to clear the current selection
    */
   public void doMultiSelection(MultiSelectionModel<? super T> selectionModel,
       HasData<T> display, int row, T rowValue, SelectAction action,
       boolean selectRange, boolean clearOthers) {
     // Determine if we will add or remove selection.
     boolean addToSelection = true;
     if (action != null) {
       switch (action) {
         case IGNORE:
           // Ignore selection.
           return;
         case SELECT:
           addToSelection = true;
           break;
         case DESELECT:
           addToSelection = false;
           break;
         case TOGGLE:
           addToSelection = !selectionModel.isSelected(rowValue);
           break;
       }
     }

     // Determine which rows will be newly selected.
     int pageStart = display.getVisibleRange().getStart();
     if (selectRange && pageStart == lastPageStart && lastSelectedIndex > -1
         && shiftAnchor > -1 && display == lastDisplay) {
       /*
        * Get the new shift bounds based on the existing shift anchor and the
        * selected row.
        */
       int start = Math.min(shiftAnchor, row); // Inclusive.
       int end = Math.max(shiftAnchor, row); // Inclusive.

       if (lastSelectedIndex < start) {
         // Revert previous selection if the user reselects a smaller range.
         setRangeSelection(selectionModel, display, new Range(lastSelectedIndex,
             start - lastSelectedIndex), !shiftAdditive, false);
       } else if (lastSelectedIndex > end) {
         // Revert previous selection if the user reselects a smaller range.
         setRangeSelection(selectionModel, display, new Range(end + 1,
             lastSelectedIndex - end), !shiftAdditive, false);
       } else {
         // Remember if we are adding or removing rows.
         shiftAdditive = addToSelection;
       }

       // Update the last selected row, but do not move the shift anchor.
       lastSelectedIndex = row;

       // Select the range.
       setRangeSelection(selectionModel, display, new Range(start, end - start
           + 1), shiftAdditive, clearOthers);
     } else {
       /*
        * If we are not selecting a range, save the last row and set the shift
        * anchor.
        */
       lastDisplay = display;
       lastPageStart = pageStart;
       lastSelectedIndex = row;
       shiftAnchor = row;
       selectOne(selectionModel, rowValue, addToSelection, clearOthers);
     }
   }

   public void onCellPreview(CellPreviewEvent<T> event) {
     // Early exit if selection is already handled or we are editing.
     if (event.isCellEditing() || event.isSelectionHandled()) {
       return;
     }

     // Early exit if we do not have a SelectionModel.
     HasData<T> display = event.getDisplay();
     SelectionModel<? super T> selectionModel = display.getSelectionModel();
     if (selectionModel == null) {
       return;
     }

     // Check for user defined actions.
     SelectAction action = (translator == null) ? SelectAction.DEFAULT
         : translator.translateSelectionEvent(event);

     // Handle the event based on the SelectionModel type.
     if (selectionModel instanceof MultiSelectionModel<?>) {
       // Add shift key support for MultiSelectionModel.
       handleMultiSelectionEvent(event, action,
           (MultiSelectionModel<? super T>) selectionModel);
     } else {
       // Use the standard handler.
       handleSelectionEvent(event, action, selectionModel);
     }
   }

   /**
    * Removes all items from the selection.
    *
    * @param selectionModel the {@link MultiSelectionModel} to clear
    */
   protected void clearSelection(MultiSelectionModel<? super T> selectionModel) {
     selectionModel.clear();
   }

   /**
    * Handle an event that could cause a value to be selected for a
    * {@link MultiSelectionModel}. This overloaded method adds support for both
    * the control and shift keys. If the shift key is held down, all rows between
    * the previous selected row and the current row are selected.
    *
    * @param event the {@link CellPreviewEvent} that triggered selection
    * @param action the action to handle
    * @param selectionModel the {@link SelectionModel} to update
    */
   protected void handleMultiSelectionEvent(CellPreviewEvent<T> event,
       SelectAction action, MultiSelectionModel<? super T> selectionModel) {
     NativeEvent nativeEvent = event.getNativeEvent();
     String type = nativeEvent.getType();
     if (BrowserEvents.CLICK.equals(type)) {
       /*
        * Update selection on click. Selection is toggled only if the user
        * presses the ctrl key. If the user does not press the control key,
        * selection is additive.
        */
       boolean shift = nativeEvent.getShiftKey();
       boolean ctrlOrMeta = nativeEvent.getCtrlKey() || nativeEvent.getMetaKey();
       boolean clearOthers = (translator == null) ? !ctrlOrMeta
           : translator.clearCurrentSelection(event);
       if (action == null || action == SelectAction.DEFAULT) {
         action = ctrlOrMeta ? SelectAction.TOGGLE : SelectAction.SELECT;
       }
       doMultiSelection(selectionModel, event.getDisplay(), event.getIndex(),
           event.getValue(), action, shift, clearOthers);
     } else if (BrowserEvents.KEYUP.equals(type)) {
       int keyCode = nativeEvent.getKeyCode();
       if (keyCode == 32) {
         /*
          * Update selection when the space bar is pressed. The spacebar always
          * toggles selection, regardless of whether the control key is pressed.
          */
         boolean shift = nativeEvent.getShiftKey();
         boolean clearOthers = (translator == null) ? false
             : translator.clearCurrentSelection(event);
         if (action == null || action == SelectAction.DEFAULT) {
           action = SelectAction.TOGGLE;
         }
         doMultiSelection(selectionModel, event.getDisplay(), event.getIndex(),
             event.getValue(), action, shift, clearOthers);
       }
     }
   }

   /**
    * Handle an event that could cause a value to be selected. This method works
    * for any {@link SelectionModel}. Pressing the space bar or ctrl+click will
    * toggle the selection state. Clicking selects the row if it is not selected.
    *
    * @param event the {@link CellPreviewEvent} that triggered selection
    * @param action the action to handle
    * @param selectionModel the {@link SelectionModel} to update
    */
   protected void handleSelectionEvent(CellPreviewEvent<T> event,
       SelectAction action, SelectionModel<? super T> selectionModel) {
     // Handle selection overrides.
     T value = event.getValue();
     if (action != null) {
       switch (action) {
         case IGNORE:
           return;
         case SELECT:
           selectionModel.setSelected(value, true);
           return;
         case DESELECT:
           selectionModel.setSelected(value, false);
           return;
         case TOGGLE:
           selectionModel.setSelected(value, !selectionModel.isSelected(value));
           return;
       }
     }

     // Handle default selection.
     NativeEvent nativeEvent = event.getNativeEvent();
     String type = nativeEvent.getType();
     if (BrowserEvents.CLICK.equals(type)) {
       if (nativeEvent.getCtrlKey() || nativeEvent.getMetaKey()) {
         // Toggle selection on ctrl+click.
         selectionModel.setSelected(value, !selectionModel.isSelected(value));
       } else {
         // Select on click.
         selectionModel.setSelected(value, true);
       }
     } else if (BrowserEvents.KEYUP.equals(type)) {
       // Toggle selection on space.
       int keyCode = nativeEvent.getKeyCode();
       if (keyCode == 32) {
         selectionModel.setSelected(value, !selectionModel.isSelected(value));
       }
     }
   }

   /**
    * Selects the given item, optionally clearing any prior selection.
    *
    * @param selectionModel the {@link MultiSelectionModel} to update
    * @param target the item to select
    * @param selected true to select, false to deselect
    * @param clearOthers true to clear all other selected items
    */
   protected void selectOne(MultiSelectionModel<? super T> selectionModel,
       T target, boolean selected, boolean clearOthers) {
     if (clearOthers) {
       clearSelection(selectionModel);
     }
     selectionModel.setSelected(target, selected);
   }

   /**
    * Select or deselect a range of row indexes, optionally deselecting all other
    * values.
    *
    * @param selectionModel the {@link MultiSelectionModel} to update
    * @param display the {@link HasData} source of the selection event
    * @param range the {@link Range} of rows to select or deselect
    * @param addToSelection true to select, false to deselect the range
    * @param clearOthers true to deselect rows not in the range
    */
   protected void setRangeSelection(
       MultiSelectionModel<? super T> selectionModel, HasData<T> display,
       Range range, boolean addToSelection, boolean clearOthers) {
     // Get the list of values to select.
     List<T> toUpdate = new ArrayList<T>();
     int itemCount = display.getVisibleItemCount();
     int relativeStart = range.getStart() - display.getVisibleRange().getStart();
     int relativeEnd = relativeStart + range.getLength();
     for (int i = relativeStart; i < relativeEnd && i < itemCount; i++) {
       toUpdate.add(display.getVisibleItem(i));
     }

     // Clear all other values.
     if (clearOthers) {
       clearSelection(selectionModel);
     }

     // Update the state of the values.
     for (T value : toUpdate) {
       selectionModel.setSelected(value, addToSelection);
     }
   }
 }
	/*
	* Copyright 2010 Google Inc.
	*
	* Licensed under the Apache License, Version 2.0 (the "License"); you may not
	* use this file except in compliance with the License. You may obtain a copy of
	* the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
	* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
	* License for the specific language governing permissions and limitations under
	* the License.
	*/
	package com.google.gwt.view.client;

	import com.google.gwt.dom.client.BrowserEvents;
	import com.google.gwt.dom.client.Element;
	import com.google.gwt.dom.client.InputElement;
	import com.google.gwt.dom.client.NativeEvent;

	import java.util.ArrayList;
	import java.util.HashSet;
	import java.util.List;
	import java.util.Set;

	/**
	* An implementation of {@link CellPreviewEvent.Handler} that adds selection
	* support via the spacebar and mouse clicks and handles the control key.
	*
	* <p>
	* If the {@link HasData} source of the selection event uses a
	* {@link MultiSelectionModel}, this manager additionally provides support for
	* shift key to select a range of values. For all other {@link SelectionModel}s,
	* only the control key is supported.
	* </p>
	*
	* @param <T> the data type of records in the list
	*/
	public class DefaultSelectionEventManager<T> implements
	CellPreviewEvent.Handler<T> {

	/**
	* An event translator that disables selection for the specified blacklisted
	* columns.
	*
	* @param <T> the data type
	*/
	public static class BlacklistEventTranslator<T> implements EventTranslator<T> {
	private final Set<Integer> blacklist = new HashSet<Integer>();

	/**
	* Construct a new {@link BlacklistEventTranslator}.
	*
	* @param blacklistedColumns the columns to blacklist
	*/
	public BlacklistEventTranslator(int... blacklistedColumns) {
	if (blacklistedColumns != null) {
	for (int i : blacklistedColumns) {
	setColumnBlacklisted(i, true);
	}
	}
	}

	/**
	* Clear all columns from the blacklist.
	*/
	public void clearBlacklist() {
	blacklist.clear();
	}

	public boolean clearCurrentSelection(CellPreviewEvent<T> event) {
	return false;
	}

	/**
	* Check if the specified column is blacklisted.
	*
	* @param index the column index
	* @return true if blacklisted, false if not
	*/
	public boolean isColumnBlacklisted(int index) {
	return blacklist.contains(index);
	}

	/**
	* Set whether or not the specified column in blacklisted.
	*
	* @param index the column index
	* @param isBlacklisted true to blacklist, false to allow selection
	*/
	public void setColumnBlacklisted(int index, boolean isBlacklisted) {
	if (isBlacklisted) {
	blacklist.add(index);
	} else {
	blacklist.remove(index);
	}
	}

	public SelectAction translateSelectionEvent(CellPreviewEvent<T> event) {
	return isColumnBlacklisted(event.getColumn()) ? SelectAction.IGNORE
	: SelectAction.DEFAULT;
	}
	}

	/**
	* Implementation of {@link EventTranslator} that only triggers selection when
	* any checkbox is selected.
	*
	* @param <T> the data type
	*/
	public static class CheckboxEventTranslator<T> implements EventTranslator<T> {

	/**
	* The column index of the checkbox. Other columns are ignored.
	*/
	private final int column;

	/**
	* Construct a new {@link CheckboxEventTranslator} that will trigger
	* selection when any checkbox in any column is selected.
	*/
	public CheckboxEventTranslator() {
	this(-1);
	}

	/**
	* Construct a new {@link CheckboxEventTranslator} that will trigger
	* selection when a checkbox in the specified column is selected.
	*
	* @param column the column index, or -1 for all columns
	*/
	public CheckboxEventTranslator(int column) {
	this.column = column;
	}

	public boolean clearCurrentSelection(CellPreviewEvent<T> event) {
	return false;
	}

	public SelectAction translateSelectionEvent(CellPreviewEvent<T> event) {
	// Handle the event.
	NativeEvent nativeEvent = event.getNativeEvent();
	if (BrowserEvents.CLICK.equals(nativeEvent.getType())) {
	// Ignore if the event didn't occur in the correct column.
	if (column > -1 && column != event.getColumn()) {
	return SelectAction.IGNORE;
	}

	// Determine if we clicked on a checkbox.
	Element target = nativeEvent.getEventTarget().cast();
	if ("input".equals(target.getTagName().toLowerCase())) {
	final InputElement input = target.cast();
	if ("checkbox".equals(input.getType().toLowerCase())) {
	// Synchronize the checkbox with the current selection state.
	input.setChecked(event.getDisplay().getSelectionModel().isSelected(
	event.getValue()));
	return SelectAction.TOGGLE;
	}
	}
	return SelectAction.IGNORE;
	}

	// For keyboard events, do the default action.
	return SelectAction.DEFAULT;
	}
	}

	/**
	* Translates {@link CellPreviewEvent}s into {@link SelectAction}s.
	*/
	public static interface EventTranslator<T> {
	/**
	* Check whether a user selection event should clear all currently selected
	* values.
	*
	* @param event the {@link CellPreviewEvent} to translate
	*/
	boolean clearCurrentSelection(CellPreviewEvent<T> event);

	/**
	* Translate the user selection event into a {@link SelectAction}.
	*
	* @param event the {@link CellPreviewEvent} to translate
	*/
	SelectAction translateSelectionEvent(CellPreviewEvent<T> event);
	}

	/**
	* The action that controls how selection is handled.
	*/
	public static enum SelectAction {
	DEFAULT, // Perform the default action.
	SELECT, // Select the value.
	DESELECT, // Deselect the value.
	TOGGLE, // Toggle the selected state of the value.
	IGNORE; // Ignore the event.
	}

	/**
	* An event translator that allows selection only for the specified
	* whitelisted columns.
	*
	* @param <T> the data type
	*/
	public static class WhitelistEventTranslator<T> implements EventTranslator<T> {
	private final Set<Integer> whitelist = new HashSet<Integer>();

	/**
	* Construct a new {@link WhitelistEventTranslator}.
	*
	* @param whitelistedColumns the columns to whitelist
	*/
	public WhitelistEventTranslator(int... whitelistedColumns) {
	if (whitelistedColumns != null) {
	for (int i : whitelistedColumns) {
	setColumnWhitelisted(i, true);
	}
	}
	}

	public boolean clearCurrentSelection(CellPreviewEvent<T> event) {
	return false;
	}

	/**
	* Clear all columns from the whitelist.
	*/
	public void clearWhitelist() {
	whitelist.clear();
	}

	/**
	* Check if the specified column is whitelisted.
	*
	* @param index the column index
	* @return true if whitelisted, false if not
	*/
	public boolean isColumnWhitelisted(int index) {
	return whitelist.contains(index);
	}

	/**
	* Set whether or not the specified column in whitelisted.
	*
	* @param index the column index
	* @param isWhitelisted true to whitelist, false to allow disallow selection
	*/
	public void setColumnWhitelisted(int index, boolean isWhitelisted) {
	if (isWhitelisted) {
	whitelist.add(index);
	} else {
	whitelist.remove(index);
	}
	}

	public SelectAction translateSelectionEvent(CellPreviewEvent<T> event) {
	return isColumnWhitelisted(event.getColumn()) ? SelectAction.DEFAULT
	: SelectAction.IGNORE;
	}
	}

	/**
	* Construct a new {@link DefaultSelectionEventManager} that ignores selection
	* for the columns in the specified blacklist.
	*
	* @param <T> the data type of the display
	* @param blacklistedColumns the columns to include in the blacklist
	* @return a {@link DefaultSelectionEventManager} instance
	*/
	public static <T> DefaultSelectionEventManager<T> createBlacklistManager(
	int... blacklistedColumns) {
	return new DefaultSelectionEventManager<T>(new BlacklistEventTranslator<T>(
	blacklistedColumns));
	}

	/**
	* Construct a new {@link DefaultSelectionEventManager} that triggers
	* selection when any checkbox in any column is clicked.
	*
	* @param <T> the data type of the display
	* @return a {@link DefaultSelectionEventManager} instance
	*/
	public static <T> DefaultSelectionEventManager<T> createCheckboxManager() {
	return new DefaultSelectionEventManager<T>(new CheckboxEventTranslator<T>());
	}

	/**
	* Construct a new {@link DefaultSelectionEventManager} that triggers
	* selection when a checkbox in the specified column is clicked.
	*
	* @param <T> the data type of the display
	* @param column the column to handle
	* @return a {@link DefaultSelectionEventManager} instance
	*/
	public static <T> DefaultSelectionEventManager<T> createCheckboxManager(
	int column) {
	return new DefaultSelectionEventManager<T>(new CheckboxEventTranslator<T>(
	column));
	}

	/**
	* Create a new {@link DefaultSelectionEventManager} using the specified
	* {@link EventTranslator} to control which {@link SelectAction} to take for
	* each event.
	*
	* @param <T> the data type of the display
	* @param translator the {@link EventTranslator} to use
	* @return a {@link DefaultSelectionEventManager} instance
	*/
	public static <T> DefaultSelectionEventManager<T> createCustomManager(
	EventTranslator<T> translator) {
	return new DefaultSelectionEventManager<T>(translator);
	}

	/**
	* Create a new {@link DefaultSelectionEventManager} that handles selection
	* via user interactions.
	*
	* @param <T> the data type of the display
	* @return a new {@link DefaultSelectionEventManager} instance
	*/
	public static <T> DefaultSelectionEventManager<T> createDefaultManager() {
	return new DefaultSelectionEventManager<T>(null);
	}

	/**
	* Construct a new {@link DefaultSelectionEventManager} that allows selection
	* only for the columns in the specified whitelist.
	*
	* @param <T> the data type of the display
	* @param whitelistedColumns the columns to include in the whitelist
	* @return a {@link DefaultSelectionEventManager} instance
	*/
	public static <T> DefaultSelectionEventManager<T> createWhitelistManager(
	int... whitelistedColumns) {
	return new DefaultSelectionEventManager<T>(new WhitelistEventTranslator<T>(
	whitelistedColumns));
	}

	/**
	* The last {@link HasData} that was handled.
	*/
	private HasData<T> lastDisplay;

	/**
	* The last page start.
	*/
	private int lastPageStart;

	/**
	* The last selected row index.
	*/
	private int lastSelectedIndex = -1;

	/**
	* A boolean indicating that the last shift selection was additive.
	*/
	private boolean shiftAdditive;

	/**
	* The last place where the user clicked without holding shift. Multi
	* selections that use the shift key are rooted at the anchor.
	*/
	private int shiftAnchor = -1;

	/**
	* The {@link EventTranslator} that controls how selection is handled.
	*/
	private final EventTranslator<T> translator;

	/**
	* Construct a new {@link DefaultSelectionEventManager} using the specified
	* {@link EventTranslator} to control which {@link SelectAction} to take for
	* each event.
	*
	* @param translator the {@link EventTranslator} to use
	*/
	protected DefaultSelectionEventManager(EventTranslator<T> translator) {
	this.translator = translator;
	}

	/**
	* Update the selection model based on a user selection event.
	*
	* @param selectionModel the selection model to update
	* @param row the absolute index of the selected row
	* @param rowValue the selected row value
	* @param action the {@link SelectAction} to apply
	* @param selectRange true to select the range from the last selected row
	* @param clearOthers true to clear the current selection
	*/
	public void doMultiSelection(MultiSelectionModel<? super T> selectionModel,
	HasData<T> display, int row, T rowValue, SelectAction action,
	boolean selectRange, boolean clearOthers) {
	// Determine if we will add or remove selection.
	boolean addToSelection = true;
	if (action != null) {
	switch (action) {
	case IGNORE:
	// Ignore selection.
	return;
	case SELECT:
	addToSelection = true;
	break;
	case DESELECT:
	addToSelection = false;
	break;
	case TOGGLE:
	addToSelection = !selectionModel.isSelected(rowValue);
	break;
	}
	}

	// Determine which rows will be newly selected.
	int pageStart = display.getVisibleRange().getStart();
	if (selectRange && pageStart == lastPageStart && lastSelectedIndex > -1
	&& shiftAnchor > -1 && display == lastDisplay) {
	/*
	* Get the new shift bounds based on the existing shift anchor and the
	* selected row.
	*/
	int start = Math.min(shiftAnchor, row); // Inclusive.
	int end = Math.max(shiftAnchor, row); // Inclusive.

	if (lastSelectedIndex < start) {
	// Revert previous selection if the user reselects a smaller range.
	setRangeSelection(selectionModel, display, new Range(lastSelectedIndex,
	start - lastSelectedIndex), !shiftAdditive, false);
	} else if (lastSelectedIndex > end) {
	// Revert previous selection if the user reselects a smaller range.
	setRangeSelection(selectionModel, display, new Range(end + 1,
	lastSelectedIndex - end), !shiftAdditive, false);
	} else {
	// Remember if we are adding or removing rows.
	shiftAdditive = addToSelection;
	}

	// Update the last selected row, but do not move the shift anchor.
	lastSelectedIndex = row;

	// Select the range.
	setRangeSelection(selectionModel, display, new Range(start, end - start
	+ 1), shiftAdditive, clearOthers);
	} else {
	/*
	* If we are not selecting a range, save the last row and set the shift
	* anchor.
	*/
	lastDisplay = display;
	lastPageStart = pageStart;
	lastSelectedIndex = row;
	shiftAnchor = row;
	selectOne(selectionModel, rowValue, addToSelection, clearOthers);
	}
	}

	public void onCellPreview(CellPreviewEvent<T> event) {
	// Early exit if selection is already handled or we are editing.
	if (event.isCellEditing() \|\| event.isSelectionHandled()) {
	return;
	}

	// Early exit if we do not have a SelectionModel.
	HasData<T> display = event.getDisplay();
	SelectionModel<? super T> selectionModel = display.getSelectionModel();
	if (selectionModel == null) {
	return;
	}

	// Check for user defined actions.
	SelectAction action = (translator == null) ? SelectAction.DEFAULT
	: translator.translateSelectionEvent(event);

	// Handle the event based on the SelectionModel type.
	if (selectionModel instanceof MultiSelectionModel<?>) {
	// Add shift key support for MultiSelectionModel.
	handleMultiSelectionEvent(event, action,
	(MultiSelectionModel<? super T>) selectionModel);
	} else {
	// Use the standard handler.
	handleSelectionEvent(event, action, selectionModel);
	}
	}

	/**
	* Removes all items from the selection.
	*
	* @param selectionModel the {@link MultiSelectionModel} to clear
	*/
	protected void clearSelection(MultiSelectionModel<? super T> selectionModel) {
	selectionModel.clear();
	}

	/**
	* Handle an event that could cause a value to be selected for a
	* {@link MultiSelectionModel}. This overloaded method adds support for both
	* the control and shift keys. If the shift key is held down, all rows between
	* the previous selected row and the current row are selected.
	*
	* @param event the {@link CellPreviewEvent} that triggered selection
	* @param action the action to handle
	* @param selectionModel the {@link SelectionModel} to update
	*/
	protected void handleMultiSelectionEvent(CellPreviewEvent<T> event,
	SelectAction action, MultiSelectionModel<? super T> selectionModel) {
	NativeEvent nativeEvent = event.getNativeEvent();
	String type = nativeEvent.getType();
	if (BrowserEvents.CLICK.equals(type)) {
	/*
	* Update selection on click. Selection is toggled only if the user
	* presses the ctrl key. If the user does not press the control key,
	* selection is additive.
	*/
	boolean shift = nativeEvent.getShiftKey();
	boolean ctrlOrMeta = nativeEvent.getCtrlKey() \|\| nativeEvent.getMetaKey();
	boolean clearOthers = (translator == null) ? !ctrlOrMeta
	: translator.clearCurrentSelection(event);
	if (action == null \|\| action == SelectAction.DEFAULT) {
	action = ctrlOrMeta ? SelectAction.TOGGLE : SelectAction.SELECT;
	}
	doMultiSelection(selectionModel, event.getDisplay(), event.getIndex(),
	event.getValue(), action, shift, clearOthers);
	} else if (BrowserEvents.KEYUP.equals(type)) {
	int keyCode = nativeEvent.getKeyCode();
	if (keyCode == 32) {
	/*
	* Update selection when the space bar is pressed. The spacebar always
	* toggles selection, regardless of whether the control key is pressed.
	*/
	boolean shift = nativeEvent.getShiftKey();
	boolean clearOthers = (translator == null) ? false
	: translator.clearCurrentSelection(event);
	if (action == null \|\| action == SelectAction.DEFAULT) {
	action = SelectAction.TOGGLE;
	}
	doMultiSelection(selectionModel, event.getDisplay(), event.getIndex(),
	event.getValue(), action, shift, clearOthers);
	}
	}
	}

	/**
	* Handle an event that could cause a value to be selected. This method works
	* for any {@link SelectionModel}. Pressing the space bar or ctrl+click will
	* toggle the selection state. Clicking selects the row if it is not selected.
	*
	* @param event the {@link CellPreviewEvent} that triggered selection
	* @param action the action to handle
	* @param selectionModel the {@link SelectionModel} to update
	*/
	protected void handleSelectionEvent(CellPreviewEvent<T> event,
	SelectAction action, SelectionModel<? super T> selectionModel) {
	// Handle selection overrides.
	T value = event.getValue();
	if (action != null) {
	switch (action) {
	case IGNORE:
	return;
	case SELECT:
	selectionModel.setSelected(value, true);
	return;
	case DESELECT:
	selectionModel.setSelected(value, false);
	return;
	case TOGGLE:
	selectionModel.setSelected(value, !selectionModel.isSelected(value));
	return;
	}
	}

	// Handle default selection.
	NativeEvent nativeEvent = event.getNativeEvent();
	String type = nativeEvent.getType();
	if (BrowserEvents.CLICK.equals(type)) {
	if (nativeEvent.getCtrlKey() \|\| nativeEvent.getMetaKey()) {
	// Toggle selection on ctrl+click.
	selectionModel.setSelected(value, !selectionModel.isSelected(value));
	} else {
	// Select on click.
	selectionModel.setSelected(value, true);
	}
	} else if (BrowserEvents.KEYUP.equals(type)) {
	// Toggle selection on space.
	int keyCode = nativeEvent.getKeyCode();
	if (keyCode == 32) {
	selectionModel.setSelected(value, !selectionModel.isSelected(value));
	}
	}
	}

	/**
	* Selects the given item, optionally clearing any prior selection.
	*
	* @param selectionModel the {@link MultiSelectionModel} to update
	* @param target the item to select
	* @param selected true to select, false to deselect
	* @param clearOthers true to clear all other selected items
	*/
	protected void selectOne(MultiSelectionModel<? super T> selectionModel,
	T target, boolean selected, boolean clearOthers) {
	if (clearOthers) {
	clearSelection(selectionModel);
	}
	selectionModel.setSelected(target, selected);
	}

	/**
	* Select or deselect a range of row indexes, optionally deselecting all other
	* values.
	*
	* @param selectionModel the {@link MultiSelectionModel} to update
	* @param display the {@link HasData} source of the selection event
	* @param range the {@link Range} of rows to select or deselect
	* @param addToSelection true to select, false to deselect the range
	* @param clearOthers true to deselect rows not in the range
	*/
	protected void setRangeSelection(
	MultiSelectionModel<? super T> selectionModel, HasData<T> display,
	Range range, boolean addToSelection, boolean clearOthers) {
	// Get the list of values to select.
	List<T> toUpdate = new ArrayList<T>();
	int itemCount = display.getVisibleItemCount();
	int relativeStart = range.getStart() - display.getVisibleRange().getStart();
	int relativeEnd = relativeStart + range.getLength();
	for (int i = relativeStart; i < relativeEnd && i < itemCount; i++) {
	toUpdate.add(display.getVisibleItem(i));
	}

	// Clear all other values.
	if (clearOthers) {
	clearSelection(selectionModel);
	}

	// Update the state of the values.
	for (T value : toUpdate) {
	selectionModel.setSelected(value, addToSelection);
	}
	}
	}