bundles/org.eclipse.jface/src/org/eclipse/jface/preference/FieldEditor.java - platform/eclipse.platform.ui - Git at Google

 /*******************************************************************************
  * Copyright (c) 2000, 2005 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  *     IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.jface.preference;

 import org.eclipse.jface.dialogs.DialogPage;
 import org.eclipse.jface.dialogs.IDialogConstants;
 import org.eclipse.jface.resource.JFaceResources;
 import org.eclipse.jface.util.Assert;
 import org.eclipse.jface.util.IPropertyChangeListener;
 import org.eclipse.jface.util.PropertyChangeEvent;
 import org.eclipse.swt.SWT;
 import org.eclipse.swt.events.DisposeEvent;
 import org.eclipse.swt.events.DisposeListener;
 import org.eclipse.swt.graphics.FontMetrics;
 import org.eclipse.swt.graphics.GC;
 import org.eclipse.swt.layout.GridData;
 import org.eclipse.swt.layout.GridLayout;
 import org.eclipse.swt.widgets.Button;
 import org.eclipse.swt.widgets.Composite;
 import org.eclipse.swt.widgets.Control;
 import org.eclipse.swt.widgets.Label;

 /**
  * Abstract base class for all field editors.
  * <p>
  * A field editor presents the value of a preference to the end
  * user. The value is loaded from a preference store; if
  * modified by the end user, the value is validated and eventually
  * stored back to the preference store. A field editor reports
  * an event when the value, or the validity of the value, changes.
  * </p>
  * <p>
  * Field editors should be used in conjunction with a field
  * editor preference page (<code>FieldEditorPreferencePage</code>)
  * which coordinates everything and provides the message line
  * which display messages emanating from the editor.
  * </p>
  * <p>
  * This package contains ready-to-use field editors for various
  * types of preferences:
  * <ul>
  *   <li><code>BooleanFieldEditor</code> - booleans</li>
  *   <li><code>IntegerFieldEditor</code> - integers</li>
  *   <li><code>StringFieldEditor</code> - text strings</li>
  *   <li><code>RadioGroupFieldEditor</code> - enumerations</li>
  *   <li><code>ColorFieldEditor</code> - RGB colors</li>
  *   <li><code>FontFieldEditor</code> - fonts</li>
  *   <li><code>DirectoryFieldEditor</code> - directories</li>
  *   <li><code>FileFieldEditor</code> - files</li>
  *   <li><code>PathEditor</code> - paths</li>
  * </ul>
  * </p>
  */
 public abstract class FieldEditor {

     /**
      * Property name constant (value <code>"field_editor_is_valid"</code>)
      * to signal a change in the validity of the value of this field editor.
      */
     public static final String IS_VALID = "field_editor_is_valid";//$NON-NLS-1$

     /**
      * Property name constant (value <code>"field_editor_value"</code>)
      * to signal a change in the value of this field editor.
      */
     public static final String VALUE = "field_editor_value";//$NON-NLS-1$

     /**
      * Gap between label and control.
      */
     protected static final int HORIZONTAL_GAP = 8;

     /**
      * The preference store, or <code>null</code> if none.
      */
     private IPreferenceStore preferenceStore = null;

     /**
      * The name of the preference displayed in this field editor.
      */
     private String preferenceName;

     /**
      * Indicates whether the default value is currently displayed,
      * initially <code>false</code>.
      */
     private boolean isDefaultPresented = false;

     /**
      * The label's text.
      */
     private String labelText;

     /**
      * The label control.
      */
     private Label label;

     /**
      * Listener, or <code>null</code> if none
      */
     private IPropertyChangeListener propertyChangeListener;

     /**
      * The page containing this field editor
      */
     private DialogPage page;

     /**
      * Creates a new field editor.
      */
     protected FieldEditor() {
     }

     /**
      * Creates a new field editor.
      *
      * @param name the name of the preference this field editor works on
      * @param labelText the label text of the field editor
      * @param parent the parent of the field editor's control
      */
     protected FieldEditor(String name, String labelText, Composite parent) {
         init(name, labelText);
         createControl(parent);
     }

     /**
      * Adjusts the horizontal span of this field editor's basic controls.
      * <p>
      * Subclasses must implement this method to adjust the horizontal span
      * of controls so they appear correct in the given number of columns.
      * </p>
      * <p>
      * The number of columns will always be equal to or greater than the
      * value returned by this editor's <code>getNumberOfControls</code> method.
      *
      * @param numColumns the number of columns
      */
     protected abstract void adjustForNumColumns(int numColumns);

     /**
      * Applies a font.
      * <p>
      * The default implementation of this framework method
      * does nothing. Subclasses should override this method
      * if they want to change the font of the SWT control to
      * a value different than the standard dialog font.
      * </p>
      */
     protected void applyFont() {
     }

     /**
      * Checks if the given parent is the current parent of the
      * supplied control; throws an (unchecked) exception if they
      * are not correctly related.
      *
      * @param control the control
      * @param parent the parent control
      */
     protected void checkParent(Control control, Composite parent) {
         Assert.isTrue(control.getParent() == parent, "Different parents");//$NON-NLS-1$
     }

     /**
      * Clears the error message from the message line.
      */
     protected void clearErrorMessage() {
         if (page != null)
             page.setErrorMessage(null);
     }

     /**
      * Clears the normal message from the message line.
      */
     protected void clearMessage() {
         if (page != null)
             page.setMessage(null);
     }

     /**
      * Returns the number of pixels corresponding to the
      * given number of horizontal dialog units.
      * <p>
      * Clients may call this framework method, but should not override it.
      * </p>
      *
      * @param control the control being sized
      * @param dlus the number of horizontal dialog units
      * @return the number of pixels
      */
     protected int convertHorizontalDLUsToPixels(Control control, int dlus) {
         GC gc = new GC(control);
         gc.setFont(control.getFont());
         int averageWidth = gc.getFontMetrics().getAverageCharWidth();
         gc.dispose();

         double horizontalDialogUnitSize = averageWidth * 0.25;

         return (int) Math.round(dlus * horizontalDialogUnitSize);
     }

     /**
      * Returns the number of pixels corresponding to the
      * given number of vertical dialog units.
      * <p>
      * Clients may call this framework method, but should not override it.
      * </p>
      *
      * @param control the control being sized
      * @param dlus the number of vertical dialog units
      * @return the number of pixels
      */
     protected int convertVerticalDLUsToPixels(Control control, int dlus) {
         GC gc = new GC(control);
         gc.setFont(control.getFont());
         int height = gc.getFontMetrics().getHeight();
         gc.dispose();

         double verticalDialogUnitSize = height * 0.125;

         return (int) Math.round(dlus * verticalDialogUnitSize);
     }

     /**
      * Creates this field editor's main control containing all of its
      * basic controls.
      *
      * @param parent the parent control
      */
     protected void createControl(Composite parent) {
         GridLayout layout = new GridLayout();
         layout.numColumns = getNumberOfControls();
         layout.marginWidth = 0;
         layout.marginHeight = 0;
         layout.horizontalSpacing = HORIZONTAL_GAP;
         parent.setLayout(layout);
         doFillIntoGrid(parent, layout.numColumns);
     }

     /**
      * Disposes the SWT resources used by this field editor.
      */
     public void dispose() {
         // nothing to dispose
     }

     /**
      * Fills this field editor's basic controls into the given parent.
      * <p>
      * Subclasses must implement this method to create the controls
      * for this field editor.
      * </p>
      *
      * @param parent the composite used as a parent for the basic controls;
      *	the parent's layout must be a <code>GridLayout</code>
      * @param numColumns the number of columns
      */
     protected abstract void doFillIntoGrid(Composite parent, int numColumns);

     /**
      * Initializes this field editor with the preference value from
      * the preference store.
      * <p>
      * Subclasses must implement this method to properly initialize
      * the field editor.
      * </p>
      */
     protected abstract void doLoad();

     /**
      * Initializes this field editor with the default preference value from
      * the preference store.
      * <p>
      * Subclasses must implement this method to properly initialize
      * the field editor.
      * </p>
      */
     protected abstract void doLoadDefault();

     /**
      * Stores the preference value from this field editor into
      * the preference store.
      * <p>
      * Subclasses must implement this method to save the entered value
      * into the preference store.
      * </p>
      */
     protected abstract void doStore();

     /**
      * Fills this field editor's basic controls into the given parent.
      *
      * @param parent the composite used as a parent for the basic controls;
      *	the parent's layout must be a <code>GridLayout</code>
      * @param numColumns the number of columns
      */
     public void fillIntoGrid(Composite parent, int numColumns) {
         Assert.isTrue(numColumns >= getNumberOfControls());
         Assert.isTrue(parent.getLayout() instanceof GridLayout);
         doFillIntoGrid(parent, numColumns);
     }

     /**
      * Informs this field editor's listener, if it has one, about a change to
      * one of this field editor's boolean-valued properties. Does nothing
      * if the old and new values are the same.
      *
      * @param property the field editor property name,
      *   such as <code>VALUE</code> or <code>IS_VALID</code>
      * @param oldValue the old value
      * @param newValue the new value
      */
     protected void fireStateChanged(String property, boolean oldValue,
             boolean newValue) {
         if (oldValue == newValue)
             return;
         fireValueChanged(property, new Boolean(oldValue), new Boolean(newValue));
     }

     /**
      * Informs this field editor's listener, if it has one, about a change to
      * one of this field editor's properties.
      *
      * @param property the field editor property name,
      *   such as <code>VALUE</code> or <code>IS_VALID</code>
      * @param oldValue the old value object, or <code>null</code>
      * @param newValue the new value, or <code>null</code>
      */
     protected void fireValueChanged(String property, Object oldValue,
             Object newValue) {
         if (propertyChangeListener == null)
             return;
         propertyChangeListener.propertyChange(new PropertyChangeEvent(this,
                 property, oldValue, newValue));
     }

     /**
      * Returns the symbolic font name used by this field editor.
      *
      * @return the symbolic font name
      */
     public String getFieldEditorFontName() {
         return JFaceResources.DIALOG_FONT;
     }

     /**
      * Returns the label control.
      *
      * @return the label control, or <code>null</code>
      *  if no label control has been created
      */
     protected Label getLabelControl() {
         return label;
     }

     /**
      * Returns this field editor's label component.
      * <p>
      * The label is created if it does not already exist
      * </p>
      *
      * @param parent the parent
      * @return the label control
      */
     public Label getLabelControl(Composite parent) {
         if (label == null) {
             label = new Label(parent, SWT.LEFT);
             label.setFont(parent.getFont());
             String text = getLabelText();
             if (text != null)
                 label.setText(text);
             label.addDisposeListener(new DisposeListener() {
                 public void widgetDisposed(DisposeEvent event) {
                     label = null;
                 }
             });
         } else {
             checkParent(label, parent);
         }
         return label;
     }

     /**
      * Returns this field editor's label text.
      *
      * @return the label text
      */
     public String getLabelText() {
         return labelText;
     }

     /**
      * Returns the number of basic controls this field editor consists of.
      *
      * @return the number of controls
      */
     public abstract int getNumberOfControls();

     /**
      * Returns the name of the preference this field editor operates on.
      *
      * @return the name of the preference
      */
     public String getPreferenceName() {
         return preferenceName;
     }

     /**
      * Returns the preference page in which this field editor
      * appears.
      *
      * @return the preference page, or <code>null</code> if none
      * @deprecated use #getPage()
      */
     protected PreferencePage getPreferencePage() {
     	if(page != null && page instanceof PreferencePage)
         	return (PreferencePage) page;
     	return null;
     }

     /**
      * Return the DialogPage that the receiver is sending
      * updates to.
      *
      * @return DialogPage or <code>null</code> if it
      * has not been set.
      *
      * @since 3.1
      */
     protected DialogPage getPage(){
     	return page;
     }

     /**
      * Returns the preference store used by this field editor.
      *
      * @return the preference store, or <code>null</code> if none
      * @see #setPreferenceStore
      */
     public IPreferenceStore getPreferenceStore() {
         return preferenceStore;
     }

     /**
      * Initialize the field editor with the given preference name and label.
      *
      * @param name the name of the preference this field editor works on
      * @param text the label text of the field editor
      */
     protected void init(String name, String text) {
         Assert.isNotNull(name);
         Assert.isNotNull(text);
         preferenceName = name;
         this.labelText = text;
     }

     /**
      * Returns whether this field editor contains a valid value.
      * <p>
      * The default implementation of this framework method
      * returns <code>true</code>. Subclasses wishing to perform
      * validation should override both this method and
      * <code>refreshValidState</code>.
      * </p>
      *
      * @return <code>true</code> if the field value is valid,
      *   and <code>false</code> if invalid
      * @see #refreshValidState()
      */
     public boolean isValid() {
         return true;
     }

     /**
      * Initializes this field editor with the preference value from
      * the preference store.
      */
     public void load() {
         if (preferenceStore != null) {
             isDefaultPresented = false;
             doLoad();
             refreshValidState();
         }
     }

     /**
      * Initializes this field editor with the default preference value
      * from the preference store.
      */
     public void loadDefault() {
         if (preferenceStore != null) {
             isDefaultPresented = true;
             doLoadDefault();
             refreshValidState();
         }
     }

     /**
      * Returns whether this field editor currently presents the
      * default value for its preference.
      *
      * @return <code>true</code> if the default value is presented,
      *   and <code>false</code> otherwise
      */
     public boolean presentsDefaultValue() {
         return isDefaultPresented;
     }

     /**
      * Refreshes this field editor's valid state after a value change
      * and fires an <code>IS_VALID</code> property change event if
      * warranted.
      * <p>
      * The default implementation of this framework method does
      * nothing. Subclasses wishing to perform validation should override
      * both this method and <code>isValid</code>.
      * </p>
      *
      * @see #isValid
      */
     protected void refreshValidState() {
     }

     /**
      * Sets the focus to this field editor.
      * <p>
      * The default implementation of this framework method
      * does nothing. Subclasses may reimplement.
      * </p>
      */
     public void setFocus() {
         // do nothing;
     }

     /**
      * Sets this field editor's label text.
      * The label is typically presented to the left of the entry field.
      *
      * @param text the label text
      */
     public void setLabelText(String text) {
         Assert.isNotNull(text);
         labelText = text;
         if (label != null)
             label.setText(text);
     }

     /**
      * Sets the name of the preference this field editor operates on.
      * <p>
      * The ability to change this allows the same field editor object
      * to be reused for different preferences.
      * </p>
      * <p>
      * For example: <p>
      * <pre>
      * 	...
      *  editor.setPreferenceName("font");
      * 	editor.load();
      * </pre>
      * </p>
      *
      * @param name the name of the preference
      */
     public void setPreferenceName(String name) {
         preferenceName = name;
     }

     /**
      * Sets the preference page in which this field editor
      * appears.
      *
      * @param preferencePage the preference page, or <code>null</code> if none
      * @deprecated use #setPage(DialogPage)
      */
     public void setPreferencePage(PreferencePage preferencePage) {
         setPage(preferencePage);
     }


     /**
      * Set the page to be the receiver.
 	 * @param dialogPage
 	 *
 	 * @since 3.1
 	 */
 	public void setPage(DialogPage dialogPage) {
 		page = dialogPage;

 	}

 	/**
      * Sets the preference store used by this field editor.
      *
      * @param store the preference store, or <code>null</code> if none
      * @see #getPreferenceStore
      */
     public void setPreferenceStore(IPreferenceStore store) {
         preferenceStore = store;
     }

     /**
      * Sets whether this field editor is presenting the default value.
      *
      * @param booleanValue <code>true</code> if the default value is being presented,
      *  and <code>false</code> otherwise
      */
     protected void setPresentsDefaultValue(boolean booleanValue) {
         isDefaultPresented = booleanValue;
     }

     /**
      * Sets or removes the property change listener for this field editor.
      * <p>
      * Note that field editors can support only a single listener.
      * </p>
      *
      * @param listener a property change listener, or <code>null</code>
      *  to remove
      */
     public void setPropertyChangeListener(IPropertyChangeListener listener) {
         propertyChangeListener = listener;
     }

     /**
      * Shows the given error message in the page for this
      * field editor if it has one.
      *
      * @param msg the error message
      */
     protected void showErrorMessage(String msg) {
         if (page != null)
             page.setErrorMessage(msg);
     }

     /**
      * Shows the given message in the page for this
      * field editor if it has one.
      *
      * @param msg the message
      */
     protected void showMessage(String msg) {
         if (page != null)
             page.setErrorMessage(msg);
     }

     /**
      * Stores this field editor's value back into the preference store.
      */
     public void store() {
         if (preferenceStore == null)
             return;

         if (isDefaultPresented) {
             preferenceStore.setToDefault(preferenceName);
         } else {
             doStore();
         }
     }

     /**
      * Set the GridData on button to be one that is spaced for the
      * current font.
      * @param button the button the data is being set on.
      */

     protected void setButtonLayoutData(Button button) {

         GridData data = new GridData(GridData.HORIZONTAL_ALIGN_FILL);

         // Compute and store a font metric
         GC gc = new GC(button);
         gc.setFont(button.getFont());
         FontMetrics fontMetrics = gc.getFontMetrics();
         gc.dispose();

         int widthHint = org.eclipse.jface.dialogs.Dialog
                 .convertVerticalDLUsToPixels(fontMetrics,
                         IDialogConstants.BUTTON_WIDTH);
         data.widthHint = Math.max(widthHint, button.computeSize(SWT.DEFAULT,
                 SWT.DEFAULT, true).x);
         button.setLayoutData(data);
     }

     /**
      * Set whether or not the controls in the field editor
      * are enabled.
      * @param enabled The enabled state.
      * @param parent The parent of the controls in the group.
      *  Used to create the controls if required.
      */
     public void setEnabled(boolean enabled, Composite parent) {
         getLabelControl(parent).setEnabled(enabled);
     }

 }
	/*******************************************************************************
	* Copyright (c) 2000, 2005 IBM Corporation and others.
	* All rights reserved. This program and the accompanying materials
	* are made available under the terms of the Eclipse Public License v1.0
	* which accompanies this distribution, and is available at
	* http://www.eclipse.org/legal/epl-v10.html
	*
	* Contributors:
	* IBM Corporation - initial API and implementation
	*******************************************************************************/
	package org.eclipse.jface.preference;

	import org.eclipse.jface.dialogs.DialogPage;
	import org.eclipse.jface.dialogs.IDialogConstants;
	import org.eclipse.jface.resource.JFaceResources;
	import org.eclipse.jface.util.Assert;
	import org.eclipse.jface.util.IPropertyChangeListener;
	import org.eclipse.jface.util.PropertyChangeEvent;
	import org.eclipse.swt.SWT;
	import org.eclipse.swt.events.DisposeEvent;
	import org.eclipse.swt.events.DisposeListener;
	import org.eclipse.swt.graphics.FontMetrics;
	import org.eclipse.swt.graphics.GC;
	import org.eclipse.swt.layout.GridData;
	import org.eclipse.swt.layout.GridLayout;
	import org.eclipse.swt.widgets.Button;
	import org.eclipse.swt.widgets.Composite;
	import org.eclipse.swt.widgets.Control;
	import org.eclipse.swt.widgets.Label;

	/**
	* Abstract base class for all field editors.
	* <p>
	* A field editor presents the value of a preference to the end
	* user. The value is loaded from a preference store; if
	* modified by the end user, the value is validated and eventually
	* stored back to the preference store. A field editor reports
	* an event when the value, or the validity of the value, changes.
	* </p>
	* <p>
	* Field editors should be used in conjunction with a field
	* editor preference page (<code>FieldEditorPreferencePage</code>)
	* which coordinates everything and provides the message line
	* which display messages emanating from the editor.
	* </p>
	* <p>
	* This package contains ready-to-use field editors for various
	* types of preferences:
	* <ul>
	* <li><code>BooleanFieldEditor</code> - booleans</li>
	* <li><code>IntegerFieldEditor</code> - integers</li>
	* <li><code>StringFieldEditor</code> - text strings</li>
	* <li><code>RadioGroupFieldEditor</code> - enumerations</li>
	* <li><code>ColorFieldEditor</code> - RGB colors</li>
	* <li><code>FontFieldEditor</code> - fonts</li>
	* <li><code>DirectoryFieldEditor</code> - directories</li>
	* <li><code>FileFieldEditor</code> - files</li>
	* <li><code>PathEditor</code> - paths</li>
	* </ul>
	* </p>
	*/
	public abstract class FieldEditor {

	/**
	* Property name constant (value <code>"field_editor_is_valid"</code>)
	* to signal a change in the validity of the value of this field editor.
	*/
	public static final String IS_VALID = "field_editor_is_valid";//$NON-NLS-1$

	/**
	* Property name constant (value <code>"field_editor_value"</code>)
	* to signal a change in the value of this field editor.
	*/
	public static final String VALUE = "field_editor_value";//$NON-NLS-1$

	/**
	* Gap between label and control.
	*/
	protected static final int HORIZONTAL_GAP = 8;

	/**
	* The preference store, or <code>null</code> if none.
	*/
	private IPreferenceStore preferenceStore = null;

	/**
	* The name of the preference displayed in this field editor.
	*/
	private String preferenceName;

	/**
	* Indicates whether the default value is currently displayed,
	* initially <code>false</code>.
	*/
	private boolean isDefaultPresented = false;

	/**
	* The label's text.
	*/
	private String labelText;

	/**
	* The label control.
	*/
	private Label label;

	/**
	* Listener, or <code>null</code> if none
	*/
	private IPropertyChangeListener propertyChangeListener;

	/**
	* The page containing this field editor
	*/
	private DialogPage page;

	/**
	* Creates a new field editor.
	*/
	protected FieldEditor() {
	}

	/**
	* Creates a new field editor.
	*
	* @param name the name of the preference this field editor works on
	* @param labelText the label text of the field editor
	* @param parent the parent of the field editor's control
	*/
	protected FieldEditor(String name, String labelText, Composite parent) {
	init(name, labelText);
	createControl(parent);
	}

	/**
	* Adjusts the horizontal span of this field editor's basic controls.
	* <p>
	* Subclasses must implement this method to adjust the horizontal span
	* of controls so they appear correct in the given number of columns.
	* </p>
	* <p>
	* The number of columns will always be equal to or greater than the
	* value returned by this editor's <code>getNumberOfControls</code> method.
	*
	* @param numColumns the number of columns
	*/
	protected abstract void adjustForNumColumns(int numColumns);

	/**
	* Applies a font.
	* <p>
	* The default implementation of this framework method
	* does nothing. Subclasses should override this method
	* if they want to change the font of the SWT control to
	* a value different than the standard dialog font.
	* </p>
	*/
	protected void applyFont() {
	}

	/**
	* Checks if the given parent is the current parent of the
	* supplied control; throws an (unchecked) exception if they
	* are not correctly related.
	*
	* @param control the control
	* @param parent the parent control
	*/
	protected void checkParent(Control control, Composite parent) {
	Assert.isTrue(control.getParent() == parent, "Different parents");//$NON-NLS-1$
	}

	/**
	* Clears the error message from the message line.
	*/
	protected void clearErrorMessage() {
	if (page != null)
	page.setErrorMessage(null);
	}

	/**
	* Clears the normal message from the message line.
	*/
	protected void clearMessage() {
	if (page != null)
	page.setMessage(null);
	}

	/**
	* Returns the number of pixels corresponding to the
	* given number of horizontal dialog units.
	* <p>
	* Clients may call this framework method, but should not override it.
	* </p>
	*
	* @param control the control being sized
	* @param dlus the number of horizontal dialog units
	* @return the number of pixels
	*/
	protected int convertHorizontalDLUsToPixels(Control control, int dlus) {
	GC gc = new GC(control);
	gc.setFont(control.getFont());
	int averageWidth = gc.getFontMetrics().getAverageCharWidth();
	gc.dispose();

	double horizontalDialogUnitSize = averageWidth * 0.25;

	return (int) Math.round(dlus * horizontalDialogUnitSize);
	}

	/**
	* Returns the number of pixels corresponding to the
	* given number of vertical dialog units.
	* <p>
	* Clients may call this framework method, but should not override it.
	* </p>
	*
	* @param control the control being sized
	* @param dlus the number of vertical dialog units
	* @return the number of pixels
	*/
	protected int convertVerticalDLUsToPixels(Control control, int dlus) {
	GC gc = new GC(control);
	gc.setFont(control.getFont());
	int height = gc.getFontMetrics().getHeight();
	gc.dispose();

	double verticalDialogUnitSize = height * 0.125;

	return (int) Math.round(dlus * verticalDialogUnitSize);
	}

	/**
	* Creates this field editor's main control containing all of its
	* basic controls.
	*
	* @param parent the parent control
	*/
	protected void createControl(Composite parent) {
	GridLayout layout = new GridLayout();
	layout.numColumns = getNumberOfControls();
	layout.marginWidth = 0;
	layout.marginHeight = 0;
	layout.horizontalSpacing = HORIZONTAL_GAP;
	parent.setLayout(layout);
	doFillIntoGrid(parent, layout.numColumns);
	}

	/**
	* Disposes the SWT resources used by this field editor.
	*/
	public void dispose() {
	// nothing to dispose
	}

	/**
	* Fills this field editor's basic controls into the given parent.
	* <p>
	* Subclasses must implement this method to create the controls
	* for this field editor.
	* </p>
	*
	* @param parent the composite used as a parent for the basic controls;
	* the parent's layout must be a <code>GridLayout</code>
	* @param numColumns the number of columns
	*/
	protected abstract void doFillIntoGrid(Composite parent, int numColumns);

	/**
	* Initializes this field editor with the preference value from
	* the preference store.
	* <p>
	* Subclasses must implement this method to properly initialize
	* the field editor.
	* </p>
	*/
	protected abstract void doLoad();

	/**
	* Initializes this field editor with the default preference value from
	* the preference store.
	* <p>
	* Subclasses must implement this method to properly initialize
	* the field editor.
	* </p>
	*/
	protected abstract void doLoadDefault();

	/**
	* Stores the preference value from this field editor into
	* the preference store.
	* <p>
	* Subclasses must implement this method to save the entered value
	* into the preference store.
	* </p>
	*/
	protected abstract void doStore();

	/**
	* Fills this field editor's basic controls into the given parent.
	*
	* @param parent the composite used as a parent for the basic controls;
	* the parent's layout must be a <code>GridLayout</code>
	* @param numColumns the number of columns
	*/
	public void fillIntoGrid(Composite parent, int numColumns) {
	Assert.isTrue(numColumns >= getNumberOfControls());
	Assert.isTrue(parent.getLayout() instanceof GridLayout);
	doFillIntoGrid(parent, numColumns);
	}

	/**
	* Informs this field editor's listener, if it has one, about a change to
	* one of this field editor's boolean-valued properties. Does nothing
	* if the old and new values are the same.
	*
	* @param property the field editor property name,
	* such as <code>VALUE</code> or <code>IS_VALID</code>
	* @param oldValue the old value
	* @param newValue the new value
	*/
	protected void fireStateChanged(String property, boolean oldValue,
	boolean newValue) {
	if (oldValue == newValue)
	return;
	fireValueChanged(property, new Boolean(oldValue), new Boolean(newValue));
	}

	/**
	* Informs this field editor's listener, if it has one, about a change to
	* one of this field editor's properties.
	*
	* @param property the field editor property name,
	* such as <code>VALUE</code> or <code>IS_VALID</code>
	* @param oldValue the old value object, or <code>null</code>
	* @param newValue the new value, or <code>null</code>
	*/
	protected void fireValueChanged(String property, Object oldValue,
	Object newValue) {
	if (propertyChangeListener == null)
	return;
	propertyChangeListener.propertyChange(new PropertyChangeEvent(this,
	property, oldValue, newValue));
	}

	/**
	* Returns the symbolic font name used by this field editor.
	*
	* @return the symbolic font name
	*/
	public String getFieldEditorFontName() {
	return JFaceResources.DIALOG_FONT;
	}

	/**
	* Returns the label control.
	*
	* @return the label control, or <code>null</code>
	* if no label control has been created
	*/
	protected Label getLabelControl() {
	return label;
	}

	/**
	* Returns this field editor's label component.
	* <p>
	* The label is created if it does not already exist
	* </p>
	*
	* @param parent the parent
	* @return the label control
	*/
	public Label getLabelControl(Composite parent) {
	if (label == null) {
	label = new Label(parent, SWT.LEFT);
	label.setFont(parent.getFont());
	String text = getLabelText();
	if (text != null)
	label.setText(text);
	label.addDisposeListener(new DisposeListener() {
	public void widgetDisposed(DisposeEvent event) {
	label = null;
	}
	});
	} else {
	checkParent(label, parent);
	}
	return label;
	}

	/**
	* Returns this field editor's label text.
	*
	* @return the label text
	*/
	public String getLabelText() {
	return labelText;
	}

	/**
	* Returns the number of basic controls this field editor consists of.
	*
	* @return the number of controls
	*/
	public abstract int getNumberOfControls();

	/**
	* Returns the name of the preference this field editor operates on.
	*
	* @return the name of the preference
	*/
	public String getPreferenceName() {
	return preferenceName;
	}

	/**
	* Returns the preference page in which this field editor
	* appears.
	*
	* @return the preference page, or <code>null</code> if none
	* @deprecated use #getPage()
	*/
	protected PreferencePage getPreferencePage() {
	if(page != null && page instanceof PreferencePage)
	return (PreferencePage) page;
	return null;
	}

	/**
	* Return the DialogPage that the receiver is sending
	* updates to.
	*
	* @return DialogPage or <code>null</code> if it
	* has not been set.
	*
	* @since 3.1
	*/
	protected DialogPage getPage(){
	return page;
	}

	/**
	* Returns the preference store used by this field editor.
	*
	* @return the preference store, or <code>null</code> if none
	* @see #setPreferenceStore
	*/
	public IPreferenceStore getPreferenceStore() {
	return preferenceStore;
	}

	/**
	* Initialize the field editor with the given preference name and label.
	*
	* @param name the name of the preference this field editor works on
	* @param text the label text of the field editor
	*/
	protected void init(String name, String text) {
	Assert.isNotNull(name);
	Assert.isNotNull(text);
	preferenceName = name;
	this.labelText = text;
	}

	/**
	* Returns whether this field editor contains a valid value.
	* <p>
	* The default implementation of this framework method
	* returns <code>true</code>. Subclasses wishing to perform
	* validation should override both this method and
	* <code>refreshValidState</code>.
	* </p>
	*
	* @return <code>true</code> if the field value is valid,
	* and <code>false</code> if invalid
	* @see #refreshValidState()
	*/
	public boolean isValid() {
	return true;
	}

	/**
	* Initializes this field editor with the preference value from
	* the preference store.
	*/
	public void load() {
	if (preferenceStore != null) {
	isDefaultPresented = false;
	doLoad();
	refreshValidState();
	}
	}

	/**
	* Initializes this field editor with the default preference value
	* from the preference store.
	*/
	public void loadDefault() {
	if (preferenceStore != null) {
	isDefaultPresented = true;
	doLoadDefault();
	refreshValidState();
	}
	}

	/**
	* Returns whether this field editor currently presents the
	* default value for its preference.
	*
	* @return <code>true</code> if the default value is presented,
	* and <code>false</code> otherwise
	*/
	public boolean presentsDefaultValue() {
	return isDefaultPresented;
	}

	/**
	* Refreshes this field editor's valid state after a value change
	* and fires an <code>IS_VALID</code> property change event if
	* warranted.
	* <p>
	* The default implementation of this framework method does
	* nothing. Subclasses wishing to perform validation should override
	* both this method and <code>isValid</code>.
	* </p>
	*
	* @see #isValid
	*/
	protected void refreshValidState() {
	}

	/**
	* Sets the focus to this field editor.
	* <p>
	* The default implementation of this framework method
	* does nothing. Subclasses may reimplement.
	* </p>
	*/
	public void setFocus() {
	// do nothing;
	}

	/**
	* Sets this field editor's label text.
	* The label is typically presented to the left of the entry field.
	*
	* @param text the label text
	*/
	public void setLabelText(String text) {
	Assert.isNotNull(text);
	labelText = text;
	if (label != null)
	label.setText(text);
	}

	/**
	* Sets the name of the preference this field editor operates on.
	* <p>
	* The ability to change this allows the same field editor object
	* to be reused for different preferences.
	* </p>
	* <p>
	* For example: <p>
	* <pre>
	* ...
	* editor.setPreferenceName("font");
	* editor.load();
	* </pre>
	* </p>
	*
	* @param name the name of the preference
	*/
	public void setPreferenceName(String name) {
	preferenceName = name;
	}

	/**
	* Sets the preference page in which this field editor
	* appears.
	*
	* @param preferencePage the preference page, or <code>null</code> if none
	* @deprecated use #setPage(DialogPage)
	*/
	public void setPreferencePage(PreferencePage preferencePage) {
	setPage(preferencePage);
	}


	/**
	* Set the page to be the receiver.
	* @param dialogPage
	*
	* @since 3.1
	*/
	public void setPage(DialogPage dialogPage) {
	page = dialogPage;

	}

	/**
	* Sets the preference store used by this field editor.
	*
	* @param store the preference store, or <code>null</code> if none
	* @see #getPreferenceStore
	*/
	public void setPreferenceStore(IPreferenceStore store) {
	preferenceStore = store;
	}

	/**
	* Sets whether this field editor is presenting the default value.
	*
	* @param booleanValue <code>true</code> if the default value is being presented,
	* and <code>false</code> otherwise
	*/
	protected void setPresentsDefaultValue(boolean booleanValue) {
	isDefaultPresented = booleanValue;
	}

	/**
	* Sets or removes the property change listener for this field editor.
	* <p>
	* Note that field editors can support only a single listener.
	* </p>
	*
	* @param listener a property change listener, or <code>null</code>
	* to remove
	*/
	public void setPropertyChangeListener(IPropertyChangeListener listener) {
	propertyChangeListener = listener;
	}

	/**
	* Shows the given error message in the page for this
	* field editor if it has one.
	*
	* @param msg the error message
	*/
	protected void showErrorMessage(String msg) {
	if (page != null)
	page.setErrorMessage(msg);
	}

	/**
	* Shows the given message in the page for this
	* field editor if it has one.
	*
	* @param msg the message
	*/
	protected void showMessage(String msg) {
	if (page != null)
	page.setErrorMessage(msg);
	}

	/**
	* Stores this field editor's value back into the preference store.
	*/
	public void store() {
	if (preferenceStore == null)
	return;

	if (isDefaultPresented) {
	preferenceStore.setToDefault(preferenceName);
	} else {
	doStore();
	}
	}

	/**
	* Set the GridData on button to be one that is spaced for the
	* current font.
	* @param button the button the data is being set on.
	*/

	protected void setButtonLayoutData(Button button) {

	GridData data = new GridData(GridData.HORIZONTAL_ALIGN_FILL);

	// Compute and store a font metric
	GC gc = new GC(button);
	gc.setFont(button.getFont());
	FontMetrics fontMetrics = gc.getFontMetrics();
	gc.dispose();

	int widthHint = org.eclipse.jface.dialogs.Dialog
	.convertVerticalDLUsToPixels(fontMetrics,
	IDialogConstants.BUTTON_WIDTH);
	data.widthHint = Math.max(widthHint, button.computeSize(SWT.DEFAULT,
	SWT.DEFAULT, true).x);
	button.setLayoutData(data);
	}

	/**
	* Set whether or not the controls in the field editor
	* are enabled.
	* @param enabled The enabled state.
	* @param parent The parent of the controls in the group.
	* Used to create the controls if required.
	*/
	public void setEnabled(boolean enabled, Composite parent) {
	getLabelControl(parent).setEnabled(enabled);
	}

	}