stringfieldeditor.java

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/*******************************************************************************
 * Copyright (c) 2000, 2006 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.resource.JFaceResources;
import org.eclipse.jface.util.Assert;
import org.eclipse.swt.SWT;
import org.eclipse.swt.events.DisposeEvent;
import org.eclipse.swt.events.DisposeListener;
import org.eclipse.swt.events.FocusAdapter;
import org.eclipse.swt.events.FocusEvent;
import org.eclipse.swt.events.KeyAdapter;
import org.eclipse.swt.events.KeyEvent;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Text;

/**
 * A field editor for a string type preference.
 * <p>
 * This class may be used as is, or subclassed as required.
 * </p>
 */
public class StringFieldEditor extends FieldEditor {

    /**
     * Validation strategy constant (value <code>0</code>) indicating that
     * the editor should perform validation after every key stroke.
     *
     * @see #setValidateStrategy
     */
    public static final int VALIDATE_ON_KEY_STROKE = 0;

    /**
     * Validation strategy constant (value <code>1</code>) indicating that
     * the editor should perform validation only when the text widget 
     * loses focus.
     *
     * @see #setValidateStrategy
     */
    public static final int VALIDATE_ON_FOCUS_LOST = 1;

    /**
     * Text limit constant (value <code>-1</code>) indicating unlimited
     * text limit and width.
     */
    public static int UNLIMITED = -1;

    /**
     * Cached valid state.
     */
    private boolean isValid;

    /**
     * Old text value.
     */
    private String oldValue;

    /**
     * The text field, or <code>null</code> if none.
     */
    Text textField;

    /**
     * Width of text field in characters; initially unlimited.
     */
    private int widthInChars = UNLIMITED;

    /**
     * Text limit of text field in characters; initially unlimited.
     */
    private int textLimit = UNLIMITED;

    /**
     * The error message, or <code>null</code> if none.
     */
    private String errorMessage;

    /**
     * Indicates whether the empty string is legal;
     * <code>true</code> by default.
     */
    private boolean emptyStringAllowed = true;

    /**
     * The validation strategy; 
     * <code>VALIDATE_ON_KEY_STROKE</code> by default.
     */
    private int validateStrategy = VALIDATE_ON_KEY_STROKE;

    /**
     * Creates a new string field editor 
     */
    protected StringFieldEditor() {
    }

    /**
     * Creates a string field editor.
     * Use the method <code>setTextLimit</code> to limit the text.
     * 
     * @param name the name of the preference this field editor works on
     * @param labelText the label text of the field editor
     * @param width the width of the text input field in characters,
     *  or <code>UNLIMITED</code> for no limit
     * @param strategy either <code>VALIDATE_ON_KEY_STROKE</code> to perform
     *  on the fly checking (the default), or <code>VALIDATE_ON_FOCUS_LOST</code> to
     *  perform validation only after the text has been typed in
     * @param parent the parent of the field editor's control
     * @since 2.0
     */
    public StringFieldEditor(String name, String labelText, int width,
            int strategy, Composite parent) {
        init(name, labelText);
        widthInChars = width;
        setValidateStrategy(strategy);
        isValid = false;
        errorMessage = JFaceResources
                .getString("StringFieldEditor.errorMessage");//$NON-NLS-1$
        createControl(parent);
    }

    /**
     * Creates a string field editor.
     * Use the method <code>setTextLimit</code> to limit the text.
     * 
     * @param name the name of the preference this field editor works on
     * @param labelText the label text of the field editor
     * @param width the width of the text input field in characters,
     *  or <code>UNLIMITED</code> for no limit
     * @param parent the parent of the field editor's control
     */
    public StringFieldEditor(String name, String labelText, int width,
            Composite parent) {
        this(name, labelText, width, VALIDATE_ON_KEY_STROKE, parent);
    }

    /**
     * Creates a string field editor of unlimited width.
     * Use the method <code>setTextLimit</code> to limit the text.
     * 
     * @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
     */
    public StringFieldEditor(String name, String labelText, Composite parent) {
        this(name, labelText, UNLIMITED, parent);
    }

    /* (non-Javadoc)
     * Method declared on FieldEditor.
     */
    protected void adjustForNumColumns(int numColumns) {
        GridData gd = (GridData) textField.getLayoutData();
        gd.horizontalSpan = numColumns - 1;
        // We only grab excess space if we have to
        // If another field editor has more columns then
        // we assume it is setting the width.
        gd.grabExcessHorizontalSpace = gd.horizontalSpan == 1;
    }

    /**
     * Checks whether the text input field contains a valid value or not.
     *
     * @return <code>true</code> if the field value is valid,
     *   and <code>false</code> if invalid
     */
    protected boolean checkState() {
        boolean result = false;
        if (emptyStringAllowed) {
			result = true;
		}

        if (textField == null) {
			result = false;
		}

        String txt = textField.getText();

        result = (txt.trim().length() > 0) || emptyStringAllowed;

        // call hook for subclasses
        result = result && doCheckState();

        if (result) {
			clearErrorMessage();
		} else {
			showErrorMessage(errorMessage);
		}

        return result;
    }

    /**
     * Hook for subclasses to do specific state checks.
     * <p>
     * The default implementation of this framework method does
     * nothing and returns <code>true</code>.  Subclasses should 
     * override this method to specific state checks.
     * </p>
     *
     * @return <code>true</code> if the field value is valid,
     *   and <code>false</code> if invalid
     */
    protected boolean doCheckState() {
        return true;
    }

    /**
     * Fills this field editor's basic controls into the given parent.
     * <p>
     * The string field implementation of this <code>FieldEditor</code>
     * framework method contributes the text field. Subclasses may override
     * but must call <code>super.doFillIntoGrid</code>.
     * </p>
     */
    protected void doFillIntoGrid(Composite parent, int numColumns) {
        getLabelControl(parent);

        textField = getTextControl(parent);
        GridData gd = new GridData();
        gd.horizontalSpan = numColumns - 1;
        if (widthInChars != UNLIMITED) {
            GC gc = new GC(textField);
            try {
                Point extent = gc.textExtent("X");//$NON-NLS-1$
                gd.widthHint = widthInChars * extent.x;
            } finally {
                gc.dispose();
            }
        } else {
            gd.horizontalAlignment = GridData.FILL;
            gd.grabExcessHorizontalSpace = true;
        }
        textField.setLayoutData(gd);
    }

    /* (non-Javadoc)
     * Method declared on FieldEditor.
     */
    protected void doLoad() {
        if (textField != null) {
            String value = getPreferenceStore().getString(getPreferenceName());
            textField.setText(value);
            oldValue = value;
        }
    }

    /* (non-Javadoc)
     * Method declared on FieldEditor.
     */
    protected void doLoadDefault() {