bundles/org.eclipse.ui.views/src/org/eclipse/ui/views/properties/PropertyDescriptor.java

/*******************************************************************************
 * Copyright (c) 2000, 2004 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.ui.views.properties;

import org.eclipse.jface.util.Assert;
import org.eclipse.jface.viewers.CellEditor;
import org.eclipse.jface.viewers.ICellEditorValidator;
import org.eclipse.jface.viewers.ILabelProvider;
import org.eclipse.jface.viewers.LabelProvider;
import org.eclipse.swt.widgets.Composite;

/**
 * Standard implementation for property descriptors.
 * <p>
 * The required attributes of property descriptors (id and display name) are
 * passed to the constructor; the optional attributes can be configured using
 * the various set methods (all have reasonable default values):
 * <ul>
 *   <li><code>setDescription</code></li>
 *   <li><code>setCategory</code></li>
 *   <li><code>setLabelProvider</code></li>
 *   <li><code>setHelpContexts</code></li>
 * </ul>
 * Subclasses should reimplement <code>getPropertyEditor</code> to provide a
 * cell editor for changing the value; otherwise the property will be 
 * effectively read only.
 * </p>
 * <p>
 * There are several concrete subclasses provided in this package that cover
 * the most common cases:
 * <ul>
 *   <li><code>TextPropertyDescriptor</code> - edits with a 
 *      <code>TextCellEditor</code></li>
 *   <li><code>ComboBoxPropertyDescriptor - edits with a
 *      <code>ComboBoxCellEditor</code></code></li>
 *   <li><code>ColorPropertyDescriptor - edits with a 
 *      <code>ColorCellEditor</code></code></li>
 * </ul>
 * </p>
 */
public class PropertyDescriptor implements IPropertyDescriptor {

    /**
     * The property id.
     */
    private Object id;

    /**
     * The name to display for the property.
     */
    private String display;

    /**
     * Category name, or <code>null</code> if none (the default).
     */
    private String category = null;

    /**
     * Description of the property, or <code>null</code> if none (the default). 
     */
    private String description = null;

    /**
     * The help context ids, or <code>null</code> if none (the default). 
     */
    private Object helpIds;

    /**
     * The flags used to filter the property.
     */
    private String[] filterFlags;

    /**
     * The object that provides the property value's text and image, or 
     * <code>null</code> if the default label provider is used (the default).
     */
    private ILabelProvider labelProvider = null;

    /**
     * The object to validate the values in the cell editor, or <code>null</code>
     * if none (the default).
     */
    private ICellEditorValidator validator;

    /**
     * Indicates if the descriptor is compatible with other descriptors of this
     * type. <code>false</code> by default.
     */
    private boolean incompatible = false;

    /**
     * Creates a new property descriptor with the given id and display name
     */
    public PropertyDescriptor(Object id, String displayName) {
        Assert.isNotNull(id);
        Assert.isNotNull(displayName);
        this.id = id;
        this.display = displayName;
    }

    /**
     * The <code>PropertyDescriptor</code> implementation of this 
     * <code>IPropertyDescriptor</code> method returns <code>null</code>.
     * <p>
     * Since no cell editor is returned, the property is read only.
     * </p>
     */
    public CellEditor createPropertyEditor(Composite parent) {
        return null;
    }

    /**
     * Returns <code>true</code> if this property descriptor is to be always 
     * considered incompatible with any other property descriptor.
     * This prevents a property from displaying during multiple 
     * selection.
     *
     * @return <code>true</code> to indicate always incompatible
     */
    protected boolean getAlwaysIncompatible() {
        return incompatible;
    }

    /**
     * The <code>PropertyDescriptor</code> implementation of this 
     * <code>IPropertyDescriptor</code> method returns the value set by
     * the <code>setCategory</code> method. If unset, this method returns
     * <code>null</code> indicating the default category.
     *
     * @see #setCategory
     */
    public String getCategory() {
        return category;
    }

    /**
     * The <code>PropertyDescriptor</code> implementation of this 
     * <code>IPropertyDescriptor</code> method returns the value set by
     * the <code>setDescription</code> method. If unset, this method returns
     * <code>null</code> indicating no description.
     *
     * @see #setDescription
     */
    public String getDescription() {
        return description;
    }

    /**
     * The <code>SimplePropertyDescriptor</code> implementation of this 
     * <code>IPropertyDescriptor</code> method returns the value supplied
     * on the constructor.
     */
    public String getDisplayName() {
        return display;
    }

    /**
     * The <code>SimplePropertyDescriptor</code> implementation of this 
     * <code>IPropertyDescriptor</code> method returns the value set by
     * the <code>setFilterFlags</code> method. If unset, this method returns
     * <code>null</code>.
     * <p>
     * Valid values for these flags are declared as constants on 
     *  <code>IPropertySheetEntry</code>
     */
    public String[] getFilterFlags() {
        return filterFlags;
    }

    /**
     * The <code>SimplePropertyDescriptor</code> implementation of this 
     * <code>IPropertyDescriptor</code> method returns the value set by
     * the <code>setHelpContextId</code> method. If unset, this method returns
     * <code>null</code>.
     *
     * @see #setHelpContextIds
     */
    public Object getHelpContextIds() {
        return helpIds;
    }

    /**
     * The <code>PropertyDescriptor</code> implementation of this 
     * <code>IPropertyDescriptor</code> method returns the value supplied
     * on the constructor.
     */
    public Object getId() {
        return id;
    }

    /**
     * The <code>PropertyDescriptor</code> implementation of this 
     * <code>IPropertyDescriptor</code> method returns the value set by
     * the <code>setProvider</code> method or, if no value has been set
     * it returns a <code>LabelProvider</code>
     *
     * @see #setLabelProvider
     */
    public ILabelProvider getLabelProvider() {
        if (labelProvider != null)
            return labelProvider;
        else
            return new LabelProvider();
    }

    /**
     * Returns the input validator for editing the property.
     *
     * @return the validator used to verify correct values for this property,
     *   or <code>null</code>
     */
    protected ICellEditorValidator getValidator() {
        return validator;
    }

    /** 
     * Returns whether a label provider has been set on the receiver.
     * @return whether a label provider has been set on the receiver.
     * @see #setLabelProvider
     * @since 3.0
     */
    public boolean isLabelProviderSet() {
        return labelProvider != null;
    }

    /**
     * The <code>SimplePropertyDescriptor</code> implementation of this 
     * <code>IPropertyDescriptor</code> method returns true if the other
     * property has the same id and category and <code>getAlwaysIncompatible()</code>
     * returns false
     */
    public boolean isCompatibleWith(IPropertyDescriptor anotherProperty) {
        if (getAlwaysIncompatible())
            return false;

        // Compare id		
        Object id1 = getId();
        Object id2 = anotherProperty.getId();
        if (!id1.equals(id2))
            return false;

        // Compare Category (may be null)
        if (getCategory() == null) {
            if (anotherProperty.getCategory() != null)
                return false;
        } else {
            if (!getCategory().equals(anotherProperty.getCategory()))
                return false;
        }

        return true;
    }

    /**
     * Sets a flag indicating whether this property descriptor is to be always 
     * considered incompatible with any other property descriptor.
     * Setting this flag prevents a property from displaying during multiple 
     * selection.
     *
     * @param flag <code>true</code> to indicate always incompatible
     */
    public void setAlwaysIncompatible(boolean flag) {
        incompatible = flag;
    }

    /**
     * Sets the category for this property descriptor.
     * 
     * @param category the category for the descriptor, or <code>null</code> if none
     * @see #getCategory
     */
    public void setCategory(String category) {
        this.category = category;
    }

    /**
     * Sets the description for this property descriptor.
     * The description should be limited to a single line so that it can be
     * displayed in the status line.
     * 
     * @param description the description, or <code>null</code> if none
     * @see #getDescription
     */
    public void setDescription(String description) {
        this.description = description;
    }

    /**
     * Sets the the filter flags for this property descriptor.
     * The description should be limited to a single line so that it can be
     * displayed in the status line.
     * <p>
     * Valid values for these flags are declared as constants on 
     *  <code>IPropertySheetEntry</code>
     * </p>
     * 
     * @param value the filter flags
     * @see #getFilterFlags
     */
    public void setFilterFlags(String value[]) {
        filterFlags = value;
    }

    /**
     * Sets the help context id for this property descriptor.
     *
     * NOTE: Help support system API's changed since 2.0 and arrays
     * of contexts are no longer supported.
     * </p>
     * <p>
     * Thus the only valid parameter type for this method
     * is a <code>String</code> representing a context id. 
     * The previously valid parameter types are deprecated. 
     * The plural name for this method is unfortunate.
     * </p>
     * 
     * @param contextIds the help context ids, or <code>null</code> if none
     * @see #getHelpContextIds
     */
    public void setHelpContextIds(Object contextIds) {
        helpIds = contextIds;
    }

    /**
     * Sets the label provider for this property descriptor.
     * <p>
     * If no label provider is set an instance of <code>LabelProvider</code>
     * will be created as the default when needed.
     * </p>
     * 
     * @param provider the label provider for the descriptor, or 
     *   <code>null</code> if the default label provider should be used
     * @see #getLabelProvider
     */
    public void setLabelProvider(ILabelProvider provider) {
        labelProvider = provider;
    }

    /**
     * Sets the input validator for the cell editor for this property descriptor.
     * <p>
     * [Issue: This method should be unnecessary is the cell editor's own
     *  validator is used.
     * ]
     * </p>
     * 
     * @param validator the cell input validator, or <code>null</code> if none
     */
    public void setValidator(ICellEditorValidator validator) {
        this.validator = validator;
    }
}