source: trunk/gcc/libjava/java/beans/PropertyEditor.java

/* java.beans.PropertyEditor
   Copyright (C) 1998 Free Software Foundation, Inc.

This file is part of GNU Classpath.

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it under the terms of the GNU General Public License as published by
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exception statement from your version. */


package java.beans;

/**
 ** PropertyEditors are custom GUI editors for specific types of values.
 **
 ** A PropertyEditor can be used, for example, if you are editing a type of value
 ** that can be more easily represented graphically, such as a Point, or one that
 ** can be more easily represented by a list, such as a boolean (true/false).<P>
 **
 ** A PropertyEditor must be able to display its contents when asked to and
 ** be able to allow the user to change its underlying field value.  However, it
 ** is not the PropertyEditor's responsibility to make the change to the
 ** underlying Object; in fact, the PropertyEditor does not even know about the
 ** Object it is actually editing--only about the property it is currently
 ** editing.  When a change is made to the property, the PropertyEditor must
 ** simply fire a PropertyChangeEvent and allow the RAD tool to actually set
 ** the property in the underlying Bean.<P>
 **
 ** PropertyEditors should not change the Objects they are given by setValue().
 ** These Objects may or may not be the actual Objects which are properties of
 ** the Bean being edited.  Instead, PropertyEditors should create a new Object
 ** and fire a PropertyChangeEvent with the old and new values.<P>
 **
 ** PropertyEditors also must support the ability to return a Java
 ** initialization string.  See the getJavaInitializationString() method for
 ** details.<P>
 **
 ** There are several different ways a PropertyEditor may display and control
 ** editing of its value.  When multiple types of input and display are
 ** given by a single PropertyEditor, the RAD tool may decide which of the call
 ** to support.  Some RAD tools may even be text-only, so even if you support
 ** a graphical set and get, it may choose the text set and get whenever it can.
 ** <OL>
 **   <LI>Every PropertyEditor must support getValue() and setValue().  For
 **       setValue(), the component must only support it when the argument is
 **       the same type that the PropertyEditor supports.</LI>
 **   <LI>Every PropertyEditor must support getJavaInitializationString().</LI>
 **   <LI>You may support painting the value yourself if you wish.  To do this,
 **       have isPaintable() return true and implement the paintValue() method.
 **       This method does not determine in any way how the value is edited;
 **       merely how it is displayed.</LI>
 **   <LU>Let the caller of the PropertyEditor give the user a text input.  Do
 **       this by returning a non-null String from getAsText().  If you support
 **       text input, you *must* support setAsText().</LI>
 **   <LI>Give the caller a set of possible values, such as "true"/"false", that
 **       the user must select from.  To do this, return the list of Strings
 **       from the getTags() method.  The RAD tool may choose to implement the
 **       user input any way it wishes, and only guarantees that setAsText() will
 **       only be called with one of the Strings returned from getTags().</LI>
 **   <LI>You may support a whole custom editing control by supporting
 **       getCustomEditor().  To do this, return true from supportsCustomEditor()
 **       and return a Component that does the job.  It is the component's job,
 **       or the PropertyEditor's job, to make sure that when the editor changes
 **       its value, the PropertyChangeEvent is thrown.</LI>
 ** </OL>
 **
 ** The PropertyEditor for a particular Bean can be found using the
 ** PropertyEditorManager class, which goes through a series of different
 ** checks to find the appropriate class.<P>
 **
 ** A PropertyChangeEvent should be thrown from the PropertyEditor whenever a
 ** bound  property (a property PropertyDescriptor.isBound() set to true)
 ** changes.  When this happens, the editor itself should *not* change the value
 ** itself, but rather allow the RAD tool to call setValue() or setAsText().
 **
 ** @author John Keiser
 ** @since JDK1.1
 ** @version 1.1.0, 30 June 1998
 ** @see java.beans.PropertyEditorManager
 ** @see java.beans.PropertyEditorSupport
 **/

public interface PropertyEditor {
        /** Called by the RAD tool to set the value of this property for the PropertyEditor.
         ** If the property type is native, it should be wrapped in the appropriate
         ** wrapper type.
         ** @param value the value to set this property to.
         **/
        public abstract void setValue(Object value);

        /** Accessor method to get the current value the PropertyEditor is working with.
         ** If the property type is native, it will be wrapped in the appropriate
         ** wrapper type.
         ** @return the current value of the PropertyEditor.
         **/
        public abstract Object getValue();


        /** Set the value of this property using a String.
         ** Whether or not this PropertyEditor is editing a String type, this converts
         ** the String into the type of the PropertyEditor.
         ** @param text the text to set it to.
         ** @exception IllegalArgumentException if the String is in the wrong format or setAsText() is not supported.
         **/
        public abstract void setAsText(String text) throws IllegalArgumentException;

        /** Get the value of this property in String format.
         ** Many times this can simply use Object.toString().<P>
         ** Return null if you do not support getAsText()/setAsText().
         ** <code>setAsText(getAsText())</code> should be valid; i.e. the stuff you spit out in
         ** getAsText() should be able to go into setAsText().
         ** @return the value of this property in String format.
         **/
        public abstract String getAsText();

        /** Get a list of possible Strings which this property type can have.
         ** The value of these will be used by the RAD tool to construct some sort
         ** of list box or to check text box input, and the resulting String passed
         ** to setAsText() should be one of these.  Note, however, that like most things
         ** with this mammoth, unwieldy interface, this is not guaranteed.  Thus, you
         ** must check the value in setAsText() anyway.
         ** @return the list of possible String values for this property type.
         **/
        public abstract String[] getTags();


        /** The RAD tool calls this to find out whether the PropertyEditor can paint itself.
         ** @return true if it can paint itself graphically, false if it cannot.
         **/
        public abstract boolean isPaintable();

        /** The RAD tool calls this to paint the actual value of the property.
         ** The Graphics context will have the same current font, color, etc. as the
         ** parent Container.  You may safely change the font, color, etc. and not
         ** change them back.<P>
         ** This method should do a silent no-op if isPaintable() is false.
         ** @param g the Graphics context to paint on
         ** @param bounds the rectangle you have reserved to work in
         **/
        public abstract void paintValue(java.awt.Graphics g, java.awt.Rectangle bounds);


        /** The RAD tool calls this to find out whether the PropertyEditor supports a custom component to edit and display itself.
         ** @return true if getCustomEditor() will return a component, false if not.
         **/
        public abstract boolean supportsCustomEditor();

        /** The RAD tool calls this to grab the component that can edit this type.
         ** The component may be painted anywhere the RAD tool wants to paint it--
         ** even in its own window.<P>
         ** The component must hook up with the PropertyEditor and, whenever a
         ** change to the value is made, fire a PropertyChangeEvent to the source.<P>
         ** @return the custom editor for this property type.
         **/
        public abstract java.awt.Component getCustomEditor();


        /** Adds a property change listener to this PropertyEditor.
         ** @param listener the listener to add
         **/
        public abstract void addPropertyChangeListener(PropertyChangeListener listener);

        /** Removes a property change listener from this PropertyEditor.
         ** @param listener the listener to remove
         **/
        public abstract void removePropertyChangeListener(PropertyChangeListener listener);

        /** Get a Java language-specific String which could be used to create an Object
         ** of the specified type.  Every PropertyEditor must support this.<P>
         ** The reason for this is that while most RAD tools will serialize the Beans
         ** and deserialize them at runtime, some RAD tools will generate code that
         ** creates the Beans.  Examples of Java initialization strings would be:<P>
         ** <OL>
         **     <LI><CODE>2</CODE></LI>
         **     <LI><CODE>"I am a String"</CODE></LI>
         **     <LI><CODE>new MyObject(2, "String", new StringBuffer())</CODE></LI>
         ** </OL>
         ** @return the initialization string for this object in Java.
         **/
        public abstract String getJavaInitializationString();
}