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/* java.beans.PropertyEditor

   Copyright (C) 1998 Free Software Foundation, Inc.

This file is part of GNU Classpath.

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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>

 **   <LI>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.

         **/

        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.

         **/

        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.

         **/

        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.

         **/

        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.

         **/

        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.

         **/

        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

         **/

        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.

         **/

        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.

         **/

        java.awt.Component getCustomEditor();

        /** Adds a property change listener to this PropertyEditor.

         ** @param listener the listener to add

         **/

        void addPropertyChangeListener(PropertyChangeListener listener);

        /** Removes a property change listener from this PropertyEditor.

         ** @param listener the listener to remove

         **/

        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.

         **/

        String getJavaInitializationString();

}