src/java.desktop/share/classes/java/awt/im/InputMethodRequests.java

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package java.awt.im;

import java.awt.Rectangle;
import java.awt.font.TextHitInfo;
import java.text.AttributedCharacterIterator;
import java.text.AttributedCharacterIterator.Attribute;

/**
 * InputMethodRequests defines the requests that a text editing component
 * has to handle in order to work with input methods. The component
 * can implement this interface itself or use a separate object that
 * implements it. The object implementing this interface must be returned
 * from the component's getInputMethodRequests method.
 *
 * <p>
 * The text editing component also has to provide an input method event
 * listener.
 *
 * <p>
 * The interface is designed to support one of two input user interfaces:
 * <ul>
 * <li><em>on-the-spot</em> input, where the composed text is displayed as part
 *     of the text component's text body.
 * <li><em>below-the-spot</em> input, where the composed text is displayed in
 *     a separate composition window just below the insertion point where
 *     the text will be inserted when it is committed. Note that, if text is
 *     selected within the component's text body, this text will be replaced by
 *     the committed text upon commitment; therefore it is not considered part
 *     of the context that the text is input into.
 * </ul>
 *
 * @see java.awt.Component#getInputMethodRequests
 * @see java.awt.event.InputMethodListener
 *
 * @author JavaSoft Asia/Pacific
 * @since 1.2
 */

public interface InputMethodRequests {

    /**
     * Gets the location of a specified offset in the current composed text,
     * or of the selection in committed text.
     * This information is, for example, used to position the candidate window
     * near the composed text, or a composition window near the location
     * where committed text will be inserted.
     *
     * <p>
     * If the component has composed text (because the most recent
     * InputMethodEvent sent to it contained composed text), then the offset is
     * relative to the composed text - offset 0 indicates the first character
     * in the composed text. The location returned should be for this character.
     *
     * <p>
     * If the component doesn't have composed text, the offset should be ignored,
     * and the location returned should reflect the beginning (in line
     * direction) of the highlight in the last line containing selected text.
     * For example, for horizontal left-to-right text (such as English), the
     * location to the left of the left-most character on the last line
     * containing selected text is returned. For vertical top-to-bottom text,
     * with lines proceeding from right to left, the location to the top of the
     * left-most line containing selected text is returned.
     *
     * <p>
     * The location is represented as a 0-thickness caret, that is, it has 0
     * width if the text is drawn horizontally, and 0 height if the text is
     * drawn vertically. Other text orientations need to be mapped to
     * horizontal or vertical orientation. The rectangle uses absolute screen
     * coordinates.
     *
     * @param offset the offset within the composed text, if there is composed
     * text; null otherwise
     * @return a rectangle representing the screen location of the offset
     */
    Rectangle getTextLocation(TextHitInfo offset);

    /**
     * Gets the offset within the composed text for the specified absolute x
     * and y coordinates on the screen. This information is used, for example
     * to handle mouse clicks and the mouse cursor. The offset is relative to
     * the composed text, so offset 0 indicates the beginning of the composed
     * text.
     *
     * <p>
     * Return null if the location is outside the area occupied by the composed
     * text.
     *
     * @param x the absolute x coordinate on screen
     * @param y the absolute y coordinate on screen
     * @return a text hit info describing the offset in the composed text.
     */
    TextHitInfo getLocationOffset(int x, int y);

    /**
     * Gets the offset of the insert position in the committed text contained
     * in the text editing component. This is the offset at which characters
     * entered through an input method are inserted. This information is used
     * by an input method, for example, to examine the text surrounding the
     * insert position.
     *
     * @return the offset of the insert position
     */
    int getInsertPositionOffset();

    /**
     * Gets an iterator providing access to the entire text and attributes
     * contained in the text editing component except for uncommitted
     * text. Uncommitted (composed) text should be ignored for index
     * calculations and should not be made accessible through the iterator.
     *
     * <p>
     * The input method may provide a list of attributes that it is
     * interested in. In that case, information about other attributes that
     * the implementor may have need not be made accessible through the
     * iterator. If the list is null, all available attribute information
     * should be made accessible.
     *
     * @param beginIndex the index of the first character
     * @param endIndex the index of the character following the last character
     * @param attributes a list of attributes that the input method is
     * interested in
     * @return an iterator providing access to the text and its attributes
     */
    AttributedCharacterIterator getCommittedText(int beginIndex, int endIndex,
                                                 Attribute[] attributes);

    /**
     * Gets the length of the entire text contained in the text
     * editing component except for uncommitted (composed) text.
     *
     * @return the length of the text except for uncommitted text
     */
    int getCommittedTextLength();

    /**
     * Gets the latest committed text from the text editing component and
     * removes it from the component's text body.
     * This is used for the "Undo Commit" feature in some input methods, where
     * the committed text reverts to its previous composed state. The composed
     * text will be sent to the component using an InputMethodEvent.
     *
     * <p>
     * Generally, this feature should only be supported immediately after the
     * text was committed, not after the user performed other operations on the
     * text. When the feature is not supported, return null.
     *
     * <p>
     * The input method may provide a list of attributes that it is
     * interested in. In that case, information about other attributes that
     * the implementor may have need not be made accessible through the
     * iterator. If the list is null, all available attribute information
     * should be made accessible.
     *
     * @param attributes a list of attributes that the input method is
     * interested in
     * @return the latest committed text, or null when the "Undo Commit"
     * feature is not supported
     */
    AttributedCharacterIterator cancelLatestCommittedText(Attribute[] attributes);

    /**
     * Gets the currently selected text from the text editing component.
     * This may be used for a variety of purposes.
     * One of them is the "Reconvert" feature in some input methods.
     * In this case, the input method will typically send an input method event
     * to replace the selected text with composed text. Depending on the input
     * method's capabilities, this may be the original composed text for the
     * selected text, the latest composed text entered anywhere in the text, or
     * a version of the text that's converted back from the selected text.
     *
     * <p>
     * The input method may provide a list of attributes that it is
     * interested in. In that case, information about other attributes that
     * the implementor may have need not be made accessible through the
     * iterator. If the list is null, all available attribute information
     * should be made accessible.
     *
     * @param attributes a list of attributes that the input method is
     * interested in
     * @return the currently selected text
     */
    AttributedCharacterIterator getSelectedText(Attribute[] attributes);
}