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package javax.swing.text;

import java.awt.Shape;


NavigationFilter can be used to restrict where the cursor can
be positioned. When the default cursor positioning actions attempt to
reposition the cursor they will call into the
NavigationFilter, assuming
the JTextComponent has a non-null
NavigationFilter set. In this manner
the NavigationFilter can effectively restrict where the
cursor can be positioned. Similarly DefaultCaret will call
into the NavigationFilter when the user is changing the
selection to further restrict where the cursor can be positioned.


Subclasses can conditionally call into supers implementation to restrict
where the cursor can be placed, or call directly into the
FilterBypass.

See Also:
Since:1.4
/**
 * <code>NavigationFilter</code> can be used to restrict where the cursor can
 * be positioned. When the default cursor positioning actions attempt to
 * reposition the cursor they will call into the
 * <code>NavigationFilter</code>, assuming
 * the <code>JTextComponent</code> has a non-null
 * <code>NavigationFilter</code> set. In this manner
 * the <code>NavigationFilter</code> can effectively restrict where the
 * cursor can be positioned. Similarly <code>DefaultCaret</code> will call
 * into the <code>NavigationFilter</code> when the user is changing the
 * selection to further restrict where the cursor can be positioned.
 * <p>
 * Subclasses can conditionally call into supers implementation to restrict
 * where the cursor can be placed, or call directly into the
 * <code>FilterBypass</code>.
 *
 * @see javax.swing.text.Caret
 * @see javax.swing.text.DefaultCaret
 * @see javax.swing.text.View
 *
 * @since 1.4
 */
public class NavigationFilter {
    
Invoked prior to the Caret setting the dot. The default implementation
calls directly into the FilterBypass with the passed
in arguments. Subclasses may wish to conditionally
call super with a different location, or invoke the necessary method
on the FilterBypass

Params:
  • fb – FilterBypass that can be used to mutate caret position
  • dot – the position >= 0
  • bias – Bias to place the dot at
/**
     * Invoked prior to the Caret setting the dot. The default implementation
     * calls directly into the <code>FilterBypass</code> with the passed
     * in arguments. Subclasses may wish to conditionally
     * call super with a different location, or invoke the necessary method
     * on the <code>FilterBypass</code>
     *
     * @param fb FilterBypass that can be used to mutate caret position
     * @param dot the position &gt;= 0
     * @param bias Bias to place the dot at
     */
    public void setDot(FilterBypass fb, int dot, Position.Bias bias) {
        fb.setDot(dot, bias);
    }

    
Invoked prior to the Caret moving the dot. The default implementation
calls directly into the FilterBypass with the passed
in arguments. Subclasses may wish to conditionally
call super with a different location, or invoke the necessary
methods on the FilterBypass.

Params:
  • fb – FilterBypass that can be used to mutate caret position
  • dot – the position >= 0
  • bias – Bias for new location
/**
     * Invoked prior to the Caret moving the dot. The default implementation
     * calls directly into the <code>FilterBypass</code> with the passed
     * in arguments. Subclasses may wish to conditionally
     * call super with a different location, or invoke the necessary
     * methods on the <code>FilterBypass</code>.
     *
     * @param fb FilterBypass that can be used to mutate caret position
     * @param dot the position &gt;= 0
     * @param bias Bias for new location
     */
    public void moveDot(FilterBypass fb, int dot, Position.Bias bias) {
        fb.moveDot(dot, bias);
    }

    
Returns the next visual position to place the caret at from an
existing position. The default implementation simply forwards the
method to the root View. Subclasses may wish to further restrict the
location based on additional criteria.

Params:
  • text – JTextComponent containing text
  • pos – Position used in determining next position
  • bias – Bias used in determining next position
  • direction – the direction from the current position that can
 be thought of as the arrow keys typically found on a keyboard.
 This will be one of the following values:

      

    • SwingConstants.WEST

    • SwingConstants.EAST

    • SwingConstants.NORTH

    • SwingConstants.SOUTH

  • biasRet – Used to return resulting Bias of next position
Throws:
Returns:the location within the model that best represents the next
 location visual position
/**
     * Returns the next visual position to place the caret at from an
     * existing position. The default implementation simply forwards the
     * method to the root View. Subclasses may wish to further restrict the
     * location based on additional criteria.
     *
     * @param text JTextComponent containing text
     * @param pos Position used in determining next position
     * @param bias Bias used in determining next position
     * @param direction the direction from the current position that can
     *  be thought of as the arrow keys typically found on a keyboard.
     *  This will be one of the following values:
     * <ul>
     * <li>SwingConstants.WEST
     * <li>SwingConstants.EAST
     * <li>SwingConstants.NORTH
     * <li>SwingConstants.SOUTH
     * </ul>
     * @param biasRet Used to return resulting Bias of next position
     * @return the location within the model that best represents the next
     *  location visual position
     * @exception BadLocationException for a bad location within a document model
     * @exception IllegalArgumentException if <code>direction</code>
     *          doesn't have one of the legal values above
     */
    public int getNextVisualPositionFrom(JTextComponent text, int pos,
                                         Position.Bias bias, int direction,
                                         Position.Bias[] biasRet)
                                           throws BadLocationException {
        return text.getUI().getNextVisualPositionFrom(text, pos, bias,
                                                      direction, biasRet);
    }


    
Used as a way to circumvent calling back into the caret to
position the cursor. Caret implementations that wish to support
a NavigationFilter must provide an implementation that will
not callback into the NavigationFilter.

Since:1.4
/**
     * Used as a way to circumvent calling back into the caret to
     * position the cursor. Caret implementations that wish to support
     * a NavigationFilter must provide an implementation that will
     * not callback into the NavigationFilter.
     * @since 1.4
     */
    public abstract static class FilterBypass {
        
Returns the Caret that is changing.

Returns:Caret that is changing
/**
         * Returns the Caret that is changing.
         *
         * @return Caret that is changing
         */
        public abstract Caret getCaret();

        
Sets the caret location, bypassing the NavigationFilter.

Params:
  • dot – the position >= 0
  • bias – Bias to place the dot at
/**
         * Sets the caret location, bypassing the NavigationFilter.
         *
         * @param dot the position &gt;= 0
         * @param bias Bias to place the dot at
         */
        public abstract void setDot(int dot, Position.Bias bias);

        
Moves the caret location, bypassing the NavigationFilter.

Params:
  • dot – the position >= 0
  • bias – Bias for new location
/**
         * Moves the caret location, bypassing the NavigationFilter.
         *
         * @param dot the position &gt;= 0
         * @param bias Bias for new location
         */
        public abstract void moveDot(int dot, Position.Bias bias);
    }
}