lineview.java

Mobile 应用程序使用 Java Micro Edition (Java ME) 平台

/*
 * @(#)LineView.java	1.19 05/11/17
 *
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
package javax.swing.text.html;

import java.util.Enumeration;
import java.awt.*;
import javax.swing.*;
import javax.swing.border.*;
import javax.swing.event.*;
import javax.swing.text.*;

/**
 * A view implementation to display an unwrapped 
 * preformatted line.<p>
 * This subclasses ParagraphView, but this really only contains one
 * Row of text.
 *
 * @author  Timothy Prinzing
 * @version 1.19 11/17/05
 */
class LineView extends ParagraphView {
    /** Last place painted at. */
    int tabBase;

    /**
     * Creates a LineView object.
     *
     * @param elem the element to wrap in a view
     */
    public LineView(Element elem) {
	super(elem);
    }

    /**
     * Preformatted lines are not suppressed if they 
     * have only whitespace, so they are always visible.
     */
    public boolean isVisible() {
	return true;
    }

    /**
     * Determines the minimum span for this view along an
     * axis.  The preformatted line should refuse to be 
     * sized less than the preferred size.
     *
     * @param axis may be either <code>View.X_AXIS</code> or 
     *	<code>View.Y_AXIS</code>
     * @return  the minimum span the view can be rendered into
     * @see View#getPreferredSpan
     */
    public float getMinimumSpan(int axis) {
	return getPreferredSpan(axis);
    }

    /**
     * Gets the resize weight for the specified axis.
     *
     * @param axis may be either X_AXIS or Y_AXIS
     * @return the weight
     */
    public int getResizeWeight(int axis) {
	switch (axis) {
	case View.X_AXIS:
	    return 1;
	case View.Y_AXIS:
	    return 0;
	default:
	    throw new IllegalArgumentException("Invalid axis: " + axis);
	}
    }

    /**
     * Gets the alignment for an axis.
     *
     * @param axis may be either X_AXIS or Y_AXIS
     * @return the alignment
     */
    public float getAlignment(int axis) {
	if (axis == View.X_AXIS) {
	    return 0;
	}
	return super.getAlignment(axis);
    }

    /**
     * Lays out the children.  If the layout span has changed,
     * the rows are rebuilt.  The superclass functionality
     * is called after checking and possibly rebuilding the
     * rows.  If the height has changed, the 
     * <code>preferenceChanged</code> method is called
     * on the parent since the vertical preference is 
     * rigid.
     *
     * @param width  the width to lay out against >= 0.  This is
     *   the width inside of the inset area.
     * @param height the height to lay out against >= 0 (not used
     *   by paragraph, but used by the superclass).  This
     *   is the height inside of the inset area.
     */
    protected void layout(int width, int height) {
	super.layout(Integer.MAX_VALUE - 1, height);
    }

    /**
     * Returns the next tab stop position given a reference position.
     * This view implements the tab coordinate system, and calls
     * <code>getTabbedSpan</code> on the logical children in the process 
     * of layout to determine the desired span of the children.  The
     * logical children can delegate their tab expansion upward to
     * the paragraph which knows how to expand tabs. 
     * <code>LabelView</code> is an example of a view that delegates
     * its tab expansion needs upward to the paragraph.
     * <p>
     * This is implemented to try and locate a <code>TabSet</code>
     * in the paragraph element's attribute set.  If one can be
     * found, its settings will be used, otherwise a default expansion
     * will be provided.  The base location for for tab expansion
     * is the left inset from the paragraphs most recent allocation
     * (which is what the layout of the children is based upon).
     *
     * @param x the X reference position
     * @param tabOffset the position within the text stream
     *   that the tab occurred at >= 0.
     * @return the trailing end of the tab expansion >= 0
     * @see TabSet
     * @see TabStop
     * @see LabelView
     */
    public float nextTabStop(float x, int tabOffset) {
	// If the text isn't left justified, offset by 10 pixels!
	if (getTabSet() == null &&
	    StyleConstants.getAlignment(getAttributes()) ==
	    StyleConstants.ALIGN_LEFT) {
	    return getPreTab(x, tabOffset);
	}
	return super.nextTabStop(x, tabOffset);
    }

    /**
     * Returns the location for the tab.
     */
    protected float getPreTab(float x, int tabOffset) {
	Document d = getDocument();
	View v = getViewAtPosition(tabOffset, null);
	if ((d instanceof StyledDocument) && v != null) {
	    // Assume f is fixed point.
	    Font f = ((StyledDocument)d).getFont(v.getAttributes());
            Container c = getContainer();
	    FontMetrics fm = (c != null) ? c.getFontMetrics(f) :
                Toolkit.getDefaultToolkit().getFontMetrics(f);
	    int width = getCharactersPerTab() * fm.charWidth('W');
	    int tb = (int)getTabBase();
	    return (float)((((int)x - tb) / width + 1) * width + tb);
	}
	return 10.0f + x;
    }

    /**
     * @return number of characters per tab, 8.
     */
    protected int getCharactersPerTab() {
	return 8;
    }
}