gcc/libjava/javax/swing/text/Utilities.java

/* Utilities.java --
   Copyright (C) 2004 Free Software Foundation, Inc.

This file is part of GNU Classpath.

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package javax.swing.text;

import java.awt.FontMetrics;
import java.awt.Graphics;

/**
 * A set of utilities to deal with text. This is used by several other classes
 * inside this package.
 *
 * @author Roman Kennke <roman@ontographics.com>
 */
public class Utilities
{
  /**
   * The length of the char buffer that holds the characters to be drawn.
   */
  private static final int BUF_LENGTH = 64;

  /**
   * Creates a new <code>Utilities</code> object.
   */
  public Utilities()
  {
    // Nothing to be done here.
  }

  /**
   * Draws the given text segment. Contained tabs and newline characters
   * are taken into account. Tabs are expanded using the
   * specified {@link TabExpander}.
   *
   * @param s the text fragment to be drawn.
   * @param x the x position for drawing.
   * @param y the y position for drawing.
   * @param g the {@link Graphics} context for drawing.
   * @param e the {@link TabExpander} which specifies the Tab-expanding
   *     technique.
   * @param startOffset starting offset in the text.
   * @return the x coordinate at the end of the drawn text.
   */
  public static final int drawTabbedText(Segment s, int x, int y, Graphics g,
                                         TabExpander e, int startOffset)
  {
    // This buffers the chars to be drawn.
    char[] buffer = s.array;


    // The current x and y pixel coordinates.
    int pixelX = x;
    int pixelY = y;

    // The font metrics of the current selected font.
    FontMetrics metrics = g.getFontMetrics();
    int ascent = metrics.getAscent();

    for (int offset = s.offset; offset < (s.offset + s.count); ++offset)
      {
	switch (buffer[offset])
	  {
	  case '\t':
	    // In case we have a tab, we just 'jump' over the tab.
	    // When we have no tab expander we just use the width of 'm'.
	    if (e != null)
	      pixelX = (int) e.nextTabStop((float) pixelX,
					   startOffset + offset - s.offset);
	    else
	      pixelX += metrics.charWidth(' ');
	    break;
	  case '\n':
	    // In case we have a newline, we must draw
	    // the buffer and jump on the next line.
	    g.drawChars(buffer, offset, 1, pixelX, y);
	    pixelY += metrics.getHeight();
	    pixelX = x;
	    break;
	  default:
	    // Here we draw the char.
	    g.drawChars(buffer, offset, 1, pixelX, pixelY + ascent);
	    pixelX += metrics.charWidth(buffer[offset]);
	    break;
	  }
      }

    return pixelX;
  }

  /**
   * Determines the width, that the given text <code>s</code> would take
   * if it was printed with the given {@link java.awt.FontMetrics} on the
   * specified screen position.
   * @param s the text fragment
   * @param metrics the font metrics of the font to be used
   * @param x the x coordinate of the point at which drawing should be done
   * @param e the {@link TabExpander} to be used
   * @param startOffset the index in <code>s</code> where to start
   * @returns the width of the given text s. This takes tabs and newlines
   * into account.
   */
  public static final int getTabbedTextWidth(Segment s, FontMetrics metrics,
                                             int x, TabExpander e,
                                             int startOffset)
  {
    // This buffers the chars to be drawn.
    char[] buffer = s.array;

    // The current x coordinate.
    int pixelX = x;

    // The current maximum width.
    int maxWidth = 0;

    for (int offset = s.offset; offset < (s.offset + s.count); ++offset)
      {
	switch (buffer[offset])
	  {
	  case '\t':
	    // In case we have a tab, we just 'jump' over the tab.
	    // When we have no tab expander we just use the width of 'm'.
	    if (e != null)
	      pixelX = (int) e.nextTabStop((float) pixelX,
					   startOffset + offset - s.offset);
	    else
	      pixelX += metrics.charWidth(' ');
	    break;
	  case '\n':
	    // In case we have a newline, we must 'draw'
	    // the buffer and jump on the next line.
	    pixelX += metrics.charWidth(buffer[offset]);
	    maxWidth = Math.max(maxWidth, pixelX - x);
	    pixelX = x;
	    break;
	  default:
	    // Here we draw the char.
	    pixelX += metrics.charWidth(buffer[offset]);
	    break;
	  }
      }

    // Take the last line into account.
    maxWidth = Math.max(maxWidth, pixelX - x);

    return maxWidth;
  }
}