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DOS/V Power Report 1998 February
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FontMetrics.java
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1997-10-27
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/*
* @(#)FontMetrics.java 1.16 97/02/20
*
* Copyright (c) 1995, 1996 Sun Microsystems, Inc. All Rights Reserved.
*
* This software is the confidential and proprietary information of Sun
* Microsystems, Inc. ("Confidential Information"). You shall not
* disclose such Confidential Information and shall use it only in
* accordance with the terms of the license agreement you entered into
* with Sun.
*
* SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE
* SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
* IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
* PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR ANY DAMAGES
* SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING
* THIS SOFTWARE OR ITS DERIVATIVES.
*
* CopyrightVersion 1.1_beta
*
*/
package java.awt;
/**
* A font metrics object. Note that the implementations of these
* methods are inefficient, they are usually overridden with more
* efficient toolkit specific implementations.
* <p>
* <b>Note to subclassers</b>: Since many of these methods form closed
* mutually recursive loops, you must take care that you implement
* at least one of the methods in each such loop in order to prevent
* infinite recursion when your subclass is used.
* In particular, the following is the minimal suggested set of methods
* to override in order to ensure correctness and prevent infinite
* recursion (though other subsets are equally feasible):
* <ul>
* <li><a href=#getAscent>getAscent</a>()
* <li><a href=#getAscent>getDescent</a>()
* <li><a href=#getLeading>getLeading</a>()
* <li><a href=#getMaxAdvance>getMaxAdvance</a>()
* <li><a href="#charWidth(char)">charWidth</a>(char ch)
* <li><a href="#charsWidth(char[], int, int)">charsWidth</a>(char data[], int off, int len)
* </ul>
*
* @version 1.16 02/20/97
* @author Jim Graham
*/
public abstract class FontMetrics implements java.io.Serializable {
/**
* The actual font.
* @see #getFont
*/
protected Font font;
/*
* JDK 1.1 serialVersionUID
*/
private static final long serialVersionUID = 1681126225205050147L;
/**
* Creates a new FontMetrics object with the specified font.
* @param font the font
* @see Font
*/
protected FontMetrics(Font font) {
this.font = font;
}
/**
* Gets the font.
*/
public Font getFont() {
return font;
}
/**
* Gets the standard leading, or line spacing, for the font.
* This is the logical amount of space to be reserved between the
* descent of one line of text and the ascent of the next line.
* The height metric is calculated to include this extra space.
*/
public int getLeading() {
return 0;
}
/**
* Gets the font ascent. The font ascent is the distance from the
* base line to the top of most Alphanumeric characters. Note,
* however, that some characters in the font may extend above
* this height.
* @see #getMaxAscent
*/
public int getAscent() {
return font.getSize();
}
/**
* Gets the font descent. The font descent is the distance from the
* base line to the bottom of most Alphanumeric characters. Note,
* however, that some characters in the font may extend below this
* height.
* @see #getMaxDescent
*/
public int getDescent() {
return 0;
}
/**
* Gets the standard height of a line of text in this font. This
* is the distance between the baseline of adjacent lines of text.
* It is the sum of the leading + ascent + descent. There is no
* guarantee that lines of text spaced at this distance will be
* disjoint; such lines may overlap if some characters overshoot
* either the standard ascent or the standard descent metric.
*/
public int getHeight() {
return getLeading() + getAscent() + getDescent();
}
/**
* Gets the maximum ascent of all characters in this Font.
* No character will extend further above the baseline than this
* distance.
* @see #getAscent
*/
public int getMaxAscent() {
return getAscent();
}
/**
* Gets the maximum descent of all characters in this Font.
* No character will descend futher below the baseline than this
* distance.
* @see #getDescent
*/
public int getMaxDescent() {
return getDescent();
}
/**
* For backward compatibility only.
* @see #getMaxDescent
* @deprecated As of JDK version 1.1.1,
* replaced by getMaxDescent().
*/
public int getMaxDecent() {
return getMaxDescent();
}
/**
* Gets the maximum advance width of any character in this Font.
* The advance width is the amount by which the current point is
* moved from one character to the next in a line of text.
* @return -1 if the max advance is not known.
*/
public int getMaxAdvance() {
return -1;
}
/**
* Returns the advance width of the specified character in this Font.
* The advance width is the amount by which the current point is
* moved from one character to the next in a line of text.
* @param ch the character to be measured
* @see #stringWidth
*/
public int charWidth(int ch) {
return charWidth((char)ch);
}
/**
* Returns the advance width of the specified character in this Font.
* The advance width is the amount by which the current point is
* moved from one character to the next in a line of text.
* @param ch the character to be measured
* @see #stringWidth
*/
public int charWidth(char ch) {
if (ch < 256) {
return getWidths()[ch];
}
char data[] = {ch};
return charsWidth(data, 0, 1);
}
/**
* Returns the total advance width for showing the specified String
* in this Font.
* The advance width is the amount by which the current point is
* moved from one character to the next in a line of text.
* @param str the String to be measured
* @see #charsWidth
* @see #bytesWidth
*/
public int stringWidth(String str) {
int len = str.length();
char data[] = new char[len];
str.getChars(0, len, data, 0);
return charsWidth(data, 0, len);
}
/**
* Returns the total advance width for showing the specified array
* of characters in this Font.
* The advance width is the amount by which the current point is
* moved from one character to the next in a line of text.
* @param data the array of characters to be measured
* @param off the start offset of the characters in the array
* @param len the number of characters to be measured from the array
* @see #stringWidth
* @see #bytesWidth
*/
public int charsWidth(char data[], int off, int len) {
return stringWidth(new String(data, off, len));
}
/**
* Returns the total advance width for showing the specified array
* of bytes in this Font.
* The advance width is the amount by which the current point is
* moved from one character to the next in a line of text.
* @param data the array of bytes to be measured
* @param off the start offset of the bytes in the array
* @param len the number of bytes to be measured from the array
* @see #stringWidth
* @see #charsWidth
*/
public int bytesWidth(byte data[], int off, int len) {
return stringWidth(new String(data, 0, off, len));
}
/**
* Gets the advance widths of the first 256 characters in the Font.
* The advance width is the amount by which the current point is
* moved from one character to the next in a line of text.
*/
public int[] getWidths() {
int widths[] = new int[256];
for (char ch = 0 ; ch < 256 ; ch++) {
widths[ch] = charWidth(ch);
}
return widths;
}
/**
* Returns the String representation of this FontMetric's values.
*/
public String toString() {
return getClass().getName() + "[font=" + getFont() + "ascent=" +
getAscent() + ", descent=" + getDescent() + ", height=" + getHeight() + "]";
}
}