java.awt

Class FontMetrics

java.lang.Object

java.awt.FontMetrics

All Implemented Interfaces:

Serializable

public abstract class FontMetrics
extends Object
implements Serializable

The FontMetrics class defines a font metrics object, which encapsulates information about the rendering of a particular font on a particular screen.

Note to subclassers: 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 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):

• getAscent()
• getLeading()
• getMaxAdvance()
• charWidth(char)
• charsWidth(char[], int, int)

Note that the implementations of these methods are inefficient, so they are usually overridden with more efficient toolkit-specific implementations.

When an application asks to place a character at the position (x, y), the character is placed so that its reference point (shown as the dot in the accompanying image) is put at that position. The reference point specifies a horizontal line called the baseline of the character. In normal printing, the baselines of characters should align.

In addition, every character in a font has an ascent, a descent, and an advance width. The ascent is the amount by which the character ascends above the baseline. The descent is the amount by which the character descends below the baseline. The advance width indicates the position at which AWT should place the next character.

An array of characters or a string can also have an ascent, a descent, and an advance width. The ascent of the array is the maximum ascent of any character in the array. The descent is the maximum descent of any character in the array. The advance width is the sum of the advance widths of each of the characters in the character array. The advance of a String is the distance along the baseline of the String. This distance is the width that should be used for centering or right-aligning the String.

Note that the advance of a String is not necessarily the sum of the advances of its characters measured in isolation because the width of a character can vary depending on its context. For example, in Arabic text, the shape of a character can change in order to connect to other characters. Also, in some scripts, certain character sequences can be represented by a single shape, called a ligature. Measuring characters individually does not account for these transformations.

Font metrics are baseline-relative, meaning that they are generally independent of the rotation applied to the font (modulo possible grid hinting effects). See Font.

Since:

JDK1.0

See Also:

Font, Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
protected Font	font	The actual Font from which the font metrics are created.

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	FontMetrics(Font font)	Creates a new FontMetrics object for finding out height and width information about the specified Font and specific character glyphs in that Font.

Method Summary

Modifier and Type	Method	Description
int	bytesWidth(byte[] data, int off, int len)	Returns the total advance width for showing the specified array of bytes in this Font.
int	charsWidth(char[] data, int off, int len)	Returns the total advance width for showing the specified array of characters in this Font.
int	charWidth(char ch)	Returns the advance width of the specified character in this Font.
int	charWidth(int codePoint)	Returns the advance width of the specified character in this Font.
int	getAscent()	Determines the font ascent of the Font described by this FontMetrics object.
int	getDescent()	Determines the font descent of the Font described by this FontMetrics object.
Font	getFont()	Gets the Font described by this FontMetrics object.
FontRenderContext	getFontRenderContext()	Gets the FontRenderContext used by this FontMetrics object to measure text.
int	getHeight()	Gets the standard height of a line of text in this font.
int	getLeading()	Determines the standard leading of the Font described by this FontMetrics object.
LineMetrics	getLineMetrics(char[] chars, int beginIndex, int limit, Graphics context)	Returns the LineMetrics object for the specified character array in the specified Graphics context.
LineMetrics	getLineMetrics(CharacterIterator ci, int beginIndex, int limit, Graphics context)	Returns the LineMetrics object for the specified CharacterIterator in the specified Graphics context.
LineMetrics	getLineMetrics(String str,