Package java.awt

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Class FontMetrics

public  abstract  class  java.awt.FontMetrics
    extends  java.lang.Object  
{
        // Fields
    protected Font font;	

        // Constructors
    protected FontMetrics(Font  font);	

        // Methods
    public int bytesWidth(byte  data[], int  off, int len);	
    public int charsWidth(char  data[], int  off, int len);	
    public int charWidth(char  ch);	
    public int charWidth(int  ch);	
    public int getAscent();	
    public int getDescent();	
    public Font getFont();	
    public int getHeight();	
    public int getLeading();	
    public int getMaxAdvance();	
    public int getMaxAscent();	
    public int getMaxDescent();	
    public int[] getWidths();	
    public int stringWidth(String  str);	
    public String toString();	
}

This class represents a font metrics object, which gives information about the rendering of a particular font on a particular screen.

When an application asks the AWT to place a character at the position (x,y), the character is placed so that its reference point (shown as the dot in the picture on the right) is put at that position. The reference point specifies a horizontal line called the baseline of the character. In normal printing, the baselines of the 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. If the current character is placed with its reference point at the position (x,y), and the character's advance width is w, then the following character is placed with its reference point at the position (x+w, y). The advance width is often the same as the width of character's bounding box, but need not be so. It particular, slanted and italic fonts often have characters whose top-right corner extends slightly beyond the advance width.

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 array.

The default implementations of these methods are inefficient; they are usually overridden with more efficient toolkit-specific implementations.

Fields

font

protected Font font 

The actual font.

See Also: getFont .

Constructors

FontMetrics

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.

Parameter	Description
font	the font

See Also: Font .

Methods

bytesWidth

public int bytesWidth(byte  data[], int  off, int  len) 

Return Value:

Returns the advance width of the subarray of the specified byte array in the font described by this font metric.

Parameter	Description
data	an array of characters
off	the start offset of the data
len	the number of bytes to be measured

See Also: stringWidth charsWidth .

charsWidth

public int charsWidth(char  data[], int  off, int  len) 

Return Value:

Returns the advance width of the subarray of the specified char array in the font described by this font metric.

Parameter	Description
data	an array of characters
off	the start offset of the data
len	the number of bytes measured

See Also: stringWidth bytesWidth .

charWidth

public int charWidth(char  ch) 

Return Value:

Returns the advance width of the specified char in the font described by this font metric.

Parameter	Description
ch	a char

See Also: stringWidth .

charWidth

public int charWidth(int  ch) 

Return Value:

Returns the advance width of the specified character in the font described by this font metric.

Parameter	Description
ch	a char

See Also: stringWidth .

getAscent

public int getAscent() 

Determines the font ascent of the font described by this font metric. The font ascent is the distance from the base line to the top of most alphanumeric characters. Some characters in the font may extend above this distance..

Return Value:

Returns the font ascent of the font.

See Also: getMaxAscent .

getDescent

public int getDescent() 

Determines the font descent of the font described this font metric. The font descent is the distance from the base line to the bottom of most alphanumeric characters. Some characters in the font may extend below this distance.

Return Value:

Returns the font descent of the font.

See Also: getMaxDescent .

getFont

public Font getFont() 

Return Value:

Returns the font described by this font metric.

getHeight

public int getHeight() 

Determines the standard height of a line of text in the font described by this font metric. This standard height is the distance between the baseline of adjacent lines of text. It is computed as the sum

	getLeading() + getAscent() + getDescent() 

There is no guarantee that lines of text spaced at this distance must be disjoint; such lines may overlap if some characters overshoot either the standard ascent or the standard descent.

Return Value:

Returns the standard height of the font.

getLeading

public int getLeading() 

Determines the standard leading of the font described by this font metric. The standard leading (inter-line spacing) 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.

Return Value:

Returns the standard leading of the font.

getMaxAdvance

public int getMaxAdvance() 

Return Value:

Returns the maximum advance width of any character in the font, or -1 if the maximum advance is not known.

getMaxAscent

public int getMaxAscent() 

Determines the maximum ascent of the font described by this font metric. No character extends further above the baseline than this height.

Return Value:

Returns the maximum ascent of any character in the font.

See Also: getAscent .

getMaxDescent

public int getMaxDescent() 

Determines the maximum descent of the font described by this font metric. No character extends further below the baseline than this height.

Return Value:

Returns the maximum descent of any character in the font.

See Also: getDescent .

getWidths

public int[] getWidths() 

Return Value:

Returns any array giving the advance widths of the first 256 characters in the font described by this font metric.

stringWidth

public int stringWidth(String  str) 

Return Value:

Returns the advance width of the specified string in the font described by this font metric.

Parameter	Description
str	a string

See Also: charsWidth bytesWidth .

toString

public String toString() 

Return Value:

Returns a string representation of this font metric.

Overrides:

toString in class Object .