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):
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:
- 1.0
- See Also:
-
Font
, Serialized Form
Field Summary
Modifier and Type | Field | Description |
---|---|---|
protected Font | font | The actual |
Constructor Summary
Modifier | Constructor | Description |
---|---|---|
protected | FontMetrics(Font font) | Creates a new |
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 |
int | charsWidth(char[] data,
int off,
int len) | Returns the total advance width for showing the specified array of characters in this |
int | charWidth(char ch) | Returns the advance width of the specified character in this |
int | charWidth(int codePoint) | Returns the advance width of the specified character in this |
int | getAscent() | Determines the font ascent of the |
int | getDescent() | Determines the font descent of the |
Font | getFont() | Gets the |
FontRenderContext | getFontRenderContext() | Gets the |
int | getHeight() | Gets the standard height of a line of text in this font. |
int | getLeading() | Determines the standard leading of the |
LineMetrics | getLineMetrics(char[] chars,
int beginIndex,
int limit,
Graphics context) | Returns the |
LineMetrics | getLineMetrics(String str,
int beginIndex,
int limit,
Graphics context) | Returns the |
LineMetrics | getLineMetrics(String str,
Graphics context) | Returns the |
LineMetrics | getLineMetrics(CharacterIterator ci,
int beginIndex,
int limit,
Graphics context) | Returns the |
int | getMaxAdvance() | Gets the maximum advance width of any character in this |
int | getMaxAscent() | Determines the maximum ascent of the |
Rectangle2D | getMaxCharBounds(Graphics context) | Returns the bounds for the character with the maximum bounds in the specified |
int | getMaxDecent() | Deprecated. As of JDK version 1.1.1, replaced by getMaxDescent() . |
int | getMaxDescent() | Determines the maximum descent of the |
Rectangle2D | getStringBounds(char[] chars,
int beginIndex,
int limit,
Graphics context) | Returns the bounds of the specified array of characters in the specified |
Rectangle2D | getStringBounds(String str,
int beginIndex,
int limit,
Graphics context) | Returns the bounds of the specified |
Rectangle2D | getStringBounds(String str,
Graphics context) | Returns the bounds of the specified |
Rectangle2D | getStringBounds(CharacterIterator ci,
int beginIndex,
int limit,
Graphics context) | Returns the bounds of the characters indexed in the specified |
int[] | getWidths() | Gets the advance widths of the first 256 characters in the |
boolean | hasUniformLineMetrics() | Checks to see if the |
int | stringWidth(String str) | Returns the total advance width for showing the specified |
String | toString() | Returns a representation of this |
Methods declared in class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
Field Detail
font
protected Font font
The actual Font
from which the font metrics are created. This cannot be null.
- See Also:
getFont()
Constructor Detail
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
.
- Parameters:
-
font
- theFont
- See Also:
Font
Method Detail
getFont
public Font getFont()
Gets the Font
described by this FontMetrics
object.
- Returns:
- the
Font
described by thisFontMetrics
object.
getFontRenderContext
public FontRenderContext getFontRenderContext()
Gets the FontRenderContext
used by this FontMetrics
object to measure text.
Note that methods in this class which take a Graphics
parameter measure text using the FontRenderContext
of that Graphics
object, and not this FontRenderContext
- Returns:
- the
FontRenderContext
used by thisFontMetrics
object. - Since:
- 1.6
getLeading
public int getLeading()
Determines the standard leading of the Font
described by this FontMetrics
object. The standard leading, or interline 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.
- Returns:
- the standard leading of the
Font
. - See Also:
-
getHeight()
,getAscent()
,getDescent()
getAscent
public int getAscent()
Determines the font ascent of the Font
described by this FontMetrics
object. The font ascent is the distance from the font's baseline to the top of most alphanumeric characters. Some characters in the Font
might extend above the font ascent line.
- Returns:
- the font ascent of the
Font
. - See Also:
getMaxAscent()
getDescent
public int getDescent()
Determines the font descent of the Font
described by this FontMetrics
object. The font descent is the distance from the font's baseline to the bottom of most alphanumeric characters with descenders. Some characters in the Font
might extend below the font descent line.
- Returns:
- the font descent of the
Font
. - See Also:
getMaxDescent()
getHeight
public int getHeight()
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. Due to rounding this may not be the same as getAscent() + getDescent() + getLeading(). There is no guarantee that lines of text spaced at this distance are disjoint; such lines may overlap if some characters overshoot either the standard ascent or the standard descent metric.
- Returns:
- the standard height of the font.
- See Also:
-
getLeading()
,getAscent()
,getDescent()
getMaxAscent
public int getMaxAscent()
Determines the maximum ascent of the Font
described by this FontMetrics
object. No character extends further above the font's baseline than this height.
- 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 FontMetrics
object. No character extends further below the font's baseline than this height.
- Returns:
- the maximum descent of any character in the
Font
. - See Also:
getDescent()
getMaxDecent
@Deprecated public int getMaxDecent()
getMaxDescent()
.For backward compatibility only.
- Returns:
- the maximum descent of any character in the
Font
. - See Also:
getMaxDescent()
getMaxAdvance
public int getMaxAdvance()
Gets the maximum advance width of any character in this Font
. The advance is the distance from the leftmost point to the rightmost point on the string's baseline. The advance of a String
is not necessarily the sum of the advances of its characters.
- Returns:
- the maximum advance width of any character in the
Font
, or-1
if the maximum advance width is not known.
charWidth
public int charWidth(int codePoint)
Returns the advance width of the specified character in this Font
. The advance is the distance from the leftmost point to the rightmost point on the character's baseline. Note that the advance of a String
is not necessarily the sum of the advances of its characters.
This method doesn't validate the specified character to be a valid Unicode code point. The caller must validate the character value using Character.isValidCodePoint
if necessary.
- Parameters:
-
codePoint
- the character (Unicode code point) to be measured - Returns:
- the advance width of the specified character in the
Font
described by thisFontMetrics
object. - See Also:
-
charsWidth(char[], int, int)
,stringWidth(String)
charWidth
public int charWidth(char ch)
Returns the advance width of the specified character in this Font
. The advance is the distance from the leftmost point to the rightmost point on the character's baseline. Note that the advance of a String
is not necessarily the sum of the advances of its characters.
Note: This method cannot handle supplementary characters. To support all Unicode characters, including supplementary characters, use the charWidth(int)
method.
- Parameters:
-
ch
- the character to be measured - Returns:
- the advance width of the specified character in the
Font
described by thisFontMetrics
object. - See Also:
-
charsWidth(char[], int, int)
,stringWidth(String)
stringWidth
public int stringWidth(String str)
Returns the total advance width for showing the specified String
in this Font
. The advance is the distance from the leftmost point to the rightmost point on the string's baseline.
Note that the advance of a String
is not necessarily the sum of the advances of its characters.
- Parameters:
-
str
- theString
to be measured - Returns:
- the advance width of the specified
String
in theFont
described by thisFontMetrics
. - Throws:
-
NullPointerException
- if str is null. - See Also:
-
bytesWidth(byte[], int, int)
,charsWidth(char[], int, int)
,getStringBounds(String, Graphics)
charsWidth
public int charsWidth(char[] data, int off, int len)
Returns the total advance width for showing the specified array of characters in this Font
. The advance is the distance from the leftmost point to the rightmost point on the string's baseline. The advance of a String
is not necessarily the sum of the advances of its characters. This is equivalent to measuring a String
of the characters in the specified range.
- Parameters:
-
data
- the array of characters to be measured -
off
- the start offset of the characters in the array -
len
- the number of characters to be measured from the array - Returns:
- the advance width of the subarray of the specified
char
array in the font described by thisFontMetrics
object. - Throws:
-
NullPointerException
- ifdata
is null. -
IndexOutOfBoundsException
- if theoff
andlen
arguments index characters outside the bounds of thedata
array. - See Also:
-
charWidth(int)
,charWidth(char)
,bytesWidth(byte[], int, int)
,stringWidth(String)
bytesWidth
public int bytesWidth(byte[] data, int off, int len)
Returns the total advance width for showing the specified array of bytes in this Font
. The advance is the distance from the leftmost point to the rightmost point on the string's baseline. The advance of a String
is not necessarily the sum of the advances of its characters. This is equivalent to measuring a String
of the characters in the specified range.
- Parameters:
-
data
- the array of bytes to be measured -
off
- the start offset of the bytes in the array -
len
- the number of bytes to be measured from the array - Returns:
- the advance width of the subarray of the specified
byte
array in theFont
described by thisFontMetrics
object. - Throws:
-
NullPointerException
- ifdata
is null. -
IndexOutOfBoundsException
- if theoff
andlen
arguments index bytes outside the bounds of thedata
array. - See Also:
-
charsWidth(char[], int, int)
,stringWidth(String)
getWidths
public int[] getWidths()
Gets the advance widths of the first 256 characters in the Font
. The advance is the distance from the leftmost point to the rightmost point on the character's baseline. Note that the advance of a String
is not necessarily the sum of the advances of its characters.
- Returns:
- an array storing the advance widths of the characters in the
Font
described by thisFontMetrics
object.
hasUniformLineMetrics
public boolean hasUniformLineMetrics()
Checks to see if the Font
has uniform line metrics. A composite font may consist of several different fonts to cover various character sets. In such cases, the FontLineMetrics
objects are not uniform. Different fonts may have a different ascent, descent, metrics and so on. This information is sometimes necessary for line measuring and line breaking.
- Returns:
-
true
if the font has uniform line metrics;false
otherwise. - See Also:
Font.hasUniformLineMetrics()
getLineMetrics
public LineMetrics getLineMetrics(String str, Graphics context)
Returns the LineMetrics
object for the specified String
in the specified Graphics
context.
- Parameters:
-
str
- the specifiedString
-
context
- the specifiedGraphics
context - Returns:
- a
LineMetrics
object created with the specifiedString
andGraphics
context. - See Also:
Font.getLineMetrics(String, FontRenderContext)
getLineMetrics
public LineMetrics getLineMetrics(String str, int beginIndex, int limit, Graphics context)
Returns the LineMetrics
object for the specified String
in the specified Graphics
context.
- Parameters:
-
str
- the specifiedString
-
beginIndex
- the initial offset ofstr
-
limit
- the end offset ofstr
-
context
- the specifiedGraphics
context - Returns:
- a
LineMetrics
object created with the specifiedString
andGraphics
context. - See Also:
Font.getLineMetrics(String, int, int, FontRenderContext)
getLineMetrics
public LineMetrics getLineMetrics(char[] chars, int beginIndex, int limit, Graphics context)
Returns the LineMetrics
object for the specified character array in the specified Graphics
context.
- Parameters:
-
chars
- the specified character array -
beginIndex
- the initial offset ofchars
-
limit
- the end offset ofchars
-
context
- the specifiedGraphics
context - Returns:
- a
LineMetrics
object created with the specified character array andGraphics
context. - See Also:
Font.getLineMetrics(char[], int, int, FontRenderContext)
getLineMetrics
public LineMetrics getLineMetrics(CharacterIterator ci, int beginIndex, int limit, Graphics context)
Returns the LineMetrics
object for the specified CharacterIterator
in the specified Graphics
context.
- Parameters:
-
ci
- the specifiedCharacterIterator
-
beginIndex
- the initial offset inci
-
limit
- the end index ofci
-
context
- the specifiedGraphics
context - Returns:
- a
LineMetrics
object created with the specified arguments. - See Also:
Font.getLineMetrics(CharacterIterator, int, int, FontRenderContext)
getStringBounds
public Rectangle2D getStringBounds(String str, Graphics context)
Returns the bounds of the specified String
in the specified Graphics
context. The bounds is used to layout the String
.
Note: The returned bounds is in baseline-relative coordinates (see class notes
).
- Parameters:
-
str
- the specifiedString
-
context
- the specifiedGraphics
context - Returns:
- a
Rectangle2D
that is the bounding box of the specifiedString
in the specifiedGraphics
context. - See Also:
Font.getStringBounds(String, FontRenderContext)
getStringBounds
public Rectangle2D getStringBounds(String str, int beginIndex, int limit, Graphics context)
Returns the bounds of the specified String
in the specified Graphics
context. The bounds is used to layout the String
.
Note: The returned bounds is in baseline-relative coordinates (see class notes
).
- Parameters:
-
str
- the specifiedString
-
beginIndex
- the offset of the beginning ofstr
-
limit
- the end offset ofstr
-
context
- the specifiedGraphics
context - Returns:
- a
Rectangle2D
that is the bounding box of the specifiedString
in the specifiedGraphics
context. - See Also:
Font.getStringBounds(String, int, int, FontRenderContext)
getStringBounds
public Rectangle2D getStringBounds(char[] chars, int beginIndex, int limit, Graphics context)
Returns the bounds of the specified array of characters in the specified Graphics
context. The bounds is used to layout the String
created with the specified array of characters, beginIndex
and limit
.
Note: The returned bounds is in baseline-relative coordinates (see class notes
).
- Parameters:
-
chars
- an array of characters -
beginIndex
- the initial offset of the array of characters -
limit
- the end offset of the array of characters -
context
- the specifiedGraphics
context - Returns:
- a
Rectangle2D
that is the bounding box of the specified character array in the specifiedGraphics
context. - See Also:
Font.getStringBounds(char[], int, int, FontRenderContext)
getStringBounds
public Rectangle2D getStringBounds(CharacterIterator ci, int beginIndex, int limit, Graphics context)
Returns the bounds of the characters indexed in the specified CharacterIterator
in the specified Graphics
context.
Note: The returned bounds is in baseline-relative coordinates (see class notes
).
- Parameters:
-
ci
- the specifiedCharacterIterator
-
beginIndex
- the initial offset inci
-
limit
- the end index ofci
-
context
- the specifiedGraphics
context - Returns:
- a
Rectangle2D
that is the bounding box of the characters indexed in the specifiedCharacterIterator
in the specifiedGraphics
context. - See Also:
Font.getStringBounds(CharacterIterator, int, int, FontRenderContext)
getMaxCharBounds
public Rectangle2D getMaxCharBounds(Graphics context)
Returns the bounds for the character with the maximum bounds in the specified Graphics
context.
- Parameters:
-
context
- the specifiedGraphics
context - Returns:
- a
Rectangle2D
that is the bounding box for the character with the maximum bounds. - See Also:
Font.getMaxCharBounds(FontRenderContext)
toString
public String toString()
Returns a representation of this FontMetrics
object's values as a String
.