Serializable
public abstract class FontMetrics extends Object implements Serializable
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
.
Modifier and Type | Field | Description |
---|---|---|
protected Font |
font |
The actual Font from which the font metrics are created. |
Modifier | Constructor | Description |
---|---|---|
protected |
Creates a new FontMetrics object for finding out height and width information about the specified Font and specific character glyphs in that Font . |
Modifier and Type | Method | Description |
---|---|---|
int |
bytesWidth |
Returns the total advance width for showing the specified array of bytes in this Font . |
int |
charsWidth |
Returns the total advance width for showing the specified array of characters in this Font . |
int |
charWidth |
Returns the advance width of the specified character in this Font . |
int |
charWidth |
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 |
Returns the LineMetrics object for the specified character array in the specified Graphics context. |
LineMetrics |
getLineMetrics |
|
LineMetrics |
getLineMetrics |
|
LineMetrics |
getLineMetrics |
Returns the LineMetrics object for the specified CharacterIterator in the specified Graphics context. |
int |
getMaxAdvance() |
Returns an estimate of the maximum advance width of any character in the Font described by this FontMetrics object, with important caveats, enumerated below. |
int |
getMaxAscent() |
Determines the maximum ascent of the Font described by this FontMetrics object. |
Rectangle2D |
getMaxCharBounds |
Returns the bounds for the character with the maximum bounds in the specified Graphics context. |
int |
getMaxDecent() |
Deprecated. |
int |
getMaxDescent() |
Determines the maximum descent of the Font described by this FontMetrics object. |
Rectangle2D |
getStringBounds |
Returns the bounds of the specified array of characters in the specified Graphics context. |
Rectangle2D |
getStringBounds |
Returns the bounds of the specified String in the specified Graphics context. |
Rectangle2D |
getStringBounds |
Returns the bounds of the specified String in the specified Graphics context. |
Rectangle2D |
getStringBounds |
Returns the bounds of the characters indexed in the specified CharacterIterator in the specified Graphics context. |
int[] |
getWidths() |
Gets the advance widths of the first 256 characters in the Font . |
boolean |
hasUniformLineMetrics() |
Checks to see if the Font has uniform line metrics. |
int |
stringWidth |
Returns the total advance width for showing the specified String in this Font . |
String |
toString() |
Returns a representation of this FontMetrics object's values as a String . |
protected Font font
Font
from which the font metrics are created. This cannot be null.protected FontMetrics(Font font)
FontMetrics
object for finding out height and width information about the specified Font
and specific character glyphs in that Font
.font
- the Font
public Font getFont()
Font
described by this FontMetrics
object.Font
described by this FontMetrics
object.public FontRenderContext getFontRenderContext()
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
FontRenderContext
used by this FontMetrics
object.public int getLeading()
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.Font
.public int getAscent()
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.Font
.public int getDescent()
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.Font
.public int getHeight()
public int getMaxAscent()
Font
described by this FontMetrics
object. No character extends further above the font's baseline than this height.Font
.public int getMaxDescent()
Font
described by this FontMetrics
object. No character extends further below the font's baseline than this height.Font
.@Deprecated public int getMaxDecent()
getMaxDescent()
.Font
.public int getMaxAdvance()
Font
described by this FontMetrics
object, with important caveats, enumerated below. The advance is the distance from the leftmost point used to position the character to the rightmost point along the baseline. This is not the same thing as the visible width of the glyph image representing the character.
The advance of a String
is not necessarily the sum of the advances of its characters. It may differ substantially if complex text layout is required for proper rendering.
Some of the caveats of the reported value include
Font.BOLD
, for which no exact match is available, then techniques to satisfy the requested rendering may similarly result in glyphs that are wider than the reported maximum. Font.MONOSPACED
can render glyphs that are not all the same width. String
is not necessarily the sum of the advances the value still needs to be used with caution. In summary, this method makes no absolute guarantee, nor can it even make a guarantee to be correct within some margin of error. So it should be used at most only for estimating the total space sufficient to display some number of as yet unknown characters from the font. And that might be either an overestimate, or an underestimate depending on the specific text and rendering context.
Font
, or -1
if the maximum advance width is not known.public int charWidth(int codePoint)
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.
codePoint
- the character (Unicode code point) to be measuredFont
described by this FontMetrics
object.public int charWidth(char ch)
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.
ch
- the character to be measuredFont
described by this FontMetrics
object.public int stringWidth(String str)
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.
str
- the String
to be measuredString
in the Font
described by this FontMetrics
.NullPointerException
- if str is null.public int charsWidth(char[] data, int off, int len)
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.data
- the array of characters to be measuredoff
- the start offset of the characters in the arraylen
- the number of characters to be measured from the arraychar
array in the font described by this FontMetrics
object.NullPointerException
- if data
is null.IndexOutOfBoundsException
- if the off
and len
arguments index characters outside the bounds of the data
array.public int bytesWidth(byte[] data, int off, int len)
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.data
- the array of bytes to be measuredoff
- the start offset of the bytes in the arraylen
- the number of bytes to be measured from the arraybyte
array in the Font
described by this FontMetrics
object.NullPointerException
- if data
is null.IndexOutOfBoundsException
- if the off
and len
arguments index bytes outside the bounds of the data
array.public int[] getWidths()
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.Font
described by this FontMetrics
object.public boolean hasUniformLineMetrics()
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.true
if the font has uniform line metrics; false
otherwise.public LineMetrics getLineMetrics(String str, Graphics context)
str
- the specified String
context
- the specified Graphics
contextLineMetrics
object created with the specified String
and Graphics
context.public LineMetrics getLineMetrics(String str, int beginIndex, int limit, Graphics context)
str
- the specified String
beginIndex
- the initial offset of str
limit
- the end offset of str
context
- the specified Graphics
contextLineMetrics
object created with the specified String
and Graphics
context.public LineMetrics getLineMetrics(char[] chars, int beginIndex, int limit, Graphics context)
LineMetrics
object for the specified character array in the specified Graphics
context.chars
- the specified character arraybeginIndex
- the initial offset of chars
limit
- the end offset of chars
context
- the specified Graphics
contextLineMetrics
object created with the specified character array and Graphics
context.public LineMetrics getLineMetrics(CharacterIterator ci, int beginIndex, int limit, Graphics context)
LineMetrics
object for the specified CharacterIterator
in the specified Graphics
context.ci
- the specified CharacterIterator
beginIndex
- the initial offset in ci
limit
- the end index of ci
context
- the specified Graphics
contextLineMetrics
object created with the specified arguments.public Rectangle2D getStringBounds(String str, Graphics context)
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
).
str
- the specified String
context
- the specified Graphics
contextRectangle2D
that is the bounding box of the specified String
in the specified Graphics
context.public Rectangle2D getStringBounds(String str, int beginIndex, int limit, Graphics context)
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
).
str
- the specified String
beginIndex
- the offset of the beginning of str
limit
- the end offset of str
context
- the specified Graphics
contextRectangle2D
that is the bounding box of the specified String
in the specified Graphics
context.public Rectangle2D getStringBounds(char[] chars, int beginIndex, int limit, Graphics context)
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
).
chars
- an array of charactersbeginIndex
- the initial offset of the array of characterslimit
- the end offset of the array of characterscontext
- the specified Graphics
contextRectangle2D
that is the bounding box of the specified character array in the specified Graphics
context.public Rectangle2D getStringBounds(CharacterIterator ci, int beginIndex, int limit, Graphics context)
CharacterIterator
in the specified Graphics
context. Note: The returned bounds is in baseline-relative coordinates (see class notes
).
ci
- the specified CharacterIterator
beginIndex
- the initial offset in ci
limit
- the end index of ci
context
- the specified Graphics
contextRectangle2D
that is the bounding box of the characters indexed in the specified CharacterIterator
in the specified Graphics
context.public Rectangle2D getMaxCharBounds(Graphics context)
Graphics
context.context
- the specified Graphics
contextRectangle2D
that is the bounding box for the character with the maximum bounds.public String toString()
FontMetrics
object's values as a String
.
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https://docs.oracle.com/en/java/javase/21/docs/api/java.desktop/java/awt/FontMetrics.html
getMaxDescent()
.