Class FontMetrics
- All Implemented Interfaces:
- 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.
 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:
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Field SummaryFields
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Constructor SummaryConstructorsModifierConstructorDescriptionprotectedFontMetrics(Font font) Creates a newFontMetricsobject for finding out height and width information about the specifiedFontand specific character glyphs in thatFont.
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Method SummaryModifier and TypeMethodDescriptionintbytesWidth(byte[] data, int off, int len) Returns the total advance width for showing the specified array of bytes in thisFont.intcharsWidth(char[] data, int off, int len) Returns the total advance width for showing the specified array of characters in thisFont.intcharWidth(char ch) Returns the advance width of the specified character in thisFont.intcharWidth(int codePoint) Returns the advance width of the specified character in thisFont.intDetermines the font ascent of theFontdescribed by thisFontMetricsobject.intDetermines the font descent of theFontdescribed by thisFontMetricsobject.getFont()Gets theFontdescribed by thisFontMetricsobject.Gets theFontRenderContextused by thisFontMetricsobject to measure text.intGets the standard height of a line of text in this font.intDetermines the standard leading of theFontdescribed by thisFontMetricsobject.getLineMetrics(char[] chars, int beginIndex, int limit, Graphics context) Returns theLineMetricsobject for the specified character array in the specifiedGraphicscontext.getLineMetrics(String str, int beginIndex, int limit, Graphics context) getLineMetrics(String str, Graphics context) getLineMetrics(CharacterIterator ci, int beginIndex, int limit, Graphics context) Returns theLineMetricsobject for the specifiedCharacterIteratorin the specifiedGraphicscontext.intReturns an estimate of the maximum advance width of any character in theFontdescribed by thisFontMetricsobject, with important caveats, enumerated below.intDetermines the maximum ascent of theFontdescribed by thisFontMetricsobject.getMaxCharBounds(Graphics context) Returns the bounds for the character with the maximum bounds in the specifiedGraphicscontext.intDeprecated.intDetermines the maximum descent of theFontdescribed by thisFontMetricsobject.getStringBounds(char[] chars, int beginIndex, int limit, Graphics context) Returns the bounds of the specified array of characters in the specifiedGraphicscontext.getStringBounds(String str, int beginIndex, int limit, Graphics context) Returns the bounds of the specifiedStringin the specifiedGraphicscontext.getStringBounds(String str, Graphics context) Returns the bounds of the specifiedStringin the specifiedGraphicscontext.getStringBounds(CharacterIterator ci, int beginIndex, int limit, Graphics context) Returns the bounds of the characters indexed in the specifiedCharacterIteratorin the specifiedGraphicscontext.int[]Gets the advance widths of the first 256 characters in theFont.booleanChecks to see if theFonthas uniform line metrics.intstringWidth(String str) Returns the total advance width for showing the specifiedStringin thisFont.toString()Returns a representation of thisFontMetricsobject's values as aString.
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Field Details- 
font
 
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Constructor Details- 
FontMetricsCreates a newFontMetricsobject for finding out height and width information about the specifiedFontand specific character glyphs in thatFont.- Parameters:
- font- the- Font
- See Also:
 
 
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Method Details- 
getFontGets theFontdescribed by thisFontMetricsobject.- Returns:
- the Fontdescribed by thisFontMetricsobject.
 
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getFontRenderContextGets theFontRenderContextused by thisFontMetricsobject to measure text.Note that methods in this class which take a Graphicsparameter measure text using theFontRenderContextof thatGraphicsobject, and not thisFontRenderContext- Returns:
- the FontRenderContextused by thisFontMetricsobject.
- Since:
- 1.6
 
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getLeadingpublic int getLeading()Determines the standard leading of theFontdescribed by thisFontMetricsobject. 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:
 
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getAscentpublic int getAscent()Determines the font ascent of theFontdescribed by thisFontMetricsobject. The font ascent is the distance from the font's baseline to the top of most alphanumeric characters. Some characters in theFontmight extend above the font ascent line.- Returns:
- the font ascent of the Font.
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getDescentpublic int getDescent()Determines the font descent of theFontdescribed by thisFontMetricsobject. The font descent is the distance from the font's baseline to the bottom of most alphanumeric characters with descenders. Some characters in theFontmight extend below the font descent line.- Returns:
- the font descent of the Font.
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getHeightpublic 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.
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getMaxAscentpublic int getMaxAscent()Determines the maximum ascent of theFontdescribed by thisFontMetricsobject. No character extends further above the font's baseline than this height.- Returns:
- the maximum ascent of any character in the
 Font.
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getMaxDescentpublic int getMaxDescent()Determines the maximum descent of theFontdescribed by thisFontMetricsobject. No character extends further below the font's baseline than this height.- Returns:
- the maximum descent of any character in the
 Font.
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getMaxDecentDeprecated.As of JDK version 1.1.1, replaced bygetMaxDescent().For backward compatibility only.- Returns:
- the maximum descent of any character in the
 Font.
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getMaxAdvancepublic int getMaxAdvance()Returns an estimate of the maximum advance width of any character in theFontdescribed by thisFontMetricsobject, 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 Stringis 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 - The returned value is relying upon information from some underlying system font, and the correctness of that information is outside of AWT's control.
- When specific characters are mapped into glyphs in some rendering context, instructions in the font itself together with the rasterization process may cause some glyph to have a wider advance than reported.
-  When a font is requested in some style, eg 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.
-  Depending on the implementation, an AWT logical font or
 physical font may need to locate some characters from one or more
 "fall back" fonts, when the primary underlying physical font does not
 support the character. These fonts may not all be known or considered
 in the calculation of the reported maximum advance. It is common
 for the design center of such fall back fonts to be for a different
 script than the design center of the primary font, so their
 advances can be quite different. This can also lead to the
 unexpected result that a font such as Font.MONOSPACEDcan render glyphs that are not all the same width.
 Stringis 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. - Returns:
- an estimate of the maximum advance width of any character
            in the Font, or-1if the maximum advance width is not known.
 
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charWidthpublic int charWidth(int codePoint) Returns the advance width of the specified character in thisFont. The advance is the distance from the leftmost point to the rightmost point on the character's baseline. Note that the advance of aStringis 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.isValidCodePointif necessary.- Parameters:
- codePoint- the character (Unicode code point) to be measured
- Returns:
- the advance width of the specified character
            in the Fontdescribed by thisFontMetricsobject.
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charWidthpublic int charWidth(char ch) Returns the advance width of the specified character in thisFont. The advance is the distance from the leftmost point to the rightmost point on the character's baseline. Note that the advance of aStringis 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 Fontdescribed by thisFontMetricsobject.
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stringWidthReturns the total advance width for showing the specifiedStringin thisFont. The advance is the distance from the leftmost point to the rightmost point on the string's baseline.Note that the advance of a Stringis not necessarily the sum of the advances of its characters.- Parameters:
- str- the- Stringto be measured
- Returns:
- the advance width of the specified Stringin theFontdescribed by thisFontMetrics.
- Throws:
- NullPointerException- if str is null.
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charsWidthpublic int charsWidth(char[] data, int off, int len) Returns the total advance width for showing the specified array of characters in thisFont. The advance is the distance from the leftmost point to the rightmost point on the string's baseline. The advance of aStringis not necessarily the sum of the advances of its characters. This is equivalent to measuring aStringof 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
               chararray in the font described by thisFontMetricsobject.
- Throws:
- NullPointerException- if- datais null.
- IndexOutOfBoundsException- if the- offand- lenarguments index characters outside the bounds of the- dataarray.
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bytesWidthpublic int bytesWidth(byte[] data, int off, int len) Returns the total advance width for showing the specified array of bytes in thisFont. The advance is the distance from the leftmost point to the rightmost point on the string's baseline. The advance of aStringis not necessarily the sum of the advances of its characters. This is equivalent to measuring aStringof 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
               bytearray in theFontdescribed by thisFontMetricsobject.
- Throws:
- NullPointerException- if- datais null.
- IndexOutOfBoundsException- if the- offand- lenarguments index bytes outside the bounds of the- dataarray.
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getWidthspublic int[] getWidths()Gets the advance widths of the first 256 characters in theFont. The advance is the distance from the leftmost point to the rightmost point on the character's baseline. Note that the advance of aStringis not necessarily the sum of the advances of its characters.- Returns:
- an array storing the advance widths of the
                 characters in the Fontdescribed by thisFontMetricsobject.
 
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hasUniformLineMetricspublic boolean hasUniformLineMetrics()Checks to see if theFonthas uniform line metrics. A composite font may consist of several different fonts to cover various character sets. In such cases, theFontLineMetricsobjects 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:
- trueif the font has uniform line metrics;- falseotherwise.
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getLineMetrics- Parameters:
- str- the specified- String
- context- the specified- Graphicscontext
- Returns:
- a LineMetricsobject created with the specifiedStringandGraphicscontext.
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getLineMetrics- Parameters:
- str- the specified- String
- beginIndex- the initial offset of- str
- limit- the end offset of- str
- context- the specified- Graphicscontext
- Returns:
- a LineMetricsobject created with the specifiedStringandGraphicscontext.
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getLineMetricsReturns theLineMetricsobject for the specified character array in the specifiedGraphicscontext.- Parameters:
- chars- the specified character array
- beginIndex- the initial offset of- chars
- limit- the end offset of- chars
- context- the specified- Graphicscontext
- Returns:
- a LineMetricsobject created with the specified character array andGraphicscontext.
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getLineMetricspublic LineMetrics getLineMetrics(CharacterIterator ci, int beginIndex, int limit, Graphics context) Returns theLineMetricsobject for the specifiedCharacterIteratorin the specifiedGraphicscontext.- Parameters:
- ci- the specified- CharacterIterator
- beginIndex- the initial offset in- ci
- limit- the end index of- ci
- context- the specified- Graphicscontext
- Returns:
- a LineMetricsobject created with the specified arguments.
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getStringBoundsReturns the bounds of the specifiedStringin the specifiedGraphicscontext. The bounds is used to layout theString.Note: The returned bounds is in baseline-relative coordinates (see class notes).- Parameters:
- str- the specified- String
- context- the specified- Graphicscontext
- Returns:
- a Rectangle2Dthat is the bounding box of the specifiedStringin the specifiedGraphicscontext.
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getStringBoundsReturns the bounds of the specifiedStringin the specifiedGraphicscontext. The bounds is used to layout theString.Note: The returned bounds is in baseline-relative coordinates (see class notes).- Parameters:
- str- the specified- String
- beginIndex- the offset of the beginning of- str
- limit- the end offset of- str
- context- the specified- Graphicscontext
- Returns:
- a Rectangle2Dthat is the bounding box of the specifiedStringin the specifiedGraphicscontext.
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getStringBoundsReturns the bounds of the specified array of characters in the specifiedGraphicscontext. The bounds is used to layout theStringcreated with the specified array of characters,beginIndexandlimit.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 specified- Graphicscontext
- Returns:
- a Rectangle2Dthat is the bounding box of the specified character array in the specifiedGraphicscontext.
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getStringBoundspublic Rectangle2D getStringBounds(CharacterIterator ci, int beginIndex, int limit, Graphics context) Returns the bounds of the characters indexed in the specifiedCharacterIteratorin the specifiedGraphicscontext.Note: The returned bounds is in baseline-relative coordinates (see class notes).- Parameters:
- ci- the specified- CharacterIterator
- beginIndex- the initial offset in- ci
- limit- the end index of- ci
- context- the specified- Graphicscontext
- Returns:
- a Rectangle2Dthat is the bounding box of the characters indexed in the specifiedCharacterIteratorin the specifiedGraphicscontext.
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getMaxCharBoundsReturns the bounds for the character with the maximum bounds in the specifiedGraphicscontext.- Parameters:
- context- the specified- Graphicscontext
- Returns:
- a Rectangle2Dthat is the bounding box for the character with the maximum bounds.
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toString
 
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getMaxDescent().