java::awt::FontMetrics Class Reference

Inheritance diagram for java::awt::FontMetrics:

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java::lang::Object
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Collaboration diagram for java::awt::FontMetrics:

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java::lang::Objectjava::lang::ObjectRefjava::lang::Interfacejava::lang::Comparable
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List of all members.


Detailed Description

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):

FontMetrics-1.gif
Note that the implementations of these methods are inefficient, so they are usually overridden with more efficient toolkit-specific implementations.

When an application asks AWT to place a character at the position (xy), 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.

const Color Color::RED(255,0,0); const Color Color::PINK(255,175,175); const Color Color::ORANGE(255,200,0); const Color Color::YELLOW(255,255,0); 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.

Version:
1.49 01/23/03
Author:
Jim Graham
See also:
java.awt.Font
Since:
JDK1.0

Public Member Functions

 FontMetrics (const Ref< Font > &font=0)
 Creates a new FontMetrics object for finding out height and width information about the specified Font and specific character glyphs in that Font.
virtual Ref< FontgetFont () const
 Gets the Font described by this FontMetrics object.
virtual jint getLeading () const
 Determines the standard leading of the Font described by this FontMetrics object.
virtual jint getAscent () const
 Determines the font ascent of the Font described by this FontMetrics object.
virtual jint getDescent () const
 Determines the font descent of the Font described by this FontMetrics object.
virtual jint getHeight () const
 Gets the standard height of a line of text in this font.
virtual jint getMaxAscent () const
 Determines the maximum ascent of the Font described by this FontMetrics object.
virtual jint getMaxDescent () const
 Determines the maximum descent of the Font described by this FontMetrics object.
virtual jint getMaxAdvance () const
 Gets the maximum advance width of any character in this Font.
virtual jint charWidth (jchar ch) const
 Returns the advance width of the specified character in this Font.
virtual jint stringWidth (const String &str) const
 Returns the total advance width for showing the specified String in this Font.
virtual Array< jintgetWidths () const
 Gets the advance widths of the first 256 characters in the Font.
virtual String toString () const
 Returns a representation of this FontMetrics object's values as a String.

Constructor & Destructor Documentation

java::awt::FontMetrics::FontMetrics ( const Ref< Font > &  font = 0  ) 

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 the Font
See also:
java.awt.Font


Member Function Documentation

virtual Ref<Font> java::awt::FontMetrics::getFont (  )  const [virtual]

Gets the Font described by this FontMetrics object.

Returns:
the Font described by this FontMetrics object.

virtual jint java::awt::FontMetrics::getLeading (  )  const [virtual]

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()

virtual jint java::awt::FontMetrics::getAscent (  )  const [virtual]

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()

virtual jint java::awt::FontMetrics::getDescent (  )  const [virtual]

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()

virtual jint java::awt::FontMetrics::getHeight (  )  const [virtual]

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()

virtual jint java::awt::FontMetrics::getMaxAscent (  )  const [virtual]

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()

virtual jint java::awt::FontMetrics::getMaxDescent (  )  const [virtual]

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()

virtual jint java::awt::FontMetrics::getMaxAdvance (  )  const [virtual]

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.

virtual jint java::awt::FontMetrics::charWidth ( jchar  ch  )  const [virtual]

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.

Parameters:
ch the character to be measured
Returns:
the advance width of the specified char in the Font described by this FontMetrics object.
See also:
charsWidth(char[], int, int)

stringWidth(String)

virtual jint java::awt::FontMetrics::stringWidth ( const String str  )  const [virtual]

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 total advance width returned from this method does not take into account the rendering context. Therefore, the anti-aliasing and fractional metrics hints can affect the value of the advance. When enabling the anti-aliasing and fractional metrics hints, use getStringBounds(String, Graphics) instead of this method. The advance of a String is not necessarily the sum of the advances of its characters.

Parameters:
str the String to be measured
Returns:
the advance width of the specified String in the Font described by this FontMetrics.
See also:
bytesWidth(byte[], int, int)

charsWidth(char[], int, int)

getStringBounds(String, Graphics)

virtual Array<jint> java::awt::FontMetrics::getWidths (  )  const [virtual]

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 this FontMetrics object.

virtual String java::awt::FontMetrics::toString (  )  const [virtual]

Returns a representation of this FontMetrics object's values as a String.

Returns:
a String representation of this FontMetrics object.
Since:
JDK1.0.

Reimplemented from java::lang::Object.


The documentation for this class was generated from the following file:
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