Java™ Platform
Standard Ed. 6

java.awt.font
Class FontRenderContext

java.lang.Object
  extended by java.awt.font.FontRenderContext

public class FontRenderContext
extends Object

The FontRenderContext class is a container for the information needed to correctly measure text. The measurement of text can vary because of rules that map outlines to pixels, and rendering hints provided by an application.

One such piece of information is a transform that scales typographical points to pixels. (A point is defined to be exactly 1/72 of an inch, which is slightly different than the traditional mechanical measurement of a point.) A character that is rendered at 12pt on a 600dpi device might have a different size than the same character rendered at 12pt on a 72dpi device because of such factors as rounding to pixel boundaries and hints that the font designer may have specified.

Anti-aliasing and Fractional-metrics specified by an application can also affect the size of a character because of rounding to pixel boundaries.

Typically, instances of FontRenderContext are obtained from a Graphics2D object. A FontRenderContext which is directly constructed will most likely not represent any actual graphics device, and may lead to unexpected or incorrect results.

See Also:
RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.KEY_FRACTIONALMETRICS, Graphics2D.getFontRenderContext(), LineMetrics

Constructor Summary
protected FontRenderContext()
          Constructs a new FontRenderContext object.
  FontRenderContext(AffineTransform tx, boolean isAntiAliased, boolean usesFractionalMetrics)
          Constructs a FontRenderContext object from an optional AffineTransform and two boolean values that determine if the newly constructed object has anti-aliasing or fractional metrics.
  FontRenderContext(AffineTransform tx, Object aaHint, Object fmHint)
          Constructs a FontRenderContext object from an optional AffineTransform and two Object values that determine if the newly constructed object has anti-aliasing or fractional metrics.
 
Method Summary
 boolean equals(FontRenderContext rhs)
          Return true if rhs has the same transform, antialiasing, and fractional metrics values as this.
 boolean equals(Object obj)
          Return true if obj is an instance of FontRenderContext and has the same transform, antialiasing, and fractional metrics values as this.
 Object getAntiAliasingHint()
          Return the text anti-aliasing rendering mode hint used in this FontRenderContext.
 Object getFractionalMetricsHint()
          Return the text fractional metrics rendering mode hint used in this FontRenderContext.
 AffineTransform getTransform()
          Gets the transform that is used to scale typographical points to pixels in this FontRenderContext.
 int getTransformType()
          Returns the integer type of the affine transform for this FontRenderContext as specified by AffineTransform.getType()
 int hashCode()
          Return a hashcode for this FontRenderContext.
 boolean isAntiAliased()
          Returns a boolean which indicates whether or not some form of antialiasing is specified by this FontRenderContext.
 boolean isTransformed()
          Indicates whether or not this FontRenderContext object measures text in a transformed render context.
 boolean usesFractionalMetrics()
          Returns a boolean which whether text fractional metrics mode is used in this FontRenderContext.
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

FontRenderContext

protected FontRenderContext()
Constructs a new FontRenderContext object.


FontRenderContext

public FontRenderContext(AffineTransform tx,
                         boolean isAntiAliased,
                         boolean usesFractionalMetrics)
Constructs a FontRenderContext object from an optional AffineTransform and two boolean values that determine if the newly constructed object has anti-aliasing or fractional metrics. In each case the boolean values true and false correspond to the rendering hint values ON and OFF respectively.

To specify other hint values, use the constructor which specifies the rendering hint values as parameters : FontRenderContext(AffineTransform, Object, Object).

Parameters:
tx - the transform which is used to scale typographical points to pixels in this FontRenderContext. If null, an identity transform is used.
isAntiAliased - determines if the newly constructed object has anti-aliasing.
usesFractionalMetrics - determines if the newly constructed object has fractional metrics.

FontRenderContext

public FontRenderContext(AffineTransform tx,
                         Object aaHint,
                         Object fmHint)
Constructs a FontRenderContext object from an optional AffineTransform and two Object values that determine if the newly constructed object has anti-aliasing or fractional metrics.

Parameters:
tx - the transform which is used to scale typographical points to pixels in this FontRenderContext. If null, an identity tranform is used.
aaHint - - one of the text antialiasing rendering hint values defined in java.awt.RenderingHints. Any other value will throw IllegalArgumentException. VALUE_TEXT_ANTIALIAS_DEFAULT may be specified, in which case the mode used is implementation dependent.
fmHint - - one of the text fractional rendering hint values defined in java.awt.RenderingHints. VALUE_FRACTIONALMETRICS_DEFAULT may be specified, in which case the mode used is implementation dependent. Any other value will throw IllegalArgumentException
Throws:
IllegalArgumentException - if the hints are not one of the legal values.
Since:
1.6
Method Detail

isTransformed

public boolean isTransformed()
Indicates whether or not this FontRenderContext object measures text in a transformed render context.

Returns:
true if this FontRenderContext object has a non-identity AffineTransform attribute. false otherwise.
Since:
1.6
See Also:
getTransform()

getTransformType

public int getTransformType()
Returns the integer type of the affine transform for this FontRenderContext as specified by AffineTransform.getType()

Returns:
the type of the transform.
Since:
1.6
See Also:
AffineTransform

getTransform

public AffineTransform getTransform()
Gets the transform that is used to scale typographical points to pixels in this FontRenderContext.

Returns:
the AffineTransform of this FontRenderContext.
See Also:
AffineTransform

isAntiAliased

public boolean isAntiAliased()
Returns a boolean which indicates whether or not some form of antialiasing is specified by this FontRenderContext. Call getAntiAliasingHint() for the specific rendering hint value.

Returns:
true, if text is anti-aliased in this FontRenderContext; false otherwise.
See Also:
RenderingHints.KEY_TEXT_ANTIALIASING, FontRenderContext(AffineTransform,boolean,boolean), FontRenderContext(AffineTransform,Object,Object)

usesFractionalMetrics

public boolean usesFractionalMetrics()
Returns a boolean which whether text fractional metrics mode is used in this FontRenderContext. Call getFractionalMetricsHint() to obtain the corresponding rendering hint value.

Returns:
true, if layout should be performed with fractional metrics; false otherwise. in this FontRenderContext.
See Also:
RenderingHints.KEY_FRACTIONALMETRICS, FontRenderContext(AffineTransform,boolean,boolean), FontRenderContext(AffineTransform,Object,Object)

getAntiAliasingHint

public Object getAntiAliasingHint()
Return the text anti-aliasing rendering mode hint used in this FontRenderContext. This will be one of the text antialiasing rendering hint values defined in java.awt.RenderingHints.

Returns:
text anti-aliasing rendering mode hint used in this FontRenderContext.
Since:
1.6

getFractionalMetricsHint

public Object getFractionalMetricsHint()
Return the text fractional metrics rendering mode hint used in this FontRenderContext. This will be one of the text fractional metrics rendering hint values defined in java.awt.RenderingHints.

Returns:
the text fractional metrics rendering mode hint used in this FontRenderContext.
Since:
1.6

equals

public boolean equals(Object obj)
Return true if obj is an instance of FontRenderContext and has the same transform, antialiasing, and fractional metrics values as this.

Overrides:
equals in class Object
Parameters:
obj - the object to test for equality
Returns:
true if the specified object is equal to this FontRenderContext; false otherwise.
See Also:
Object.hashCode(), Hashtable

equals

public boolean equals(FontRenderContext rhs)
Return true if rhs has the same transform, antialiasing, and fractional metrics values as this.

Parameters:
rhs - the FontRenderContext to test for equality
Returns:
true if rhs is equal to this FontRenderContext; false otherwise.
Since:
1.4

hashCode

public int hashCode()
Return a hashcode for this FontRenderContext.

Overrides:
hashCode in class Object
Returns:
a hash code value for this object.
See Also:
Object.equals(java.lang.Object), Hashtable

Java™ Platform
Standard Ed. 6

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