FontRenderContext (Java SE 21 & JDK 21)
Description: declaration: module: java.desktop, package: java.awt.font, class: FontRenderContext
Keywords: java.awt.font.FontRenderContext class

Module java.desktop
Package java.awt.font

# Class FontRenderContext

java.lang.Object
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

  Constructors
  Modifier
  Constructor
  Description
  `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

  Modifier and Type
  Method
  Description
  `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 declared in class java.lang.Object

  `clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait`

- ## Constructor Details

  - ### 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 transform 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 Details

  - ### 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()`
      - `HashMap`

  - ### 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)`
      - `System.identityHashCode(java.lang.Object)`