Painter (Java Platform SE 8 )
Keywords: javax.swing.Painter interface
Date: 2020-03-26

javax.swing

## Interface Painter<T>

- All Known Implementing Classes:
    AbstractRegionPainter

      public interface Painter<T>

  A painting delegate. The Painter interface defines exactly one method, `paint`. It is used in situations where the developer can change the painting routine of a component without having to resort to subclassing the component. It is also generically useful when doing any form of painting delegation.

  `Painter`s are simply encapsulations of Java2D code and make it fairly trivial to reuse existing `Painter`s or to combine them together. Implementations of this interface are also trivial to write, such that if you can't find a `Painter` that does what you need, you can write one with minimal effort. Writing a `Painter` requires knowledge of Java2D.

  A `Painter` may be created with a type parameter. This type will be expected in the `paint` method. For example, you may wish to write a `Painter` that only works with subclasses of `Component`. In that case, when the `Painter` is declared, you may declare that it requires a `Component`, allowing the paint method to be type safe. Ex:

       Painter<Component> p = new Painter<Component>() {
           public void paint(Graphics2D g, Component c, int width, int height) {
               g.setColor(c.getBackground());
               //and so forth
           }
       }

  This interface makes no guarantees of threadsafety.

- - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `paint(Graphics2D g, T object, int width, int height)` Renders to the given `Graphics2D` object.

- - ### Method Detail

    - #### paint

          void paint(Graphics2D g,
                     T object,
                     int width,
                     int height)

      Renders to the given `Graphics2D` object. Implementations of this method may modify state on the `Graphics2D`, and are not required to restore that state upon completion. In most cases, it is recommended that the caller pass in a scratch graphics object. The `Graphics2D` must never be null.

      State on the graphics object may be honored by the `paint` method, but may not be. For instance, setting the antialiasing rendering hint on the graphics may or may not be respected by the `Painter` implementation.

      The supplied object parameter acts as an optional configuration argument. For example, it could be of type `Component`. A `Painter` that expected it could then read state from that `Component` and use the state for painting. For example, an implementation may read the backgroundColor and use that.

      Generally, to enhance reusability, most standard `Painter`s ignore this parameter. They can thus be reused in any context. The `object` may be null. Implementations must not throw a NullPointerException if the object parameter is null.

      Finally, the `width` and `height` arguments specify the width and height that the `Painter` should paint into. More specifically, the specified width and height instruct the painter that it should paint fully within this width and height. Any specified clip on the `g` param will further constrain the region.

      For example, suppose I have a `Painter` implementation that draws a gradient. The gradient goes from white to black. It "stretches" to fill the painted region. Thus, if I use this `Painter` to paint a 500 x 500 region, the far left would be black, the far right would be white, and a smooth gradient would be painted between. I could then, without modification, reuse the `Painter` to paint a region that is 20x20 in size. This region would also be black on the left, white on the right, and a smooth gradient painted between.

      Parameters:
        `g` - The Graphics2D to render to. This must not be null.
        `object` - an optional configuration parameter. This may be null.
        `width` - width of the area to paint.
        `height` - height of the area to paint.

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