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.
Painters are simply encapsulations of Java2D code and make
* it fairly trivial to reuse existing Painters 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 {@link java.awt.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:
*
* {@code
* Painter p = new Painter() {
* 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.
* * @author rbair */ public interface PainterRenders to the given {@link java.awt.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 Painters 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.