BufferStrategy class represents the mechanism with which
* to organize complex memory on a particular Canvas or
* Window. Hardware and software limitations determine whether and
* how a particular buffer strategy can be implemented. These limitations
* are detectible through the capabilities of the
* GraphicsConfiguration used when creating the
* Canvas or Window.
* * It is worth noting that the terms buffer and surface are meant * to be synonymous: an area of contiguous memory, either in video device * memory or in system memory. *
* There are several types of complex buffer strategies, including * sequential ring buffering and blit buffering. * Sequential ring buffering (i.e., double or triple * buffering) is the most common; an application draws to a single back * buffer and then moves the contents to the front (display) in a single * step, either by copying the data or moving the video pointer. * Moving the video pointer exchanges the buffers so that the first buffer * drawn becomes the front buffer, or what is currently displayed on the * device; this is called page flipping. *
* Alternatively, the contents of the back buffer can be copied, or * blitted forward in a chain instead of moving the video pointer. *
*
* Double buffering: * * *********** *********** * * * ------> * * * [To display] <---- * Front B * Show * Back B. * <---- Rendering * * * <------ * * * *********** *********** * * Triple buffering: * * [To *********** *********** *********** * display] * * --------+---------+------> * * * <---- * Front B * Show * Mid. B. * * Back B. * <---- Rendering * * * <------ * * <----- * * * *********** *********** *********** * **
* Here is an example of how buffer strategies can be created and used: *
*
* // Check the capabilities of the GraphicsConfiguration
* ...
*
* // Create our component
* Window w = new Window(gc);
*
* // Show our window
* w.setVisible(true);
*
* // Create a general double-buffering strategy
* w.createBufferStrategy(2);
* BufferStrategy strategy = w.getBufferStrategy();
*
* // Main loop
* while (!done) {
* // Prepare for rendering the next frame
* // ...
*
* // Render single frame
* do {
* // The following loop ensures that the contents of the drawing buffer
* // are consistent in case the underlying surface was recreated
* do {
* // Get a new graphics context every time through the loop
* // to make sure the strategy is validated
* Graphics graphics = strategy.getDrawGraphics();
*
* // Render to graphics
* // ...
*
* // Dispose the graphics
* graphics.dispose();
*
* // Repeat the rendering if the drawing buffer contents
* // were restored
* } while (strategy.contentsRestored());
*
* // Display the buffer
* strategy.show();
*
* // Repeat the rendering if the drawing buffer was lost
* } while (strategy.contentsLost());
* }
*
* // Dispose the window
* w.setVisible(false);
* w.dispose();
* BufferCapabilities for this
* BufferStrategy.
*
* @return the buffering capabilities of this strategy
*/
public abstract BufferCapabilities getCapabilities();
/**
* Creates a graphics context for the drawing buffer. This method may not
* be synchronized for performance reasons; use of this method by multiple
* threads should be handled at the application level. Disposal of the
* graphics object obtained must be handled by the application.
*
* @return a graphics context for the drawing buffer
*/
public abstract Graphics getDrawGraphics();
/**
* Returns whether the drawing buffer was lost since the last call to
* getDrawGraphics. Since the buffers in a buffer strategy
* are usually type VolatileImage, they may become lost.
* For a discussion on lost buffers, see VolatileImage.
*
* @return Whether or not the drawing buffer was lost since the last call
* to getDrawGraphics.
* @see java.awt.image.VolatileImage
*/
public abstract boolean contentsLost();
/**
* Returns whether the drawing buffer was recently restored from a lost
* state and reinitialized to the default background color (white).
* Since the buffers in a buffer strategy are usually type
* VolatileImage, they may become lost. If a surface has
* been recently restored from a lost state since the last call to
* getDrawGraphics, it may require repainting.
* For a discussion on lost buffers, see VolatileImage.
*
* @return Whether or not the drawing buffer was restored since the last
* call to getDrawGraphics.
* @see java.awt.image.VolatileImage
*/
public abstract boolean contentsRestored();
/**
* Makes the next available buffer visible by either copying the memory
* (blitting) or changing the display pointer (flipping).
*/
public abstract void show();
/**
* Releases system resources currently consumed by this
* BufferStrategy and
* removes it from the associated Component. After invoking this
* method, getBufferStrategy will return null. Trying
* to use a BufferStrategy after it has been disposed will
* result in undefined behavior.
*
* @see java.awt.Window#createBufferStrategy
* @see java.awt.Canvas#createBufferStrategy
* @see java.awt.Window#getBufferStrategy
* @see java.awt.Canvas#getBufferStrategy
* @since 1.6
*/
public void dispose() {
}
}