The 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;
sequential ring buffering, blit buffering, and stereo buffering are
common types. 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
* * <------ * * <----- * *
*********** *********** ***********
Stereo buffering is for hardware that supports rendering separate images for
a left and right eye. It is similar to sequential ring buffering, but
there are two buffer chains, one for each eye. Both buffer chains flip
simultaneously:
Stereo buffering:
*********** ***********
* * ------> * *
[To left eye] <---- * Front B * * Back B. * <---- Rendering
* * <------ * *
*********** ***********
Show
*********** ***********
* * ------> * *
[To right eye] <--- * Front 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();
// Render loop
while (!done) {
Graphics g = strategy.getDrawGraphics();
// Draw to graphics
...
strategy.show();
}
// Dispose the window
w.setVisible(false);
w.dispose();
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