FSEM and Double Buffering

[Mertail]

I'm using createBufferStrategy(2).  As I read the documentation, this creates two memory buffers for display.  I've checked and my Mac system is using PRIOR as its Flipping Strategy.  I had assumed that, if I wrote something one the first buffer and used show to flip it, it would reappear the next time that buffer was reused (i.e. every second frame).  Instead, the system appears to be acting as if it's copying the last frame instead of keeping the prior contents.  ALl the examples I've seen completely redraw the screen.  I was hoping to avoid that for a FSEM full-background image demo I'm trying to create for a game engine course I teach next September.  I suspect I'm missing something vital here and any help would be appreciated.

[Riven]

Verify that:

1	bufferStrategy.getCapabilities().isPageFlipping()

is true.

[Mertail]

It is true