If you can put together a complete test which shows
that you can render to a Graphics object after it's
been disposed (and stuff shows up in the destination),
that would be a bug.
If you can, please send the test over. Otherwise it
is hard to tell what could be wrong.
Thanks,
Dmitri
Ken Warner wrote:
Ken Warner wrote:
According to the documentation on:
http://java.sun.com/javase/6/docs/api/java/awt/image/BufferStrategy.html
One is supposed to
do {
Graphics graphics = strategy.getDrawGraphics();
//render here
graphics.dispose();
} while (strategy.contentsRestored());
So I did that where I render:
do {
do {
bg = (Graphics2D)bs.getDrawGraphics();
mis.newPixels(pixels, cm, 0, thisW); //MemoryImageSource
bg.drawImage(canvasImage, 0, 0, thisW, thisH, this);
bg.dispose();
} while (bs.contentsRestored());
bs.show();
} while (bs.contentsLost());
So I'm disposing of bg -- the BufferStrategy graphics after I render.
The question is --
how come I can still use the buffer graphics (bg)
at other times to draw stuff.
My applet draws onto the BufferStrategy (bs) in many other places at
various times. And it works after I have dispose()'ed of the
buffergraphics (bg) and the loop above is the only place I
getDrawGraphics();
For example -- here's my paint() method -- no problem -- no drawGraphics.
public void paint(Graphics g)
{
//System.err.println("paint()");
bg.drawImage(canvasImage, 0, 0, thisW, thisH, this);
bs.show();
}
paint() should fail but it works just fine.
I don't understand how paint can drawImage if bg is disposed.
Ken
Dmitri Trembovetski wrote:
Ken Warner wrote:
Hi Dmitri,
I don't call repaint() from my code ever. I have ignoreRepaint() set for
the Canvas component. paint() is only called from the AWT eventloop on
expose and events like that -- do I understand that right?
The loop below is called from my own looping thread when I get some
newPixels for my MemoryImageSource. I have not seen any problems.
But I know that my applet is not accelerated on my machine. It only
has unaccelerated bitblt from the BufferStrategy. I can't test
real acceleration. My machine is too old.
What I'm trying to say -- clumsily -- is that I believe that only one
thread at a time could render to my buffer -- I think...
OK.. Then what's the question, again? I'm sorry, I'm just
not following.
Thanks,
Dmitri
Ken
Dmitri Trembovetski wrote:
Hi Ken,
first of all, rendering to the same graphics context from
multiple thread is not a good idea. Java2D does not
guarantee thread safety, and doing so could
lead to unpredictable results (and even crashes due
to bugs in our code). So, please don't do that.
As to your question why it "works" - you just got
lucky and the paint on EDT executed while another
thread was in between the getDrawGraphics() and dispose().
After the dispose() all rendering operations to a
graphics context become no-ops, so by definition you
would only see something rendered the paint event
happened to be while the graphics was still valid.
Thank you,
Dmitri
Java2D Team
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