Hi, Anthony.
On 18.10.2013 15:17, Anthony Petrov wrote:
Hi Sergey,
In XAWT, we usually use the StateLock to synchronize access to peer
fields (such as background, label, etc.) I don't think that
switching to volatile is a good idea since it prevents us from
performing atomic read/writes to the fields. And this is exactly
what we need for this fix, actually. In other words, the following
pattern works perfectly:
synchronized (lock) {
if (a != b) {
a = b;
// do stuff, or set a flag to do it later w/o the lock
}
}
whereas the following doesn't:
volatile a;
if (a != b) {
a = b;
// do stuff
}
The latter doesn't work because the value of 'a' may change from
another thread after the if() statement in the first thread is
executed.
If it will be changed that's ok. It is safe in this context since
there is no races. a will be the latest setted value and repaint
action will be done after a was set. Non trivial setters(like
setLabel/setText) are called under the locks in shared code.
Please note that this is critical for AWT because it is a
multi-threaded GUI toolkit.
src/solaris/classes/sun/awt/X11/XListPeer.java
- target.paint(g);
+ handleExposeEvent(target, 0, 0, getWidth(),
getHeight());
(the same applies to XWindow.repaint): can you please rename
XWindow.handleExposeEvent(Component...) to postPaintEvent() and make
it final? A good javadoc for this method would also be appreciated,
because currently seeing the name handle*() I'd think it needs to be
done under the awtLock().
Will do.
Also, for the corresponding changes in XWindow.repaint(), could you
please elaborate a bit more? Looking at the code I see that
XWindow.paint() calls paintPeer(). And in repaint(), you either call
paint() or paintPeer() depending on the current thread. Why is it
needed? Can we just call paintPeer() (or paint() for that matter)
unconditionally since they both seem to result in the same call?
paintPeer is used to draw the native part of the peer(text of the
label, border of the button etc).
paint is a part of Component.paintAll(). And as a result of it call
it should paint the native part of the peer and it should call
appropriate paint method from the target.
Also, why don't we post an event if reapint() is invoked on the EDT?
We do this in osx, but in xawt there are "smart" caches, which are
initialized during the paint of the peer. See
XLabelPeer&cachedFontMetrics for example . Note that this cache is
completely broken.
--
best regards,
Anthony
On 10/16/2013 06:00 PM, Sergey Bylokhov wrote:
Hello.
Please review the fix for jdk 8.
The fix has two parts
- Repaint method in the peer now paint the component in place if it
was called on EDT only.
- Most of setters were changed to stop recursion if they were called
on EDT.
Bug: https://bugs.openjdk.java.net/browse/JDK-7090424
Webrev can be found at:
http://cr.openjdk.java.net/~serb/7090424/webrev.00
