bug: pressing BACK hangs webclient
Files touched
File: DocumentLoadEvent.java Status: Locally Modified
Made the constants final so they can be used in a
switch statement
File: EMWindow.java Status: Locally Modified
Modified eventDispatched() so it doesn't call any webclient
events. This was causing the hang. Took advantage of
the newly implemented ability to pass a string from the
mozilla event handler into java.
File: DocumentLoaderObserverImpl.cpp Status: Locally Modified
Create a jstring from the url in the OnStartDocumentLoad event.
Pass it on to java.
File: jni_util.cpp Status: Locally Modified
Wrapped JNU_GetEnv in BAL stuff so it works from Star.
File: WebclinetEventListener.java Status: Locally Modified
Added comment to eventDispatched.
r=shaver
a=edburns
Native code changes: This fix eradicates all
occurrences of the following symbols
nsComponentManager nsServiceManeger
And replaces them with their nsI counterparts.
The following ns* classes still are used in
webclient, and no plans exist to replace them
with nsI counterparts: nsresult nsCOMPtr
nsCRT nsnull * nsServiceManager occurrences
were replaced with do_GetService(), using a
PROGID. * nsComponentManager occurrences were replaced with a call on the global class gComponentManager, declared in the new file ns_globals.h, and defined in WrapperFactoryImpl.cpp. ns_globals.h is included in jni_util.h. See the attachment to bug 33099 for ns_globals.h * Added deallocation code to WindowControlImpl.cpp nativeTerminate. I know it doesn't do much, but it's correct. Java code changes: * Added static method BrowserControlFactory.appTerminate(). This method simply calls the existing BrowserControlImpl.appTerminate(), which calls WrapperFactoryImpl.cpp nativeTerminate(). BrowserControlFactory.appTerminate() is called from EmbeddedMozilla's WindowListener, which gets fired when the user signals she wants the app to terminate.
r=ashuk
a=edburns
Add an "eventData" argument to WebclientEvent and subclasses.
This argument is sub-event specific. For example, when a user
gets a DocumentLoadEvent, with an event type of
STATUS_URL_LOAD, the eventData is a String containing
the status string from the browser.
NativeEventThread's run() method's infinite loop was implemented. The
loop looks like this:
while (null != this.browserControlCanvas) {
synchronized (this.browserControlCanvas.getTreeLock()) {
nativeProcessEvents(nativeWebShell);
if (null != listenersToAdd && !listenersToAdd.isEmpty()) {
tempEnum = listenersToAdd.elements();
while (tempEnum.hasMoreElements()) {
nativeAddListener(nativeWebShell,
(WebclientEventListener)
tempEnum.nextElement());
}
listenersToAdd.clear();
}
}
}
The problem I was observing was that
nativeProcessEvents(nativeWebShell) would crash due to the fact that
the nativeWebShell, which is actually an WebShellInitContext instance,
had been de-allocated. This de-allocation happens as a result of the
WindowControlImpl.delete() method, which looks like this:
public void delete()
{
Assert.assert(null != eventThread, "eventThread shouldn't be null at delete time");
eventThread.delete();
eventThread = null;
nativeDestroyInitContext(nativeWebShell);
nativeWebShell = -1;
}
nativeDestroyInitContext de-allocates the WebShellInitContextInstance.
You can see that the first thing done is to delete the eventThread().
NativeEventThread.delete() looks like this:
public void delete()
{
// setting this to null causes the run thread to exit
synchronized(this.browserControlCanvas.getTreeLock()) {
browserControlCanvas = null;
}
...
}
If you compare NativeEventThread.delete() with the infinite loop in
NativeEventThread.run(), you'll see that the fact that they both
synchronize on the same object doesn't protect us from the following
case:
NativeEventThread: The infinite loop checks to see if the
browserControlCanvas is null, then does synchronize on
browserControlCanvas.getTreeLock(), then calls processNativeEvents().
meanwhile
WindowControlImpl thread: delete() calls NativeEventThread.delete(),
which does synchronize on browserControlCanvas.getTreeLock().
During NativeEventThread.delete(), synchronized section,
browserControlCanvas is set to null.
NativeEventThread: because the check for null browserControlCanvas
occurrs outside of the synchronized block, it's not recheked, and
thus, the event loop continues to process when it shouldn't.
The fix is to change the event loop to look like this:
while (true) {
synchronized (this.browserControlCanvas.getTreeLock()) {
// this has to be inside the synchronized block!
if (null == this.browserControlCanvas) {
return;
}
nativeProcessEvents(nativeWebShell);
if (null != listenersToAdd && !listenersToAdd.isEmpty()) {
tempEnum = listenersToAdd.elements();
while (tempEnum.hasMoreElements()) {
nativeAddListener(nativeWebShell,
(WebclientEventListener)
tempEnum.nextElement());
}
listenersToAdd.clear();
}
}
}
also modifies EmbeddedMozilla so this code is exercised.
I have changed EmbeddedMozilla to be a stub-like class that simply
displays a Frame with a single Button, titled "New Window". Pressing
this button causes an EMWindow to be created and displayed. EMWindow is
basically the former EmbeddedMozilla renamed, with modifications to the
WindowListener implementation to call the BrowserControl deallocation
method.
I've added a delete() method to ImplObect:
* I know Java has automatic garbage collection and all, but explicitly
* adding a delete method helps the gc algorithm out. <P>
* Subclasses should override this and call super.delete() at the end of
* their overridden delete() method.
* @see org.mozilla.webclient.wrapper_native.ImplObjectNative#delete
and ImplObjectNative:
* Note how we call super.delete() at the end. THIS IS VERY IMPORTANT. <P>
* Also, note how we don't de-allocate nativeWebShell, that is done in
* the class that owns the nativeWebShell reference, WindowControlImpl.
* ImplObjectNative subclasses that further override delete() are <P>
<CODE><PRE>
BookmarksImpl.java
EventRegistrationImpl.java
NativeEventThread.java
WindowControlImpl.java
</PRE><CODE> <P>
* All other ImplObject subclasses don't have any local Ivars and thus
* don't need to override delete().
I've added a delete() method to BrowserControlImpl:
* Called from BrowserControlFactory.deleteBrowserControl() <P>
* The order of deletion of objects is very important! <P>
* We don't allow deletion if the Canvas is showing. <P>
In BrowserControlImpl's delete(), the important delete()s is for
WindowControlImpl:
* First, we delete our eventThread, which causes the eventThread to
* stop running. Then we call nativeDestroyInitContext(), which
* deallocates native resources for this window.
As stated above, NativeEventThread.delete() is called:
* This is a very delicate method, and possibly subject to race
* condition problems. To combat this, our first step is to set our
* browserControlCanvas to null, within a synchronized block which
* synchronizes on the same object used in the run() method's event
* loop. By setting the browserControlCanvas ivar to null, we cause the
* run method to return.
After all of this deleting, we return from
BrowserControlFactory.delete().
edburns%acm.org
ashuk%eng.sun.com