DOM objects referenced as JavaScript objects can still be deleted. For instance, load the code below into a Mozilla window. Click the "Make a Window" button. Close that window and then click the "Talk about that Window" button and cover your head. The window has been deleted in spite of the fact that it's still referenced by an otherwise valid JavaScript object.. <?xml version="1.0"?> <?xml-stylesheet href="xul.css" type="text/css"?> <!DOCTYPE window> <!-- Simple sample interface for bringing up a nonmodal dialog --> <xul:window xmlns:html="http://www.w3.org/TR/REC-html40" xmlns:xul ="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul" title = "Dialog creation sample"> <html:script> var lastWindow = null; // make a window function MakeWindow() { return window.open("http://www.mozilla.org", "new"); } // pick some random property of a window and dump it to debug output function PeekWindow(theWindow) { dump("get ready to crash...\n"); dump(theWindow.screenX + "\n"); dump("all done crashing\n"); } </html:script> <xul:toolbox> <xul:toolbar> <xul:titledbutton value="Make a Window" onclick="lastWindow=MakeWindow()" style="background-color:rgb(192,192,192);"/> <xul:titledbutton value="Talk About That Window" onclick="PeekWindow(lastWindow)" style="background-color:rgb(192,192,192);"/> </xul:toolbar> </xul:toolbox> </xul:window>

You'll probably find that the nsGlobalWindow instance sticks around as it should, but it's possible that a weak reference that it maintains somehow doesn't get cleared. Will look at it soon. Tom, feel free to comment on this.

Fixed on 6/14/99. We now have slightly different reference counting rules for nsGlobalWindow. The global JSObject now maintains a live reference to the nsGlobalWindow. The circular reference (the nsGlobalWindow has a JS root corresponding to the global object) is broken when the containing webshell tells us it's going away. The nsGlobalWindow stays around as long as the reference to the global JSObject stays around. It also tries to deal gracefully with being orphaned.