Most nsIDocumentObservers don't care about all the 20 notifications on that interface, yet we send the notifications for all of them to every observer (most of whom just return NS_OK; from nearly all the functions). We should fix that.

Two possibilities we have come up with: (a) pass a flag when you register as an observer saying what notifications you want to receive; (b) break it down into a few smaller, saner observer interfaces where people are more likely to listen to all or most of the events I prefer (b) breaking it down. Here is a VERY ROUGH START at this that should be sort of reasonable: nsIDocumentContentChangeObserver { BeginUpdate EndUpdate ContentChanged ContentStatesChanged AttributeChanged ContentAppended ContentInserted ContentRemoved ContentReplaced } nsIDocumentStyleObserver { StyleSheetAdded StyleSheetRemoved StyleSheetDisabledStateChanged StyleRuleChanged StyleRuleAdded StyleRuleRemoved } nsIDocumentObserver { BeginLoad EndLoad BeginReflow EndReflow DocumentWillBeDestroyed } The positioning of StyleSheetAdded/Removed/Disabled, and ContentStatesChanged, may be wrong--this is a rough sketch that seems to fit things pretty well without being totally horrible. BeginReflow/EndReflow, however, seem like they should be notifications from the PresShell, though, another possible change.

https://bugzilla.mozilla.org/show_bug.cgi?id=1472046 Move all DOM bugs that haven’t been updated in more than 3 years and has no one currently assigned to P5. If you have questions, please contact :mdaly.