On Sun, 19 Jul 2026 13:01:42 GMT, John Hendrikx <[email protected]> wrote:
>> This provides and uses a new implementation of `ExpressionHelper`, called >> `ListenerManager` with improved semantics. >> >> See also #837 for a previous attempt which instead of triggering nested >> emissions immediately (like this PR and `ExpressionHelper`) would wait until >> the current emission finishes and then start a new (non-nested) emission. >> >> # Behavior >> >> |Listener...|ExpressionHelper|ListenerManager| >> |---|---|---| >> |Invocation Order|In order they were registered, invalidation listeners >> always before change listeners|(unchanged)| >> |Removal during Notification|All listeners present when notification started >> are notified, but excluded for any nested changes|Listeners are removed >> immediately regardless of nesting| >> |Addition during Notification|Only listeners present when notification >> started are notified, but included for any nested changes|New listeners are >> never called during the current notification regardless of nesting| >> >> ## Nested notifications: >> >> | |ExpressionHelper|ListenerManager| >> |---|---|---| >> |Type|Depth first (call stack increases for each nested level)|(same)| >> |# of Calls|Listeners * Depth (using incorrect old values)|Collapses nested >> changes, skipping non-changes| >> |Vetoing Possible?|No|Yes| >> |Old Value correctness|Only for listeners called before listeners making >> nested changes|Always| >> >> # Performance >> >> |Listener|ExpressionHelper|ListenerManager| >> |---|---|---| >> |Addition|Array based, append in empty slot, resize as needed|(same)| >> |Removal|Array based, shift array, resize as needed|(same)| >> |Addition during notification|Array is copied, removing collected >> WeakListeners in the process|Appended when notification finishes| >> |Removal during notification|As above|Entry is `null`ed (to avoid moving >> elements in array that is being iterated)| >> |Notification completion with changes|-|Null entries (and collected >> WeakListeners) are removed| >> |Notifying Invalidation Listeners|1 ns each|(same)| >> |Notifying Change Listeners|1 ns each (*)|2-3 ns each| >> >> (*) a simple for loop is close to optimal, but unfortunately does not >> provide correct old values >> >> # Memory Use >> >> Does not include alignment, and assumes a 32-bit VM or one that is using >> compressed oops. >> >> |Listener|ExpressionHelper|ListenerManager|OldValueCaching ListenerManager| >> |---|---|---|---| >> |No Listeners|none|none|none| >> |Single InvalidationListener|16 bytes overhead|none|none| >> |Single ChangeListener|20 bytes overhead|none|16 bytes overhe... > > John Hendrikx has updated the pull request incrementally with one additional > commit since the last revision: > > Fix warnings I think what you listed in the first code block is good, as it always unlocks even if an exception is thrown (and if not, all is well). The second question about eating (I mean, forwarding) the exception coming from a listener and then continue calling other listeners, if I understand you correctly, is a different issue. It might be a better approach, but I don't know the implications. I noticed that javafx feels more brittle when something breaks wrt Swing. In Swing the program typically continues maybe with some broken components, but in javafx the whole layout is gone, and often reloading the pane does not help (like in the monkey tester, when switching to a different page and back re-creates the page). Also, what if it's not an `Exception` but an `Error` ? Do we want to catch Throwable and forward everything to the `uncaughtExceptionHandler`? I often do in my apps, but the next question is what do we do if the app wants to catch the exceptions instead of using the `uncaughtExceptionHandler`? ------------- PR Comment: https://git.openjdk.org/jfx/pull/1081#issuecomment-5038958472
