On Mon, 17 Feb 2025 15:37:56 GMT, John Hendrikx <[email protected]> wrote:
>> This provides and uses a new implementation of `ExpressionHelper`, called
>> `ListenerManager` with improved semantics.
>>
>> # 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 overhead|
>> |Multiple listeners|57 + 4 per listener (excluding unused slots)|57 + 4 per
>> listener (excluding unused slots)|61 + 4 per listener (excluding unused
>> slots)|
>>
>> # About nested changes
>>
>> Nested changes are simply changes...
>
> John Hendrikx has updated the pull request incrementally with one additional
> commit since the last revision:
>
> Fix fix for regression :)
modules/javafx.base/src/main/java/com/sun/javafx/binding/ListenerManagerBase.java
line 41:
> 39: * @param <I> the type of the instance providing listener data
> 40: */
> 41: public abstract class ListenerManagerBase<T, I extends ObservableValue<?
> extends T>> {
Is this a class and not an interface because of the need for `protected`
methods?
-------------
PR Review Comment: https://git.openjdk.org/jfx/pull/1081#discussion_r1966029617
