> 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 overhead| > |Multiple listeners|57 + 4 per listener (excluding unused slots)|57 + 4 per > listener...
John Hendrikx has updated the pull request incrementally with three additional commits since the last revision: - Small fixes from review comments - Use switch expression where reasonable - Update docs regarding NullPointerExceptions ------------- Changes: - all: https://git.openjdk.org/jfx/pull/1081/files - new: https://git.openjdk.org/jfx/pull/1081/files/5863932f..3c385444 Webrevs: - full: https://webrevs.openjdk.org/?repo=jfx&pr=1081&range=11 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1081&range=10-11 Stats: 84 lines in 4 files changed: 13 ins; 32 del; 39 mod Patch: https://git.openjdk.org/jfx/pull/1081.diff Fetch: git fetch https://git.openjdk.org/jfx.git pull/1081/head:pull/1081 PR: https://git.openjdk.org/jfx/pull/1081
