RFR: JDK-8290310: ChangeListener events are incorrect or misleading when a nested change occurs [v8]

[John Hendrikx]

> 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 WeakListeneres in the process|Tracked (append at end)|
> |Removal during notification|As above|Entry is `null`ed|
> |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 that are made to a property that is currently in the process of notifying its listeners. This all occurs on the same thread, and a nested change is nothing more th...

John Hendrikx has updated the pull request incrementally with one additional commit since the last revision:

  Prevent removal of weak listeners during unlock

-------------

Changes:
  - all: https://git.openjdk.org/jfx/pull/1081/files
  - new: https://git.openjdk.org/jfx/pull/1081/files/b97c574a..09feb52c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1081&range=07
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1081&range=06-07

  Stats: 176 lines in 2 files changed: 156 ins; 10 del; 10 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