Zitat von Andy Goryachev <andy.goryac...@oracle.com>:
Hi Andy,
good idea to move our discussion from the issues to the mailling -
it's both easier and reaches a broader audience :)
Will answer in about a week or so, for now just stumbled across
We can see the damage caused by looking at
JDK-8241364<https://bugs.openjdk.org/browse/JDK-8241364> ☂ Cleanup
skin implementations to allow switching, which refers a number of
bugs:
Hmm .. might be me, but looks like you are implying that with the
proposal in place (and used throughout our skins) those issues
wouldn't have existed? If that's not the case, could you please
clarify what you mean?. On the other hand, if yes, I disagree: the
majority of the issues (in particular those already fixed) are about
an incorrect/incomplete implementation of dispose - that's unrelated
to enhancing/cleaning up the install process. A subset (of the
unfixed) is indeed due to the parallel existence of two skins pointing
to the same control (and modifying its properties)
Cheers, Jeanette
Hi,
I'd like to propose an API change in Skin interface (details below).
Your feedback will be greatly appreciated!
Thank you,
-andy
Summary
-------
Introduce a new Skin.install() method with an empty default
implementation. Modify Control.setSkin(Skin) implementation to
invoke install() on the new skin after the old skin has been removed
with dispose().
Problem
-------
Presently, switching skins is a two-step process: first, a new skin
is constructed against the target Control instance, and is attached
(i.s. listeners added, child nodes added) to that instance in the
constructor. Then, Control.setSkin() is invoked with a new skin -
and inside, the old skin is detached via its dispose() method.
This creates two problems:
1. if the new skin instance is discarded before setSkin(), it
remains attached, leaving the control in a weird state with two
skins attached, causing memory leaks and performance degradation.
2. if, in addition to adding listeners and child nodes, the skin
sets a property, such as an event listener, or a handler, it
overwrites the current value irreversibly. As a result, either the
old skin would not be able to cleanly remove itself, or the new skin
would not be able to set the new values, as it does not know whether
it should overwrite or keep a handler installed earlier (possibly by
design). Unsurprisingly, this also might cause memory leaks.
We can see the damage caused by looking at
JDK-8241364<https://bugs.openjdk.org/browse/JDK-8241364> ☂ Cleanup
skin implementations to allow switching, which refers a number of
bugs:
JDK-8245145 Spinner: throws IllegalArgumentException when replacing skin
JDK-8245303 InputMap: memory leak due to incomplete cleanup on remove mapping
JDK-8268877 TextInputControlSkin: incorrect inputMethod event
handler after switching skin
JDK-8236840 Memory leak when switching ButtonSkin
JDK-8240506 TextFieldSkin/Behavior: misbehavior on switching skin
JDK-8242621 TabPane: Memory leak when switching skin
JDK-8244657 ChoiceBox/ToolBarSkin: misbehavior on switching skin
JDK-8245282 Button/Combo Behavior: memory leak on dispose
JDK-8246195 ListViewSkin/Behavior: misbehavior on switching skin
JDK-8246202 ChoiceBoxSkin: misbehavior on switching skin, part 2
JDK-8246745 ListCell/Skin: misbehavior on switching skin
JDK-8247576 Labeled/SkinBase: misbehavior on switching skin
JDK-8253634 TreeCell/Skin: misbehavior on switching skin
JDK-8256821 TreeViewSkin/Behavior: misbehavior on switching skin
JDK-8269081 Tree/ListViewSkin: must remove flow on dispose
JDK-8273071 SeparatorSkin: must remove child on dispose
JDK-8274061 Tree-/TableRowSkin: misbehavior on switching skin
JDK-8244419 TextAreaSkin: throws UnsupportedOperation on dispose
JDK-8244531 Tests: add support to identify recurring issues with
controls et al
Solution
--------
This problem does not exist in e.g. Swing because the steps of
instantiation, uninstalling the old ComponentUI ("skin"), and
installing a new skin are cleanly separated. ComponentUI
constructor does not alter the component itself,
ComponentUI.uninstallUI(JComponent) cleanly removes the old skin,
ComponentUI.installUI(JComponent) installs the new skin. We should
follow the same model in javafx.
Specifically, I'd like to propose the following changes:
1. Add Skin.install() with a default no-op implementation.
2. Clarify skin creation-attachment-detachment sequence in Skin and
Skin.install() javadoc
3. Modify Control.setSkin(Skin) method (== invalidate listener in
skin property) to call oldSkin.dispose() followed by newSkin.install()
4. Many existing skins that do not set properties in the
corresponding control may remain unchanged. The skins that do, such
as TextInputControlSkin (JDK-8268877), must be refactored to utilize
the new install() method. I think the refactoring would simply move
all the code that accesses its control instance away from the
constructor to install().
Impact Analysis
-------------
The changes should be fairly trivial. Only a subset of skins needs
to be refactored, and the refactoring itself is trivial.
The new API is backwards compatible with the existing code, the
customer-developed skins can remain unchanged (thanks to default
implementation). In case where customers could benefit from the new
API, the change is trivial.
The change will require CSR as it modifies a public API.
