Thank you, Phil and Kevin.
@Override
public final void setSkin(Skin<?> value) throws IllegalArgumentException {
-andy
*From: *Kevin Rushforth <kevin.rushfo...@oracle.com>
*Date: *Friday, 2022/07/22 at 14:20
*To: *Andy Goryachev <andy.goryac...@oracle.com>,
openjfx-dev@openjdk.org <openjfx-dev@openjdk.org>
*Subject: *Re: [External] : Aw: Proposal: Add Skin.install() method
No, sorry. Error doesn't communicate the right thing. This is exactly
is what RuntimeException is intended to be used for. It's no different
from passing an out of range numerical value or a null to a method
that doesn't take null. In all similar cases, the method will document
the exception cases with '@throws' javadoc tags, and the developer can
then understand that they passed something bad to the method. FWIW,
I've never seen any Java API throw Error in this manner.
-- Kevin
On 7/22/2022 2:02 PM, Andy Goryachev wrote:
I do mean java.lang.Error.
The goal is to prevent an incorrect code from being shipped to the
end user. There are no tools at the API level to enforce the 1:1
relationship, so it cannot be checked at compile time.
The next best thing is to fail during the development, thus an
Error. It should be an error and not a RuntimeException because
it communicates a design error, and not a run time, i.e. a
legitimate run time condition. It is also not an
IllegalArgumentException because there should be no scenario when
this could happen.
In other words, the condition should get fixed by a redesign
rather than by handling/ignoring an exception. As stated in the
Error javadoc
An Error is a subclass of Throwable that indicates serious
problems that a reasonable application should not try to catch.
Most such errors are abnormal conditions. The ThreadDeath error,
though a "normal" condition, is also a subclass of Error because
most applications should not try to catch it.
if this idea seems to radical, I am ok with making it an
IllegalArgumentException.
-andy
*From: *Kevin Rushforth <kevin.rushfo...@oracle.com>
<mailto:kevin.rushfo...@oracle.com>
*Date: *Friday, 2022/07/22 at 13:42
*To: *Andy Goryachev <andy.goryac...@oracle.com>
<mailto:andy.goryac...@oracle.com>, openjfx-dev@openjdk.org
<openjfx-dev@openjdk.org> <mailto:openjfx-dev@openjdk.org>
*Subject: *Re: [External] : Aw: Proposal: Add Skin.install() method
I don't know if you really meant Error, as in java.lang.Error, but
it would need to be a subclass of RuntimeException.
IllegalArgumentException seems the natural choice (a case could
possibly be made for IllegalStateException). Throwing an Error is
not the right thing for a library to do in response to an
application passing in an illegal or unexpected argument to a
method or constructor. It is for truly exceptional things that a
programmer cannot anticipate (like running out of memory).
-- Kevin
On 7/22/2022 12:37 PM, Andy Goryachev wrote:
I would rather throw an Error in Skinnable.setSkin() when
mismatch is detected. This is a design error that should be
caught early in development rather than a run time exception.
-andy
*From: *openjfx-dev <openjfx-dev-r...@openjdk.org>
<mailto:openjfx-dev-r...@openjdk.org> on behalf of Kevin
Rushforth <kevin.rushfo...@oracle.com>
<mailto:kevin.rushfo...@oracle.com>
*Date: *Friday, 2022/07/22 at 12:33
*To: *openjfx-dev@openjdk.org <openjfx-dev@openjdk.org>
<mailto:openjfx-dev@openjdk.org>
*Subject: *Re: [External] : Aw: Proposal: Add Skin.install()
method
I would not be in favor of adding a no-arg constructor to
SkinBase, for the reasons Andy gave. Additionally, there would
be no way to avoid braking the contract of Skin::getSkinnable
which says:
"This value will only ever go from a non-null to null value
when the Skin is removed from the Skinnable, and only as a
consequence of a call to dispose()."
At the very minimum, we should explain in Skin javadoc
that creating a skin for one control and setting it in the
other is a no-no. Or, perhaps we should explicitly check
for this condition in setSkin().
I agree completely. At a minimum this enhancement should
change the docs for setSkin to say that a skin created for one
control should not (must not?) be used in another control. And
unless there is a legitimate use case I haven't thought of, I
think we could consider an explicit check, and either throw an
Exception (this seems the best choice, unless there are
compatibility concerns), or else log a warning and treat it as
a no-op.
-- Kevin
On 7/22/2022 9:13 AM, Andy Goryachev wrote:
You do bring a good point! I don't know the rationale
behind passing control pointer to the Skin constructor.
I think Swing got it right, clearly separating
1. instantiation (using either a no-arg constructor, or
any other constructor that does not require component
pointer)
2. configuration (optional step, possibly widely
separated in time and space)
3. uninstallation of the old skin
4. installation of the new skin
What you are proposing - moving to a default constructor
makes the most sense. It comes with a high price though -
everyone with a custom skin implementation would need to
change their code.
At the very minimum, we should explain in Skin javadoc
that creating a skin for one control and setting it in the
other is a no-no. Or, perhaps we should explicitly check
for this condition in setSkin().
Thank you
-andy
*From: *Marius Hanl <mariush...@web.de>
<mailto:mariush...@web.de>
*Date: *Friday, 2022/07/22 at 05:06
*To: *openjfx-dev@openjdk.org <openjfx-dev@openjdk.org>
<mailto:openjfx-dev@openjdk.org>, Andy Goryachev
<andy.goryac...@oracle.com> <mailto:andy.goryac...@oracle.com>
*Subject: *[External] : Aw: Proposal: Add Skin.install()
method
I had a similar idea in the past and like the idea.
Ideally, setting/switching a skin is a one step process.
Currently you can construct a skin for a control and set
it after to a different control.
Your approach sounds good, if you can set a skin by
creating a new skin (with a default constructor) and then
the setSkin() method will actually trigger the install
process on the control (this), this will work and solve
the problem above. But for backward compatibilty we still
need to keep the skin constructor with the control as
parameter and think about deprecating it.
-- Marius
Am 20.07.22, 23:40 schrieb Andy Goryachev
<andy.goryac...@oracle.com>
<mailto:andy.goryac...@oracle.com>:
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.
