Dear John:
I'm unsure what the JEP format would contribute here
The benefit of JEP format is
a) to explicitly state the problem being solved (in the Motivation
section)
b) to enumerate the public APIs
I have several proposals, and some are too big for a single proposal
(IMHO) which would you like me to focus on?
The main reason I am asking you to go through the process is because
you effectively blocked by InputMap proposal. I keep hearing that my
proposal is not good for various reasons, while there is a much better
way for doing things, so let’s see it in full detail. It would be
nice to have proof-of-concept code based on a complex control rather
than a simple Button, but it is not a requirement, at least initially.
I still want to see code examples (pseudo code is fine) for my questions:
Q1. Changing an existing key binding from one key combination to another.
Q2. Remapping an existing key binding to a different function.
Q3. Unmapping an existing key binding.
Q4. Adding a new key binding mapped to a new function.
Q5. (Q1...Q4) scenarios, at run time.
Q6. How the set behavior handles a change from the default skin to a
custom skin with some visual elements that expects input removed, and
some added.
Q7. Once the key binding has been modified, is it possible to invoke
the default functionality?
Q8. How are the platform-specific key bindings created?
Q9. How are the skin-specific (see Q6) handlers removed when changing
the skins?
Q10. When a key press happens, does it cause a linear search through
listeners or just a map lookup?
I think it is important to answer all questions during the discussion,
as it helps all sides to understand how things work, and possibly make
corrections. Since the bulk of my proposal deals with key bindings
and user-/skin- installed handlers, I would like to see how you
propose to deal with these problems.
Another reason I asked you for a JEP is that you seem to brush aside
my objections. For example, my objection to the stateless behavior
was dealt with by inventing BehaviorContext, which I basically take as
an acknowledgement that behaviors are not stateless. So let’s see
exactly you envision things by describing the public API and perhaps
the proof of concept code should also have two non-trivial controls,
just to see whether BehaviorContext depends on the control class or not.
How key bindings are done is IMHO more of an implementation detail of
**specific** behaviors,
I categorically disagree with this statement. As an application
developer, I want to be able to set/modify/unmap key bindings via
common public mechanism, make sure that the user mappings and handlers
always take precedence over the skin ones, and make sure that skin
changes leave the user mappings and handlers in place.
It is certainly not an implementation detail and not a property of any
specific behavior.
Thank you, and I am looking forward to seeing answers to the questions
posted earlier.
-andy
*From: *John Hendrikx <john.hendr...@gmail.com>
*Date: *Saturday, October 28, 2023 at 12:55
*To: *Andy Goryachev <andy.goryac...@oracle.com>,
openjfx-dev@openjdk.org <openjfx-dev@openjdk.org>, Kevin Rushforth
<kevin.rushfo...@oracle.com>
*Subject: *Re: [External] : Re: Proof of concept pull request for
Behavior API (PR 1265)
Hi Andy,
On 27/10/2023 19:10, Andy Goryachev wrote:
Dear John:
I think our goal is for all of us to agree on a solution which
solves the problems. We are still talking, right?
I have to say - it is very difficult to have a meaningful
conversation when questions are not being answered. It is even
more difficult to do over email and time zones, as the context can
often be lost.
I'm really a bit surprised, as I think I responded quite quickly to a
lot of the posts surrounding the proposals, and also answered quite a
lot of questions. The mailinglist format seems to have served Java
quite well for this purpose for years now, and if memory serves,
earlier FX proposals also were discussed here. I'm unsure what the
JEP format would contribute here, given that it does not allow for
inline comments or threads, but I'm not unwilling to try my hand at one.
To reiterate, a proposal in a JEP format would be nice, so we can
see the public API.
Alright, this will take a bit of time. I have several proposals, and
some are too big for a single proposal (IMHO) which would you like me
to focus on?
1. A public Behavior API with the initial focus on being able to reuse
and replace default behaviors
This proposal would like to achieve a clear definition of a Behavior
and clear separation (to aid in reusability and creation). It would
define a Behavior interface, and a clean way of
installing/uninstalling a behavior on controls. This would be
primarily the Behavior/BehaviorContext part of my sample PR
https://github.com/openjdk/jfx/pull/1265
<https://urldefense.com/v3/__https:/github.com/openjdk/jfx/pull/1265__;!!ACWV5N9M2RV99hQ!LvWBWlmjB-JYcKnpZTbvjYwd1CItXTmycfx2D-BYmkbS7lxG6f4kwt2bmokpBwh63Gg_MNX5JzP747J1wgPuPY6Rq1H1$>,
leaving the more controversial event definition parts out for now
1.1. A possible extension of the above Behavior API to allow changing
high level behavior
I'm not sure yet what would be a good approach here. I would probably
either lean towards reusing the Event system for this, or doing this
with overridable methods; ie. in order to override a function, listen
for its event and call different code or trigger a different event;
or, ensure there is an overridable method so it can be overriden
directly in code.
1.2. An extension to the above behavior API to allow for more user
friendly key rebinding
The idea here would be to create a custom behavior (allowed by 1.),
call into a behavior you want to modify to install its defaults, and
then make changes after. There is more than one possible approach
here. One I raised earlier was offering more specific methods on
BehaviorContext. Another possiblity is to make it specific to certain
behaviors only (MappableBehavior), or behaviors that can somehow
provide an InputMap (without entangling everything).
2. An improved event handling system (Michael Strauss already did some
work there) that would allow users to override or disable default
event processing
This would be a low-level improvement that would allow 3rd parties to
override large parts of JavaFX in a supported manner. It would open
the way to a 3rd party behavior system or navigation system, but also
simpler things like just changing a key mapping, even ones claimed by
behaviors currently. As it is a low level API, this would be somewhat
cumbersome for seemingly simple tasks, and the various platforms would
need to be supported manually.
In essence the above proposal would allow user installed event
handlers to receive any event before a default handler can get to it,
so that say remapping the LEFT_ARROW key is actualy possible and
doesn't magically disappear (many new users, including me at the time
were/are somewhat surprised that an event handler installed on the
control is not receiving all events). The root cause of this is the
sharing of the event handling lists on the control with (magically)
installed behaviors. The above proposal would change this (in a
backwards compatible way) to work more like how default exception
handlers work -- only unconsumed events that bubble up to the root
level are considered for default behavior actions.
------
As you can see, one my problems with answering the key rebinding
questions is that IMHO this more of a later extension on a Behavior
API; this means to get to the key remapping design, there first would
need to be a Behavior API design. How key bindings are done is IMHO
more of an implementation detail of **specific** behaviors, as there
are probably more ways to do this. So for my proposals, a somewhat
fleshed out Behavior API design is an important prerequisite before
offering key rebinding.
If we can advance this design far enough, we may see a way to do this
without needing a Behavior API first; for example, we could have a
Behavior interface, and a subtype, MappableBehavior; only behaviors of
that sub type support key remapping, while general behaviors don't
have to. This would make the key rebinding just something that
**some** behaviors support, and not a general feature if it instead
was added to say Control, Behavior or BehaviorContext. This may be a
short cut that we could take to get to key rebinding quickly, without
closing off a future behavior API.
Again, thanks for reading, I look forward to some feedback, and as
said, I will try put some time towards writing a JEP. I'm also happy
to collaborate on this once a design direction becomes a bit more clear.
--John
Please, if you have time, answer these questions. A short
pseudo-code example will be fine.
Q1. Changing an existing key binding from one key combination to
another.
Q2. Remapping an existing key binding to a different function.
Q3. Unmapping an existing key binding.
Q4. Adding a new key binding mapped to a new function.
Q5. (Q1...Q4) scenarios, at run time.
Q6. How the set behavior handles a change from the default skin to
a custom skin with some visual elements that expects input
removed, and some added.
Q7. Once the key binding has been modified, is it possible to
invoke the default functionality?
Q8. How are the platform-specific key bindings created?
Q9. How are the skin-specific (see Q6) handlers removed when
changing the skins?
Q10. When a key press happens, does it cause a linear search
through listeners or just a map lookup?
Lastly, I do think prototyping the alternative proposal using
simple control like Button is insufficient. TextArea would be
much better, as it has a ton of key bindings, platform-specific
logic, various handlers that do and do not consume events by default.
Thank you
-andy
P.S. I noticed that I switched my PR to Open by mistake. Sorry,
it’s back in Draft.
*From: *John Hendrikx <john.hendr...@gmail.com>
<mailto:john.hendr...@gmail.com>
*Date: *Thursday, October 26, 2023 at 02:15
*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>, Kevin
Rushforth <kevin.rushfo...@oracle.com>
<mailto:kevin.rushfo...@oracle.com>
*Subject: *Re: [External] : Re: Proof of concept pull request for
Behavior API (PR 1265)
The normal procedure I think is also to first provide a JEP for
review, before starting on the implementation...
Given the doubts raised, feedback given and potential alternatives
proposed, I don't see why you are still moving forward with your
own proposal. The critiques I've given have been mostly hand waved
with arguments that have no place in JEP evaluation (time
restrictions, existing code already works this way, false
equivalency with MVC pattern), and therefore have IMHO not been
taken serious at all.
This leaves me in the position of putting in a lot of work that
will essentially be ignored as I feel an (internal) decision has
already been reached, regardless of the feedback on the mailinglist.
The (partial) proposal I've made, and also simpler proposals so
that 3rd parties could do a keybinding implementation, should be
sufficient to reconsider the current proposal that is being moved
forward.
I'll reiterate my problems with your proposal:
- Introduces a lot of API for what is essentially the
configuration of internal event handlers
- The proposed API partially overlaps with the existing event
handler API, meaning that some keys could be changed with just
event handlers, while some can only be changed with the
BaseBehavior API; it also provides for creating new functions and
assigning them to keys, essentially a new (very limited) API for
what was already possible in the much more flexible event handling API
- Introduces the term "Behavior" in public API without clearly
specifying what that is, nor showing enough forethought that may
make it possible in the future to have public Behaviors
- Introduces the term "InputMap" in public API, which is just an
implementation detail of the internal event handlers
- Doesn't address the real issue IMHO, which is that JavaFX
Skins/Behaviors install their Event Handlers directly on Controls,
mixing them with user event handlers leading to all sorts of
unpredictable behavior due to call order and internal handlers
essentially stealing and consuming events before the user has a
chance to look at them (and thus blocking any 3rd party key
alterations) which leads to the (false) need to change key
bindings and Behaviors directly...
So if you want me to work on such a proposal, fully fleshing it
out, I would like to know if it will be given consideration. I
would also like some more feedback on what is already there, as I
think it is sufficient to decide if a full proposal is worth it or
not.
My proposals in short:
1.
- Fix the issues with Events being stolen before users can get a them
- Users should be able to have priority on Events, Michael
Strauss already has a PR that fixes the issue in part
- Events should not be consumed when not used (navigation does
this) as this precludes the user being able to change their meaning
- Even better would be if internal event handlers were
isolated and did not mix themselves with user event handlers at all
The above can be done separately, and should already make it
possible to do a lot of things that were close to impossible
before when it comes to changing key handling, but certainly not
everything.
- Building on top of the improved event handling system, introduce
a flag to indicate an event is not to be consumed by internal
event handlers
These two together can form the basis for a 3rd party Behavior
implementation as standard behavior can be prevented from
occurring. It leaves platform dependent behavior to be addressed
by such a 3rd party / user implementation as it is a very low
level API. Any key remapping logic would be provided by the 3rd
party API.
2.
I also have a more fleshed out alternative proposal that attempts
to introduce Behaviors into JavaFX as a first class concept,
instead of a potential 3rd party add-on. Recap:
- Introduce a Behavior interface with a single method "install" to
be called by a Control
- The "install" method is provided a context object,
BehaviorContext. This indirects any changes the Behavior can make
to a Control, so the Control is fully aware of all changes and can
uninstall them without further co-operation from the behavior.
- The BehaviorContext provides low level functions to add/remove
event handlers and listeners, but can also provide higher level
functions (in perhap a later PR) to allow for some kind of control
provided input map system
- Standard Behaviors can be made public and can be easily
subclassed or composed as they need not have any state. State is
tracked inside the behavorial installed listeners and handlers
themselves (either directly or by referring to some shared State
object).
- Clear separation of concerns; Behaviors, a resuable concept that
can be applied to a control; BehaviorContext, manages behavior
lifecycle by abstracting away direct Control access; behavior
state management left up to the implementation and created (on
demand and as needed) when "install" is called.
- Indirection from key mapping to semantic meaning is provided by
introducing control specific events. These semantic events can be
handled, filtered and consumed like all other events, allowing for
changing/remapping/blocking or ignoring; this part can be left out
from an initial implementation to further evaluate how such events
might interact with Skins that need specific events (there is
nothing stopping us from having some of these semantic events be
handled by the Control directly, and some by the specific needs of
the Skin)
To get at the internal key mappings, you'd need to subclass or
compose a Behavior. The Behaviors are setup to allow this
easily. To modify the bindings of a Control, one would install
such a modified Behavior as a whole; overkill perhaps for one
binding change, but convenient when multiple bindings are changed,
and reusable accross controls (the Behavior only need to be
created once).
The proposal also includes an indirection between Key/Mouse event
and its semantic meaning. This is achieved by firing higher level
more meaningful events, but that's not the only option; it could
also be done with overridable methods on the Behavior, or a
behavior specific interface if the Event based proposal is seen as
too audacious.
This proposal advocates a clear seperation of the Behavior from
the Skin, essentially making them Controller and View, where the
View has no knowledge of the Controller. I see no reason why this
wouldn't be possible, given that it is a standard pattern. That
existing controls may be difficult to untangle is IMHO irrelevant,
especially when this can be done one at a time. I realize that
Controllers (Behaviors) may have functions that are sort of View
(Skin) specific; this is not an issue, as it should be fine to
trigger a behavior without it being consumed; unconsumed
behaviorial events just bubble up. This allows Behaviors to have
events specific to a Skin without them interfering if they're
unused by an alternative Skin. An alternative Skin that also
needs new behavior will also need to create a new behavior to go
along with it (or when paired with the standard one, accept that
those new behaviors won't be triggered).
Thanks for reading.
--John
On 26/10/2023 00:59, Andy Goryachev wrote:
Dear John:
It is difficult to review the alternative proposal for a
number of reasons. A prototype is a good start, but for any
proposal to go forward we need a bit more work. Let me
enumerate the steps that we expect:
1. Provide an overview of the proposal following a JEP outline:
*Summary*
*Goals*
*Non-Goals*
*Motivation*
*Description*
*Alternatives*
*Risks and Assumptions*
*Dependencies*
2. A draft PR that provides a proof of concept, using, in this
case, a few complex controls like TextArea, TableView, ComboBox.
3. Address the question raised earlier, perhaps by providing
code examples (pseudo code is acceptable, I think).
More specifically, I’d like to know how the following concerns
will be addressed by the new proposal:
Q1. Changing an existing key binding from one key combination
to another.
Q2. Remapping an existing key binding to a different function.
Q3. Unmapping an existing key binding.
Q4. Adding a new key binding mapped to a new function.
Q5. (Q1...Q4) scenarios, at run time.
Q6. How the set behavior handles a change from the default
skin to a custom skin with some visual elements that expects
input removed, and some added.
Q7. Once the key binding has been modified, is it possible to
invoke the default functionality?
Q8. How are the platform-specific key bindings created?
Q9. How are the skin-specific (see Q6) handlers removed when
changing the skins?
Q10. When a key press happens, does it cause a linear search
or a map lookup?
Thank you
-andy
*From: *John Hendrikx <john.hendr...@gmail.com>
<mailto:john.hendr...@gmail.com>
*Date: *Tuesday, October 24, 2023 at 04:58
*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] : Re: Proof of concept pull request
for Behavior API (PR 1265)
On 23/10/2023 23:57, Andy Goryachev wrote:
You'd create a new class, `MyBehavior`,
By “customizing” I also mean at run time. Creating new
classes wouldn’t work.
This would also work at runtime, as the class you create can
be instantiated with parameters that control its key binding
behavior. Even though the standard Behaviors should probably
be singletons (so they can be reused and composed) or have
public well documented constructors, a custom behavior created
by the user has no such re-usability restrictions.
coupling
I don’t think it is our choice - it is up to the skin
designed. If they add a node that needs to take input, or
if the behavior is drastically different, it is almost
impossible to create a common interface. So skin and
behaviors are coupled, besides we have to design for the
worst case (of a totally different skin). The division
between S and B comes mostly from the division between V
and C in MVC. From a distance, the user does not see it
at all - all they see is a control.
JavaFX is not doing MVC.
In MVC, the 3 components are not entangled; Model refers View,
Controller refers View and Model, View refers nothing; in
JavaFX the View (Skin) creates the Controller (Behavior); the
View especially normally can be created without any
dependencies, and can be tested as such; with Skins being
tightly coupled to both Behaviors and Controls, that doesn't
even come close.
For it to be MVC you'd need to:
- Remove reference from Skin to Control
- Do not let Skins create Behaviors
- Instantation order should be, create a Skin first (with no
Control reference), then create the Control (with Skin as
parameter or setter), then create a Behavior (with Control as
parameter, and one or more Views (Skins))
What JavaFX is exactly, I don't know. It doesn't follow MVC
(even though it claims to) because in the current setup the
Skin is both V and C; that's not MVC. At most it is MS (Model
Skin), and so there is no reason to expose anything beyond the
Skin then, as that would just be pretending to be something
that it is not.
This suggest another metric at judging the usefulness of a
design - how easy it is to understand and perform 80% of
most common tasks.
Now that I explained how key remappings would work, I don't
see how this would disqualify the alternative proposal.
There are more interesting ideas at the end of the message
I am replying to - fxml, css, global changes - these go
far beyond the simple input map improvement. I did
mention this already, but neither open source community,
nor my employer might have the resources to make such
drastic changes.
I didn't mention FXML, but yes, I gave some other things to
think about. As for how drastic any of those are, that
remains to be seen. Certainly the global changes would not be
that hard at all. The CSS proposal would need some research
if there is some will to go there; it assumes that the
information needed can be transported in a reasonable manner
to the key binding system using the existing CSS infrastructure.
So we have to be realistic, I think. We are travelling to
a different planet in a small spaceship and we only have
so much material and oxygen to play with. A simple
improvement that helps 80% of use cases might be better
than a major redesign (I still think the event proposal
involves major redesign).
I think that if that's the case that we'd better focus on
making it possible for 3rd parties to deliver these features,
and do the simplest thing that would allow them to do so. That
would be prioritized event handlers (so a 3rd party can always
intercept before the Skin/Behavior gets to it) + a flag to
skip system event handlers (ala consumed) to allow bubbling up.
On top of that any key remapping or behavior change system can
be constructed already.
--John
