[External] : Re: [Request for Comments] Behavior / InputMap

[Andy Goryachev]

Dear Martin:

This basically is the minimal API surface as far as InputMap is concerned.  There are probably some methods still missing, such as ...

Say I want Ctrl-J to be Copy instead of whatever it’s default binding is.


InputMap.unbind(FunctionTag.COPY); • missing method.  Or we could add InputMap.getKeyBindingfor(FunctionTag)

followed by

InputMap.registerKey(KeyBinding.ctrl(KeyCode.J), COPY);

So, basically, one or two methods are missing!



Any control will need to ensure that it ignore tags it doesn’t understand. Who cares if Ctrl-A maps to SELECT_ALL for a button? It will just ignore it.
But I do get your point. If we ask a Control to map an event to an operation we should ensure that the control actually supports that operation. So we don’t need multiple SELECT_ALL tags, just a verification step so we don’t return bogus tags.

Well, if we try to think of a union of all possible functions, it is just not right.  The functions have different semantics for different controls, even SELECT_ALL would be different, or there will be multiple flavors of SELECT_ALL or COPY.  I just don’t think it’s necessary.

Each control declares a bunch of public methods specific to that control, and also declares a method identifiers corresponding to these methods (that’s FunctionTags).  If we try to add a key binding to a button passing a function tag from TextArea it will essentially be ignored because Button does not have the corresponding method.

I don’t think there are methods that are common for *every* control.  So we have control-specific tags that might be in the control or its base class such as TextInputControl.

-andy

P.S. thank you for uncovering a gap in the API!




From: Martin Fox <martin at martinfox.com>
Date: Tuesday, October 31, 2023 at 16:21
To: Andy Goryachev <andy.goryachev at oracle.com>
Cc: Kevin Rushforth <kevin.rushforth at oracle.com>, openjfx-dev <openjfx-dev at openjdk.org>
Subject: Re: [External] : Re: [Request for Comments] Behavior / InputMap
Andy,

I should have been clearer on why I wrote this up. I think once you’ve identified the minimum API surface that’s probably all you should implement.

More important to me is whether reducing the API to a bunch of function tags and two API calls does everything that needs to be done. For example, that reduction means you can’t enumerate the list of function tags a control supports or the full set of key bindings. Is that an issue? Is there a use case for these enumerations?


3) Provide an API that asks a control to map an Event to a FunctionTag. This enables blocking existing mappings; if a user wants to block the default mappings for, say, COPY they can simply discard/consume any events that the control would map to COPY.

Supported via InputMap.registerFunction(FunctionTag, Runnable).  Just do registerFunction(COPY, () -> { }).

Sorry I didn’t make myself clear. Say I want Ctrl-J to be Copy instead of whatever it’s default binding is. The flow would be:

if the event is Ctrl-J
ask the control to perform the COPY operation
else if the control maps this event to COPY
discard the event (it’s the default binding)

They are not.  There is no SELECT_ALL in Button control, for example.  Where the hierarchy exists, so does the hierarchy of tags, for example TextInputControl.SELECT_ALL which is applicable/used in TextField and TextArea.  But we can’t extend it to TableView, for example, as there is no common ancestor - unless we invent one (an interface).

Any control will need to ensure that it ignore tags it doesn’t understand. Who cares if Ctrl-A maps to SELECT_ALL for a button? It will just ignore it.

But I do get your point. If we ask a Control to map an event to an operation we should ensure that the control actually supports that operation. So we don’t need multiple SELECT_ALL tags, just a verification step so we don’t return bogus tags.



What do you think?

Thank you
-andy



From: Martin Fox <martin at martinfox.com>
Date: Monday, October 30, 2023 at 17:24
To: Andy Goryachev <andy.goryachev at oracle.com>
Cc: Kevin Rushforth <kevin.rushforth at oracle.com>, openjfx-dev <openjfx-dev at openjdk.org>
Subject: [External] : Re: [Request for Comments] Behavior / InputMap
I was looking over the InputMap proposal with an eye toward paring it down to the bare minimum.

From the perspective of a user who wants to manipulate a control without subclassing it I think there are only a few essential components.

1) Ensure the user gets events before the control does. That’s a topic for a different thread.

2) Provide an API that asks a control to perform the operation identified by a FunctionTag. This is the only way to access operations like COPY and MOVE_RIGHT that are implemented behind the scenes.

3) Provide an API that asks a control to map an Event to a FunctionTag. This enables blocking existing mappings; if a user wants to block the default mappings for, say, COPY they can simply discard/consume any events that the control would map to COPY.

If a user wants to subclass an existing control they could also use these API’s to do full customization but only if they can guarantee that their subclass will process events before the superclass. That, too, might be a separate discussion.

I would like to discuss these API’s without getting too deep into implementation details. With that said, I do have one implementation suggestion: since most of the event => FunctionTag mappings are common (SELECT_ALL is always Shortcut+A) there should be an internal shared object containing the common mappings.

Martin



On Oct 30, 2023, at 3:11 PM, Andy Goryachev <andy.goryachev at oracle.com> wrote:

Dear Kevin:

Thank you for providing a summary to our (lively) discussion.  Even though I think I answered these concerns, I don’t mind to have another go at it.

Please find the updated proposal here (same link):

https://gist.github.com/andy-goryachev-oracle/294d8e4b3094fe16f8d55f6dd8b21c09<https://urldefense.com/v3/__https:/gist.github.com/andy-goryachev-oracle/294d8e4b3094fe16f8d55f6dd8b21c09__;!!ACWV5N9M2RV99hQ!MAhFywXruyvFlvk6whGVWBb9fTI-f1D-16YuJbRGdJe52rX503CFBK8S6IamyzPVzQBcJZmg6c_Jh1CfsDxVFw$>

Let me first define what I mean by “behavior” in the context of this proposal.  A behavior is a translation layer between input events - coming either from the control, or from some nodes contained in the skin, or from the platform itself - into some actions.  These translation mappings are maintained by a new property in Control - the InputMap.  The InputMap has two sides - one for the user application, and another - for the skins/behaviors.  Both are “public APIs” but the latter is represented as protected methods of BehaviorBase class which forms a foundation of the behavior part of the skins that want to use the InputMap paradigm.

Back to individual concerns.

* We should not make anything related to Behaviors public without a full design of how Behaviors should work, what their responsibilities are, how they interact with Skins



And we don’t.  We recommend to use BehaviorBase, but it’s still possible to use event handlers or any other home-grown mechanism to implement skins/behaviors and suffer from the lack of functionality as a result.  If BehaviorBase is not the right name, we can call it InputMapAccessorForSkinUse any other name.

* This proposal doesn't solve the coupling of Skins and behaviors

The skins and behaviors are tightly coupled in some cases.  It is possible that a simple control such as Button does not require tight coupling, but a complex control such as TextArea does (see TextAreaSkin:1214).

With the InputMap, we now can separate user mappings from skin mappings and handlers.  Changing a skin will unregister all of the handlers added by the associated behavior, leaving the user mappings intact.

* Function tags are defined in control class, but don't match the functionality of control class
NOTE: this begs the question of whether there should always be a method on control for each such function (even if the implementation just delegates to the behavior



May be it was not described extensively, but it is being suggested to have one public method for each function tag, which does invoke the said tag.  This enabled indirection via InputMap which in turn allows the app- or skin- developer to redefine the functionality (in effect, allowing for changing the behavior without subclassing the behavior).

So, for example, SomeControl.copy() would invoke execute(TAG_COPY), which by default would invoke SomeControlBehavior.copy().

This proposal did not make this change for the subset of controls - intentionally - because it can be done later in a separate PR.

* An input map should not refer to the node and be stateless and sharable among all (or some) instances of the same class; this would mean mapping input events to Control::method rather than to instance::method or to some arbitrary lambda
NOTE: this would depend on the previous being resolved

I think we are confusing two things.  The InputMap allows for per-control mapping, so it cannot be shareable or static.  Period.

Now, the other thing is a possible requirement to allow for changing the mapping on per-control-type basis, to overwrite the behavior for each instance of a particular control.  This I did not address because it’s an implementation detail for that control type.  I did not want to add child maps, but perhaps we could add another API to the skin/behavior side of InputMap to allow for such a static map.

Personally, I don’t like the idea as it basically adds nothing: event handlers still need to be added to each control and each Node in the skin (if any) and there is an extra complexity added.  A better solution would be to subclass the control class and add the mappings for each instance just like we do today.

* Arbitrary key mapping seems out of scope for the core of JavaFX; this sort of mapping could be done by the application if the event order problem was solved, and if we had public API on control for all functions that are called by the behavior.

Arbitrary (user) key bindings are enabled by the proposed InputMap.  Any alternative proposal, in my opinion, should support this function out of the box.

* Should Input map be immutable?

The value of InputMap is ability to change the mapping, so I don’t understand where this requirement is coming from.  Perhaps an example or a use case could be provided?

* Changes to the Behavior system should focus on replacing complete behaviors, and being able to use these by default for a certain subset of controls (like -fx-skin provide in CSS)



As I mentioned earlier, the skin and its behavior might be tightly coupled.  So if a use case exists for changing the behavior, we already have a solution - a custom skin.  May be a use case or an example of why we can’t do that with the existing architecture would help here.

And finally, I would like to emphasize that even though the InputMap proposal is fairly well developed and validated using a number of non-trivial controls and some new controls (RichTextArea https://github.com/andy-goryachev-oracle/jfx/pull/1<https://urldefense.com/v3/__https:/github.com/andy-goryachev-oracle/jfx/pull/1__;!!ACWV5N9M2RV99hQ!MAhFywXruyvFlvk6whGVWBb9fTI-f1D-16YuJbRGdJe52rX503CFBK8S6IamyzPVzQBcJZmg6c_Jh1ACM9EGvA$> ), I am not against modifying/enhancing it based on the community feedback.  I hope we can get to a good solution in a reasonable time frame, or we all would have to learn react and program in javascript.

Cheers,
-andy





From: openjfx-dev <openjfx-dev-retn at openjdk.org> on behalf of Kevin Rushforth <kevin.rushforth at oracle.com>
Date: Friday, October 27, 2023 at 16:34
To: openjfx-dev <openjfx-dev at openjdk.org>
Subject: Re: [Request for Comments] Behavior / InputMap
I've mostly caught up on the (lively) discussion surrounding this feature request.

It is clear that we do not yet have general agreement on the direction this proposal should take, so let's continue to discuss the proposal, its shortcomings, and any alternative approaches.

We should start by making sure that the motivation for doing this -- what problem is being solved -- is well understood. Andy will rework the initial sections of the proposal to make it more clear.

If I can summarize what I see are the main concerns that have been raised:

* We should not make anything related to Behaviors public without a full design of how Behaviors should work, what their responsibilities are, how they interact with Skins

* This proposal doesn't solve the coupling of Skins and behaviors

* Function tags are defined in control class, but don't match the functionality of control class
NOTE: this begs the question of whether there should always be a method on control for each such function (even if the implementation just delegates to the behavior

* An input map should not refer to the node and be stateless and sharable among all (or some) instances of the same class; this would mean mapping input events to Control::method rather than to instance::method or to some arbitrary lambda
NOTE: this would depend on the previous being resolved

* Arbitrary key mapping seems out of scope for the core of JavaFX; this sort of mapping could be done by the application if the event order problem was solved, and if we had public API on control for all functions that are called by the behavior.

* Should Input map be immutable?

* Changes to the Behavior system should focus on replacing complete behaviors, and being able to use these by default for a certain subset of controls (like -fx-skin provide in CSS)

There are probably other concerns as well.

Finally, one of the comments made, which I completely agree with, is that API design needs to come first. It needs to be fully fleshed out, and needs to be forward-looking. We should only expose as public API what is needed to solve the problem and no more.

Let's continue the discussion with this in mind.

-- Kevin



On 9/29/2023 3:44 PM, Andy Goryachev wrote:
Dear fellow JavaFX developers:

For some time now, we’ve been working to identify missing features in JavaFX that hinder application development.  We’ve been working on adding some of the missing features (for which we’ll have a separate announcement), but I feel that engaging wider community is a rather important part of the process.

I would like to share with you one such missing feature - ability to extend behavior of the existing components (and make the task of creating new components easier) by adding a public InputMap and BehaviorBase.

Please find the actual proposal here
https://gist.github.com/andy-goryachev-oracle/294d8e4b3094fe16f8d55f6dd8b21c09<https://urldefense.com/v3/__https:/gist.github.com/andy-goryachev-oracle/294d8e4b3094fe16f8d55f6dd8b21c09__;!!ACWV5N9M2RV99hQ!MAhFywXruyvFlvk6whGVWBb9fTI-f1D-16YuJbRGdJe52rX503CFBK8S6IamyzPVzQBcJZmg6c_Jh1CfsDxVFw$>

We are very much interested in your feedback.  Thank you in advance.

-andy

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mail.openjdk.org/pipermail/openjfx-dev/attachments/20231101/0d3b8de4/attachment-0001.htm>