[Request for Comments] Behavior / InputMap

[Andy Goryachev]

Dear John:

Seems like addEventFilter() was specifically designed to intercept events before any other handlers, so I see no problem there.

I somewhat disagree about the purpose of the key mapping system – the proposed solution solves two existing issues (the skin/behavior mappings and the user mappings) in one neat package.  Every other instrument such as addEventHandler/Filter is still there.

And, if we look at the three bullet points


- Ensure user event handlers have priority over behavior/inputmap added ones
- Ensure all behavior actions are available as methods on controls
- Ensure that if a key is handled by the control, that it is ONLY consumed when it actually triggers an action (navigation keys get consumed regardless, even if no focus change results, that's wrong).
I absolutely agree, and in fact the first three are indeed a part of the proposal.  Well, the 3rd one might unfortunately be a subject of backward compatibility limitation since one of the requirements was no behavior change w.r.t. the earlier versions.  We can always change the behavior if we have a completing reason and go through the usual process, nothing in the proposal precludes that.

Making the behaviors completely independent with setBehavior() and FXML, as you said, might be a future effort, perhaps we could attempt opening up certain controls at some point.  On one hand, I am for increasing the extensibility of FX, on the other hand the same argument can be made against it (as in solidifying a particular way of constructing skins and behaviors), but I feel it’s a separate issue that is independent of this proposal.


-andy



From: openjfx-dev <openjfx-dev-retn at openjdk.org> on behalf of John Hendrikx <john.hendrikx at gmail.com>
Date: Wednesday, October 11, 2023 at 01:04
To: openjfx-dev at openjdk.org <openjfx-dev at openjdk.org>
Subject: Re: [Request for Comments] Behavior / InputMap

I'm sorry, but that providing an arbitrary key mapping system seems completely out of scope and not something that JavaFX should concern itself with.  It's much too high level, when the key mappings involved should only be for actions that the control can provide on its own.
I think the problem we should be solving is that JavaFX control behaviors shouldn't be first in line when it comes to consuming events (which currently is only the case due to event handlers being added at the earliest possible opportunity, and event handlers being called in order).  If something as trivial as:

       control.addEventHandler(KeyEvent.KEY_PRESSED, e -> {
              if (e.getCode() == KeyCode.LEFT) {
                    e.consume();  // stop default behavior
              }
       });

... actually worked, then there is much less need to redefine/disable behavior key mappings, and no need for a secondary system that deals with mappings (the first system, event handlers, can simply be used for this).  If user event handlers had priority over behavior ones, then everything you want can be achieved with the above, including:

- Stopping default behavior
- Triggering different behavior (just call something on control, of course, make sure all behavior actions are available on the control in the first place)
- Remapping (a combination of the above two)
- Adding an alternative key for the same behavior

A system to remap keys can then be left squarely in the realm of user space, and much nicer solutions can be build by users than whatever JavaFX will provide out of the box.

Changes to the Behavior system can then focus on replacing complete behaviors (including their input map) and being able to use these by default for a certain subset of controls (like -fx-skin provide in CSS), as this is something users currently can't do.

So in short, what I think this should be about is:

- Ensure user event handlers have priority over behavior/inputmap added ones
- Ensure all behavior actions are available as methods on controls
- Ensure that if a key is handled by the control, that it is ONLY consumed when it actually triggers an action (navigation keys get consumed regardless, even if no focus change results, that's wrong).

Future:

- Make behaviors public and allow Behaviors to be replaced with -fx-behavior type CSS syntax / control.setBehavior calls

--John



The focus should be on being able to modify standard behavior of controls (arrow-left, enter, ctrl-shift-right, etc.), specifically also to be able to disable these when undesired, and, on top of that, that they bubble up when NOT used even when they are configured (focus navigation keys currently are always consumed, whether they actually do something or not -- that's a big issue).  The other focus should be on providing an alternative behavior (or at least mappings) for all controls of a certain type -- I don't see the need for adding a mapping to a specific control, that's already covered with event handlers; the problem is mostly that behaviors currently steal certain events before the user can get at them.

Custom behaviors can then be constructed that provide more things that may need mapping.  I'd expect those however to be limited in scope to what the control offers, certainly not an arbitrary key/action mapping system (that wouldn't even work, as most of these would be in the scope of several controls or be global).  This kind of functionality is much better provided by event handlers at the correct level for a group of controls, and I wouldn't expect to find such an eloborate system incorporated in behaviors.

In fact, thinking about all of this a bit more,



On 10/10/2023 19:54, Andy Goryachev wrote:
Re-sending with a smaller image (256kb limit, really?).

From: Andy Goryachev <andy.goryachev at oracle.com><mailto:andy.goryachev at oracle.com>
Date: Tuesday, October 10, 2023 at 10:49
To: Michael Strauß <michaelstrau2 at gmail.com><mailto:michaelstrau2 at gmail.com>
Cc: openjfx-dev at openjdk.org<mailto:openjfx-dev at openjdk.org> <openjfx-dev at openjdk.org><mailto:openjfx-dev at openjdk.org>
Subject: Re: [Request for Comments] Behavior / InputMap
Dear Michael:

Here is a use case for (re-)mapping by the user at runtime:

[cid:part1.QozIrk7S.Ii0xHc4n at gmail.com]

(key mappings UI in Eclipse).

I can think of several other cases (mentioned in the proposal, I think) so I think we can put the concept of immutable or global InputMap to rest.

Whether the InputMap contains the reference to its control or not is a minor implementation detail, I think.

-andy


From: openjfx-dev <openjfx-dev-retn at openjdk.org><mailto:openjfx-dev-retn at openjdk.org> on behalf of Michael Strauß <michaelstrau2 at gmail.com><mailto:michaelstrau2 at gmail.com>
Date: Tuesday, October 10, 2023 at 10:36
To:
Cc: openjfx-dev at openjdk.org<mailto:openjfx-dev at openjdk.org> <openjfx-dev at openjdk.org><mailto:openjfx-dev at openjdk.org>
Subject: Re: [Request for Comments] Behavior / InputMap
> Yes, one of the features the new design provides is ability to modify key mappings by the user at runtime.  So yes, not only it needs to be mutable, but it also adds some APIs for exactly that.
>

I struggle to see a use case for this feature. I can imagine that
there might be some use cases that call for customized input mappings,
but why would this translate to a _mutable_ input map? That's quite a
departure from the way other parts of JavaFX work.

For example, skins are also immutable. If you want to have a different
skin for a control, you don't somehow modify the existing skin
instance; instead, you'd create a new skin class (or -- somehow --
extend an existing skin class), and then install that new skin on your
control.

An input map shouldn't bind input events directly to instance methods
of a particular control instance. It should define the mapping of
events to methods symbolically:

Instead of mapping Event => instance.method(), it should map Event =>
Control::method. The input map could then be stateless and immutable,
and can be set on any control instance. If you want to change the
mappings, just set a different input map instance. There's no need
that an input map would retain a reference to any particular control,
since the control reference can be passed into the input map just as
easily.
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