[Request for Comments] Behavior / InputMap

[Pedro Duque Vieira]

Hi Andy,

Sorry for the late reply but unfortunately I didn't have time to respond to
you earlier.

Yes, you're right, Swing did allow for easier extension of controls' themes
and you did see people coming up with new theme libraries that overwrote
Controls appearance/behavior through code.

I think the main issue with Skins being difficult to extend is that they're
taking on too much responsibility. They do both the View and Controller
part of the Controls (the model being the part that developers interact
with). When I talk about MVC here I mean it in a loose way, I'm
referring to any and all the MVC like patterns. If for instance there was a
clear class, in the Skin architecture, that just took care of how a Control
is displayed, and nothing else, it would be easier to overwrite, for
example, how the Control is displayed and hence override Skins.


   - What are the missing APIs in Skins that we can add to simplify
   extension of skins?

I think, as I said above, Skins would have to have a different
architecture. IMHO, their responsibilities would likely have to be split
into different classes each with a smaller set of concerns. I'm not talking
about changing the whole Control architecture, just the Skin part. This
would likely be a big effort but perhaps it could be split into smaller
tasks till the end goal is achieved.


   - Would this proposal (BehaviorBase + InputMap) prevent us from moving
   forward?

Likely no.

BTW, in the past I already had the need for this API (InputMap) for an
application I was developing that's now in production. To do what I needed
I had to call on private methods using reflection, etc, since there's no
public API to achieve this yet.
My use case was that I was creating a custom control, "inside" that control
I used a ScrollPane but ScrollPane has a bunch of default key mappings,
like SPACE, PAGE_UP, PAGE_DOWN, HOME that when pressed already do
predefined things. I needed to remove those key mappings as in this
application those keys were already meant to do something else other than
what the default JavaFX ScrollPane does with them.

Thnaks. Kind regards,

On Mon, Oct 9, 2023 at 7:38 PM Andy Goryachev <andy.goryachev at oracle.com>
wrote:

> Thank you for the feedback!
>
>
>
> You are right: even though Skins are public classes now, they are very
> difficult to extend – at least, much more difficult that Swing UIs.  It’s a
> source of constant discussions within the team – how much of it should be
> made public (protected) to allow for extension vs. how much of it should be
> hidden as implementation detail to minimize the API surface and allow for
> evolution.  While opening it all up might alleviate developers’ pain when
> extending, it poses a great(er) danger of introducing of all sorts of
> compatibility issues with respect to bug fixes and other changes.
>
>
>
> If we speak about extending skins specifically, a good question might be:
> what exactly is missing?  Which APIs do we need to enable easier extension
> of skins?
>
>
>
> One thing I would like to clarify is that the Behavior / InputMap proposal
> is not about extending skins.  It is also not about making the concrete
> behaviors public (a task which is probably as large as adding missing
> public APIs to skins).
>
>
>
> The main goal is to allow for extending and slightly modifying the
> behavior – like altering the way navigation works in a text control, or
> adding a new key binding.  As a result, the overall proposal is smaller
> than it could be.
>
>
>
> Having said that, nothing prevents us from exploring options to open up
> skins, or making behaviors public.
>
>
>
> To summarize:
>
>    - What are the missing APIs in Skins that we can add to simplify
>    extension of skins?
>    - Would this proposal (BehaviorBase + InputMap) prevent us from moving
>    forward?
>
>
>
> What do you think?
>
>
>
> -andy
>
>
>
>
>
>
>
> *From: *openjfx-dev <openjfx-dev-retn at openjdk.org> on behalf of Pedro
> Duque Vieira <pedro.duquevieira at gmail.com>
> *Date: *Saturday, October 7, 2023 at 14:05
> *To: *openjfx-dev at openjdk.org <openjfx-dev at openjdk.org>
> *Subject: *Re: [Request for Comments] Behavior / InputMap
>
> I second the opinions of others that JavaFX is too closed which, I think,
> hinders the work of library and app developers.
>
>
>
> I wonder if the reasons that were used to make this design decision back
> when JavaFX was being created still hold true. Back in the beginning there
> were more developers involved in developing JavaFX, significant features
> were added at a fast pace so the fact that it was closed wasn't such a big
> drawback as things were changing quickly and missing features that were
> spotted could be added relatively quick.
>
>
>
> Commenting more specifically on your question... I think Skins could
> benefit generally from being easier to extend. The promise of skins is that
> you could easily replace a control behavior and visuals without changing
> its model (the model being the part of the control that developers usually
> interact with) but the problem is that the JavaFX SDK control's skins are
> very difficult to extend. Say, if you only want to add a specific visual
> feature (something that CSS can't do) it takes a significant effort.
>
> What you usually see is that developers opt to create completely new
> controls rather than just new skins.
>
> My attempt at providing new skins for existing javafx sdk controls is
> here: https://github.com/dukke/FXSkins
>
> Still it required quite a bit of effort.. at least more than it could
> ideally take (I think).
>
> The advantage of this kind of approach (providing new Skins) and the
> library I created "FXSkins" is that you can enhance the controls of your
> existing app very easily by setting new skins in the CSS stylesheet. You
> won't need to change anything directly in the code.
>
>
>
> Regarding the current state of the JavaFX SDK Skins, there isn't a clear
> MVC separation, the skin does the Controller and View part at the same
> time. Perhaps ideally there would be a clear View part that could easily be
> extended to add different advanced visuals to the control (by advanced I
> mean, anything that can't be done with CSS). And then perhaps also the
> Behavior part where you can easily change the control's functionality. I
> remember at some point Richard Bair saying that it was a goal to make
> Behaviors public.
>
>
>
> Thanks!
>
> --
>
> Pedro Duque Vieira - https://www.pixelduke.com
>


-- 
Pedro Duque Vieira - https://www.pixelduke.com
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