Allow input controls to indicate significant user interaction

[Michael Strauß]

I should add that aside from the javafx.scene.input.InputNode
interface, there is no addition to or modification of the core
platform.
Nothing in javaxf.graphics uses InputNode, it is provided solely as a
contract for the "significant interaction" information, which
third-party libraries can depend on without depending explicitly on
the javafx.controls module or any particular controls implementation.

On Mon, Mar 27, 2023 at 7:02 PM Kevin Rushforth
<kevin.rushforth at oracle.com> wrote:
>
> I also am skeptical regarding the need for API in the core platform to support this.
>
> -- Kevin
>
>
> On 3/27/2023 9:46 AM, Andy Goryachev wrote:
>
> I think this functionality belongs to the application-level code, not in the platform.  It's the application that knows which parts of a form need the visual feedback and which do not.  In my opinion, there is no APIs that are missing in order to implement a validation framework of any level of complexity.
>
>
>
> Not responding to programmatic changes is easy: disable validation logic when setting values.
>
>
>
> The validation and subsequent user feedback may happen at the time of form submission, or as a result of a short timer expiring.  The timer should be restarted upon each update of the value properties being validated.
>
>
>
> In any case, this problem has a well-defined solution and, in my opinion, does not require a change in the core platform.
>
>
>
> Cheers,
>
> -andy
>
>
>
>
>
> From: openjfx-dev <openjfx-dev-retn at openjdk.org> on behalf of Michael Strauß <michaelstrau2 at gmail.com>
> Date: Sunday, March 26, 2023 at 17:49
> To: openjfx-dev <openjfx-dev at openjdk.org>
> Subject: Allow input controls to indicate significant user interaction
>
> Many form-based applications require some sort of data validation for
> input controls. It is also often desirable to visualize the validation
> state of a control directly in the user interface, for example by
> showing a red border to indicate a validation failure.
>
> However, simply validating the current value of a control and
> rendering a validation decorator often leads to an undesirable user
> experience: for example, in many cases an empty form field shouldn't
> indicate a validation failure unless the user has significantly
> interacted with the field, or validation was explicitly requested by
> pressing a "submit" button.
>
> The first of these validation conditions, "significantly interacted
> with the input control" is quite popular on contemporary web forms,
> and offers a balanced user experience compared to immediately and
> eagerly validating every control, or delaying validation until the
> very end of the form submission process (see also the proposed
> :user-valid/:user-invalid CSS pseudo-classes).
>
> Unfortunately, this is very hard to implement in JavaFX since controls
> have no way of signalling when they were significantly interacted
> with. In particular, we don't want to count programmatic
> initialization of field values as a significant interaction. What
> constitutes a significant interaction is dependent on the type of
> input control. For example, a text field might define a significant
> interaction as the sequence of gaining focus, receiving a new text
> value, and losing focus. A slider might define a significant
> interaction as the sequence of pressing the mouse button, dragging the
> slider thumb to a new value, and releasing the mouse button.
>
> The information of how an input control changed its value is only
> really knowable by its skin and associated behavior classes, both of
> which are basically black boxes for a JavaFX application. In order to
> expose this information, I propose to add the following new interface
> in the "javafx.scene.input" package:
>
> public interface InputNode {
>     ReadOnlyBooleanProperty userModifiedProperty();
>     boolean isUserModified();
>     void setUserModified(boolean value);
> }
>
> This interface identifies a node that can receive user input. It is
> implemented by the following controls: ButtonBase, ChoiceBox,
> ComboBoxBase, Slider, Spinner, and TextInputControl.
>
> The associated skins and behaviors are modified to invoke
> setUserModified(true) on the control when a significant user
> interaction is detected. Once this flag is set on a control, it can
> only be unset programmatically from application code by invoking
> setUserModified(false).
>
> You might note that userModifiedProperty() returns
> ReadOnlyBooleanProperty, while a public setter is availabe. The reason
> for this is that while applications should be able to set or clear the
> userModified flag programmatically, they shouldn't be able to bind the
> property to prevent it from being set by skins.
>
> Note also that it is not a goal of this proposal to add a data
> validation framework to JavaFX (this is best left to third-party
> libraries instead). The goal is to expose a crucial piece of
> information that is not easily accessible otherwise.
>
> I'm interested on your thoughts on this idea.
>
>