[External] : Re: Allowing a cell to commit the value on focus loss

[Andy Goryachev]

Good point.  For these cases, I suppose, one needs to stop or cancel editing explicitly.  The actions that are being triggered without focusLost need to have additional code to find out the currently focused editor and commit the values (and deal with validation errors), but this is an application responsibility.

The question is do we get the focusLost event when clicking on a focusable button, and if not it is probably a bug.

-andy


From: John Hendrikx <john.hendrikx at gmail.com>
Date: Wednesday, October 15, 2025 at 09:52
To: Andy Goryachev <andy.goryachev at oracle.com>, Marius Hanl <mariushanl at web.de>, openjfx-dev at openjdk.org <openjfx-dev at openjdk.org>
Subject: Re: [External] : Re: Allowing a cell to commit the value on focus loss


There is also the focus traversable flag that interacts with this, but perhaps there is a bug.  When a button has focusTraversable set to false, clicking it will not give it focus.  One may say that a property named "focus traversable" would only affect focus *traversal* with the keyboard (as I'd hardly call clicking with the mouse "traversal").

That still leaves mnemonic short-cuts and default actions for buttons though.  Pretty sure those also don't focus the button and aren't intended to, yet do execute the action.

--John

On 15/10/2025 17:20, Andy Goryachev wrote:

  *
Buttons are one of those (either with mouse press or keyboard short cut)

This looks like a bug to me, really.  What is the main purpose of the focus subsystem?
I know we like to reinvent the wheel, but focus in Swing works as expected, and one does get focus lost event on mouse press, and the target button gets the focus.  Why should FX be different?

-andy


From: John Hendrikx <john.hendrikx at gmail.com><mailto:john.hendrikx at gmail.com>
Date: Wednesday, October 15, 2025 at 08:05
To: Marius Hanl <mariushanl at web.de><mailto:mariushanl at web.de>, Andy Goryachev <andy.goryachev at oracle.com><mailto:andy.goryachev at oracle.com>, openjfx-dev at openjdk.org<mailto:openjfx-dev at openjdk.org> <openjfx-dev at openjdk.org><mailto:openjfx-dev at openjdk.org>
Subject: [External] : Re: Allowing a cell to commit the value on focus loss


Hi Marius,

Focus lost is currently sort of a proxy of starting an interaction with a new control, but not all controls gain focus when interacted with.  Buttons are one of those (either with mouse press or keyboard short cut), but there is I think also the scroll wheel that can interact with a control without focusing it (and perhaps even popup menu's).

I can only think of one half-baked solution to this:

- Have a new Event type that is always targetted at the current focus owner ("InterestLostEvent" ? :))
- This event is automatically fired by Scene just before an event is fired that is not targetted at the current focus owner, AND the last event fired did have the focus owner as target

What would happen in practice then would be something like:

- User edits field, keypress events go to current focus owner
- User does something else (moves mouse, scrolls, presses a hotkey, or presses a button):
    - An InterestLostEvent is fired at the current focus owner BEFORE the new event is fired
    - The delayed new event is now fired
    - No further InterestLostEvents are fired until the focus owner has received a normal event again
- User goes back to editing after playing with the mouse; events targetted at the focus owner renew the interest in that control, and so next time an InterestLostEvent is fired again when needed

It feels a bit awkward, especially because simple things like mouse moves may trigger it already (but a mouse move may trigger something that requires the model to be up to date...); perhaps it would need to be selective in some way so one can choose to only be interested in the InterestLostEvent on focus loss and mouse clicks.

I can immediately see some problems as well.  Some controls I think allow editing without focus gain/loss at all (I think some controls can be edited by just scrolling the mouse wheel over them).  When should those controls "commit" their values...?

--John


On 15/10/2025 16:39, Marius Hanl wrote:
Hi John,

you are right that there might be corner cases. I hope that we could, what Andy suggests, find all cases and have a deeper look at them.
We can also check whether the focus delegation API from Michael is something that could help us here (but might be completely unrelated).

The other options as you also mentioned, also have their problems. Even debouncing a commit on every keystroke can be unreliable if the user is too fast.
I really hope we can make the focus loss reliable, as we then do not need much of an API changes inside the Cell Framework.

-- Marius
Gesendet: Montag, 13. Oktober 2025 um 19:32
Von: "Andy Goryachev" <andy.goryachev at oracle.com><mailto:andy.goryachev at oracle.com>
An: "John Hendrikx" <john.hendrikx at gmail.com><mailto:john.hendrikx at gmail.com>, "openjfx-dev at openjdk.org"<mailto:openjfx-dev at openjdk.org> <openjfx-dev at openjdk.org><mailto:openjfx-dev at openjdk.org>
Betreff: Re: Allowing a cell to commit the value on focus loss
I wonder if we should find out exactly why onFocusLost does not work in these cases, as expected.  Then, if I understand the proposal correctly, we won't need any API changes.

-andy



From: openjfx-dev <openjfx-dev-retn at openjdk.org><mailto:openjfx-dev-retn at openjdk.org> on behalf of John Hendrikx <john.hendrikx at gmail.com><mailto:john.hendrikx at gmail.com>
Date: Monday, October 13, 2025 at 07:17
To: openjfx-dev at openjdk.org<mailto:openjfx-dev at openjdk.org> <openjfx-dev at openjdk.org><mailto:openjfx-dev at openjdk.org>
Subject: Re: Allowing a cell to commit the value on focus loss


Hi Marius,

This may be unrelated, but it may be problematic to rely on committing values using focus lost:

I've built a lot of code that relies on focus lost to "commit" values to some underlying model.  However, I noticed that a focus lost handler for committing values is insufficient when an action is triggered that doesn't trigger a loss of focus.   For example, if I have a field "email address" and a Button "Send Email", and I have a focus lost handler to commit the email address textfield to an underlying model, then pressing the Button will not trigger that handler and the underlying model may not have been updated with the latest edits.

Solutions to trigger the correct action are all a bit tricky or annoying:

- Query all fields for their current contents as focus lost is not entirely reliable for this purpose
- Have fields update models immediately (which would be on every key press...) -- this is not very efficient, and can get in the way of validation / model restrictions
- Have controls listen to a "COMMIT" event (this is fired at the current focus owner by the Button).  This event may be veto'd if committing the value resulted in a validation error, in which case the button press is cancelled

I don't like any of these, but using the last option at the moment because I like constant updates and having to requery UI components even less...

--John

I noticed however that if you edit some field (it doesn't have to be in a table view, just a regular field), and have a focus lost handler that commits the value, that this focus lost handler is insufficient...

On 13/10/2025 14:53, mariushanl at web.de<mailto:mariushanl at web.de> wrote:
All,

I created an initial poc 1* to support developers to commit the cell value when the focus is lost 2* (including 3*).
More specifically, this gives the maximum flexibility to choose what should happen when the focus is lost or the editing index changed (which may happen when clicking into another cell while editing).
All information mentioned here are also in the description of the PR.

API

- Instead of calling `cancelEdit`, every cell now calls `stopEdit` when the focus is lost or the editing index changed. The default behavior is cancelling the edit, but developers can now override the behavior and allow a `commitEdit` instead
- There are multiple 'events' that can lead to a editing change. Every change will now call `stopEdit`.
It is therefore the responsibility of the developer to decide, when it makes sense to actually commit the value instead of cancelling it. This decision was made as the behavior is manipulating the editing index, but you as a developer can as well. We do not really know what intention led to e.g. a change of the editing index.
- Every `MOUSE_PRESSED` shifts the focus to the cell container, which is undesired in case of editing the cell. So this event is now consumed.
- All `TextField` cells now commit their value (instead of cancel) on focus loss
- `TextField` Escape handling was badly implemented (it was never really called, as the cell container handled Escape before)

Considerations

- I tried to make the API minimal, and without breaking changes (other than the `TextField` cells committing their values, but we may split this up)
- The Cell Container focus behavior is, well, weird right now. That is why consuming the event is needed to better support this PR. One thing we may can consider is using the `focusWithin` property instead for all 4 Cell Containers and not calling `requestFocus` for nearly every `MOUSE_PRESSED` event. If we decide so, this is needs to be done before merging this PR.
- Clicking the `ScrollBar` now commits/cancels the edit. I checked other applications and this is very common. But something I need to note here. This probably can be fixed in the same way mentioned above (`focusWithin`)
- It might be hard for a developer to exactly know the cause why `stopEdit` is called. This does not seem like a problem, as e.g. for a `TextField`, you normally register listeners for e.g. pressing the Escape key on it, so you keep full control.

Another Approach

- Another Approach I tested could be to request the focus to a cell when clicked/edited, to ensure that the focus listener is ALWAYS called before another cell will reach the editing state. Again, we probably need to change the focus handling to e.g. use the `focusWithin` property. With this approach, we can only call `stopEdit` when the focus changed (since it is now called always), but not when the editing index changed.

1* - https://github.com/openjdk/jfx/pull/1935<https://urldefense.com/v3/__https://github.com/openjdk/jfx/pull/1935__;!!ACWV5N9M2RV99hQ!KeaTwOLaODiie2jQZ01j-vH00U9_nZNV8YxV6B0SXCExWnLFky0svIofyVK0ZPt0xawAISlouP_NCkqvMwFhYVHnQZte$>
2* - https://bugs.openjdk.org/browse/JDK-8089514
3* - https://bugs.openjdk.org/browse/JDK-8089311

-- Marius
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