The use cases I have in mind are: - have a form with multiple fields. some kind of processing is supposed to be happen after a short delay after one or more fields is modified by the user - multiple fields are modified in rapid succession (programmatically). something must be invoked once after a short delay.
There is another use case for throttling - for example, last price of a security in a trading application - but it may or may not be a good example because it would likely to be handled by a non-FX code first and then the actual property would be updated in an invokeLater(). Perhaps there are some use cases that I don't see that warrant the use of the new methods being proposed. What are those, and why do we need to them to an already large API surface instead of implementing a separate facility? Thanks! -andy From: John Hendrikx <john.hendr...@gmail.com> Date: Monday, April 3, 2023 at 14:46 To: Andy Goryachev <andy.goryac...@oracle.com>, Marius Hanl <mariush...@web.de> Cc: openjfx-dev@openjdk.org <openjfx-dev@openjdk.org> Subject: Re: [External] : Re: Gauging interest in bindings that can delay changing their value (debounce/throttle) Hi Andy, On 03/04/2023 21:14, Andy Goryachev wrote: Right. I am not saying we should take these classes as is. In my opinion, this functionality might be better supported by a separate facility(ies). Specifically, to handle the case of multiple observables. Can you elaborate on what cases you see with multiple observables? I think you mean events here; events can also benefit from debouncing or throttling, but that's something quite different. An ObservableValue is not an event source, but the values it takes on can be mapped, delayed or even interpolated. In the end however, there is always a value immediately available, making them suitable for binding. An event source on the other hand can't supply events (values) on demand, can't repeat them and it does not remember the last one -- you can't bind an event source in the same way either; at the most you can set a default value and then update it when events come in. I also think the APIs are large and complicated enough already, it might be better to add/extract (a rarely used) functionality to a separate class or set of classes. Could you clarify at what point an API is too large or too complicated? Certainly there are far larger API's in the Java ecosystem and in the JDK itself. I'm pretty sure there are far more complicated ones as well. --John -andy From: John Hendrikx <john.hendr...@gmail.com><mailto:john.hendr...@gmail.com> Date: Monday, April 3, 2023 at 12:05 To: Andy Goryachev <andy.goryac...@oracle.com><mailto:andy.goryac...@oracle.com>, Marius Hanl <mariush...@web.de><mailto:mariush...@web.de> Cc: openjfx-dev@openjdk.org<mailto:openjfx-dev@openjdk.org> <openjfx-dev@openjdk.org><mailto:openjfx-dev@openjdk.org> Subject: [External] : Re: Gauging interest in bindings that can delay changing their value (debounce/throttle) Hi Andy, Those examples seem to be just timers, it would be hard to construct the primitives like throttle and debounce with these, as they don't take into account when the value last changed, or whether or not is important that the value changed again (reset timer or not). These timers would just run forever, while the functionality I propose here would have no timers running when things are stable. The timeout would also trigger precisily on the first value change. Having a running timer is more like sampling, not throttling or debouncing. The functionality I'm proposing would be more along the lines of #reduceSucessions in https://github.com/TomasMikula/ReactFX/blob/master/reactfx/src/main/java/org/reactfx/EventStream.java<https://urldefense.com/v3/__https:/github.com/TomasMikula/ReactFX/blob/master/reactfx/src/main/java/org/reactfx/EventStream.java__;!!ACWV5N9M2RV99hQ!IUX7QjZNn8vhK8ISBY_DO3YOqEeBlcegZahboYpjq2XsYz5Xj-XoFVxWKltMxZxJS2aFla51yf2gREfkFoeF1VL_66lB$> -- except that it would never support accumulation or combining of values (that's something for streams, not for values). --John On 03/04/2023 18:47, Andy Goryachev wrote: My two cents: I think the functionality of debouncing should better be solved by a separate facility, rather than added to observables. An example would be a use case when multiple observables trigger an expensive or delayed computation or a UI update. Something along the lines of https://github.com/TomasMikula/ReactFX/blob/master/reactfx/src/main/java/org/reactfx/util/FxTimer.java<https://urldefense.com/v3/__https:/github.com/TomasMikula/ReactFX/blob/master/reactfx/src/main/java/org/reactfx/util/FxTimer.java__;!!ACWV5N9M2RV99hQ!IUX7QjZNn8vhK8ISBY_DO3YOqEeBlcegZahboYpjq2XsYz5Xj-XoFVxWKltMxZxJS2aFla51yf2gREfkFoeF1YeFiEIP$> or https://github.com/andy-goryachev/FxEditor/blob/master/src/goryachev/fx/FxTimer.java<https://urldefense.com/v3/__https:/github.com/andy-goryachev/FxEditor/blob/master/src/goryachev/fx/FxTimer.java__;!!ACWV5N9M2RV99hQ!IUX7QjZNn8vhK8ISBY_DO3YOqEeBlcegZahboYpjq2XsYz5Xj-XoFVxWKltMxZxJS2aFla51yf2gREfkFoeF1VyqfNCE$> cheers, -andy From: openjfx-dev <openjfx-dev-r...@openjdk.org><mailto:openjfx-dev-r...@openjdk.org> on behalf of Marius Hanl <mariush...@web.de><mailto:mariush...@web.de> Date: Thursday, March 30, 2023 at 15:20 To: John Hendrikx <john.hendr...@gmail.com><mailto:john.hendr...@gmail.com> Cc: openjfx-dev@openjdk.org<mailto:openjfx-dev@openjdk.org> <openjfx-dev@openjdk.org><mailto:openjfx-dev@openjdk.org> Subject: Aw: Gauging interest in bindings that can delay changing their value (debounce/throttle) + 1 for this. Debouncing is a common functionality for observables. One of the common scenarios is obviously something like a search filter functionality, where typing in characters triggers an expensive calculation. Debouncing solves the problem by doing that when nothing happened for some time, which is typically met when the user finished typing. -- Marius Gesendet: Donnerstag, 23. März 2023 um 18:09 Uhr Von: "John Hendrikx" <john.hendr...@gmail.com><mailto:john.hendr...@gmail.com> An: openjfx-dev@openjdk.org<mailto:openjfx-dev@openjdk.org> Betreff: Gauging interest in bindings that can delay changing their value (debounce/throttle) Hi list, I've been working on a potential new API (and proof of concept implementation) for adding a new type of fluent binding which can delay changing their values, and I'm wondering how much interest there is in such a thing. The main purpose of such an API is to prevent being flooded with changes when properties change often, or to simply delay certain actions until the user has settled on a selection or has stopped typing. For this purpose I would like to introduce a default method on `ObservableValue` with the signature: ObservableValue<T> throttle(Throttler throttler); The parameter `Throttler` can be obtained via static methods of a helper class named `FXThrottlers`. These provide various pre-configured throttlers that work correctly with JavaFX's event thread model. My current proof of concept provides: public static Throttler debounce(Duration quietPeriod); public static Throttler debounceTrailing(Duration quietPeriod); public static Throttler throttle(Duration period); public static Throttler throttleTrailing(Duration period); These are variations of similar concepts, and vary mostly in when exactly they will allow value changes; debouncers will wait for a period without any changes, while throttlers will periodically allow changes. The trailing variants will not immediately emit the first change but will wait for the period to elapse first; all variants will eventually take on the value of the source observable. Debouncing is typically used when you wish for an input to settle before taking action (like typing in a search bar), while throttling is used to give regular feedback but avoid doing so too often (like feedback during window resizing). Usage example which updates a preview panel when the user has finished (cursor) scrolling through a list view: ObjectProperty<T> selectedItem = listView.getSelectionModel().selectedItemProperty(); selectedItem .throttle(FXThrottlers.debounceTrailing(Duration.ofMillis(500))) .addListener((obs, old, current) -> { if (current != null) { updatePreviewPanel(current); } }); Implementation details: ObservableValue is part of javafx.base, and as such can't use animations or call Platform::runLater. The ThrottledBinding implementation has abstracted all of these out into the Throttler class, and FXThrottlers (which would live in javafx.graphics) therefore provides the necessary call backs to integrate property changes correctly back onto the JavaFX event thread. The Throttler class also simplifies testing; the test can provide its own timing source and background scheduler. The Throttler interface has the following methods: /** * Schedules a command to run on an unspecified thread after the time * given by {@code nanos} elapses. * * @param command a command to run, cannot be {@code null} * @param nanos a time in nanoseconds */ void schedule(Runnable command, long nanos); /** * Provides the current time in nanoseconds. * * @return the current time in nanoseconds */ long nanoTime(); /** * Runs the given command as soon as possible on a thread specified by this * throttler for updating property values. * * @param command a command to run, cannot be {@code null} */ void update(Runnable command); /** * Given the current elapsed time in the current change window, and the * amount of time elapsed since the last change was detected, determines * if and by how much the current change window should be extended. * * @param elapsed nanoseconds elapsed since the start of the current change window * @param elapsedSinceLastChange nanoseconds elapsed since the last change * @return nanoseconds to extend the window with */ long determineInterval(long elapsed, long elapsedSinceLastChange); For testing purposes, the schedule and nanoTime can be provided such that the throttle function can be tested deterministically. For integrating with JavaFX, update is implemented as `Platform.runLater(command)`. The schedule and nanoTime methods delegate to an Executor and System.nanoTime respectively. When using properties without JavaFX, Throttler implementations can be provided which run property updates on a scheduler thread (just calling Runnable::run on the current thread) or via some user provided executor. A sample test case looks like this (read with a mono space font :-)): @Test void testThrottleLeadingAndTrailing() { // create Throttler with deterministic behavior: Throttler throttler = create(Throttler.IntervalHandler.throttle(Duration.ofNanos(4)); // create throttled observable: ObservableValue<String> binding = source.throttle(throttler); assertChanges( binding, "--a-b--c---d-----e-------f-g-----------f-g-----", "--a---b---c---d---e------f---g---------f---g---" ); assertInvalidations( binding, "--a-b--c---d-----e-------f-g-----------f-g-----", "--i---i---i---i---i------i---i---------i---i---" ); } Thanks for reading, I look forward to your feedback! --John
