feature: Add Element Transitions and Click Outside detection to uni-dom #410
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Add CSS-class-based transition system (Transition) driven by Rx[Boolean] visibility, and click outside detection (ClickOutside) for dismissing dropdowns/modals. Closes #409. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Summary of ChangesHello @xerial, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed! This pull request significantly enhances the Highlights
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Code Review
This pull request introduces valuable Transition and ClickOutside features to uni-dom. The implementation is well-structured and follows the existing patterns in the library. The accompanying tests are thorough and cover the new functionalities well. I've identified a couple of potential race conditions and a null-safety issue in the new code. Addressing these points will enhance the robustness of these new features. Overall, this is a great contribution.
| val target = me.target.asInstanceOf[dom.Node] | ||
| if !elem.contains(target) then | ||
| callback(me) |
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The event.target property can be null in some edge cases. The current code's asInstanceOf[dom.Node] on a null value would result in null, and !elem.contains(null) evaluates to true, incorrectly triggering the onClickOutside callback. It's safer to add a null check to prevent this.
val targetNode = me.target.asInstanceOf[dom.Node]
if targetNode != null && !elem.contains(targetNode) then
callback(me)| private def waitForTransitionEnd(elem: dom.HTMLElement)(onEnd: () => Unit): Unit = | ||
| val timeoutMs = config.duration.getOrElse(5000) | ||
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| val listener: js.Function1[dom.Event, Unit] = | ||
| (_: dom.Event) => | ||
| pendingTimeout.foreach(id => dom.window.clearTimeout(id)) | ||
| pendingTimeout = js.undefined | ||
| elem.removeEventListener("transitionend", transitionListener.get) | ||
| elem.removeEventListener("animationend", transitionListener.get) | ||
| transitionListener = js.undefined | ||
| onEnd() | ||
| transitionListener = listener | ||
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| elem.addEventListener("transitionend", listener) | ||
| elem.addEventListener("animationend", listener) | ||
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| // Safety timeout fallback | ||
| pendingTimeout = dom | ||
| .window | ||
| .setTimeout( | ||
| () => | ||
| transitionListener.foreach { l => | ||
| elem.removeEventListener("transitionend", l) | ||
| elem.removeEventListener("animationend", l) | ||
| } | ||
| transitionListener = js.undefined | ||
| onEnd() | ||
| , | ||
| timeoutMs | ||
| ) |
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The current implementation of waitForTransitionEnd has race conditions related to the use of the shared transitionListener variable:
- If the safety timeout fires before the
transitionendevent, it clearstransitionListener. Whentransitionendthen fires,transitionListener.getwill throw aNoSuchElementException. - If a new transition starts on the same element,
transitionListeneris updated. If an event (eithertransitionendor timeout) from the old transition fires after this, it will incorrectly remove the listener of the new transition.
To fix this, the listener should be a lazy val to be able to reference itself, and both the event handler and the timeout handler should use this local listener for removal and check against the shared transitionListener before modifying it.
private def waitForTransitionEnd(elem: dom.HTMLElement)(onEnd: () => Unit): Unit =
val timeoutMs = config.duration.getOrElse(5000)
lazy val listener: js.Function1[dom.Event, Unit] = { (_: dom.Event) =>
pendingTimeout.foreach(id => dom.window.clearTimeout(id))
pendingTimeout = js.undefined
elem.removeEventListener("transitionend", listener)
elem.removeEventListener("animationend", listener)
// Only clear the shared listener if it's still this one
if (transitionListener.toOption.contains(listener)) {
transitionListener = js.undefined
}
onEnd()
}
transitionListener = listener
elem.addEventListener("transitionend", listener)
elem.addEventListener("animationend", listener)
// Safety timeout fallback
pendingTimeout = dom
.window
.setTimeout(
() => {
// Only act if the listener hasn't been replaced by a new transition
if (transitionListener.toOption.contains(listener)) {
elem.removeEventListener("transitionend", listener)
elem.removeEventListener("animationend", listener)
transitionListener = js.undefined
onEnd()
}
},
timeoutMs
)1 participant
Summary
Transitionsystem driven byRx[Boolean]visibility, with enter/leave class sequences, double-rAF frame precision, and safety timeout fallbacksClickOutsidedetection via document-levelmousedownlistener withsetTimeout(0)delay to avoid catching the opening clickFocusTrapRxElement pattern for Transition,DomNodebinding pattern for ClickOutside)Closes #409
Test plan
scalafmtAllpasses🤖 Generated with Claude Code