On Tue, 2 Jun 2026 16:33:05 GMT, Martin Fox <[email protected]> wrote:
>> On macOS when the user swipes on a trackpad or Magic Mouse JavaFX sees this >> as a scroll gesture. The scene tries to ensure that all the scroll events >> generated by the gesture are fired at the same target to ensure that the >> gesture's scroll events don't get split between two ScrollPanes. For >> example, while a ScrollPane is being scrolled a child ScrollPane might shift >> until it's beneath the mouse pointer. Scroll events should not fire at the >> child but remain with the parent. >> >> During the gesture the scene should target the node that's handling the >> scrolling (like a ScrollPane) but there's no good way to determine that. >> Instead it targets a descendant node, whatever was under the mouse pointer >> when the gesture started. This node is likely to shift during the scroll and >> if scrolls out of view it might get disconnected from the scene graph. At >> that point events fired at it will go nowhere and the gesture will abruptly >> stop. >> >> This PR detects when the gesture target is removed from the scene graph and >> attempts to find a new target. >> >> This bug does not reproduce on Windows since that platform doesn't generate >> a SCROLL_STARTED event so the Scene never selects a gesture target. All >> scroll events are delivered to whatever node is under the mouse pointer >> which will change as the scroll progresses. >> >> This PR might fix [JDK-8088460](https://bugs.openjdk.org/browse/JDK-8088460) >> which shows up in Ensemble if anyone wants to test that. >> >> Submitting fix for sanity checking and manual testing. Will investigate >> creating an automated test for this. >> >> --------- >> - [x] I confirm that I make this contribution in accordance with the >> [OpenJDK Interim AI Policy](https://openjdk.org/legal/ai). > > Martin Fox has updated the pull request incrementally with one additional > commit since the last revision: > > Consistent handling of null pick node. Code looks good and reasonable. Just tested the fix together with a friend on his Mac (v26.5.1). Looks good and you can clearly see the broken scrolling before and the smooth scrolling after. modules/javafx.graphics/src/main/java/javafx/scene/Scene.java line 2014: > 2012: if (gesture.target != null && (!gesture.finished || > e.isInertia())) { > 2013: pickedTarget = gesture.target.get(); > 2014: if (pickedTarget instanceof Node) { Minor suggestion Suggestion: if (pickedTarget instanceof Node node) { ------------- Marked as reviewed by mhanl (Committer). PR Review: https://git.openjdk.org/jfx/pull/2171#pullrequestreview-4532247014 PR Review Comment: https://git.openjdk.org/jfx/pull/2171#discussion_r3441983796
