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8354813: Parent.isNeedsLayout() may return wrong value in property listener #1781

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8354813: Parent.isNeedsLayout() may return wrong value in property listener #1781

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9acec1a
failing test
mstr2 Apr 16, 2025
bff099e
fix
mstr2 Apr 16, 2025
58af7e2
Merge branch 'master' into fixes/needslayout-wrong-value
mstr2 Apr 16, 2025
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5 changes: 4 additions & 1 deletion modules/javafx.graphics/src/main/java/javafx/scene/Parent.java
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Original file line number Diff line number Diff line change
Expand Up @@ -991,10 +991,13 @@ boolean isPerformingLayout() {
private double minHeightCache = -1;

void setLayoutFlag(LayoutFlags flag) {
// Needs to be set before needsLayout is updated, as otherwise a listener that
// calls isNeedsLayout() might see the old value.
layoutFlag = flag;
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This is the right change, but I suspect it might cause regression.

The JavaFX entities which call isNeedsLayout():

VirtualFlow::layoutChildren
VirtualFlow::setCellIndex

We may need to focus on List/Table/Tree/TableViews during testing.

(Anecdata: I've seen continuous layout calls in the TableView before)

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It's very unlikely to cause regressions, because needsLayoutProperty() is not used anywhere in JavaFX. The only thing that is different now is that a listener added to this property will see the correct value when calling isNeedsLayout().

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you are probably right, re:javafx. applications might listen to this property, though it's rather unlikely.

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Yes, but I don't think there's anything we can do about it short of not fixing the bug...


if (needsLayout != null) {
needsLayout.set(flag == LayoutFlags.NEEDS_LAYOUT);
}
layoutFlag = flag;
}

private void markDirtyLayout(boolean local, boolean forceParentLayout) {
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6 changes: 5 additions & 1 deletion modules/javafx.graphics/src/shims/java/javafx/scene/ParentShim.java
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
/*
* Copyright (c) 2015, 2022, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2015, 2025, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
Expand Down Expand Up @@ -45,6 +45,10 @@ public static <E extends Node> List<E> getManagedChildren(Parent p) {
return p.getManagedChildren();
}

public static void setNeedsLayout(Parent p, boolean value) {
p.setNeedsLayout(value);
}

public static List<Node> test_getRemoved(Parent p) {
return p.test_getRemoved();
}
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18 changes: 18 additions & 0 deletions modules/javafx.graphics/src/test/java/test/javafx/scene/ParentTest.java
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Expand Up @@ -53,6 +53,7 @@
import static org.junit.jupiter.api.Assertions.assertNull;
import static org.junit.jupiter.api.Assertions.assertSame;
import static org.junit.jupiter.api.Assertions.assertTrue;
import static org.junit.jupiter.api.Assertions.assertFalse;
import static org.junit.jupiter.api.Assertions.fail;
import static org.junit.jupiter.api.Assertions.assertThrows;

Expand Down Expand Up @@ -520,6 +521,23 @@ public void needsLayoutPropertyIsReadOnly() {
() -> { var _ = (Property<Boolean>)new Group().needsLayoutProperty(); });
}

@Test
public void isNeedsLayoutReturnsCorrectValueInListener() {
var g = new Group();
g.layout();
assertFalse(g.isNeedsLayout());

boolean[] flags = new boolean[2];
g.needsLayoutProperty().subscribe(value -> {
flags[0] = value;
flags[1] = g.isNeedsLayout();
});

ParentShim.setNeedsLayout(g, true);
assertTrue(flags[0]);
assertTrue(flags[1]);
}

private static class LGroup extends Group {

private boolean layoutCalled;
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