8293444: Creating ScrollPane with same content component causes memory leak

[andy-goryachev-oracle]

Using Weak*Listeners eliminates the memory leak.

---

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Issue

• JDK-8293444: Creating ScrollPane with same content component causes memory leak

Reviewers

• Kevin Rushforth (@kevinrushforth - Reviewer)
• Ambarish Rapte (@arapte - Reviewer)

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[bridgekeeper]

👋 Welcome back angorya! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[mlbridge]

Webrevs

• 02: Full - Incremental (0b22c2c9)
• 01: Full - Incremental (02330d09)
• 00: Full (b6316bbb)

[kevinrushforth]

/reviewers 2

[openjdk]

@kevinrushforth
The total number of required reviews for this PR (including the jcheck configuration and the last /reviewers command) is now set to 2 (with at least 1 Reviewer, 1 Author).

[kevinrushforth]

This looks like it will eliminate the leak. Using weak listeners like this follows the same pattern as used by some of the other skins. I'll review and test it next week.

[arapte]

Fix looks good,
Providing some minor comments for test.

[FlorianKirmaier]

A small comment about the memory test with JMemoryBuddy.
Instead of this:

<code>
List<WeakReference> refs = ...
WeakReference a = b;
refs.add(a);
<code>
for (WeakReference<ScrollPane> ref : refs) {
       JMemoryBuddy.checkCollectable(ref);
}

It is more readable this way:

JMemoryBuddy.memoryTest(checker -> {
  <code>
  checker.setAsReferenced(objects);
  checker.assertCollectable(b);
});

[andy-goryachev-oracle]

A small comment about the memory test with JMemoryBuddy.

Thank you for suggestion. I will definitely use it in other tests!
Here it won't work because in the part of the test one instance is expected to remain uncollected.

[FlorianKirmaier]

if you use checker.setAsReferenced(object) then the specified object won't be collected for the current test.
And there is also the statement assertNotCollectable() to check the reverse.

The method "checkCollectable/assertCollectable" is very slow in the negative case (but reliable in the positive case)
The method "checkNotCollectable/<assertNotCollectable" should be used, if it's expected that the object is not collectable - otherwise the test will be quite slow.

[andy-goryachev-oracle]

@FlorianKirmaier :
I am not sure if using JMemoryBuddy.memoryTest results in a clearer or more concise code, given the nature of testScrollPaneObjLeakWhenUsedSameContent().

BTW, MemoryTestAPI names are a bit confusing: "assert*Collectable" suggests assertion is done at the point when these calls are made, though it looks like they just add a reference the an internal list. Also, assertCollectable might want to skip creation of a WeakReference if the object passed to it is already a WeakReference.

With your permission, I would like to keep this test as is.

[arapte]

Looks good to me.

[FlorianKirmaier]

Of course, you can keep it this way.

The point of JMemoryBuddy.memoryTest is, that the user doesn't have to fiddle around with WeakReferences.
For the record, your test might look like this (not tested):

    @Test
    public void testScrollPaneObjLeakWhenUsedSameContent() {
        JMemoryBuddy.memoryTest(() -> {
            BorderPane bp = new BorderPane();

            Stage stage = new Stage();
            stage.setScene(new Scene(bp));
            stage.show();

            Label content = new Label("content");

            ScrollPane sp1 = new ScrollPane(content);
            bp.setCenter(sp1);
            Toolkit.getToolkit().firePulse();

            ScrollPane sp2 = new ScrollPane(content);
            bp.setCenter(sp2);
            Toolkit.getToolkit().firePulse();

            bp.setCenter(null);
            Toolkit.getToolkit().firePulse();

            // When the label is still referenced, then only one ScrollPane should stay which is its parent
            checker.setAsReferenced(label)
            checker.assertCollectable(sp1)
            checker.assertNotCollectable(sp2)
        });
    }

    @Test
    public void testScrollPaneObjLeakWhenUsedSameContent() {
        JMemoryBuddy.memoryTest(() -> {
            BorderPane bp = new BorderPane();

            Stage stage = new Stage();
            stage.setScene(new Scene(bp));
            stage.show();

            Label content = new Label("content");

            ScrollPane sp1 = new ScrollPane(content);
            bp.setCenter(sp1);
            Toolkit.getToolkit().firePulse();

            ScrollPane sp2 = new ScrollPane(content);
            bp.setCenter(sp2);
            Toolkit.getToolkit().firePulse();

            bp.setCenter(null);
            Toolkit.getToolkit().firePulse();

            // IF our label is gone, both scrollpanes shold be collectable
            checker.assertCollectable(sp1)
            checker.assertCollectable(sp2)
        });
    }

I think only the first test is the important one.

[andy-goryachev-oracle]

Thank you for clarifications, @FlorianKirmaier

[kevinrushforth]

Looks good.

[openjdk]

@andy-goryachev-oracle This change now passes all automated pre-integration checks.

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After integration, the commit message for the final commit will be:

8293444: Creating ScrollPane with same content component causes memory leak

Reviewed-by: kcr, arapte

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 8 new commits pushed to the master branch:

• cc00c8d: 8293795: [Accessibility] [Win] [Narrator] Exceptions when deleting text with continous key press in TextArea and TextField
• 35675c8: 8293971: Loading new Media from resources can sometimes fail when loading from FXML
• 03569b7: 8293883: Add tests/.classpath (Eclipse)
• 82db6cc: 8289541: Update ICU4C to 71.1
• 7c6a54d: 8293839: Documentation memory consistency effects of runLater
• a27840e: 8293368: GitHub Workflows security hardening
• 5e4552d: 8089280: horizontal scrollbar should never become visible in TableView with constrained resize policy
• cef583e: 8293214: Add support for Linux/LoongArch64

Please see this link for an up-to-date comparison between the source branch of this pull request and the master branch.
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[andy-goryachev-oracle]

/integrate

[openjdk]

@andy-goryachev-oracle
Your change (at version 0b22c2c) is now ready to be sponsored by a Committer.

[kevinrushforth]

/sponsor

[openjdk]

Going to push as commit 337c781.
Since your change was applied there have been 8 commits pushed to the master branch:

• cc00c8d: 8293795: [Accessibility] [Win] [Narrator] Exceptions when deleting text with continous key press in TextArea and TextField
• 35675c8: 8293971: Loading new Media from resources can sometimes fail when loading from FXML
• 03569b7: 8293883: Add tests/.classpath (Eclipse)
• 82db6cc: 8289541: Update ICU4C to 71.1
• 7c6a54d: 8293839: Documentation memory consistency effects of runLater
• a27840e: 8293368: GitHub Workflows security hardening
• 5e4552d: 8089280: horizontal scrollbar should never become visible in TableView with constrained resize policy
• cef583e: 8293214: Add support for Linux/LoongArch64

Your commit was automatically rebased without conflicts.

[openjdk]

@kevinrushforth @andy-goryachev-oracle Pushed as commit 337c781.

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