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8089589: [ListView] ScrollBar content moves toward-backward during scrolling. #398

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@johanvos johanvos commented Feb 9, 2021

This PR introduces a refactory for VirtualFlow, fixing a number of issues reported about inconsistent scrolling speed (see https://bugs.openjdk.java.net/browse/JDK-8089589)
The problem mentioned in the JBS issue (and in related issues) is that the VirtualFlow implementation depends on cell index and cell count, instead of on pixel count. The latter is unknown when the VirtualFlow is created, and pre-calculating the size of a large set of items would be very expensive.
Therefore, this PR uses a combination of a gradual calculation of the total size in pixels (estimatedSize) and a smoothing part that prevents the scrollback to scroll in the reverse direction as the requested change.
This PR currently breaks a number of tests that hard-coded depend on a number of evaluations. This is inherit to the approach of this PR: if we want to estimate the total size, we need to do some additional calculations. In this PR, I try to balance between consistent behavior and performance.


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  • JDK-8089589: [ListView] ScrollBar content moves toward-backward during scrolling.

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Update a local copy of the PR:
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@bridgekeeper bridgekeeper bot commented Feb 9, 2021

👋 Welcome back jvos! 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.

@johanvos johanvos changed the title [WIP] 8089589: [ListView] ScrollBar content moves toward-backward during scrolling. 8089589: [ListView] ScrollBar content moves toward-backward during scrolling. Feb 15, 2021
@openjdk openjdk bot added the rfr label Feb 15, 2021
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@mlbridge mlbridge bot commented Feb 15, 2021

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@kevinrushforth kevinrushforth commented Feb 16, 2021

/reviewers 2

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@kevinrushforth
The number of required reviews for this PR is now set to 2 (with at least 1 of role reviewers).

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@kevinrushforth kevinrushforth left a comment

I reviewed the code, and tested this, both using automated tests and various manual tests, and it looks good to me. In addition to the simple test attached to the bug report, I can reproduce the bug with HelloTableView and the HorizontalListView sample of Ensemble8.

HelloTableView

  1. Run HelloTableview program
  2. Sort by first name
  3. Slowly scroll down by dragging the thumb
    BUG: the scrolling jitters slightly when you reach the taller row (Jacob Smith Smith Smith)

Ensemble8

  1. Run Ensemble8 and select HorizontalListView sample
  2. Scroll all the way to the right
  3. Slowly scroll to the left by dragging the thumb
    BUG: the scrolling jitters slightly when you reach the wider row (Long Row 3)

All three test cases run fine with the fix.

I left a few inline questions and comments (mostly about code style w.r.t., inline whitespace, and a couple typos).

return (int) (getPosition() * getCellCount());
double total = 0;
int currentCellCount = getCellCount();
double estSize = estimatedSize/currentCellCount;
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@kevinrushforth kevinrushforth Apr 9, 2021

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MInor: missing spaces before and after /

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@johanvos johanvos Apr 12, 2021

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changed

}
// Make sure we have enough space in the cache to store this index
while (idx >= itemSizeCache.size()) {
itemSizeCache.add(itemSizeCache.size(), null);
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@kevinrushforth kevinrushforth Apr 9, 2021

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Can this be simplified to itemSizeCache.add(null);?

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@johanvos johanvos Apr 12, 2021

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That won't add enough elements. For example, in case idx = 10, and the itemSizeCache has 5 elements, we need to add 5 empty elements to the cache, as they might get queried/pushed, e.g. we might do
itemSizeCache.set(7, 123.45);

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Sure, that's why you need the while loop. What I meant is that the following two calls are equivalent for any list:

    list.add(list.size(), null);

and

    list.add(null);

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@johanvos johanvos commented Apr 12, 2021

Thanks for the review. I answered the questions, and corrected the styling errors.

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@kevinrushforth kevinrushforth left a comment

Thanks for the explanations about the algorithm. I have no more questions on the logic.

I think Ajit will review this later this week.

Btw, I did another pass over the code and noted a few more formatting inconsistencies (missing spaces).

if (viewportLength >= estimatedSize) {
setPosition(0.);
} else {
setPosition(absoluteOffset/(estimatedSize - viewportLength));
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@kevinrushforth kevinrushforth Apr 12, 2021

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Minor: spacing

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@openjdk openjdk bot commented Apr 16, 2021

@johanvos This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

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

8089589: [ListView] ScrollBar content moves toward-backward during scrolling.

Reviewed-by: kcr, aghaisas

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 44 new commits pushed to the master branch:

  • 05ab799: 8208088: Memory Leak in ControlAcceleratorSupport
  • e8689fe: 8265031: Change default macOS min version for x86_64 to 10.12 and aarch64 to 11.0
  • c8384a1: 8264928: Update to Xcode 12.4
  • 808b107: 8260245: Update ICU4C to version 68.2
  • d808dd1: 8258663: Fixed size TableCells are not removed from sene graph when column is removed
  • 28475cb: 8263807: Button types of a DialogPane are set twice, returns a wrong button
  • cc94e96: 8217955: Problems with touch input and JavaFX 11
  • 9796a83: 8263322: Calling Application.launch on FX thread should throw IllegalStateException, but causes deadlock
  • 5898858: 8263169: [macos] JavaFX windows open as tabs when system preference for documents is set
  • e63931e: 8262366: Update glib to version 2.66.7
  • ... and 34 more: https://git.openjdk.java.net/jfx/compare/d4058a181a16615d604582f95d4fc2be6bda98ab...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

@openjdk openjdk bot added the ready label Apr 16, 2021
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@johanvos johanvos commented Apr 16, 2021

/integrate

@openjdk openjdk bot closed this Apr 16, 2021
@openjdk openjdk bot added integrated and removed ready labels Apr 16, 2021
@openjdk openjdk bot removed the rfr label Apr 16, 2021
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@openjdk openjdk bot commented Apr 16, 2021

@johanvos Since your change was applied there have been 44 commits pushed to the master branch:

  • 05ab799: 8208088: Memory Leak in ControlAcceleratorSupport
  • e8689fe: 8265031: Change default macOS min version for x86_64 to 10.12 and aarch64 to 11.0
  • c8384a1: 8264928: Update to Xcode 12.4
  • 808b107: 8260245: Update ICU4C to version 68.2
  • d808dd1: 8258663: Fixed size TableCells are not removed from sene graph when column is removed
  • 28475cb: 8263807: Button types of a DialogPane are set twice, returns a wrong button
  • cc94e96: 8217955: Problems with touch input and JavaFX 11
  • 9796a83: 8263322: Calling Application.launch on FX thread should throw IllegalStateException, but causes deadlock
  • 5898858: 8263169: [macos] JavaFX windows open as tabs when system preference for documents is set
  • e63931e: 8262366: Update glib to version 2.66.7
  • ... and 34 more: https://git.openjdk.java.net/jfx/compare/d4058a181a16615d604582f95d4fc2be6bda98ab...master

Your commit was automatically rebased without conflicts.

Pushed as commit 8e54757.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

// When the position is changed explicitly, we need to make sure
// the absolute offset is changed accordingly.
adjustAbsoluteOffset();
}
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@mstr2 mstr2 Nov 3, 2021

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This seems to violate the invariant setPosition(...)positionProperty().set(...).

Your comment indicates that this is by design, but how do you prevent people from invoking positionProperty().set(...) and getting a different behavior?

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