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  1. Qt
  2. QTBUG-82989

Decide upon and document our stance on binding to parent in delegates

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Details

    • ed73efa27acd8e7c42a960ef90c2e4a898c20c30 (qt/qtdeclarative/dev) 353fb2226b1a48252ff6e43d404c725f9936e0cf (qt/qtdeclarative/5.15)

    Description

      1. https://codereview.qt-project.org/c/qt/qtdeclarative/+/282546 resulted in some warnings being printed: https://bugreports.qt.io/browse/QTBUG-81976
      2. https://codereview.qt-project.org/c/qt/qtdeclarative/+/290237 was introduced to fix the warning
      3. https://codereview.qt-project.org/c/qt/qtdeclarative/+/291389 reverted the warning because it is a "dubious use case"

      Currently, binding to the parent is not discouraged by documentation, and never has been. ListView's documentation even states what the parent of a delegate is:

      Delegates are instantiated as needed and may be destroyed at any time. They are parented to ListView's contentItem, not to the view itself. State should never be stored in a delegate.

      Whatever we decide on doing, we need to document it comprehensively, so that everyone is aware of the change in behaviour. As it stands now, users are going to run into a tonne of warnings in 5.15, and will have no documentation (or even a ChangeLog entry) to guide them.

      We should:

      • Add a ChangeLog entry somehow
      • Update the "They are parented to ListView's contentItem" line in ListView's documentation
      • Add a paragraph explaining that binding to parent should be avoided and why, and link to this section in the \sa of ListView's delegate documentation

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        Issue Links

          is duplicated by

          Task - A task that needs to be done. QTBUG-82393 Deal with parent bindings in delegates

          • P2: Important - Urgent, should be fixed, but will not stop the release.
          • Closed
          is required for

          Bug - A problem which impairs or prevents the functions of the product. QTBUG-82368 DialogButtonBox::test_attached fails

          • P1: Critical - Urgent and Important, will STOP the release if matched with set FixVersion field. This includes regressions from the last version that are not edge cases; Data loss; Build issues; All but the most unlikely crashes/lockups/hanging; Serious usability issues and embarrassing bugs & Bugs critical to a deliverable. This is the highest possible priority for requirements.
          • Closed
          relates to

          Bug - A problem which impairs or prevents the functions of the product. QTBUG-63729 [REG 5.9.1->5.9.2]: When an item loaded in a loader is destroyed then it can cause children to print warnings that referred to the parent

          • P2: Important - Urgent, should be fixed, but will not stop the release.
          • Closed

          Task - A task that needs to be done. QTBUG-77926 Implement Optional Chaining and Nullish coalescing Operator in QML

          • P3: Somewhat important - Should be fixed, but doesn't affect the release in any way.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. QTBUG-81976 ListView delegates produces "TypeError: Cannot read property 'width' of null" when removing item from QAbstractItemModel

          • P1: Critical - Urgent and Important, will STOP the release if matched with set FixVersion field. This includes regressions from the last version that are not edge cases; Data loss; Build issues; All but the most unlikely crashes/lockups/hanging; Serious usability issues and embarrassing bugs & Bugs critical to a deliverable. This is the highest possible priority for requirements.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. QTBUG-84453 "TypeError: Cannot read property 'width' of null" when running Swipe to Remove example

          • P2: Important - Urgent, should be fixed, but will not stop the release.
          • Closed
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              richard Richard Moe Gustavsen
              mitch_curtis Mitch Curtis
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                Resolved:

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