fix: use positionViewAtBeginning instead of set contentY

[BLumia]

It is not recommended to use contentX or contentY to position the view at a particular index. This is unreliable since removing items from the start of the list does not cause all other items to be repositioned, and because the actual start of the view can vary based on the size of the delegates.

PMS: BUG-356795

Summary by Sourcery

Bug Fixes:

• Use positionViewAtBeginning() to reliably scroll the app list to the top instead of setting contentY to 0.

[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Replaces direct manipulation of ListView scroll position via contentY with the recommended positionViewAtBeginning() API when resetting the app list view to the start, ensuring robust behavior when items are added/removed or delegate sizes vary.

Sequence diagram for resetting the app list view to the beginning

sequenceDiagram
    actor User
    participant AppListView
    participant ListView
    participant LauncherController

    User->>AppListView: triggerReset()
    AppListView->>ListView: set currentIndex(0)
    AppListView->>ListView: set highlightFollowsCurrentItem(false)
    AppListView->>ListView: positionViewAtBeginning()
    AppListView->>ListView: restore highlightFollowsCurrentItem(wasFollowing)
    AppListView->>LauncherController: check visible
    alt LauncherController not visible
        AppListView->>AppListView: alphabetCategoryPopup.close()
    end

Loading

File-Level Changes

Change	Details	Files
Use ListView.positionViewAtBeginning() instead of manually setting contentY when resetting the app list to the top.	Capture and temporarily disable highlightFollowsCurrentItem while resetting the ListView position to avoid highlight side effects Set currentIndex to 0 before repositioning the view so the beginning item is current Replace listView.contentY = 0 with listView.positionViewAtBeginning() to correctly align the view at the start according to ListView semantics Restore highlightFollowsCurrentItem to its previous value after repositioning	qml/windowed/AppListView.qml

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[deepin-ci-robot]

deepin pr auto review

这段代码修改主要涉及 QML 中 ListView 的滚动行为控制。以下是对该 git diff 的详细审查意见：

1. 语法逻辑审查

• 修改内容：将 listView.contentY = 0 替换为 listView.positionViewAtBeginning()。
• 分析：
  • 原代码 (contentY = 0)：这是一种强制设置视图内容 Y 轴偏移量的做法。它直接操作内部属性，假设视图的起始位置就是 0。这在大多数情况下有效，但如果列表有 header（表头）或 topMargin（顶部边距），直接设置 contentY 为 0 可能会导致视图定位不准确（例如表头被遮挡或显示不完整）。
  • 新代码 (positionViewAtBeginning())：这是 QML 提供的 API 方法，专门用于将视图滚动到列表的起始位置。它会自动处理 header 和 margins 的存在，确保列表的第一个可见项正确显示在视图中。
• 结论：逻辑上，新代码更加健壮和语义化，它封装了"回到顶部"的复杂逻辑，而不是简单地重置坐标。

2. 代码质量审查

• 可读性与可维护性：positionViewAtBeginning() 是一个自解释的函数名，清晰地表达了"将视图定位到开头"的意图。相比之下，contentY = 0 只是底层的属性赋值，阅读代码时需要脑补其意图。新代码提高了代码的可读性。
• 封装性：使用 API 方法（positionViewAtBeginning）优于直接操作内部属性（contentY），符合良好的封装原则。如果 Qt 框架在未来改变了内部实现细节，API 方法通常会保持兼容，而直接操作属性则可能失效。

3. 代码性能审查

• 动画效果：positionViewAtBeginning() 默认可能会触发平滑滚动动画（取决于 ListView 的 highlightMoveDuration 或 behavior 设置），而 contentY = 0 是瞬间跳转。
  • 如果该函数的目的是"瞬间重置"（例如刷新列表时），原代码可能在视觉上更干脆。
  • 如果该函数的目的是"用户点击回到顶部"，新代码带来的平滑滚动体验更好。
• 计算开销：两者开销差异极小，可以忽略不计。positionViewAtBeginning 内部也是计算并设置 contentY。

4. 代码安全审查

• 边界条件处理：如前所述，positionViewAtBeginning() 能更好地处理包含 header 或 margins 的列表，避免了因直接设置 contentY 导致的布局错位风险。
• 状态一致性：代码片段中先保存并禁用了 highlightFollowsCurrentItem，操作结束后再恢复。这是一个很好的做法，防止在滚动过程中高亮框产生不必要的动画跳动，保证了状态的一致性。

改进建议

虽然这次修改是正向的，但根据具体场景，可以考虑以下微调：

1. 明确滚动模式：如果业务逻辑要求必须瞬间回到顶部（例如数据重载场景），而不需要任何过渡动画，建议使用 positionViewAtBeginning() 的重载形式，明确指定模式：

   listView.positionViewAtBeginning(ListView.Beginning)
   // 或者如果需要确保不触发动画，检查具体 Qt 版本的 API，
   // 某些版本可能需要配合 highlightMoveDuration = 0 使用

   注：标准 QML positionViewAtBeginning() 默认行为通常是平滑滚动的。如果原代码 contentY = 0 是为了实现"瞬间跳变"的效果，那么这次修改可能会改变 UI 交互体验（从瞬间跳变变为平滑滚动）。请确认这是否符合预期设计。

2. 上下文检查：虽然 listView 应该已定义，但在更严格的代码审查中，确保 listView 对象在该作用域内确实存在且是 ListView 类型。

总结

这次修改是推荐的。它将直接操作属性替换为语义化的 API 调用，增强了代码的可读性和对复杂布局（如带 Header 的列表）的兼容性。唯一需要注意的是确认是否需要保留"瞬间跳转"的视觉效果，如果需要，可能需要配合禁用动画的属性使用。

[sourcery-ai]

Hey - I've reviewed your changes and they look great!

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[deepin-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: BLumia, wjyrich

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