fix: hide scroll arrows at list boundary in popup

[mhduiy]

Root Cause Analysis

In the timezone selection popup (SearchableListViewPopup.qml), the up/down scroll arrow buttons' visible property was bound only to listView.interactive (whether the list is scrollable), without checking the scroll position. This means the arrows remained visible even when the user scrolled to the top or bottom of the list. The down arrow had enabled: !listView.atYEnd but visible was still true, so it only grayed out instead of disappearing.

Key evidence: SearchableListViewPopup.qml:187 (up arrow) and :265 (down arrow) both had visible: listView.interactive without atYBeginning/atYEnd boundary checks.

Fix

Added !listView.atYBeginning to the up arrow's visible binding and !listView.atYEnd to the down arrow's visible binding, using Qt Quick ListView standard read-only properties. Only 2 lines changed, no new dependencies or refactoring.

Change Safety Assessment

Code Safety

• Risk Level: Low
• Target lines were introduced in a refactor (commit f4845fcc, DTK Popup replacement), not a previous bug fix — this change does not revert any historical fix
• No external callers reference the upButton/downButton QML component IDs; changes are local to the popup component

Business Impact Scope

The change affects the timezone list popup in Control Center's Date & Time module. When the list has more than 10 items (scrollable), scrolling to the top now hides the up arrow and scrolling to the bottom hides the down arrow. When the list has fewer than 10 items, both arrows remain hidden (unchanged behavior). The ColumnLayout automatically redistributes space when arrows become invisible, so popup height stays the same.

Verification Suggestion

Test the timezone list popup with more than 10 items: scroll to top/bottom and verify arrows hide, then scroll back to middle and verify arrows reappear. Also verify arrows stay hidden when the list has fewer than 10 items.

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根因分析

在时区选择弹窗（SearchableListViewPopup.qml）中，上下滚动箭头按钮的 visible 属性仅绑定了 listView.interactive（列表是否可滚动），未检查滚动位置。这导致用户滚动到列表顶部或底部时箭头仍然可见。下箭头虽有 enabled: !listView.atYEnd 但 visible 仍为 true，仅变灰未消失。

关键证据：SearchableListViewPopup.qml:187（上箭头）和 :265（下箭头）的 visible 绑定均缺少 atYBeginning/atYEnd 边界判断。

修复方案

在上箭头 visible 绑定中追加 !listView.atYBeginning，在下箭头 visible 绑定中追加 !listView.atYEnd，利用 Qt Quick ListView 标准只读属性。仅改动 2 行，无新依赖或重构。

改动安全评估

代码安全评估

• 风险等级: 低风险
• 目标行由重构 commit（f4845fcc，DTK Popup 替换）引入，非历史 bug 修复产物——本次修改不会撤销历史修复
• 无外部调用者引用 upButton/downButton 组件 ID，改动局限于弹窗组件内部

业务影响范围

改动影响控制中心时间和日期模块的时区列表弹窗。列表超过 10 项（可滚动）时，滚动到顶部隐藏上箭头、滚动到底部隐藏下箭头。列表不足 10 项时两个箭头均不显示（行为不变）。箭头不可见时 ColumnLayout 自动重新分配空间，弹窗高度不变。

验证建议

测试时区列表弹窗超过 10 项时：滚动到顶部/底部验证箭头消失，滚回中间验证箭头重新出现。同时验证列表不足 10 项时箭头不显示。

Summary by Sourcery

Bug Fixes:

• Hide the timezone popup’s scroll arrows when the list is already at the corresponding top or bottom boundary.

[sourcery-ai]

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[deepin-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: mhduiy

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Details

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• debian/deepin/OWNERS

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[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Updates the timezone selection popup to hide the up arrow at the list’s top and the down arrow at its bottom, while preserving the existing behavior for non-scrollable and mid-scroll states.

State diagram for timezone list arrow visibility

stateDiagram-v2
    [*] --> NonScrollable
    NonScrollable --> NonScrollable: listView.interactive = false
    ScrollableMiddle --> Top: listView.atYBeginning
    ScrollableMiddle --> Bottom: listView.atYEnd
    Top --> ScrollableMiddle: !listView.atYBeginning
    Bottom --> ScrollableMiddle: !listView.atYEnd

    state NonScrollable {
        upButton: hidden
        downButton: hidden
    }
    state Top {
        upButton: hidden
        downButton: visible
    }
    state ScrollableMiddle {
        upButton: visible
        downButton: visible
    }
    state Bottom {
        upButton: visible
        downButton: hidden
    }

Loading

File-Level Changes

Change	Details	Files
Make popup scroll arrows visible only when additional content exists in their respective direction.	Add a top-boundary check to the up-arrow visibility binding. Add a bottom-boundary check to the down-arrow visibility binding.	src/plugin-datetime/qml/SearchableListViewPopup.qml

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[mhduiy]

这里上下箭头消失会导致布局跳动，保持原有设计，滚动到顶部或者底部的时候设置为disable的状态