Fix ElasticWrapPanel not skipping hidden children when IsFillHorizontal and ItemWidth are set

[Copilot]

When IsFillHorizontal="True" and ItemWidth are set together, ElasticWrapPanel reserves layout space for invisible children. Without these properties the bug is masked because invisible children report DesiredSize of zero — but the fixed ItemWidth path bypasses that natural zero-size shortcut, assigning full slot width to hidden items regardless of visibility.

Changes

• ElasticWrapPanel.cs — Add if (!child.IsVisible) continue; at the top of the child iteration loop in both MeasureOverride and ArrangeOverride, consistently skipping invisible children before any size calculation or collection placement occurs.

foreach (var child in children)
{
    if (!child.IsVisible) continue;  // ← added
    UVSize sz;
    if (GetIsFixToRB(child)) { ... }
    else
    {
        sz = new UVSize(orientation,
            itemWidthSet ? itemWidth : child.DesiredSize.Width,  // was using itemWidth for hidden children
            ...);
    }
}

• ElasticWrapPanelTests/Tests.cs — Two new tests asserting hidden items are skipped both with and without ItemWidth/IsFillHorizontal set.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• av-build-tel-api-v1.avaloniaui.net
  • Triggering command: /usr/share/dotnet/dotnet dotnet exec --runtimeconfig /home/REDACTED/.nuget/packages/avalonia.buildservices/11.3.1/tools/netstandard2.0/runtimeconfig.json /home/REDACTED/.nuget/packages/avalonia.buildservices/11.3.1/tools/netstandard2.0/Avalonia.BuildServices.Collector.dll (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>ElasticWrapPanel控件不跳过隐藏项问题</issue_title>
<issue_description>ElasticWrapPanel控件，设置了IsFillHorizontal="True" ItemWidth="320"这两项后，隐藏的就不能跳过了，会继续占位。不设置这两个属性可以跳过隐藏项

</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes ElasticWrapPanel控件不跳过隐藏项问题 #895

---

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.

[github-actions]

Package	Line Rate	Branch Rate	Complexity	Health
Ursa	42%	32%	9055	✔
Ursa.Themes.Semi	62%	68%	1021	✔
Summary	50% (11026 / 22013)	35% (2708 / 7751)	10076	✔

[github-actions]

Test Results

726 tests  +2   726 ✅ +2   15s ⏱️ ±0s
  2 suites ±0     0 💤 ±0 
  2 files   ±0     0 ❌ ±0 

Results for commit 2287317. ± Comparison against base commit f1c9dc4.