Adaptation plan for Avalonia's customized title bar in Windows 7 environment

problem phenomenon

When using Avalonia to implement a custom title bar on Windows 7, you may encounter compatibility issues that cannot be hidden by the native title bar, resulting in abnormal interface display:

Figure 1: Abnormal display effect of title bar in Win7 environment

technical analysis

Here, I would like to thank you for your help from the WeChat [Avalonia Development and Exchange Group] group:

Figure 2: WeChat group technical exchange

There are differences in the Avalonia framework's handling of window decorations in different Windows versions:

1. • • Windows 10/11 **: Modern window styles are supported by default, and custom title bars can hide native title bars normally
2. • • Windows 7 **: Due to system composer limitations, system decorations need to be explicitly disabled

SystemDecorations属性控制窗口边框和标题栏的显示行为，其枚举值包括：

• Full：完整系统装饰（默认值）
• BorderOnly：仅显示边框
• None：完全禁用系统装饰
• ResizeBorder：仅保留可调整大小的边框

solutions

通过在窗口初始化代码中显式设置SystemDecorations属性为None，可强制隐藏原生标题栏：

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();

        // 关键设置：禁用系统装饰以支持自定义标题栏
        // 在Windows 7环境下必须显式设置，Win10+可省略
        if (OperatingSystem.IsWindows() && !OperatingSystem.IsWindowsVersionAtLeast(6, 2)) // Windows 7及以下
        {
            SystemDecorations = SystemDecorations.None;
        }
    }
}

After setting, the effect is as follows. The native title bar has been successfully hidden, and the custom title bar is displayed normally:

Figure 3: Display effect of the title bar after applying the repair

By the way, to support Win7 AOT running, don't forget to add the NuGet package:

<PackageReference Include="YY-Thunks" Version="1.1.8-Beta4" />