WinForms中ContextMenuStrip的DPI感知异常问题求助

1. 确认项目DPI感知配置完全生效 #

首先确保项目的DPI配置正确且生效：

• 检查csproj文件中的配置：

<ApplicationHighDpiMode>PerMonitorV2</ApplicationHighDpiMode>

• 在Program.cs中手动设置进程DPI感知（避免SDK自动处理的遗漏）：

[System.Runtime.InteropServices.DllImport("user32.dll")]
private static extern bool SetProcessDpiAwarenessContext(int dpiFlag);

static void Main()
{
    // 启用PerMonitorV2模式
    SetProcessDpiAwarenessContext(-4);
    ApplicationConfiguration.Initialize();
    Application.Run(new MainForm());
}

2. 监听窗口DPI变更，强制更新ContextMenuStrip #

ContextMenuStrip不会自动跟随窗口DPI变更，需要在窗口的DpiChanged事件中手动更新：
在窗体代码中添加以下逻辑：

protected override void OnDpiChanged(DpiChangedEventArgs e)
{
    base.OnDpiChanged(e);
    UpdateContextMenuStripDpi(yourContextMenuStrip, e.DeviceDpiNew);
}

private void UpdateContextMenuStripDpi(ContextMenuStrip cms, int newDpi)
{
    float scaleFactor = newDpi / 96f;
    // 更新菜单字体
    cms.Font = new Font(cms.Font.FontFamily, cms.Font.Size * scaleFactor, cms.Font.Style);
    
    // 递归更新所有子项及子菜单
    cms.SuspendLayout();
    foreach (ToolStripItem item in cms.Items)
    {
        if (item is ToolStripMenuItem menuItem && menuItem.DropDown is ContextMenuStrip subCms)
        {
            UpdateContextMenuStripDpi(subCms, newDpi);
        }
        item.Invalidate();
    }
    cms.ResumeLayout(true);
    cms.PerformLayout();
}

3. 修复勾选标记的缩放问题 #

ToolStripMenuItem的勾选标记默认不会随DPI缩放，需要手动生成适配尺寸的标记图像：
添加以下方法，并在UpdateContextMenuStripDpi中调用：

private void UpdateMenuItemCheckMark(ToolStripMenuItem item, int dpi)
{
    float scale = dpi / 96f;
    int newSize = (int)(16 * scale); // 默认勾选标记尺寸为16x16，按DPI缩放
    
    using (Bitmap bmp = new Bitmap(newSize, newSize))
    using (Graphics g = Graphics.FromImage(bmp))
    {
        g.ScaleTransform(scale, scale);
        // 绘制系统默认勾选标记
        ToolStripRenderer.Default.DrawItemCheck(g, new ToolStripItemImageRenderEventArgs(g, item, SystemIcons.Check.ToBitmap(), new Point(0, 0)));
        item.Image = new Bitmap(bmp);
    }
}

修改UpdateContextMenuStripDpi中的循环逻辑：

if (item is ToolStripMenuItem menuItem)
{
    UpdateMenuItemCheckMark(menuItem, newDpi);
    if (menuItem.DropDown is ContextMenuStrip subCms)
    {
        UpdateContextMenuStripDpi(subCms, newDpi);
    }
    item.Invalidate();
}

4. 处理跨显示器移动后的尺寸还原 #

监听窗体的LocationChanged事件，确保窗口移动时实时检查当前显示器DPI并更新：

public MainForm()
{
    InitializeComponent();
    LocationChanged += MainForm_LocationChanged;
}

private void MainForm_LocationChanged(object sender, EventArgs e)
{
    var currentScreen = Screen.FromControl(this);
    UpdateContextMenuStripDpi(yourContextMenuStrip, currentScreen.DeviceDpi);
}

内容的提问来源于stack exchange，提问作者Daniel