MyAvaloniaDemo/Attached/TextMateHelper.cs

using System;
using System.Collections.Generic;
using Avalonia;
using AvaloniaEdit;
using AvaloniaEdit.TextMate;
using TextMateSharp.Grammars;

namespace MyAvaloniaApp.Attached;

/// <summary>
/// 为 <see cref="TextEditor"/> 提供基于 TextMate 的语法高亮附加属性，
/// 通过 MVVM 绑定即可切换语法与主题。
/// </summary>
public static class TextMateHelper
{
    public static readonly AttachedProperty<string?> LanguageProperty =
        AvaloniaProperty.RegisterAttached<TextEditor, string?>(
            "Language",
            typeof(TextMateHelper));

    private static readonly AttachedProperty<RegistryOptions?> RegistryOptionsProperty =
        AvaloniaProperty.RegisterAttached<TextEditor, RegistryOptions?>(
            "RegistryOptions",
            typeof(TextMateHelper));

    private static readonly AttachedProperty<TextMate.Installation?> InstallationProperty =
        AvaloniaProperty.RegisterAttached<TextEditor, TextMate.Installation?>(
            "Installation",
            typeof(TextMateHelper));

    private static readonly IReadOnlyDictionary<string, string> LanguageScopes =
        new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase)
        {
            ["C#"] = "source.cs",
            ["JavaScript"] = "source.js",
            ["TypeScript"] = "source.ts",
            ["HTML"] = "text.html.basic",
            ["CSS"] = "source.css",
            ["JSON"] = "source.json",
            ["XML"] = "text.xml",
            ["Python"] = "source.python",
            ["Java"] = "source.java",
            ["SQL"] = "source.sql"
        };

    static TextMateHelper() => LanguageProperty.Changed.AddClassHandler<TextEditor>(OnLanguageChanged);

    public static void SetLanguage(TextEditor editor, string? value) =>
        editor.SetValue(LanguageProperty, value);

    public static string? GetLanguage(TextEditor editor) =>
        editor.GetValue(LanguageProperty);

    private static void OnLanguageChanged(TextEditor editor, AvaloniaPropertyChangedEventArgs change)
    {
        var language = change.NewValue as string;
        var registryOptions = EnsureRegistryOptions(editor);
        var installation = EnsureInstallation(editor, registryOptions);

        if (installation == null)
        {
            return;
        }

        var scope = ResolveScope(language);

        if (!string.IsNullOrWhiteSpace(scope))
        {
            try
            {
                installation.SetGrammar(scope);
            }
            catch (Exception ex)
            {
                System.Diagnostics.Debug.WriteLine($"TextMateHelper: 设置语法失败 - {ex.Message}");
            }
        }
    }

    private static RegistryOptions EnsureRegistryOptions(TextEditor editor)
    {
        var registryOptions = editor.GetValue(RegistryOptionsProperty);

        if (registryOptions == null)
        {
            registryOptions = new RegistryOptions(ThemeName.DarkPlus);
            editor.SetValue(RegistryOptionsProperty, registryOptions);
        }

        return registryOptions;
    }

    private static TextMate.Installation? EnsureInstallation(TextEditor editor, RegistryOptions registryOptions)
    {
        var installation = editor.GetValue(InstallationProperty);
        if (installation == null)
        {
            try
            {
                installation = editor.InstallTextMate(registryOptions);
                editor.SetValue(InstallationProperty, installation);
            }
            catch (Exception ex)
            {
                System.Diagnostics.Debug.WriteLine($"TextMateHelper: 安装失败 - {ex.Message}");
            }
        }

        return installation;
    }

    private static string ResolveScope(string? language)
    {
        if (string.IsNullOrWhiteSpace(language))
        {
            return "source.cs";
        }

        return LanguageScopes.TryGetValue(language, out var value)
            ? value
            : "source.cs";
    }
}