// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
 
#nullable disable
 
using System;
 
namespace Microsoft.CodeAnalysis.Editor.Tagging;
 
/// <summary>
/// The events that the <see cref="AbstractAsynchronousTaggerProvider{TTag}"/> listens to, to know when 
/// to request more tags.  For example, an <see cref="ITaggerEventSource"/> may listen to text 
/// buffer changes, and can tell the <see cref="AbstractAsynchronousTaggerProvider{TTag}"/> that it needs
/// to recompute tags.
/// </summary>
internal interface ITaggerEventSource
{
    /// <summary>
    /// Let event source know that it should start sending out events.  Implementation can use
    /// that as a point to attach to events and perform other initialization. This will only be
    /// called once. 
    /// </summary>
    void Connect();
 
    /// <summary>
    /// Let event source know that it is no longer needed.  Implementations can use this as a
    /// point to detach from events and perform other cleanup.  This will only be called once.
    /// </summary>
    void Disconnect();
 
    /// <summary>
    /// Pauses this event source and prevents it from firing the <see cref="Changed"/> event. Can be called many times
    /// (but subsequent calls have no impact if already paused).  Must be called on the UI thread.
    /// </summary>
    void Pause();
 
    /// <summary>
    /// Resumes this event source and allows firing the <see cref="Changed"/> event. Can be called many times (but
    /// subsequent calls have no impact if already resumed).  Must be called on the UI thread.
    /// </summary>
    void Resume();
 
    /// <summary>
    /// An event has happened on the thing the tagger is attached to.  The tagger should
    /// recompute tags.
    /// </summary>
    event EventHandler<TaggerEventArgs> Changed;
}