Introduced a very simple "singleton" service-locator, which allowed for a removal of specific implementations which were very limited. With this it's easier to access dependencies.

GreenshotPlugin/Core/AbstractDestination.cs

@@ -260,7 +260,7 @@ namespace GreenshotPlugin.Core {
 				location.Offset(-40, -10);
 			}
 			// This prevents the problem that the context menu shows in the task-bar
-			User32.SetForegroundWindow(PluginUtils.Host.NotifyIcon.ContextMenuStrip.Handle);
+			User32.SetForegroundWindow(SimpleServiceProvider.Current.GetInstance<NotifyIcon>().ContextMenuStrip.Handle);
 			menu.Show(location);
 			menu.Focus();
 

GreenshotPlugin/Core/Func.cs

@@ -1,29 +0,0 @@
-/*
- * Greenshot - a free and open source screenshot tool
- * Copyright (C) 2007-2020 Thomas Braun, Jens Klingen, Robin Krom
- * 
- * For more information see: http://getgreenshot.org/
- * The Greenshot project is hosted on GitHub https://github.com/greenshot/greenshot
- * 
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 1 of the License, or
- * (at your option) any later version.
- * 
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- * 
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
- */
-
-namespace GreenshotPlugin.Core
-{
-	public delegate TResult Func<out TResult>();
-	public delegate TResult Func<in T, out TResult>(T arg);
-	public delegate TResult Func<in T1, in T2, out TResult>(T1 arg1, T2 arg2);
-	public delegate TResult Func<in T1, in T2, in T3, out TResult>(T1 arg1, T2 arg2, T3 arg3);
-	public delegate TResult Func<in T1, in T2, in T3, in T4, out TResult>(T1 arg1, T2 arg2, T3 arg3, T4 arg4);
-}

GreenshotPlugin/Core/ImageHelper.cs

@@ -52,16 +52,11 @@ namespace GreenshotPlugin.Core {
 		private static readonly CoreConfiguration CoreConfig = IniConfig.GetIniSection<CoreConfiguration>();
 		private const int ExifOrientationId = 0x0112;
 
-		/// <summary>
-		/// This is a factory method to create a surface, set from the Greenshot main project
-		/// </summary>
-		public static Func<ISurface> SurfaceFactory { get; set; }
-
-		static ImageHelper()
+        static ImageHelper()
 		{
 			StreamConverters["greenshot"] = (stream, s) =>
 			{
-				var surface = SurfaceFactory();
+				var surface = SimpleServiceProvider.Current.GetInstance<Func<ISurface>>().Invoke();
 				return surface.GetImageForExport();
 			};
 

GreenshotPlugin/Core/PluginUtils.cs

@@ -45,14 +45,6 @@ namespace GreenshotPlugin.Core {
 			CoreConfig.PropertyChanged += OnIconSizeChanged;
 		}
 
-		/// <summary>
-		/// Simple global property to get the Greenshot host
-		/// </summary>
-		public static IGreenshotHost Host {
-			get;
-			set;
-		}
-
 		/// <summary>
 		/// Clear icon cache
 		/// </summary>
@@ -220,11 +212,10 @@ namespace GreenshotPlugin.Core {
 		/// <summary>
 		/// Helper method to add a plugin MenuItem to the Greenshot context menu
 		/// </summary>
-		/// <param name="host">IGreenshotHost</param>
 		/// <param name="item">ToolStripMenuItem</param>
-		public static void AddToContextMenu(IGreenshotHost host, ToolStripMenuItem item) {
-			// Here we can hang ourselves to the main context menu!
-			ContextMenuStrip contextMenu = host.MainMenu;
+		public static void AddToContextMenu(ToolStripMenuItem item) {
+            // Here we can hang ourselves to the main context menu!
+            var contextMenu = SimpleServiceProvider.Current.GetInstance<ContextMenuStrip>();
 			bool addedItem = false;
 
 			// Try to find a separator, so we insert ourselves after it 

GreenshotPlugin/Core/SimpleServiceProvider.cs

@@ -0,0 +1,55 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using GreenshotPlugin.Interfaces;
+
+namespace GreenshotPlugin.Core
+{
+    /// <summary>
+    /// A really cheap and simple DI system
+    /// </summary>
+    public class SimpleServiceProvider : IServiceLocator
+    {
+        private readonly Dictionary<Type, List<object>> _services = new Dictionary<Type, List<object>>();
+
+        public static IServiceLocator Current { get; } = new SimpleServiceProvider();
+
+        public IEnumerable<TService> GetAllInstances<TService>()
+        {
+            var typeOfService = typeof(TService);
+            if (!_services.TryGetValue(typeOfService, out var results))
+            {
+                yield break;
+            }
+            foreach (TService result in results)
+            {
+                yield return result;
+            }
+        }
+
+        public TService GetInstance<TService>()
+        {
+            return GetAllInstances<TService>().SingleOrDefault();
+        }
+
+        public void AddService<TService>(IEnumerable<TService> services)
+        {
+            var serviceType = typeof(TService);
+            if (!_services.TryGetValue(serviceType, out var currentServices))
+            {
+                currentServices = new List<object>();
+                _services.Add(serviceType, currentServices);
+            }
+
+            foreach (var service in services)
+            {
+                currentServices.Add(service);
+            }
+        }
+
+        public void AddService<TService>(params TService[] services)
+        {
+            AddService(services.AsEnumerable());
+        }
+    }
+}