Show a deprecation notice on launch

References #360

windows/TweetDuck/Configuration/Arguments.cs

@@ -9,6 +9,7 @@ static class Arguments {
 		public const string ArgIgnoreGDPR = "-nogdpr";
 		public const string ArgHttpVideo = "-httpvideo";
 		public const string ArgFreeze = "-freeze";
+		public const string ArgHideDeprecation = "-hidedeprecation";
 
 		// internal args
 		public const string ArgRestart = "-restart";

windows/TweetDuck/Dialogs/DeprecationNoticeDialog.cs

@@ -0,0 +1,36 @@
+using System;
+using System.Windows.Forms;
+using TweetLib.Core;
+
+namespace TweetDuck.Dialogs;
+
+static class DeprecationNoticeDialog {
+	public static bool Show() {
+		const string contents = """
+					TweetDuck is no longer being maintained:
+					 - Twitter has been constantly breaking TweetDeck and therefore also breaking TweetDuck.
+					 - Twitter will be replacing TweetDeck with a new version that is incompatible with most of the app's features.
+					 - Twitter is planning to put TweetDeck behind a subscription paywall.
+					
+					There will be no more updates.
+					Continue at your own risk.
+					""";
+
+		using FormMessage message = new FormMessage("TweetDuck Deprecation Notice", contents, MessageBoxIcon.Warning);
+
+		message.AddButton("Exit", DialogResult.Cancel, ControlType.Cancel);
+		message.AddButton("Continue", DialogResult.OK, ControlType.Accept | ControlType.Focused);
+
+		Button btnLearnMore = message.CreateButton("Learn More", x: 9, width: 106);
+		btnLearnMore.Anchor |= AnchorStyles.Left;
+		btnLearnMore.Margin = new Padding(0, 0, 48, 0);
+		btnLearnMore.Click += OnBtnLearnMoreClick;
+		message.AddActionControl(btnLearnMore);
+
+		return message.ShowDialog() == DialogResult.OK;
+	}
+
+	private static void OnBtnLearnMoreClick(object? sender, EventArgs args) {
+		App.SystemHandler.OpenBrowser(Program.Website + "/deprecation");
+	}
+}

windows/TweetDuck/Dialogs/FormMessage.cs

@@ -124,15 +124,7 @@ public Button AddButton(string title, ControlType type) {
 		}
 
 		public Button AddButton(string title, DialogResult result = DialogResult.OK, ControlType type = ControlType.None) {
-			Button button = new Button {
-				Anchor = AnchorStyles.Bottom,
-				Font = SystemFonts.MessageBoxFont,
-				Location = new Point(0, 12),
-				Size = new Size(BrowserUtils.Scale(88, dpiScale), BrowserUtils.Scale(26, dpiScale)),
-				TabIndex = 256 - buttonCount,
-				Text = title,
-				UseVisualStyleBackColor = true
-			};
+			Button button = CreateButton(title);
 
 			button.Click += (_, _) => {
 				ClickedButton = button;
@@ -162,6 +154,18 @@ public Button AddButton(string title, DialogResult result = DialogResult.OK, Con
 			return button;
 		}
 
+		public Button CreateButton(string title, int x = 0, int width = 88) {
+			return new Button {
+				Anchor = AnchorStyles.Bottom,
+				Font = SystemFonts.MessageBoxFont,
+				Location = new Point(x, 12),
+				Size = new Size(BrowserUtils.Scale(width, dpiScale), BrowserUtils.Scale(26, dpiScale)),
+				TabIndex = 256 - buttonCount,
+				Text = title,
+				UseVisualStyleBackColor = true
+			};
+		}
+
 		public void AddActionControl(Control control) {
 			panelActions.Controls.Add(control);
 

windows/TweetDuck/Program.cs

@@ -108,6 +108,10 @@ public void BeforeLaunch() {
 				if (Config.System.Migrate()) {
 					Config.System.Save();
 				}
+				
+				if (!Arguments.HasFlag(Arguments.ArgHideDeprecation) && !DeprecationNoticeDialog.Show()) {
+					Environment.Exit(0);
+				}
 			}
 
 			public void Launch(ResourceCache resourceCache, PluginManager pluginManager) {

windows/TweetDuck/Reporter.cs

@@ -1,6 +1,5 @@
 using System;
 using System.Diagnostics;
-using System.Drawing;
 using System.Windows.Forms;
 using TweetDuck.Dialogs;
 using TweetDuck.Management;
@@ -36,16 +35,10 @@ public void HandleException(string caption, string message, bool canIgnore, Exce
 				btnIgnore.Enabled = canIgnore;
 				form.ActiveControl = canIgnore ? btnIgnore : btnExit;
 
-				Button btnOpenLog = new Button {
-					Anchor = AnchorStyles.Bottom | AnchorStyles.Left,
-					Enabled = loggedSuccessfully,
-					Font = SystemFonts.MessageBoxFont,
-					Location = new Point(9, 12),
-					Margin = new Padding(0, 0, 48, 0),
-					Size = new Size(106, 26),
-					Text = "Show Error Log",
-					UseVisualStyleBackColor = true
-				};
+				Button btnOpenLog = form.CreateButton("Show Error Log", x: 9, width: 106);
+				btnOpenLog.Anchor |= AnchorStyles.Left;
+				btnOpenLog.Enabled = loggedSuccessfully;
+				btnOpenLog.Margin = new Padding(0, 0, 48, 0);
 
 				btnOpenLog.Click += static (_, _) => {
 					if (!OpenLogFile()) {