rl-client: show FatalErrorDialog when the client crashes

runelite-client/src/main/java/net/runelite/client/rs/ClientLoader.java

@@ -575,7 +575,7 @@ public class ClientLoader implements Supplier<Applet>
 		Class<?> clientClass = classLoader.loadClass(initialClass);
 
 		Applet rs = (Applet) clientClass.newInstance();
-		rs.setStub(new RSAppletStub(config));
+		rs.setStub(new RSAppletStub(config, runtimeConfigLoader));
 
 		if (rs instanceof Client)
 		{

runelite-client/src/main/java/net/runelite/client/rs/RSAppletStub.java

@@ -25,16 +25,28 @@
  */
 package net.runelite.client.rs;
 
+import java.applet.Applet;
 import java.applet.AppletContext;
 import java.applet.AppletStub;
+import java.applet.AudioClip;
+import java.awt.Image;
+import java.io.IOException;
+import java.io.InputStream;
 import java.net.MalformedURLException;
 import java.net.URL;
+import java.util.Enumeration;
+import java.util.Iterator;
+import javax.swing.SwingUtilities;
 import lombok.RequiredArgsConstructor;
+import net.runelite.client.RuntimeConfig;
+import net.runelite.client.RuntimeConfigLoader;
+import net.runelite.client.ui.FatalErrorDialog;
 
 @RequiredArgsConstructor
 class RSAppletStub implements AppletStub
 {
 	private final RSConfig config;
+	private final RuntimeConfigLoader runtimeConfigLoader;
 
 	@Override
 	public boolean isActive()
@@ -70,7 +82,89 @@ class RSAppletStub implements AppletStub
 	@Override
 	public AppletContext getAppletContext()
 	{
-		return null;
+		return new AppletContext()
+		{
+			@Override
+			public AudioClip getAudioClip(URL url)
+			{
+				return null;
+			}
+
+			@Override
+			public Image getImage(URL url)
+			{
+				return null;
+			}
+
+			@Override
+			public Applet getApplet(String name)
+			{
+				return null;
+			}
+
+			@Override
+			public Enumeration<Applet> getApplets()
+			{
+				return null;
+			}
+
+			@Override
+			public void showDocument(URL url)
+			{
+				if (url.getPath().startsWith("/error_game_"))
+				{
+					try
+					{
+						RuntimeConfig rtc = runtimeConfigLoader.get();
+						if (rtc.showOutageMessage())
+						{
+							return;
+						}
+					}
+					catch (Exception e)
+					{
+					}
+
+					String code = url.getPath()
+						.replace("/", "")
+						.replace(".ws", "");
+
+					SwingUtilities.invokeLater(() ->
+						new FatalErrorDialog("OldSchool RuneScape has crashed with the message: " + code + "")
+							.setTitle("RuneLite", "OldSchool RuneScape has crashed")
+							.addHelpButtons()
+							.open());
+				}
+			}
+
+			@Override
+			public void showDocument(URL url, String target)
+			{
+				showDocument(url);
+			}
+
+			@Override
+			public void showStatus(String status)
+			{
+			}
+
+			@Override
+			public void setStream(String key, InputStream stream) throws IOException
+			{
+			}
+
+			@Override
+			public InputStream getStream(String key)
+			{
+				return null;
+			}
+
+			@Override
+			public Iterator<String> getStreamKeys()
+			{
+				return null;
+			}
+		};
 	}
 
 	@Override

runelite-client/src/main/java/net/runelite/client/ui/FatalErrorDialog.java

@@ -61,6 +61,7 @@ public class FatalErrorDialog extends JDialog
 
 	private final JPanel rightColumn = new JPanel();
 	private final Font font = new Font(Font.DIALOG, Font.PLAIN, 12);
+	private final JLabel title;
 
 	public FatalErrorDialog(String message)
 	{
@@ -114,7 +115,7 @@ public class FatalErrorDialog extends JDialog
 		leftPane.setBackground(ColorScheme.DARKER_GRAY_COLOR);
 		leftPane.setLayout(new BorderLayout());
 
-		JLabel title = new JLabel("There was a fatal error starting RuneLite");
+		title = new JLabel("There was a fatal error starting RuneLite");
 		title.setForeground(Color.WHITE);
 		title.setFont(font.deriveFont(16.f));
 		title.setBorder(new EmptyBorder(10, 10, 10, 10));
@@ -186,6 +187,13 @@ public class FatalErrorDialog extends JDialog
 		return this;
 	}
 
+	public FatalErrorDialog setTitle(String windowTitle, String header)
+	{
+		super.setTitle(windowTitle);
+		title.setText(header);
+		return this;
+	}
+
 	public FatalErrorDialog addHelpButtons()
 	{
 		return addButton("Open logs folder", () -> LinkBrowser.open(RuneLite.LOGS_DIR.toString()))