When the window is closed during loading, exit the game quickly (#3858)

src/main/java/net/minecraftforge/fml/client/FMLClientHandler.java

@@ -637,6 +637,12 @@ public class FMLClientHandler implements IFMLSidedHandler
         return loading;
     }
 
+    @Override
+    public boolean isDisplayCloseRequested()
+    {
+        return Display.isCreated() && Display.isCloseRequested();
+    }
+
     @Override
     public boolean shouldServerShouldBeKilledQuietly()
     {

src/main/java/net/minecraftforge/fml/common/FMLCommonHandler.java

@@ -438,6 +438,11 @@ public class FMLCommonHandler
         if (!confirmed) StartupQuery.abort();
     }
 
+    public boolean isDisplayCloseRequested()
+    {
+        return sidedDelegate != null && sidedDelegate.isDisplayCloseRequested();
+    }
+
     public boolean shouldServerBeKilledQuietly()
     {
         if (sidedDelegate == null)

src/main/java/net/minecraftforge/fml/common/IFMLSidedHandler.java

@@ -51,6 +51,8 @@ public interface IFMLSidedHandler
 
     MinecraftServer getServer();
 
+    boolean isDisplayCloseRequested();
+
     boolean shouldServerShouldBeKilledQuietly();
 
     void addModAsResource(ModContainer container);

src/main/java/net/minecraftforge/fml/common/LoadController.java

@@ -150,6 +150,12 @@ public class LoadController
 
     public void transition(LoaderState desiredState, boolean forceState)
     {
+        if (FMLCommonHandler.instance().isDisplayCloseRequested())
+        {
+            FMLLog.info("The game window is being closed by the player, exiting.");
+            FMLCommonHandler.instance().exitJava(0, false);
+        }
+
         LoaderState oldState = state;
         state = state.transition(!errors.isEmpty());
         if (state != desiredState && !forceState)

src/main/java/net/minecraftforge/fml/server/FMLServerHandler.java

@@ -222,6 +222,12 @@ public class FMLServerHandler implements IFMLSidedHandler
         }
     }
 
+    @Override
+    public boolean isDisplayCloseRequested()
+    {
+        return false;
+    }
+
     @Override
     public boolean shouldServerShouldBeKilledQuietly()
     {