Add "Server List" button in the Minecraft pause GUI

This patch adds a new "Server List" button replacing the disabled
"Open To Lan" button in the multiplayer pause menu :)

Author: Baitinq

src/main/java/com/lambda/mixin/MixinMinecraft.java

@@ -15,6 +15,7 @@
 import net.minecraft.client.gui.GuiScreen;
 import net.minecraft.client.gui.inventory.GuiContainer;
 import net.minecraft.client.multiplayer.PlayerControllerMP;
+import net.minecraft.client.multiplayer.ServerData;
 import net.minecraft.client.multiplayer.WorldClient;
 import net.minecraft.client.settings.GameSettings;
 import net.minecraft.init.Items;
@@ -39,6 +40,7 @@ public abstract class MixinMinecraft {
     @Shadow public GuiScreen currentScreen;
     @Shadow public GameSettings gameSettings;
     @Shadow public PlayerControllerMP playerController;
+    @Shadow private ServerData currentServerData;
     @Shadow private int fpsCounter;
     private boolean handActive = false;
     private boolean isHittingBlock = false;
@@ -173,4 +175,15 @@ public void setIngameFocus(CallbackInfo info) {
         }
     }
 
+    @Inject(method = "loadWorld(Lnet/minecraft/client/multiplayer/WorldClient;Ljava/lang/String;)V", at = @At("HEAD"))
+    public void loadWorld(WorldClient worldClientIn, String loadingMessage, CallbackInfo info) {
+        // NOTE: We do this instead of hooking the GuiConnecting constructor because you can't hook into the HEAD of a
+        //       constructor, which is what would be required as we need to have access to the previous world in order
+        //       to disconnect from it :)
+        // If connecting to a server while being in a server
+        if (this.world != null && this.currentServerData != null) {
+            this.world.sendQuittingDisconnectingPacket();
+        }
+    }
+
 }

src/main/java/com/lambda/mixin/gui/MixinGuiIngameMenu.java

@@ -3,9 +3,7 @@
 import com.lambda.client.gui.mc.LambdaGuiAntiDisconnect;
 import com.lambda.client.module.modules.misc.AntiDisconnect;
 import com.lambda.client.util.Wrapper;
-import net.minecraft.client.gui.GuiButton;
-import net.minecraft.client.gui.GuiIngameMenu;
-import net.minecraft.client.gui.GuiScreen;
+import net.minecraft.client.gui.*;
 import org.spongepowered.asm.mixin.Mixin;
 import org.spongepowered.asm.mixin.injection.At;
 import org.spongepowered.asm.mixin.injection.Inject;
@@ -15,11 +13,26 @@
 public class MixinGuiIngameMenu extends GuiScreen {
     @Inject(method = "actionPerformed", at = @At("HEAD"), cancellable = true)
     public void actionPerformed(GuiButton button, CallbackInfo callbackInfo) {
-        if (button.id == 1) {
-            if (AntiDisconnect.INSTANCE.isEnabled()) {
-                Wrapper.getMinecraft().displayGuiScreen(new LambdaGuiAntiDisconnect());
-                callbackInfo.cancel();
-            }
+        switch (button.id) {
+            case 1:
+                if (AntiDisconnect.INSTANCE.isEnabled()) {
+                    Wrapper.getMinecraft().displayGuiScreen(new LambdaGuiAntiDisconnect());
+                    callbackInfo.cancel();
+                }
+                break;
+            case Integer.MIN_VALUE:
+                Wrapper.getMinecraft().displayGuiScreen(new GuiMultiplayer(this));
+                break;
+            default:
+                break;
+        }
+    }
+
+    @Inject(method = "initGui", at = @At("RETURN"))
+    public void initGui(CallbackInfo ci) {
+        if (!mc.isSingleplayer()) {
+            GuiButton openToLanButton = buttonList.remove(4);
+            buttonList.add(new GuiButton(Integer.MIN_VALUE, openToLanButton.x, openToLanButton.y, openToLanButton.width, openToLanButton.height, "Server List"));
         }
     }
 }