Fix: Virtual lecterns not displaying book contents (#5169)

Author: onebeastchris

core/src/main/java/org/geysermc/geyser/inventory/LecternContainer.java

@@ -34,26 +34,24 @@
 import org.geysermc.geyser.translator.protocol.java.inventory.JavaOpenBookTranslator;
 import org.geysermc.mcprotocollib.protocol.data.game.inventory.ContainerType;
 
+@Getter
 public class LecternContainer extends Container {
-    @Getter @Setter
+    @Setter
     private int currentBedrockPage = 0;
-    @Getter @Setter
+    @Setter
     private NbtMap blockEntityTag;
-    @Getter @Setter
+    @Setter
     private Vector3i position;
 
-    // Sigh. When the lectern container is created, we don't know (yet) if it's fake or not.
-    // So... time for a manual check :/
-    @Getter
     private boolean isFakeLectern = false;
 
     public LecternContainer(String title, int id, int size, ContainerType containerType, PlayerInventory playerInventory) {
         super(title, id, size, containerType, playerInventory);
     }
 
     /**
-     * When we are using a fake lectern, the Java server expects us to still be in a player inventory.
-     * We can't use {@link #isUsingRealBlock()} as that may not be determined yet.
+     * When the Java server asks the client to open a book in their hotbar, we create a fake lectern to show it to the client.
+     * We can't use the {@link #isUsingRealBlock()} check as we may also be dealing with a real virtual lectern (with its own inventory).
      */
     @Override
     public void setItem(int slot, @NonNull GeyserItemStack newItem, GeyserSession session) {

core/src/main/java/org/geysermc/geyser/inventory/holder/BlockInventoryHolder.java

@@ -157,7 +157,7 @@ public void openInventory(InventoryTranslator translator, GeyserSession session,
     @Override
     public void closeInventory(InventoryTranslator translator, GeyserSession session, Inventory inventory) {
         if (inventory instanceof Container container) {
-            if (container.isUsingRealBlock() && !(inventory instanceof LecternContainer)) {
+            if (container.isUsingRealBlock() && !(container instanceof LecternContainer)) {
                 // No need to reset a block since we didn't change any blocks
                 // But send a container close packet because we aren't destroying the original.
                 ContainerClosePacket packet = new ContainerClosePacket();

core/src/main/java/org/geysermc/geyser/translator/inventory/LecternInventoryTranslator.java

@@ -30,8 +30,6 @@
 import org.cloudburstmc.nbt.NbtMapBuilder;
 import org.cloudburstmc.protocol.bedrock.data.inventory.ItemData;
 import org.geysermc.erosion.util.LecternUtils;
-import org.geysermc.geyser.GeyserImpl;
-import org.geysermc.geyser.inventory.Container;
 import org.geysermc.geyser.inventory.GeyserItemStack;
 import org.geysermc.geyser.inventory.Inventory;
 import org.geysermc.geyser.inventory.LecternContainer;
@@ -55,7 +53,7 @@ public class LecternInventoryTranslator extends AbstractBlockInventoryTranslator
      * Hack: Java opens a lectern first, and then follows it up with a ClientboundContainerSetContentPacket
      * to actually send the book's contents. We delay opening the inventory until the book was sent.
      */
-    private boolean initialized = false;
+    private boolean receivedBook = false;
 
     public LecternInventoryTranslator() {
         super(1, Blocks.LECTERN, org.cloudburstmc.protocol.bedrock.data.inventory.ContainerType.LECTERN , ContainerInventoryUpdater.INSTANCE);
@@ -64,11 +62,12 @@ public LecternInventoryTranslator() {
     @Override
     public boolean prepareInventory(GeyserSession session, Inventory inventory) {
         super.prepareInventory(session, inventory);
-        if (((Container) inventory).isUsingRealBlock()) {
-            initialized = false; // We have to wait until we get the book to show to the client
+        if (((LecternContainer) inventory).isFakeLectern()) {
+            // See JavaOpenBookTranslator; this isn't a lectern but a book in the player inventory
+            updateBook(session, inventory, inventory.getItem(0));
+            receivedBook = true;
         } else {
-            updateBook(session, inventory, inventory.getItem(0)); // See JavaOpenBookTranslator; placed here manually
-            initialized = true;
+            receivedBook = false; // We have to wait until we get the book
         }
         return true;
     }
@@ -79,7 +78,7 @@ public void openInventory(GeyserSession session, Inventory inventory) {
         // "initialized" indicates whether we've received the book from the Java server yet.
         // dropping lectern book is the fun workaround when we have to enter the gui to drop the book.
         // Since we leave it immediately... don't open it!
-        if (initialized && !session.isDroppingLecternBook()) {
+        if (receivedBook && !session.isDroppingLecternBook()) {
             super.openInventory(session, inventory);
         }
     }
@@ -122,8 +121,8 @@ public void updateInventory(GeyserSession session, Inventory inventory) {
             boolean isDropping = session.isDroppingLecternBook();
             updateBook(session, inventory, itemStack);
 
-            if (!initialized && !isDropping) {
-                initialized = true;
+            if (!receivedBook && !isDropping) {
+                receivedBook = true;
                 openInventory(session, inventory);
             }
         }