prevent players from dropping and losing items

include/globals.h

@@ -91,8 +91,10 @@ typedef struct {
   uint8_t hotbar;
   uint16_t inventory_items[41];
   uint16_t craft_items[9];
+  uint16_t cursor_item;
   uint8_t inventory_count[41];
   uint8_t craft_count[9];
+  uint8_t cursor_count;
   // 0x01 - attack cooldown
   // 0x02 - has not spawned yet
   // 0x04 - sneaking

include/packets.h

@@ -32,6 +32,7 @@ int sc_setCenterChunk (int client_fd, int x, int y);
 int sc_chunkDataAndUpdateLight (int client_fd, int _x, int _z);
 int sc_keepAlive (int client_fd);
 int sc_setContainerSlot (int client_fd, int window_id, uint16_t slot, uint8_t count, uint16_t item);
+int sc_setCursorItem (int client_fd, uint16_t item, uint8_t count);
 int sc_setHeldItem (int client_fd, uint8_t slot);
 int sc_blockUpdate (int client_fd, int64_t x, int64_t y, int64_t z, uint8_t block);
 int sc_openScreen (int client_fd, uint8_t window, const char *title, uint16_t length);

include/tools.h

@@ -26,6 +26,7 @@ ssize_t writeDouble (int client_fd, double num);
 
 uint8_t readByte (int client_fd);
 uint16_t readUint16 (int client_fd);
+int16_t readInt16 (int client_fd);
 uint32_t readUint32 (int client_fd);
 uint64_t readUint64 (int client_fd);
 int64_t readInt64 (int client_fd);

src/packets.c

@@ -504,15 +504,37 @@ int cs_clickContainer (int client_fd) {
   int window_id = readVarInt(client_fd);
 
   readVarInt(client_fd); // ignore state id
-  readUint16(client_fd); // ignore clicked slot number
+
-  readByte(client_fd);   // ignore button
+  int16_t clicked_slot = readInt16(client_fd);
-  readVarInt(client_fd); // ignore operation mode
+  uint8_t button = readByte(client_fd);
+  uint8_t mode = readVarInt(client_fd);
 
   int changes_count = readVarInt(client_fd);
 
   PlayerData *player;
   if (getPlayerData(client_fd, &player)) return 1;
 
+  uint8_t apply_changes = true;
+  // prevent dropping items
+  if (mode == 4 && clicked_slot != -999) {
+    // when using drop button, re-sync the respective slot
+    uint8_t slot = clientSlotToServerSlot(window_id, clicked_slot);
+    sc_setContainerSlot(client_fd, window_id, clicked_slot, player->inventory_count[slot], player->inventory_items[slot]);
+    apply_changes = false;
+  } else if (mode == 0 && clicked_slot == -999) {
+    // when clicking outside inventory, return the dropped item to the player
+    if (button == 0) {
+      givePlayerItem(player, player->cursor_item, player->cursor_count);
+      player->cursor_item = 0;
+      player->cursor_count = 0;
+    } else {
+      givePlayerItem(player, player->cursor_item, 1);
+      player->cursor_count -= 1;
+      if (player->cursor_count == 0) player->cursor_item = 0;
+    }
+    apply_changes = false;
+  }
+
   uint8_t slot, count, craft = false;
   uint16_t item;
   int tmp;
@@ -521,10 +543,10 @@ int cs_clickContainer (int client_fd) {
 
     slot = clientSlotToServerSlot(window_id, readUint16(client_fd));
     // slots outside of the inventory overflow into the crafting buffer
-    if (slot > 40) craft = true;
+    if (slot > 40 && apply_changes) craft = true;
 
     if (!readByte(client_fd)) { // no item?
-      if (slot != 255) {
+      if (slot != 255 && apply_changes) {
         player->inventory_items[slot] = 0;
         player->inventory_count[slot] = 0;
       }
@@ -540,7 +562,7 @@ int cs_clickContainer (int client_fd) {
     tmp = readVarInt(client_fd);
     recv_all(client_fd, recv_buffer, tmp, false);
 
-    if (count > 0) {
+    if (count > 0 && apply_changes) {
       player->inventory_items[slot] = item;
       player->inventory_count[slot] = count;
     }
@@ -558,20 +580,42 @@ int cs_clickContainer (int client_fd) {
     }
   }
 
-  // read but ignore carried item slot (for now)
+  // assign cursor-carried item slot
   if (readByte(client_fd)) {
-    readVarInt(client_fd);
+    player->cursor_item = readVarInt(client_fd);
-    readVarInt(client_fd);
+    player->cursor_count = readVarInt(client_fd);
+    // ignore components
     tmp = readVarInt(client_fd);
     recv_all(client_fd, recv_buffer, tmp, false);
     tmp = readVarInt(client_fd);
     recv_all(client_fd, recv_buffer, tmp, false);
+  } else {
+    player->cursor_item = 0;
+    player->cursor_count = 0;
   }
 
   return 0;
 
 }
 
+// S->C Set Cursor Item
+int sc_setCursorItem (int client_fd, uint16_t item, uint8_t count) {
+
+  writeVarInt(client_fd, 1 + sizeVarInt(count) + (count != 0 ? sizeVarInt(item) + 2 : 0));
+  writeByte(client_fd, 0x59);
+
+  writeVarInt(client_fd, count);
+  if (count == 0) return 0;
+
+  writeVarInt(client_fd, item);
+
+  // Skip components
+  writeByte(client_fd, 0);
+  writeByte(client_fd, 0);
+
+  return 0;
+}
+
 // C->S Set Player Position And Rotation
 int cs_setPlayerPositionAndRotation (int client_fd, double *x, double *y, double *z, float *yaw, float *pitch, uint8_t *on_ground) {
 
@@ -656,6 +700,11 @@ int cs_closeContainer (int client_fd) {
     if (client_slot != 255) sc_setContainerSlot(player->client_fd, window_id, client_slot, 0, 0);
   }
 
+  givePlayerItem(player, player->cursor_item, player->cursor_count);
+  sc_setCursorItem(client_fd, 0, 0);
+  player->cursor_item = 0;
+  player->cursor_count = 0;
+
   return 0;
 }
 

src/procedures.c

@@ -572,6 +572,20 @@ uint8_t getItemStackSize (uint16_t item) {
 
 void handlePlayerAction (PlayerData *player, int action, short x, short y, short z) {
 
+  // Re-sync slot when player drops an item
+  if (action == 3 || action == 4) {
+    sc_setContainerSlot(
+      player->client_fd, 0,
+      serverSlotToClientSlot(0, player->hotbar),
+      player->inventory_count[player->hotbar],
+      player->inventory_items[player->hotbar]
+    );
+    return;
+  }
+
+  // Ignore further actions not pertaining to mining blocks
+  if (action != 0 && action != 2) return;
+
   // In creative, only the "start mining" action is sent
   // No additional verification is performed, the block is simply removed
   if (action == 0 && GAMEMODE == 1) {
@@ -579,9 +593,6 @@ void handlePlayerAction (PlayerData *player, int action, short x, short y, short
     return;
   }
 
-  // Ignore actions not pertaining to mining blocks
-  if (action != 0 && action != 2) return;
-
   uint8_t block = getBlockAt(x, y, z);
 
   // If this is a "start mining" packet, the block must be instamine

src/tools.c

@@ -134,6 +134,10 @@ uint16_t readUint16 (int client_fd) {
   recv_count = recv_all(client_fd, recv_buffer, 2, false);
   return ((uint16_t)recv_buffer[0] << 8) | recv_buffer[1];
 }
+int16_t readInt16 (int client_fd) {
+  recv_count = recv_all(client_fd, recv_buffer, 2, false);
+  return ((int16_t)recv_buffer[0] << 8) | (int16_t)recv_buffer[1];
+}
 uint32_t readUint32 (int client_fd) {
   recv_count = recv_all(client_fd, recv_buffer, 4, false);
   return ((uint32_t)recv_buffer[0] << 24) |