The bug
When a book is signed in the off-hand, when switched back to the main hand, it reverts back to a Book and Quill.
How to reproduce
Get a Book and Quill
Switch Book and Quill to off-hand
Write in the book and sign it
Switch the book back to the main hand using the
Fhotkey
Code analysis
Based on 1.11 decompiled using MCP 9.35 rc1
The problem is that the method net.minecraft.network.NetHandlerPlayServer.processCustomPayload(CPacketCustomPayload) only tests for the mainhand when it receives a MC|BEdit or MC|BSign CPacketCustomPayload packet.
Linked issues
is duplicated by 9
MC-84514
When I try to write in a book with the off hand it doesn't keep what I wrote in it.
Resolved
MC-84540
Book becomes unsigned when switching it from offhand to hotbar with F key
Resolved
MC-84738
Book and Quill Erased in Offhand
Resolved
MC-84798
Written books can't be read when in off-hand
Resolved
MC-85004
Signing a book and quill in his off-hand and put it in the main hand turns it into a book and quill.
Resolved
relates to 2
Comments 8
Still issue in 1.12 pre-7
It appears this issue also affecting command given books incorrectly displaying scoreboard and entity selector syntax if opened for first time in off-hand. Tag {resolved:#} also incorrectly triggers to 1 in offhand when clearly not resolved.
@unknown, the issue you mentioned is MC-111328
Confirmed. Workaround: Manually taking the item out of the offhand slot in the inventory.
edit: No longer works.