The bug
When signing a book and quill it only allows you to enter 15 characters. It has always been 16 in the past.
How to reproduce
Take a book and quill item
/give @s minecraft:writable_book
Try to sign it with a title of exactly 16 characters
Notice that it only allows 15 characters
Code analysis
The issue is that the field titleEdit
in net.minecraft.client.gui.screens.inventory.BookEditScreen
checks if the length is < 16
. Replacing this with <= 16
fixes the issue.
Linked issues
is duplicated by 1
Attachments
Comments 14

Think this change happened in 20w17a
I can confirm too. this does occur

I can confirm too. this does occur
Can confirm in 21w03a.
Can confirm in 1.17.
Can confirm in 1.17.1.

Can confirm in 1.18 Pre-release 1.
Can confirm in 1.18.1 and 22w06a.

I reported this as MC-265612, now listed as duplicate.
I tested this bug in 1.7.10, 1.8, 1.9, 1.10, 1.11, 1.12, 1.13, 1.14, 1.15, 1.15.2, 20w06a, 20w13b, 20w14a, 20w15a and 20w16a with negative results,
furthermore I tested 20w17a, 20w19a, 20w22a, 1.16pre 1, 1.16, 1.20.1 and 1.20.2 which all lead to positive results.
I conclude that this bug is due to changes made from 20w16a to 20w17a, as this is the earliest this bug occurs.
Changes to writable_books in 22w42a (1.20) did neither affect nor solve this issue as it persists in the current version.
Parity changes made to writing in books, editing item names in anvils, and recently changing signs, namely copying, pasting and moving the cursor haven't been added to book titles, which is probably why the bug ( a <= changed to <, as mentioned above ) was overlooked.
I suggest that if fixed the limit should be raised to the same limit of item names (50), because there is no reason as to why a book title should be shorter than if you just renamed the item in an anvil