DoubleJumpLib

A simple Minecraft datapack library which has double jump detection for Minecraft 1.21.8+

For any errors, troubleshooting or help, please contact @sadanmastermode on Discord, or open an issue request on GitHub

Features

• Automatically detects when the user presses space midair, and activates a function tag.
• Makes sure the user first releases and then presses space after the initial jump so that nothing is called on the initial jump input.
• Supports unlimited midair space inputs, though is defaulted at a max of 1 every jump.
• Easily configurable with a lot of error handling through the pack
• Multiplayer compatible
• Very simple to uninstall, removing all scoreboards and storages through a single function call.
• Stripped-down code for double-jump detection is included too under the __base_code__ namespace

Documentation

Downloading

To download the pack, you can click on the download button near the top of the page, or visit the releases tab. This will download the pack. Once downloaded, you can unzip it and put it in your datapacks folder in your world folder to import the library.

Note that the pack has only been tested in 1.21.8 and higher. This pack may break in lower versions, please exercise caution

Installing

When the pack is in your world, you must run /function doublejumplib:__install__. This will properly set up all scoreboards and configs in the pack. If you try to run functions without installing the pack, errors will come up and the pack won't run correctly.

Adding a callback

DoubleJumpLib can be configured by setting a variety of API endpoints to values you wish. These endpoints are denoted by a pair of underscores around the name, like __install__ or __help__. Do not intentionally run any functions without the pair of double underscores.

One such example of an API endpoint is the function callback. This pack will call a function tag when it detects a user has pressed a jump input in the air. The function tag is located at #doublejumplib:__on_double_jump__, and the relative path would be found at doublejumplib/tags/function/__on_double_jump__.json. Add a function from your pack into this tag to allow the pack to run it.

Inside of a callback function, the executor and position is set to the player who double-jumped. Additionally, to find the current double-jump number (how many times they've double-jumped in the current jump), it is set the player's djl.jumpCount score.

For example, to check if the player has double-jumped twice in the current jump, you can use: execute if score @s djl.jumpCount matches 2 run say I jumped twice!.

To test if the pack was installed correctly, you can try adding doublejumplib:__test__ to the function tag. If you properly installed everything, then jumping midair will send a tellraw message in chat giving some info about the jump. Do not run this function from chat, it is intended to be ran through the function tag.

Configuring the library

There are 2 main variables you can change, via scoreboards:

Playername	Objective	Function	Default
$djl.maxJumps	djl.jumpCount	Manages how many double-jumps the player can perform in a single jump before touching the ground	1
$djl.enabled	djl.debug	Manages whether the pack is ticking, and therefor whether the pack is enabled.	1 (enabled)

These are global settings, meaning any other pack using DoubleJumpLib will use these same settings too.

IMPORTANT:

To maintain compatibility across packs, it is recommended to add checks for the player's current djl.jumpCount to see what jump the player is on, in case another pack increases the limit.

For example, if your pack is intended to only activate once in a jump and gives the player a boost of upwards momentum via the gravity attribute, and another pack increases the djl.maxJumps limit to 3, then your pack will not work as intended. It is crucial in your pack to check if the player is on their first double-jump of the current jump via execute if score @s djl.jumpCount matches 1 before inversing their gravity, unless you want the other pack to allow the player to defy gravity 3 times a jump instead of 1.

There are 4 main callable function endpoints you can use.

Function Name	Use
__help__	Displays the link to the README here.
__install__	Installs the library to the world by setting up the scoreboards and all.
__uninstall__	Uninstalls the library by removing all the scoreboards and storages that were made.
__test__	Intended to be used in the function tag, this is a simple testing file to make sure the library works.

Adding the library to your pack

To add the library to your pack, simply copy-paste the doublejumplib namespace into your data folder. Make sure you also add the following entry into the tick.json under the minecraft/tags/function directory: "doublejumplib:internal/_tick" This pack is under the MIT license, which means theres almost no restrictions. It would be very much appreciated for proper credit if you do use this in your pack.

If you do want to use the main logic of this pack without all the library-slop, there is the __base_code__ namespace which holds a README.md containing info about the contents of this namespace. It mostly just contains the stripped-down code for a double-jump detection for you to implement.

How does it work?

This uses the 'new' input predicate for the type_specific predicate, as well as the on_ground flag.

The main logic is as follows. You can 'tag' the player when they're first off the ground (using the on_ground flag) and untag them when they land on the ground. Also tag them whenever they're holding space (and of course remove it when they're not)

Assuming the player has both tags (is off the ground and is holding jump), then check for some things in the previous tick:

• If they were both off the ground and NOT holding jump, then they double jumped (this is because they released the jump input after jumping first)
• If they were off the ground and holding jump, then you don't do anything (this could be the original input for jumping)
• And of course if they weren't doing anything (not off the ground and not holding space) then they just started jumping and you don't need to do anything

This is the basic thinking for the pack. The implementation was a bit different, though I tried to document most of it and keep it all readable. I can always explain this more if you contact me directly.

Contributing

Although this is a very very simple library, I am always welcome to contribution. Whether it be optimizations or logic improvements, please feel free to open a pull request or contact me on Discord about this library.

License

As per the MIT License, you are allowed to redistribute, modify and use DoubleJumpLib as long as I am credited for the original work.