Doppler Hooks

Overview

Doppler Hooks, aka dhooks, are a set of callback functions that can be called during the lifecycle of "locked" pools initialized by the DopplerHookInitializer contract.

Three main events will trigger these hooks:

• initialization: when a new pool is created

• swap: when a swap occurs in the pool

• graduation: when the pool reaches a certain price maturity

Additionally, pools associated with a Doppler Hook can have their LP fee updated by the associated timelock governance contract or a delegated address.

A couple of things to note:

• A pool initialized without a Doppler Hook can opt-in to use one later via the setHook function

• A pool initialized with a Doppler Hook can opt-out of using it later by setting the hook address to address(0)

• A pool can change its associated Doppler Hook to a different one at any time via the setHook function

• Doppler Hooks are approved by the protocol multisig

• A pool without a Doppler Hook cannot be initialized with a dynamic LP fee

Implementation

Here are the different callback functions available for the Doppler Hooks.

Note that they can be implemented selectively based on the use case:

Callback Function	Triggered By
onInitialization(address asset, PoolKey calldata key, bytes calldata data	- initialize() if a dopplerHook address is set in the InitData - setDopplerHook() if a Doppler Hook is set after the pool initialization
onSwap(address sender, PoolKey calldata key, IPoolManager.SwapParams calldata params,BalanceDelta delta, bytes calldata data) returns (Currency feeCurrency, int128 hookDelta)	afterSwap before each swap happening in the Uniswap V4 pool
onGraduation(address asset, PoolKey calldata key, bytes calldata data)	graduate if the graduation conditions are met (e.g. farTick reached)