Technical ReferenceSemantics

Mixin inventory

Every mixin in the mod: its target, its injection point, its require setting and what it promises.

3 min readInputBooster 4.1.2-alphaMinecraft 26.2 / 26.3

There are ten mixins. Two observe input, one drains the queue, one tracks screens, one adds the options button, three provide accessors and two are effectively empty.

The manifest

json

{
  "required": true,
  "minVersion": "0.8",
  "package": "dev.inputbooster.mixin",
  "compatibilityLevel": "JAVA_25",
  "client": [
    "GameTickMixin",
    "DebugHudMixin",
    "InGameHudMixin",
    "OptionsScreenMixin",
    "GuiAccessor",
    "KeyMappingAccessor",
    "KeyboardHandlerMixin",
    "MinecraftClientAccessor",
    "MouseHandlerMixin",
    "ScreenTrackingMixin"
  ],
  "injectors": {
    "defaultRequire": 1
  }
}

Every mixin is client side. The manifest requires JAVA_25.

The critical path

GameTickMixin

Target: net.minecraft.client.Minecraft.

Injection	Point	Require	Purpose
`tick`	HEAD	1	Drain the queue at the start of the tick
`startAttack`	HEAD, cancellable	1	Suppress vanilla's duplicate attack
`startUseItem`	HEAD, cancellable	1	Suppress vanilla's duplicate use
`close`	HEAD	1	Shut the mod down cleanly

These four are require = 1 on purpose. A mapping change must fail loudly instead of silently disabling input handling.

java

@Inject(method = "startAttack", at = @At("HEAD"), cancellable = true, require = 1)
private void onStartAttack(CallbackInfoReturnable<Boolean> cir) {
    if (!InputBoosterMod.active || !InputBoosterMod.initialized.get()) return;
    if (InputDrainer.consumeAttackSuppression()) {
        cir.setReturnValue(false);
    }
}

The observers

KeyboardHandlerMixin

Target: net.minecraft.client.KeyboardHandler. Priority 1100.

java

@Inject(method = "keyPress", at = @At("HEAD"), require = 0)
private void onKeyPressObserved(long window, int action, KeyEvent event, CallbackInfo ci) {
    KeyboardProcessor.onKeyEvent(event.key(), action);
}

It observes. It cancels nothing, changes no binding and does no local capture. Vanilla still routes the event to the open screen, to the key bindings and to every other mod exactly as before.

MouseHandlerMixin

Target: net.minecraft.client.MouseHandler. Priority 1100.

Injection	Method	Purpose
`onButtonObserved`	`onButton(long, MouseButtonInfo, int)`	Turn a button press or release into an edge
`onScrollObserved`	`onScroll(long, double, double)`	Count a wheel event, with an optional debounce

Scrolling is only counted. The mod never applies scroll input to the game.

The screen router

ScreenTrackingMixin

Target: net.minecraft.client.Minecraft.

java

@Inject(method = "setScreenAndShow", at = @At("HEAD"), require = 0)
private void onScreenShown(Screen screen, CallbackInfo ci) {
    KeyboardRouter.recordScreen(screen);
}

The 26.x API only exposes setScreenAndShow; setScreen was removed. A hook naming it would silently never run, which is why the startup log reports which of the two the client actually has.

The mixin only reads the screen argument. It does not cancel the call, does not touch key mappings and does not see another mod's input.

The interface hooks

OptionsScreenMixin

Target: net.minecraft.client.OptionsScreen.

java

@Inject(method = "init", at = @At("TAIL"), require = 0)
private void onInitTail(CallbackInfo ci) {
    addRenderableWidget(Button.builder(
        Component.translatable("options.inputbooster.button"),
        button -> { ... }
    ).bounds(this.width - 110, 6, 100, 20).build());
}

require = 0 is deliberate: this is a convenience button. A mapping change should remove the button, not stop Minecraft from starting.

InGameHudMixin

Target: net.minecraft.client.gui.Gui. Priority 900.

java

@Inject(method = "extractRenderState", at = @At("TAIL"), require = 0)
private void onExtractRenderStateTail(DeltaTracker deltaTracker, boolean renderLevel, boolean renderHotbar, CallbackInfo ci) {
    DebugOverlayManager.extractRenderState(Minecraft.getInstance());
}

The signature changed in 26.x: extractRenderState(DeltaTracker, boolean, boolean) replaced the graphics-extractor overload used on 26.1.

DebugHudMixin

Target: net.minecraft.client.gui.components.DebugScreenOverlay. Priority 900.

Intentionally empty. The class exists so the mixin list stays stable, but it injects nothing. An earlier version hooked getLeftText and getRightText, whose names differ across mapping versions, which produced "Cannot remap" warnings and an injection that never ran. The overlay now draws through the HUD render state instead, with no mapping dependency.

The accessors

Mixin	Target	Exposes
`GuiAccessor`	`Gui`	The GUI render state
`KeyMappingAccessor`	`KeyMapping`	The bound key code
`MinecraftClientAccessor`	`Minecraft`	The vanilla pick-block helper

The rules, summarised

Rule	Why
A critical-path injection uses `require = 1`	A missing hook must fail loudly
An optional hook uses `require = 0`	A missing hook must degrade, not crash
Observers run at HEAD and cancel nothing	Another mod's input stays untouched
Handler parameters must match the target exactly	A mismatch is fatal even with `require = 0`
An accessor for a class target is an `abstract class`	An interface mixin aborts the transformation
A mixin contains no non-private static method	A public helper aborts the transformation
Accessor helpers live in `MixinAccess`	Keeps the mixins to members only

The startup check

verifyClientHooks() runs during initialisation and reports what applied:

text

[Mixin] All client hooks present.
[Mixin] Screen hooks: setScreenAndShow=true, setScreen=false
[Mixin] Missing vanilla method(s): tick — input handling is degraded.
[Mixin] No screen hook found; screen state falls back to the HUD check each tick.

The mixins use require = 0 so an API change degrades instead of crashing. Without this check, a silent failure would disable input handling with no explanation at all.

Building and testing — the two tests that guard these rules.
Input pipeline — where each hook sits.
Limitations — the pick-block caveat.