Client APIs

Key bindings

Implement OMLKeyBindingProvider on the @Mod class to declare bindings. OML calls declareKeyBindings once after onInitialize:

@Mod(id = "my_mod", name = "My Mod", version = "1.0.0")
class MyMod : OMLModInitializer, OMLKeyBindingProvider {
    override fun declareKeyBindings(keyBindings: OMLKeyBindingRegistry) {
        keyBindings.register("zoom", "key.keyboard.k") {
            println("K pressed")
        }
    }
}

• The binding's game name is key.<modId>.<id> (key.my_mod.zoom) — the controls screen and keybinding export files refer to it by that name.
• Bindings appear under the shared oml category in the controls screen.
• defaultKey is an InputConstants key name (e.g. "key.keyboard.k"); an unresolvable name degrades to an unbound key instead of failing startup.
• Bindings are applied lazily on the first client tick, so registration may happen at any point during mod initialization.
• Client-only: declareKeyBindings is never invoked on a dedicated server.

HUD rendering

Events.HUD_RENDER fires once per frame while a world is loaded, before the HUD is drawn:

Events.HUD_RENDER.register { event ->
    val surface = event.graphics.platform // the frame's draw surface (version-specific type)
}

Event	Fired	Cancellable	Fields
HUD_RENDER	every frame with a world loaded	–	graphics: OMLGuiGraphics

OMLGuiGraphics.platform is the game's draw surface for the frame. It is a version-specific type (on 26.3: GuiGraphicsExtractor); code touching it directly belongs in version-specific paths.

TIP

The event means "the HUD pass begins", not "pixels will follow": the pass's internal early-returns (loading screens, F1) sit inside it.

Creative tab

Every item a mod materializes is added automatically to the shared oml creative tab (itemGroup.oml.main), visible in the creative screen — no API needed.