src/game/java/net/minecraft/client/gui/navigation/FocusNavigationEvent.java

package net.minecraft.client.gui.navigation;

import net.minecraftforge.api.distmarker.Dist;
import net.minecraftforge.api.distmarker.OnlyIn;

@OnlyIn(Dist.CLIENT)
public interface FocusNavigationEvent {
    ScreenDirection getVerticalDirectionForInitialFocus();

    @OnlyIn(Dist.CLIENT)
    public static record ArrowNavigation(ScreenDirection direction) implements FocusNavigationEvent {
        @Override
        public ScreenDirection getVerticalDirectionForInitialFocus() {
            return this.direction.getAxis() == ScreenAxis.VERTICAL ? this.direction : ScreenDirection.DOWN;
        }
    }

    @OnlyIn(Dist.CLIENT)
    public static class InitialFocus implements FocusNavigationEvent {
        @Override
        public ScreenDirection getVerticalDirectionForInitialFocus() {
            return ScreenDirection.DOWN;
        }
    }

    @OnlyIn(Dist.CLIENT)
    public static record TabNavigation(boolean forward) implements FocusNavigationEvent {
        @Override
        public ScreenDirection getVerticalDirectionForInitialFocus() {
            return this.forward ? ScreenDirection.DOWN : ScreenDirection.UP;
        }
    }
}