Prevent Zero Length skybox bouncing

docs/PORTING.md

@@ -304,6 +304,11 @@ random outcome using its effective one-in-seven grammar weight. Zero Length
 freezes an Age at its generated phase without changing the global daylight
 cycle, while nonzero Ages retain their independently scaled clocks.
 
+Version 0.2.20.2 gives Zero Length Ages a stationary per-dimension clock rate
+instead of advancing and correcting their time once per tick. This keeps the
+integer day time fixed while preventing the client skybox from visually
+bouncing between adjacent celestial positions.
+
 Version 0.2.14.0 restores the legacy Linking and Descriptive Book artwork for
 inventory items and gives each book its matching open-book texture when placed
 on a Book Stand. Return Linking Books created inside another Age also retain and

gradle.properties

@@ -35,7 +35,7 @@ mod_name=Rivencraft
 # The license of the mod. Review your options at https://choosealicense.com/. All Rights Reserved is the default.
 mod_license=LGPL-3.0-or-later
 # The mod version. Rivencraft uses the x.y.z.b policy documented in README.md.
-mod_version=0.2.20.1
+mod_version=0.2.20.2
 immersive_portals_version=6.0.7
 # The group ID for the mod. It is only important when publishing as an artifact to a Maven repository.
 # This should match the base package used for the mod sources.

src/main/java/net/dnorberg/rivencraft/Rivencraft.java

@@ -13,7 +13,6 @@ import net.dnorberg.rivencraft.config.RivencraftConfig;
 import net.dnorberg.rivencraft.config.RivencraftClientConfig;
 import net.dnorberg.rivencraft.book.AgeDimensionService;
 import net.dnorberg.rivencraft.book.AgeWeatherService;
-import net.dnorberg.rivencraft.book.AgeCelestialService;
 import net.neoforged.bus.api.IEventBus;
 import net.neoforged.fml.ModContainer;
 import net.neoforged.fml.common.Mod;
@@ -39,7 +38,6 @@ public final class Rivencraft {
         ModCreativeTabs.register(modEventBus);
         NeoForge.EVENT_BUS.addListener(BookStandConversionHandler::onRightClickBlock);
         NeoForge.EVENT_BUS.addListener(AgeWeatherService::onLevelTickPost);
-        NeoForge.EVENT_BUS.addListener(AgeCelestialService::onLevelTickPost);
         LOGGER.info("Initializing Rivencraft");
     }
 }

src/main/java/net/dnorberg/rivencraft/book/AgeCelestialService.java

@@ -1,31 +0,0 @@
-package net.dnorberg.rivencraft.book;
-
-import java.util.Map;
-import java.util.WeakHashMap;
-import net.minecraft.server.level.ServerLevel;
-import net.neoforged.neoforge.event.tick.LevelTickEvent;
-
-/** Holds Zero Length Age clocks without changing the server-wide daylight gamerule. */
-public final class AgeCelestialService {
-    private static final Map<ServerLevel, Long> FROZEN_TIMES = new WeakHashMap<>();
-
-    private AgeCelestialService() {
-    }
-
-    public static void freezeAt(ServerLevel level, long dayTime) {
-        FROZEN_TIMES.put(level, dayTime);
-    }
-
-    public static void unfreeze(ServerLevel level) {
-        FROZEN_TIMES.remove(level);
-    }
-
-    public static void onLevelTickPost(LevelTickEvent.Post event) {
-        if (event.getLevel() instanceof ServerLevel level) {
-            Long frozenTime = FROZEN_TIMES.get(level);
-            if (frozenTime != null && level.getDayTime() != frozenTime) {
-                level.setDayTime(frozenTime);
-            }
-        }
-    }
-}

src/main/java/net/dnorberg/rivencraft/book/AgeDimensionService.java

@@ -104,10 +104,12 @@ public final class AgeDimensionService {
 
     private static void applyCelestialClock(ServerLevel level, AgeDefinition age) {
         if (age.traits().hasStoppedCelestialCycle()) {
-            level.setDayTimePerTick(-1.0F);
-            AgeCelestialService.freezeAt(level, level.getDayTime());
+            // NeoForge rejects an exact zero rate. The smallest positive float
+            // never advances the integer clock during a practical world
+            // lifetime and avoids a one-tick-forward/one-tick-back correction
+            // that makes the client sky visibly bounce.
+            level.setDayTimePerTick(Float.MIN_VALUE);
         } else {
-            AgeCelestialService.unfreeze(level);
             level.setDayTimePerTick((float)(1.0D / age.traits().celestialPeriod()));
         }
     }
@@ -115,9 +117,6 @@ public final class AgeDimensionService {
     private static void applyInitialCelestialPhase(ServerLevel level, AgeDefinition age) {
         long phaseTime = (long)(age.traits().celestialPhase() * Level.TICKS_PER_DAY);
         level.setDayTime(phaseTime);
-        if (age.traits().hasStoppedCelestialCycle()) {
-            AgeCelestialService.freezeAt(level, phaseTime);
-        }
     }
 
     private static void synchronizeImmersivePortals(MinecraftServer server) {

src/main/java/net/dnorberg/rivencraft/gametest/LinkingGameTests.java

@@ -188,8 +188,8 @@ public final class LinkingGameTests {
             helper.assertTrue(Math.abs(level.dimensionType().ambientLight() - expectedAmbientLight) < 0.0001F,
                     "The runtime dimension must apply the persisted lighting trait");
             if (definition.traits().hasStoppedCelestialCycle()) {
-                helper.assertTrue(level.getDayTimePerTick() < 0.0F,
-                        "A Zero Length Age must leave vanilla clock advancement under the freeze controller");
+                helper.assertValueEqual(level.getDayTimePerTick(), Float.MIN_VALUE,
+                        "A Zero Length Age must use the stationary nonzero clock rate");
             } else {
                 float expectedDaySpeed = (float)(1.0D / definition.traits().celestialPeriod());
                 helper.assertTrue(Math.abs(level.getDayTimePerTick() - expectedDaySpeed) < 0.0001F,