From 8f7d263ad9cd6fbbb8c1c302256ddfdc0b5bd009 Mon Sep 17 00:00:00 2001
From: Jonas Herzig <jonas@spark-squared.com>
Date: Wed, 8 Apr 2020 14:18:25 +0200
Subject: [PATCH] Fix livelock caused by OF not properly resetting
 ChunkVisibility

This can lead to a livelock when rendering with shaders after exiting a
singleplayer world (3/4 chance of breakage on each exit).
---
 .../shaders/mixin/MixinChunkVisibility.java   | 32 +++++++++++++++++++
 .../mixins.compat.shaders.replaymod.json      |  3 ++
 2 files changed, 35 insertions(+)
 create mode 100644 src/main/java/com/replaymod/compat/shaders/mixin/MixinChunkVisibility.java

diff --git a/src/main/java/com/replaymod/compat/shaders/mixin/MixinChunkVisibility.java b/src/main/java/com/replaymod/compat/shaders/mixin/MixinChunkVisibility.java
new file mode 100644
index 00000000..f1c58c07
--- /dev/null
+++ b/src/main/java/com/replaymod/compat/shaders/mixin/MixinChunkVisibility.java
@@ -0,0 +1,32 @@
+//#if MC>=11500
+package com.replaymod.compat.shaders.mixin;
+
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Pseudo;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+@Pseudo
+@Mixin(targets = "net/optifine/render/ChunkVisibility", remap = false)
+public abstract class MixinChunkVisibility {
+    @Shadow
+    private static int counter;
+
+    /**
+     * OF doesn't properly reset the counter when exiting a world.
+     * It'll only be reset when getMaxChunkY is called which only happens for
+     * SP worlds (i.e. not in a replay or MP).
+     * As a result, it may end up in a non-0 state, which will cause isFinished
+     * to unconditionally return false, therefore unconditionally setting
+     * needsTerrainUpdate to true on each call to WorldRenderer.setupTerrain,
+     * therefore unnecessarily consuming resources and live-locking when
+     * rendering the shader pass.
+     */
+    @Inject(method = "reset", at = @At("HEAD"), remap = false)
+    private static void replayModCompat_fixImproperReset(CallbackInfo ci) {
+        MixinChunkVisibility.counter = 0;
+    }
+}
+//#endif
diff --git a/src/main/resources/mixins.compat.shaders.replaymod.json b/src/main/resources/mixins.compat.shaders.replaymod.json
index 9d1bc2db..133b1106 100644
--- a/src/main/resources/mixins.compat.shaders.replaymod.json
+++ b/src/main/resources/mixins.compat.shaders.replaymod.json
@@ -4,6 +4,9 @@
   "mixins": [],
   "server": [],
   "client": [
+    //#if MC>=11500
+    "MixinChunkVisibility",
+    //#endif
     //#if MC>=10800
     "MixinShaderEntityRenderer",
     "MixinShaderRenderChunk",