Fix chunks being invisible after temporarily leaving an area

src/main/java/eu/crushedpixel/replaymod/mixin/MixinViewFrustum.java

@@ -0,0 +1,70 @@
+package eu.crushedpixel.replaymod.mixin;
+
+import eu.crushedpixel.replaymod.replay.ReplayHandler;
+import net.minecraft.client.renderer.RenderGlobal;
+import net.minecraft.client.renderer.ViewFrustum;
+import net.minecraft.client.renderer.chunk.IRenderChunkFactory;
+import net.minecraft.client.renderer.chunk.RenderChunk;
+import net.minecraft.util.BlockPos;
+import net.minecraft.util.MathHelper;
+import net.minecraft.world.World;
+import org.spongepowered.asm.mixin.Mixin;
+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;
+
+@Mixin(ViewFrustum.class)
+public abstract class MixinViewFrustum {
+    private IRenderChunkFactory renderChunkFactory;
+
+    @Shadow protected RenderGlobal renderGlobal;
+    @Shadow protected World world;
+    @Shadow protected int countChunksY;
+    @Shadow protected int countChunksX;
+    @Shadow protected int countChunksZ;
+    @Shadow public RenderChunk[] renderChunks;
+
+    @Inject(method = "<init>", at = @At("RETURN"))
+    private void setRenderChunkFactory(World a1, int a2, RenderGlobal a3, IRenderChunkFactory rcf, CallbackInfo ci) {
+        this.renderChunkFactory = rcf;
+    }
+
+    /**
+     * Instead of calling {@link RenderChunk#setPosition(BlockPos)} we recreate the render chunk
+     * which seems to solve the problem that chunks are invisible when you leave an area and return
+     * to it.
+     * Any better fixes are welcome.
+     * Note: Most of this code is copied from {@link ViewFrustum#updateChunkPositions(double, double)}
+     */
+    @Inject(method = "updateChunkPositions", at = @At("HEAD"), cancellable = true)
+    public void fixedUpdateChunkPositions(double viewEntityX, double viewEntityZ, CallbackInfo ci) {
+        if (!ReplayHandler.isInReplay()) {
+            return;
+        }
+
+        int i = MathHelper.floor_double(viewEntityX) - 8;
+        int j = MathHelper.floor_double(viewEntityZ) - 8;
+        int k = this.countChunksX * 16;
+
+        for (int l = 0; l < this.countChunksX; ++l) {
+            int i1 = this.func_178157_a(i, k, l);
+            for (int j1 = 0; j1 < this.countChunksZ; ++j1) {
+                int k1 = this.func_178157_a(j, k, j1);
+                for (int l1 = 0; l1 < this.countChunksY; ++l1) {
+                    int i2 = l1 * 16;
+                    RenderChunk renderchunk = this.renderChunks[(j1 * this.countChunksY + l1) * this.countChunksX + l];
+                    BlockPos blockpos = new BlockPos(i1, i2, k1);
+                    if (!blockpos.equals(renderchunk.getPosition())) {
+                        // Recreate render chunk instead of setting its position
+                        renderChunks[(j1 * this.countChunksY + l1) * this.countChunksX + l] =
+                                renderChunkFactory.makeRenderChunk(world, renderGlobal, blockpos, 0);
+                    }
+                }
+            }
+        }
+        ci.cancel();
+    }
+
+    @Shadow abstract int func_178157_a(int p_178157_1_, int p_178157_2_, int p_178157_3_);
+}

src/main/resources/mixins.replaymod.json

@@ -14,7 +14,8 @@
     "MixinRenderGlobal",
     "MixinRenderItem",
     "MixinRenderManager",
-    "MixinTileEntityEndPortalRenderer"
+    "MixinTileEntityEndPortalRenderer",
+    "MixinViewFrustum"
   ],
   "server": [],
   "client": [],