Fixed grass surface generation with custom bottom Y

Author: mineLdiver

station-flattening-v0/src/main/java/net/modificationstation/stationapi/mixin/flattening/OverworldChunkGeneratorMixin.java

@@ -1,5 +1,6 @@
 package net.modificationstation.stationapi.mixin.flattening;
 
+import com.llamalad7.mixinextras.injector.ModifyExpressionValue;
 import com.llamalad7.mixinextras.injector.wrapoperation.Operation;
 import com.llamalad7.mixinextras.injector.wrapoperation.WrapOperation;
 import com.llamalad7.mixinextras.sugar.Share;
@@ -21,7 +22,7 @@
 import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
 import org.spongepowered.asm.mixin.injection.callback.LocalCapture;
 
-@Mixin(class_538.class)
+@Mixin(value = class_538.class, priority = 4000)
 class OverworldChunkGeneratorMixin {
     @Shadow private World field_2260;
     @Shadow private double[] field_2261;
@@ -167,7 +168,26 @@ private int stationapi_changeFillStep(int original, @Share("height") LocalIntRef
 
     @Inject(method = "method_1797", at = @At("HEAD"))
     private void stationapi_initLocals(int j, int bs, byte[] args, Biome[] par4, CallbackInfo ci, @Share("vertical2") LocalIntRef vertical2) {
-        vertical2.set(1 << MathHelper.ceilLog2(field_2260.getHeight()));
+        vertical2.set(MathHelper.smallestEncompassingPowerOfTwo(field_2260.getHeight()));
+    }
+
+    @ModifyExpressionValue(
+            method = "method_1797",
+            at = @At(
+                    value = "CONSTANT",
+                    args = "intValue=127"
+            )
+    )
+    private int stationapi_changeTopYM1(int constant) {
+        return field_2260.getTopY() - 1;
+    }
+
+    @ModifyConstant(
+            method = "method_1797",
+            constant = @Constant(expandZeroConditions = Constant.Condition.LESS_THAN_ZERO)
+    )
+    private int stationapi_changeBottomY(int constant) {
+        return field_2260.getBottomY();
     }
 
     @ModifyConstant(
@@ -177,6 +197,15 @@ private void stationapi_initLocals(int j, int bs, byte[] args, Biome[] par4, Cal
     private int stationapi_changeFillStep2(int original, @Share("vertical2") LocalIntRef vertical2) {
         return vertical2.get();
     }
+
+    @ModifyVariable(
+            method = "method_1797",
+            at = @At("STORE"),
+            index = 18
+    )
+    private int stationapi_adjustForDepth(int value) {
+        return value - field_2260.getBottomY();
+    }
 
     @ModifyConstant(
             method = "method_1798",

station-worldgen-api-v0/src/main/java/net/modificationstation/stationapi/mixin/worldgen/OverworldWorldSourceMixin.java

@@ -1,5 +1,6 @@
 package net.modificationstation.stationapi.mixin.worldgen;
 
+import com.llamalad7.mixinextras.injector.ModifyExpressionValue;
 import com.llamalad7.mixinextras.sugar.Local;
 import net.minecraft.block.SandBlock;
 import net.minecraft.class_51;
@@ -12,12 +13,10 @@
 import org.spongepowered.asm.mixin.Shadow;
 import org.spongepowered.asm.mixin.injection.At;
 import org.spongepowered.asm.mixin.injection.At.Shift;
-import org.spongepowered.asm.mixin.injection.Constant;
 import org.spongepowered.asm.mixin.injection.Inject;
-import org.spongepowered.asm.mixin.injection.ModifyConstant;
 import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
 
-@Mixin(class_538.class)
+@Mixin(value = class_538.class, priority = 2000)
 class OverworldWorldSourceMixin {
     @Shadow
     private World field_2260;
@@ -44,12 +43,15 @@ private void stationapi_cancelFeatureGeneration(class_51 source, int cx, int cz,
         }
     }
 
-    @ModifyConstant(
+    @ModifyExpressionValue(
             method = "method_1797",
-            constant = @Constant(intValue = 127)
+            at = @At(
+                    value = "CONSTANT",
+                    args = "intValue=127"
+            )
     )
     private int stationapi_cancelSurfaceMaking(int constant, @Local Biome biome) {
-        return biome.noSurfaceRules() ? field_2260.getTopY() - 1 : -1;
+        return biome.noSurfaceRules() ? constant : Integer.MIN_VALUE;
     }
 
     @Inject(