refactor: modernize hollow client rendering

JVM_DOWNGRADER_HANDOFF.md

@@ -6,8 +6,9 @@ The scoped integration is implemented on `algent/java`, building on baseline `65
 are preserved. `build.gradle` adds two tasks; `StackAnalyserLogic` uses pattern and arrow-rule switches,
 `JavaTraitRegistration` and `ClassInfoLookup` use Java 21 pattern variables, and `ScalaSignatureParser` uses switch
 expressions. `HollowMicroblockTraitLogic` and `PostMicroblockClientLogic` use the same scoped path for internal
-microblock control flow. The nine Scala sources, Scala 2.11.5 dependency, source layout, and normal Gradle entry points
-remain in place. Production tasks do not read a frozen jar or any files under `run/jvmdg-trial/`.
+microblock control flow, as does `HollowMicroblockClientLogic` for its slot renderer. The nine Scala sources, Scala
+2.11.5 dependency, source layout, and normal Gradle entry points remain in place. Production tasks do not read a frozen
+jar or any files under `run/jvmdg-trial/`.
 
 The subsequent `StackAnalyser` initializer extraction is recorded in `JAVA_MIGRATION_HANDOFF.md`. The exact-byte
 comparisons and frozen-version reproduction below describe checkpoint `5f0e329`; later helper edits need their own
@@ -78,11 +79,11 @@ Recommended order:
    Scala-facing declarations. `StackAnalyserLogic.java` remains the original proven example.
 2. Continue only where modern syntax produces a concrete control-flow gain. `ScalaSignatureParser.java`, the remaining
    opcode switches in `StackAnalyserLogic.java`, and the hollow/post-client microblock helper group are complete.
-   `HollowMicroblockClientLogic.java` is the next useful internal candidate because its slot dispatcher can use arrow
-   rules. `ScalaTraitRegistration.java` should not move merely to restyle its erased `Some` checks.
-3. Consider public core implementations such as `RedstoneInteractions$.java`, `TileMultipart.java` and the registries
-   only after the internal batches. Modern method bodies are technically possible, but their published ABI and frozen
-   behavior make the review cost higher.
+   `ScalaTraitRegistration.java` should not move merely to restyle its erased `Some` checks.
+3. The next queue is dependency-closure audits for public implementation bodies: start with
+   `RedstoneInteractions$.java`, then `BlockMultipart.java`, then the previously deferred renderer group. Each has useful
+   cast/control-flow cleanup and focused characterization tests, but must bring any joint-compiled Java callers that
+   cannot resolve an excluded declaration. Do not assume one-file routing will work.
 4. Defer registered Java trait inputs under `scalatraits/`. Their transformer forbids or rewrites several bytecode
    shapes, including inner classes, lambdas, string switches and primitive-array allocation; syntax changes need
    transformer-specific fixtures rather than ordinary compilation success.
@@ -123,6 +124,10 @@ version 52, and neither helper has an executable JVM Downgrader API reference. `
 from the batch: the retained Scala declaration does not expose `getShape()` through `PostMicroblock`, so its explicit
 `Microblock` cast is required and modern pattern syntax provides no useful replacement.
 
+The `HollowMicroblockClientLogic` slot-renderer batch has the same clean-build, 576-test, 289-test, version-52 and
+134-dump results. Its non-private ABI and callback ordering are unchanged, and its packaged classes have no executable
+JVM Downgrader API reference.
+
 ### fastutil audit
 
 GTNHLib 0.11.44 currently contributes `it.unimi.dsi:fastutil:8.5.18` to `compileClasspath`. It does **not** contribute
@@ -183,8 +188,8 @@ working syntax and record the blocker and revisit condition. Do not add fragile
 
 The production source tree now contains 231 Java files and nine Scala files / 782 nonblank Scala lines. Of the 224 Java
 sources in the Scala source tree, only `StackAnalyserLogic`, `JavaTraitRegistration`, `ClassInfoLookup`,
-`ScalaSignatureParser`, `HollowMicroblockTraitLogic` and `PostMicroblockClientLogic` bypass joint compilation. Retained
-models, trait
+`ScalaSignatureParser`, `HollowMicroblockTraitLogic`, `PostMicroblockClientLogic` and `HollowMicroblockClientLogic`
+bypass joint compilation. Retained models, trait
 metadata, synthetic super accessors, and downstream Scala consumers prevent treating the last nine files as a
 mechanical deletion queue. Modern GTNH runtime support does not remove the retained Scala compiler's Java 8
 requirement. The main migration plan and working handoff carry the current API/adoption priorities and source counts.

build.gradle

@@ -18,6 +18,7 @@ def modernJavaSources = sourceSets.main.scala.matching {
     include 'codechicken/multipart/asm/ScalaSignatureParser.java'
     include 'codechicken/microblock/HollowMicroblockTraitLogic.java'
     include 'codechicken/microblock/PostMicroblockClientLogic.java'
+    include 'codechicken/microblock/HollowMicroblockClientLogic.java'
 }
 def legacyScala = tasks.named('compileScala') {
     // Zinc does not invalidate joint-compiled Java annotations when Tags.VERSION changes.
@@ -29,6 +30,7 @@ def legacyScala = tasks.named('compileScala') {
     exclude 'codechicken/multipart/asm/ScalaSignatureParser.java'
     exclude 'codechicken/microblock/HollowMicroblockTraitLogic.java'
     exclude 'codechicken/microblock/PostMicroblockClientLogic.java'
+    exclude 'codechicken/microblock/HollowMicroblockClientLogic.java'
     scalaCompileOptions.additionalParameters = ['-sourcepath', file('src/main/scala').absolutePath]
     inputs.files(modernJavaSources).withPropertyName('modernJavaDeclarations').withPathSensitivity(PathSensitivity.RELATIVE)
 }

src/main/scala/codechicken/microblock/HollowMicroblockClientLogic.java

@@ -75,8 +75,7 @@ final class HollowMicroblockClientLogic {
         int slot = part.getSlot();
         int internalMask = 0;
         switch (slot) {
-            case 0:
-            case 1:
+            case 0, 1 -> {
                 if (face) internalMask = 0x3c;
                 f.apply(pos, material, pass, new Cuboid6(d1, y1, d2, d2, y2, z2), 0x3b | internalMask);
                 f.apply(pos, material, pass, new Cuboid6(d1, y1, z1, d2, y2, d1), 0x37 | internalMask);
@@ -84,9 +83,8 @@ final class HollowMicroblockClientLogic {
                 f.apply(pos, material, pass, new Cuboid6(x1, y1, d1, d1, y2, d2), sideMask & 0x13 | 0xc | internalMask);
                 f.apply(pos, material, pass, new Cuboid6(x1, y1, d2, x2, y2, z2), sideMask & 0x3b | 4 | internalMask);
                 f.apply(pos, material, pass, new Cuboid6(x1, y1, z1, x2, y2, d1), sideMask & 0x37 | 8 | internalMask);
-                break;
-            case 2:
-            case 3:
+            }
+            case 2, 3 -> {
                 if (face) internalMask = 0x33;
                 f.apply(pos, material, pass, new Cuboid6(d2, d1, z1, x2, d2, z2), 0x2f | internalMask);
                 f.apply(pos, material, pass, new Cuboid6(x1, d1, z1, d1, d2, z2), 0x1f | internalMask);
@@ -104,9 +102,8 @@ final class HollowMicroblockClientLogic {
                         pass,
                         new Cuboid6(x1, y1, z1, d1, y2, z2),
                         sideMask & 0x1f | 0x20 | internalMask);
-                break;
-            case 4:
-            case 5:
+            }
+            case 4, 5 -> {
                 if (face) internalMask = 0xf;
                 f.apply(pos, material, pass, new Cuboid6(x1, d2, d1, x2, y2, d2), 0x3e | internalMask);
                 f.apply(pos, material, pass, new Cuboid6(x1, y1, d1, x2, d1, d2), 0x3d | internalMask);
@@ -114,9 +111,8 @@ final class HollowMicroblockClientLogic {
                 f.apply(pos, material, pass, new Cuboid6(x1, d1, z1, x2, d2, d1), sideMask & 0x34 | 3 | internalMask);
                 f.apply(pos, material, pass, new Cuboid6(x1, d2, z1, x2, y2, z2), sideMask & 0x3e | 1 | internalMask);
                 f.apply(pos, material, pass, new Cuboid6(x1, y1, z1, x2, d1, z2), sideMask & 0x3d | 2 | internalMask);
-                break;
-            default:
-                throw new MatchError(slot);
+            }
+            default -> throw new MatchError(slot);
         }
     }