fix(entity): keep variant fields a metadata update leaves out

src/client/entity/EntityTracker.cpp

@@ -309,8 +309,10 @@ namespace perlin::entity {
     PERLIN_ENTITY_SET(SetBoundingBox(uint64_t rid, float width, float height), e.boxWidth = width;
                       e.boxHeight = height)
     PERLIN_ENTITY_SET(SetNameTag(uint64_t rid, const std::string& nameTag), e.nameTag = nameTag)
-    PERLIN_ENTITY_SET(SetVariant(uint64_t rid, int variant, int markVariant, int color), e.variant = variant;
-                      e.markVariant = markVariant; e.color = color)
+    PERLIN_ENTITY_SET(SetVariant(uint64_t rid, std::optional<int> variant, std::optional<int> markVariant,
+                                 std::optional<int> color),
+                      if (variant) e.variant = *variant;
+                      if (markVariant) e.markVariant = *markVariant; if (color) e.color = *color)
     PERLIN_ENTITY_SET(SetHealth(uint64_t rid, float health), e.health = health;
                       if (health <= 0.0f && !e.isItem) e.dying = true;
                       else if (health > 0.0f) e.dying = false)

src/client/entity/EntityTracker.hpp

@@ -1,4 +1,5 @@
 #pragma once
+#include <optional>
 #include <chrono>
 #include <functional>
 #include <glm/glm.hpp>
@@ -193,7 +194,9 @@ namespace perlin::entity {
         void SetScale(uint64_t rid, float scale);
         void SetBoundingBox(uint64_t rid, float width, float height);
         void SetNameTag(uint64_t rid, const std::string& nameTag);
-        void SetVariant(uint64_t rid, int variant, int markVariant, int color);
+        // an update that leaves a field out keeps its value: servers resend only what changed
+        void SetVariant(uint64_t rid, std::optional<int> variant, std::optional<int> markVariant,
+                        std::optional<int> color);
         void SetHealth(uint64_t rid, float health);
         void SetAttribute(uint64_t rid, const std::string& name, float min, float value, float max);
         void SetOwner(uint64_t rid, int64_t ownerUid);

src/client/multiplayer/BedrockHandlers.cpp

@@ -108,7 +108,7 @@ namespace perlin {
 
         void ApplyMetadata(entity::EntityTracker& tracker, uint64_t rid,
                            const std::vector<MetadataDictionaryEntry>& metadata) {
-            int variant = -1, mark = -1, color = -1;
+            std::optional<int> variant, mark, color;
             float boxWidth = 0.0f, boxHeight = 0.0f;
             static const bool debugTags = std::getenv("PERLIN_DEBUG_NAMETAGS") != nullptr;
             for (const MetadataDictionaryEntry& m : metadata) {
@@ -191,8 +191,9 @@ namespace perlin {
                     break;
                 }
             }
-            if (variant >= 0 || mark >= 0 || color >= 0)
-                tracker.SetVariant(rid, std::max(variant, 0), std::max(mark, 0), std::max(color, 0));
+            const auto clamp = [](std::optional<int> v) { return v ? std::optional<int>(std::max(*v, 0)) : v; };
+            if (variant || mark || color)
+                tracker.SetVariant(rid, clamp(variant), clamp(mark), clamp(color));
             if (boxWidth > 0.0f && boxHeight > 0.0f)
                 tracker.SetBoundingBox(rid, boxWidth, boxHeight);
         }