DEBUG #4294: log each chunk sent with its neighbours (never merge)

crates/horizon-client/src/lan/chunks.rs

@@ -559,6 +559,12 @@ impl ChunkEncoder {
         bits
     }
 
+    /// DEBUG #4294: the highest non-air section.
+    pub fn debug_top(&self, chunk: &Chunk) -> Option<usize> {
+        let bits = self.occupied(chunk);
+        (0..64).rev().find(|&i| bits.contains(i))
+    }
+
     /// The non-air sections of the column and its neighbours, as bits.
     fn around(&self, chunk: &Chunk, world: &crate::world::World) -> SectionMask {
         let mut around = SectionMask::EMPTY;

crates/horizon-client/src/lan/hub.rs

@@ -1437,6 +1437,16 @@ impl Hub {
             })
             .collect();
         self.encoder.warm(&columns);
+        for c in &columns {
+            let around: Vec<String> = (-1..=1)
+                .flat_map(|dz| (-1..=1).map(move |dx| (dx, dz)))
+                .map(|(dx, dz)| match world.chunks.get(&(c.x + dx, c.z + dz)) {
+                    Some(n) => format!("{dx},{dz}:{:?}{}", self.encoder.debug_top(n), if n.lit { "" } else { "u" }),
+                    None => format!("{dx},{dz}:-"),
+                })
+                .collect();
+            eprintln!("LLDEBUG tick {} send {},{} {}", self.ticks, c.x, c.z, around.join(" "));
+        }
         let mut bodies: Vec<Vec<u8>> = columns
             .iter()
             .map(|c| self.encoder.body_in(c, world))