v0.4.5: panel-center audio, preload chat feedback, defensive BE check

- audio: distance attenuation now uses the panel center (width/2, height/2
  offset from the anchor along the renderer's right/up axes) instead of the
  anchor block corner, so a 4x4 panel sounds like it's coming from the
  middle of the screen and not the bottom-left.
- preload: each client now posts a chat line on start / completion / failure
  / cache-hit, so a command-block sequence like /videopreload -> /videoplace
  can be timed against the visible "[videopreload] 완료" message.
- safety: VideoPlayback.tick() verifies the anchor BE still exists at each
  active position and forcibly stops playback if it doesn't — covers any
  edge case where BLOCK_ENTITY_UNLOAD doesn't fire.
- /videopreload feedback now explicitly states "완료 알림 후 재생하세요".

src/main/java/com/ejclaw/videoplayer/VideoPlayerClient.java

@@ -76,17 +76,20 @@ public class VideoPlayerClient implements ClientModInitializer {
         VideoPlayerMod.LOG.info("[{}] client initialized", VideoPlayerMod.MOD_ID);
     }
 
-    /** SPEC §6 — recompute per-anchor audio gain from player distance every tick. */
+    /**
+     * SPEC §6 — recompute per-anchor audio gain from player distance every tick.
+     * Distance is measured from the player's eye to the <em>panel center</em>, not the anchor
+     * block corner — for a 4×4 panel the corner is ~2 blocks off from where the screen visually
+     * sits, which made the audio feel like it was off to the side.
+     */
     private static void updateDistanceGains(Minecraft client) {
         LocalPlayer p = client.player;
         if (p == null || client.level == null) return;
         Vec3 eye = p.getEyePosition();
         for (BlockPos pos : VideoPlayback.activePositions()) {
             if (!(client.level.getBlockEntity(pos) instanceof VideoAnchorBlockEntity be)) continue;
-            double dx = (pos.getX() + 0.5) - eye.x;
-            double dy = (pos.getY() + 0.5) - eye.y;
-            double dz = (pos.getZ() + 0.5) - eye.z;
-            double d  = Math.sqrt(dx * dx + dy * dy + dz * dz);
+            Vec3 center = be.panelCenter();
+            double d = center.distanceTo(eye);
             float attenuation = (float) Math.max(0.0, Math.min(1.0, 1.0 - d / 16.0));
             float gain = be.isMuted() ? 0F : be.getVolume() * attenuation;
             VideoPlayback.setGain(pos, gain);

src/main/java/com/ejclaw/videoplayer/block/VideoAnchorBlockEntity.java

@@ -8,6 +8,7 @@ import net.minecraft.world.level.block.entity.BlockEntity;
 import net.minecraft.world.level.block.state.BlockState;
 import net.minecraft.world.level.storage.ValueInput;
 import net.minecraft.world.level.storage.ValueOutput;
+import net.minecraft.world.phys.Vec3;
 
 /**
  * Anchor BE — holds per-block config that drives playback.
@@ -52,6 +53,37 @@ public class VideoAnchorBlockEntity extends BlockEntity {
         setChanged();
     }
 
+    /**
+     * World-space center of the rendered panel. Used for distance-based audio attenuation so
+     * the sound source feels like it's coming from the middle of the screen, not the corner
+     * (anchor block). Geometry mirrors {@code VideoAnchorRenderer#submit}:
+     * the panel's bottom-left corner sits on the wall surface at
+     * {@code anchorCenter + (-0.5)*facing + (-0.5)*right + (-0.5)*up}, and the panel extends
+     * {@code width × height} blocks along {@code right} and {@code up}. So the center is
+     * {@code anchorCenter + (w/2 - 0.5)*right + (h/2 - 0.5)*up + (-0.5)*facing}.
+     */
+    public Vec3 panelCenter() {
+        Vec3 right, up;
+        switch (facing) {
+            case NORTH -> { right = new Vec3(-1, 0,  0); up = new Vec3(0,  1, 0); }
+            case SOUTH -> { right = new Vec3( 1, 0,  0); up = new Vec3(0,  1, 0); }
+            case EAST  -> { right = new Vec3( 0, 0, -1); up = new Vec3(0,  1, 0); }
+            case WEST  -> { right = new Vec3( 0, 0,  1); up = new Vec3(0,  1, 0); }
+            case UP    -> { right = new Vec3( 1, 0,  0); up = new Vec3(0,  0, -1); }
+            case DOWN  -> { right = new Vec3( 1, 0,  0); up = new Vec3(0,  0,  1); }
+            default    -> { right = new Vec3( 1, 0,  0); up = new Vec3(0,  1,  0); }
+        }
+        Vec3 facingVec = new Vec3(facing.getStepX(), facing.getStepY(), facing.getStepZ());
+        BlockPos p = getBlockPos();
+        Vec3 anchorCenter = new Vec3(p.getX() + 0.5, p.getY() + 0.5, p.getZ() + 0.5);
+        double offR = width  / 2.0 - 0.5;
+        double offU = height / 2.0 - 0.5;
+        return anchorCenter
+            .add(right.scale(offR))
+            .add(up.scale(offU))
+            .add(facingVec.scale(-0.5));
+    }
+
     /** Wire-format NBT used by SaveConfig/SyncAnchor payloads. */
     public CompoundTag toNbt() {
         CompoundTag nbt = new CompoundTag();

src/main/java/com/ejclaw/videoplayer/client/playback/VideoCache.java

@@ -3,7 +3,9 @@ package com.ejclaw.videoplayer.client.playback;
 import com.ejclaw.videoplayer.VideoPlayerMod;
 import net.fabricmc.api.EnvType;
 import net.fabricmc.api.Environment;
+import net.minecraft.ChatFormatting;
 import net.minecraft.client.Minecraft;
+import net.minecraft.network.chat.Component;
 
 import java.io.InputStream;
 import java.io.OutputStream;
@@ -48,12 +50,15 @@ public final class VideoCache {
         if (!(url.startsWith("http://") || url.startsWith("https://"))) return;
         if (READY.containsKey(url)) {
             VideoPlayerMod.LOG.info("[{}] preload: already cached {}", VideoPlayerMod.MOD_ID, url);
+            notifyChat("[videopreload] 이미 캐시됨: " + url, ChatFormatting.GRAY);
             return;
         }
         if (!IN_FLIGHT.add(url)) {
             VideoPlayerMod.LOG.info("[{}] preload: already downloading {}", VideoPlayerMod.MOD_ID, url);
+            notifyChat("[videopreload] 이미 다운로드 중: " + url, ChatFormatting.GRAY);
             return;
         }
+        notifyChat("[videopreload] 다운로드 시작: " + url, ChatFormatting.YELLOW);
         Thread t = new Thread(() -> download(url), "video_player-preload");
         t.setDaemon(true);
         t.start();
@@ -101,6 +106,7 @@ public final class VideoCache {
                 READY.put(url, finalPath);
                 VideoPlayerMod.LOG.info("[{}] preload: indexed existing cache {} -> {}",
                     VideoPlayerMod.MOD_ID, url, finalPath.getFileName());
+                notifyChat("[videopreload] 기존 캐시 사용: " + url, ChatFormatting.GREEN);
                 return;
             }
 
@@ -114,6 +120,7 @@ public final class VideoCache {
                 if (code >= 400) {
                     VideoPlayerMod.LOG.warn("[{}] preload: HTTP {} for {}",
                         VideoPlayerMod.MOD_ID, code, url);
+                    notifyChat("[videopreload] 실패 (HTTP " + code + "): " + url, ChatFormatting.RED);
                     return;
                 }
             }
@@ -130,6 +137,7 @@ public final class VideoCache {
                             "[{}] preload: {} exceeded {} MB cap; aborting",
                             VideoPlayerMod.MOD_ID, url, MAX_BYTES / (1024 * 1024));
                         try { Files.deleteIfExists(partPath); } catch (Throwable ignored) {}
+                        notifyChat("[videopreload] 실패 (512MB 초과): " + url, ChatFormatting.RED);
                         return;
                     }
                     out.write(buf, 0, n);
@@ -141,14 +149,28 @@ public final class VideoCache {
             READY.put(url, finalPath);
             VideoPlayerMod.LOG.info("[{}] preload: cached {} ({} bytes) -> {}",
                 VideoPlayerMod.MOD_ID, url, total, finalPath.getFileName());
+            long mb = Math.max(1, total / (1024 * 1024));
+            notifyChat("[videopreload] 완료 (" + mb + " MB): " + url, ChatFormatting.GREEN);
         } catch (Throwable t) {
             VideoPlayerMod.LOG.warn("[{}] preload failed for {}: {}",
                 VideoPlayerMod.MOD_ID, url, t.toString());
+            notifyChat("[videopreload] 실패 (" + t.getClass().getSimpleName() + "): " + url,
+                ChatFormatting.RED);
         } finally {
             IN_FLIGHT.remove(url);
         }
     }
 
+    /** Post a status line to the local player's chat. No-op if there's no client/player yet. */
+    private static void notifyChat(String text, ChatFormatting color) {
+        Minecraft mc = Minecraft.getInstance();
+        if (mc == null) return;
+        mc.execute(() -> {
+            if (mc.player == null) return;
+            mc.player.sendSystemMessage(Component.literal(text).withStyle(color));
+        });
+    }
+
     private static Path cacheDir() {
         Minecraft mc = Minecraft.getInstance();
         if (mc == null || mc.gameDirectory == null) return null;

src/main/java/com/ejclaw/videoplayer/client/playback/VideoPlayback.java

@@ -95,11 +95,22 @@ public final class VideoPlayback {
 
     /** Called every client tick to upload new frames into the GPU texture. */
     public static void tick() {
-        if (Minecraft.getInstance() == null) return;
+        Minecraft mc = Minecraft.getInstance();
+        if (mc == null) return;
         Iterator<Map.Entry<BlockPos, Entry>> it = ENTRIES.entrySet().iterator();
         while (it.hasNext()) {
             Map.Entry<BlockPos, Entry> me = it.next();
+            BlockPos pos = me.getKey();
             Entry e = me.getValue();
+            // Belt-and-suspenders for the audio-on-delete bug: if BLOCK_ENTITY_UNLOAD didn't
+            // fire for some edge case (dimension change, chunk torn down before event runs,
+            // etc.), the BE will be gone from the level but our Entry still holds an open
+            // audio line. Catch it here and stop next tick.
+            if (mc.level == null || !(mc.level.getBlockEntity(pos) instanceof VideoAnchorBlockEntity)) {
+                e.close();
+                it.remove();
+                continue;
+            }
             if (!e.backend.isReady()) continue;
             ByteBuffer buf = e.backend.pollFrame();
             if (buf == null) continue;

src/main/java/com/ejclaw/videoplayer/command/VideoPreloadCommand.java

@@ -64,9 +64,11 @@ public final class VideoPreloadCommand {
         }
         final int sentFinal = sent;
         // Use sendSuccess(..., false) so the chat noise is local-only and command blocks don't
-        // spam every operator on each tick.
+        // spam every operator on each tick. Be explicit that this is fire-and-forget: each
+        // client posts its own "[videopreload] 완료" chat line when the download finishes.
         src.sendSuccess(() -> Component.literal(
-            "preload requested for " + sentFinal + " client(s): " + payload.url()), false);
+            "preload 요청을 " + sentFinal + " 클라이언트에 전송: " + payload.url()
+                + " (완료 알림 후 재생하세요)"), false);
         return sent;
     }
 }