From 1219df3c27404ca0bd2d967a3fa490d604486ec9 Mon Sep 17 00:00:00 2001
From: Jan Svabenik <jan@svabi.ch>
Date: Mon, 25 May 2026 16:12:09 +0200
Subject: [PATCH] fix: struct padding bug in viz loopback, overflow in stopped
 state
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

- viz/capture.go: waveFormatExtensibleEx now flat struct (not embedded)
  Go pads waveFormatEx to 20 bytes (uint32 alignment), but the Windows
  C struct is 18 bytes — embedding caused SubFormat to land at wrong
  offset, breaking float32 detection (float=false bug)
- server.go: clamp position/length values > 24h to 0
  Winamp returns 0xFFFFFFFF for these fields when stopped/no track loaded
- .gitignore: exclude winamp/ dir and runtime .dat files
- config.yaml: added (gitignored) pointing to winamp/winamp.exe

Tested: Winamp 5.9 portable in winamp/, IPC connection verified,
viz loopback correctly detects 48kHz float32 stereo

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 .gitignore                | 10 ++++++++++
 internal/server/server.go |  9 +++++++--
 internal/viz/capture.go   | 18 ++++++++++++++----
 3 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/.gitignore b/.gitignore
index 270e6a5..622170c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -21,5 +21,15 @@ vendor/
 .DS_Store
 Thumbs.db
 
+# Dev config (has local paths — use config.yaml.example as template)
+config.yaml
+
 # Config with secrets
 config.local.yaml
+
+# Portable Winamp (extracted locally for dev — not committed)
+winamp/
+
+# Runtime data files
+killist.dat
+resume.dat
diff --git a/internal/server/server.go b/internal/server/server.go
index e12d372..33b574e 100644
--- a/internal/server/server.go
+++ b/internal/server/server.go
@@ -266,8 +266,13 @@ func (s *Server) statusMsg() ([]byte, error) {
 			msg.State = "stopped"
 		}
 		msg.Title = s.wa.GetTitle()
-		msg.Position = s.wa.GetPosition()
-		msg.Length = s.wa.GetLength()
+		// Winamp returns 0xFFFFFFFF when stopped/no track — clamp to 0.
+		pos := s.wa.GetPosition()
+		length := s.wa.GetLength()
+		if pos > 86400 { pos = 0 }      // > 24h → garbage value
+		if length > 86400 { length = 0 }
+		msg.Position = pos
+		msg.Length = length
 		msg.PlaylistPos = s.wa.GetPlaylistPosition()
 		msg.PlaylistLength = s.wa.GetPlaylistLength()
 		msg.Version = s.wa.GetVersion()
diff --git a/internal/viz/capture.go b/internal/viz/capture.go
index a0c9870..98efb61 100644
--- a/internal/viz/capture.go
+++ b/internal/viz/capture.go
@@ -72,11 +72,21 @@ type waveFormatEx struct {
 	Size           uint16
 }
 
+// waveFormatExtensibleEx is a flat representation of WAVEFORMATEXTENSIBLE.
+// We cannot embed waveFormatEx because Go pads the struct to 20 bytes
+// (alignment of largest field = uint32), but the C layout is 18 bytes —
+// so SubFormat would land at the wrong offset if we used struct embedding.
 type waveFormatExtensibleEx struct {
-	Format      waveFormatEx
-	Samples     uint16
-	ChannelMask uint32
-	SubFormat   windows.GUID
+	FormatTag      uint16
+	Channels       uint16
+	SamplesPerSec  uint32
+	AvgBytesPerSec uint32
+	BlockAlign     uint16
+	BitsPerSample  uint16
+	Size           uint16
+	Samples        uint16       // wValidBitsPerSample / wSamplesPerBlock
+	ChannelMask    uint32
+	SubFormat      windows.GUID // 16 bytes → total 40 bytes, matches C layout
 }
 
 // ── DLL procs ─────────────────────────────────────────────────────────────────