From 2185b47d5f1dc1266e05730bf3ba59a788f3a443 Mon Sep 17 00:00:00 2001
From: Anthony Brandon <anthony.brandon@gmail.com>
Date: Wed, 24 Jun 2026 17:19:46 +0200
Subject: [PATCH] [Matroska] Clear size listeners before adding

Each time save is called registerSizeListener will add
new size listeners. If save is called multiple times this causes the
same delta being add/subtracted multiple times, resulting in incorrect
element sizes.

This can be observed in TestMatroska::testRepeatedSave.
Although the test passes, some sizes are incorrect resulting in the
following messages being printed during the test:

  TagLib: Failed to read VINT size
  TagLib: Failed to parse EMBL ElementID

Signed-off-by: Anthony Brandon <anthony.brandon@gmail.com>
---
 taglib/matroska/matroskaelement.cpp | 5 +++++
 taglib/matroska/matroskaelement.h   | 1 +
 taglib/matroska/matroskafile.cpp    | 4 ++++
 3 files changed, 10 insertions(+)

diff --git a/taglib/matroska/matroskaelement.cpp b/taglib/matroska/matroskaelement.cpp
index 27babd50..e57b262b 100644
--- a/taglib/matroska/matroskaelement.cpp
+++ b/taglib/matroska/matroskaelement.cpp
@@ -101,6 +101,11 @@ Matroska::Element::ID Matroska::Element::id() const
   return e->id;
 }
 
+void Matroska::Element::clearSizeListeners()
+{
+  e->sizeListeners.clear();
+}
+
 void Matroska::Element::addSizeListener(Element *element)
 {
   e->sizeListeners.append(element);
diff --git a/taglib/matroska/matroskaelement.h b/taglib/matroska/matroskaelement.h
index 881750d7..e70fcc6f 100644
--- a/taglib/matroska/matroskaelement.h
+++ b/taglib/matroska/matroskaelement.h
@@ -53,6 +53,7 @@ namespace TagLib {
       void setData(const ByteVector &data);
       const ByteVector &data() const;
       virtual void write(TagLib::File &file);
+      void clearSizeListeners();
       void addSizeListener(Element *element);
       void addSizeListeners(const List<Element *> &elements);
       bool emitSizeChanged(offset_t delta);
diff --git a/taglib/matroska/matroskafile.cpp b/taglib/matroska/matroskafile.cpp
index 920a50cd..627f0810 100644
--- a/taglib/matroska/matroskafile.cpp
+++ b/taglib/matroska/matroskafile.cpp
@@ -595,6 +595,7 @@ bool Matroska::File::save(WriteStyle writeStyle)
 
   // Set up listeners, add seek head and segment length to the end
   for(auto it = renderList.begin(); it != renderList.end(); ++it) {
+    (*it)->clearSizeListeners();
     for(auto it2 = std::next(it); it2 != renderList.end(); ++it2)
       (*it)->addSizeListener(*it2);
     if(d->cues)
@@ -605,6 +606,7 @@ bool Matroska::File::save(WriteStyle writeStyle)
   }
   if(d->cues) {
     renderList.append(d->cues.get());
+    d->cues->clearSizeListeners();
     d->cues->addSizeListeners(renderList);
     if(d->seekHead) {
       d->cues->addSizeListener(d->seekHead.get());
@@ -613,9 +615,11 @@ bool Matroska::File::save(WriteStyle writeStyle)
   }
   if(d->seekHead) {
     renderList.append(d->seekHead.get());
+    d->seekHead->clearSizeListeners();
     d->seekHead->addSizeListeners(renderList);
     d->seekHead->addSizeListener(d->segment.get());
   }
+  d->segment->clearSizeListeners();
   d->segment->addSizeListeners(renderList);
   renderList.append(d->segment.get());