From b9308d732586d78e55abe7ebb99ea85fcd8fe3de Mon Sep 17 00:00:00 2001
From: pajlada <rasmus.karlsson@pajlada.com>
Date: Sat, 24 Dec 2022 11:32:08 +0100
Subject: [PATCH] Add Thread Guard for debugging simple threading issues
 (#4254)

* Add ThreadGuard class

* Use ThreadGuard when accessing a ChannelView's messageSnapshot
---
 src/CMakeLists.txt                 |  1 +
 src/util/ThreadGuard.hpp           | 35 ++++++++++++++++++++++++++++++
 src/widgets/helper/ChannelView.cpp |  1 +
 src/widgets/helper/ChannelView.hpp |  2 ++
 4 files changed, 39 insertions(+)
 create mode 100644 src/util/ThreadGuard.hpp

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index f7912f44..ec157314 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -364,6 +364,7 @@ set(SOURCE_FILES
         util/StreamLink.hpp
         util/StreamerMode.cpp
         util/StreamerMode.hpp
+        util/ThreadGuard.hpp
         util/Twitch.cpp
         util/Twitch.hpp
         util/TypeName.hpp
diff --git a/src/util/ThreadGuard.hpp b/src/util/ThreadGuard.hpp
new file mode 100644
index 00000000..6f272ac4
--- /dev/null
+++ b/src/util/ThreadGuard.hpp
@@ -0,0 +1,35 @@
+#pragma once
+
+#include <cassert>
+#include <mutex>
+#include <optional>
+#include <thread>
+
+namespace chatterino {
+
+// Debug-class which asserts if guard of the same object has been called from different threads
+struct ThreadGuard {
+#ifndef NDEBUG
+    std::mutex mutex;
+    std::optional<std::thread::id> threadID;
+#endif
+
+    inline void guard()
+    {
+#ifndef NDEBUG
+        std::unique_lock lock(this->mutex);
+
+        auto currentThreadID = std::this_thread::get_id();
+
+        if (!this->threadID.has_value())
+        {
+            this->threadID = currentThreadID;
+            return;
+        }
+
+        assert(this->threadID == currentThreadID);
+#endif
+    }
+};
+
+}  // namespace chatterino
diff --git a/src/widgets/helper/ChannelView.cpp b/src/widgets/helper/ChannelView.cpp
index 14746c72..cfaf0d0d 100644
--- a/src/widgets/helper/ChannelView.cpp
+++ b/src/widgets/helper/ChannelView.cpp
@@ -628,6 +628,7 @@ const boost::optional<MessageElementFlags> &ChannelView::getOverrideFlags()
 
 LimitedQueueSnapshot<MessageLayoutPtr> &ChannelView::getMessagesSnapshot()
 {
+    this->snapshotGuard_.guard();
     if (!this->paused() /*|| this->scrollBar_->isVisible()*/)
     {
         this->snapshot_ = this->messages_.getSnapshot();
diff --git a/src/widgets/helper/ChannelView.hpp b/src/widgets/helper/ChannelView.hpp
index dc614118..afb1e836 100644
--- a/src/widgets/helper/ChannelView.hpp
+++ b/src/widgets/helper/ChannelView.hpp
@@ -6,6 +6,7 @@
 #include "messages/LimitedQueue.hpp"
 #include "messages/LimitedQueueSnapshot.hpp"
 #include "messages/Selection.hpp"
+#include "util/ThreadGuard.hpp"
 #include "widgets/BaseWidget.hpp"
 
 #include <pajlada/signals/signal.hpp>
@@ -270,6 +271,7 @@ private:
     boost::optional<MessageElementFlags> overrideFlags_;
     MessageLayoutPtr lastReadMessage_;
 
+    ThreadGuard snapshotGuard_;
     LimitedQueueSnapshot<MessageLayoutPtr> snapshot_;
 
     ChannelPtr channel_ = nullptr;