Add tools to help debug image GC (#4578)

`/debug-force-image-gc` will force garbage collection on all unused images
`/debug-force-image-unload` will force unload all images

Co-authored-by: Rasmus Karlsson <rasmus.karlsson@pajlada.com>

CHANGELOG.md

@@ -9,6 +9,7 @@
 - Dev: Added test cases for emote and tab completion. (#4644)
 - Dev: Fixed `clang-tidy-review` action not picking up dependencies. (#4648)
 - Dev: Expanded upon `$$$` test channels. (#4655)
+- Dev: Added tools to help debug image GC. (#4578)
 
 ## 2.4.4
 

src/controllers/commands/CommandController.cpp

@@ -16,6 +16,7 @@
 #include "controllers/commands/CommandModel.hpp"
 #include "controllers/plugins/PluginController.hpp"
 #include "controllers/userdata/UserDataController.hpp"
+#include "messages/Image.hpp"
 #include "messages/Message.hpp"
 #include "messages/MessageBuilder.hpp"
 #include "messages/MessageElement.hpp"
@@ -38,6 +39,7 @@
 #include "util/FormatTime.hpp"
 #include "util/Helpers.hpp"
 #include "util/IncognitoBrowser.hpp"
+#include "util/PostToThread.hpp"
 #include "util/Qt.hpp"
 #include "util/StreamerMode.hpp"
 #include "util/StreamLink.hpp"
@@ -3211,6 +3213,28 @@ void CommandController::initialize(Settings &, Paths &paths)
         return "";
     });
 
+    this->registerCommand(
+        "/debug-force-image-gc",
+        [](const QStringList & /*words*/, auto /*channel*/) -> QString {
+            runInGuiThread([] {
+                using namespace chatterino::detail;
+                auto &iep = ImageExpirationPool::instance();
+                iep.freeOld();
+            });
+            return "";
+        });
+
+    this->registerCommand(
+        "/debug-force-image-unload",
+        [](const QStringList & /*words*/, auto /*channel*/) -> QString {
+            runInGuiThread([] {
+                using namespace chatterino::detail;
+                auto &iep = ImageExpirationPool::instance();
+                iep.freeAll();
+            });
+            return "";
+        });
+
     this->registerCommand("/shield", &commands::shieldModeOn);
     this->registerCommand("/shieldoff", &commands::shieldModeOff);
 

src/messages/Image.cpp

@@ -76,6 +76,8 @@ namespace detail {
                 60000);
         }
         this->processOffset();
+        DebugCount::increase("image bytes", this->memoryUsage());
+        DebugCount::increase("image bytes (ever loaded)", this->memoryUsage());
     }
 
     Frames::~Frames()
@@ -91,10 +93,27 @@ namespace detail {
         {
             DebugCount::decrease("animated images");
         }
+        DebugCount::decrease("image bytes", this->memoryUsage());
+        DebugCount::increase("image bytes (ever unloaded)",
+                             this->memoryUsage());
 
         this->gifTimerConnection_.disconnect();
     }
 
+    int64_t Frames::memoryUsage() const
+    {
+        int64_t usage = 0;
+        for (const auto &frame : this->items_)
+        {
+            auto sz = frame.image.size();
+            auto area = sz.width() * sz.height();
+            auto memory = area * frame.image.depth();
+
+            usage += memory;
+        }
+        return usage;
+    }
+
     void Frames::advance()
     {
         this->durationOffset_ += GIF_FRAME_LENGTH;
@@ -131,6 +150,9 @@ namespace detail {
         {
             DebugCount::decrease("loaded images");
         }
+        DebugCount::decrease("image bytes", this->memoryUsage());
+        DebugCount::increase("image bytes (ever unloaded)",
+                             this->memoryUsage());
 
         this->items_.clear();
         this->index_ = 0;
@@ -589,14 +611,26 @@ void ImageExpirationPool::removeImagePtr(Image *rawPtr)
     this->allImages_.erase(rawPtr);
 }
 
+void ImageExpirationPool::freeAll()
+{
+    {
+        std::lock_guard<std::mutex> lock(this->mutex_);
+        for (auto it = this->allImages_.begin(); it != this->allImages_.end();)
+        {
+            auto img = it->second.lock();
+            img->expireFrames();
+            it = this->allImages_.erase(it);
+        }
+    }
+    this->freeOld();
+}
+
 void ImageExpirationPool::freeOld()
 {
     std::lock_guard<std::mutex> lock(this->mutex_);
 
-#    ifndef NDEBUG
     size_t numExpired = 0;
     size_t eligible = 0;
-#    endif
 
     auto now = std::chrono::steady_clock::now();
     for (auto it = this->allImages_.begin(); it != this->allImages_.end();)
@@ -617,17 +651,13 @@ void ImageExpirationPool::freeOld()
             continue;
         }
 
-#    ifndef NDEBUG
         ++eligible;
-#    endif
 
         // Check if image has expired and, if so, expire its frame data
         auto diff = now - img->lastUsed_;
         if (diff > IMAGE_POOL_IMAGE_LIFETIME)
         {
-#    ifndef NDEBUG
             ++numExpired;
-#    endif
             img->expireFrames();
             // erase without mutex locking issue
             it = this->allImages_.erase(it);
@@ -641,6 +671,9 @@ void ImageExpirationPool::freeOld()
     qCDebug(chatterinoImage) << "freed frame data for" << numExpired << "/"
                              << eligible << "eligible images";
 #    endif
+    DebugCount::set("last image gc: expired", numExpired);
+    DebugCount::set("last image gc: eligible", eligible);
+    DebugCount::set("last image gc: left after gc", this->allImages_.size());
 }
 
 #endif

src/messages/Image.hpp

@@ -41,6 +41,7 @@ namespace detail {
         boost::optional<QPixmap> first() const;
 
     private:
+        int64_t memoryUsage() const;
         void processOffset();
         QVector<Frame<QPixmap>> items_;
         int index_{0};
@@ -111,6 +112,7 @@ class ImageExpirationPool
 {
 private:
     friend class Image;
+    friend class CommandController;
 
     ImageExpirationPool();
     static ImageExpirationPool &instance();
@@ -126,6 +128,12 @@ private:
      */
     void freeOld();
 
+    /*
+     * Debug function that unloads all images in the pool. This is intended to
+     * test for possible memory leaks from tracked images.
+     */
+    void freeAll();
+
 private:
     // Timer to periodically run freeOld()
     QTimer *freeTimer_;

src/util/DebugCount.hpp

@@ -27,6 +27,22 @@ public:
             reinterpret_cast<int64_t &>(it.value())++;
         }
     }
+
+    static void set(const QString &name, const int64_t &amount)
+    {
+        auto counts = counts_.access();
+
+        auto it = counts->find(name);
+        if (it == counts->end())
+        {
+            counts->insert(name, amount);
+        }
+        else
+        {
+            reinterpret_cast<int64_t &>(it.value()) = amount;
+        }
+    }
+
     static void increase(const QString &name, const int64_t &amount)
     {
         auto counts = counts_.access();