DebugActor use ring buffer to collect frame statistics

src/kiwano/2d/DebugActor.cpp

@@ -45,6 +45,7 @@ private:
 }  // namespace
 
 DebugActor::DebugActor()
+    : frame_buffer_(70 /* pre-alloc for 70 frames */)
 {
     SetName("kiwano-debug-actor");
     SetPosition(Point{ 10, 10 });
@@ -77,10 +78,10 @@ void DebugActor::OnRender(RenderContext& ctx)
     ctx.FillRoundedRectangle(GetBounds(), Vec2{ 5.f, 5.f });
     ctx.DrawTextLayout(debug_text_, Point(10, 10));
 
-    frame_time_.push_back(Time::Now());
+    frame_buffer_.PushBack(Time::Now());
-    while (frame_time_.back() - frame_time_.front() >= Duration::Second)
+    while (frame_buffer_.Back() - frame_buffer_.Front() >= Duration::Second)
     {
-        frame_time_.erase(frame_time_.begin());
+        frame_buffer_.PopFront();
     }
 }
 
@@ -93,7 +94,7 @@ void DebugActor::OnUpdate(Duration dt)
     // For formatting integers with commas
     (void)ss.imbue(comma_locale_);
 
-    ss << "Fps: " << frame_time_.size() << std::endl;
+    ss << "Fps: " << frame_buffer_.Size() << std::endl;
 
 #if defined(KGE_DEBUG)
     if (ObjectBase::IsTracingLeaks())
@@ -106,7 +107,7 @@ void DebugActor::OnUpdate(Duration dt)
 
     ss << "Render: " << status.duration.Milliseconds() << "ms" << std::endl;
 
-    ss << "Primitives / sec: " << std::fixed << status.primitives * frame_time_.size() << std::endl;
+    ss << "Primitives / sec: " << std::fixed << status.primitives * frame_buffer_.Size() << std::endl;
 
     ss << "Memory: ";
     {

src/kiwano/2d/DebugActor.h

@@ -24,6 +24,99 @@
 
 namespace kiwano
 {
+
+template <typename T>
+class SimpleRingBuffer
+{
+public:
+    SimpleRingBuffer(size_t capcity)
+    {
+        Reserve(capcity);
+    }
+
+    void PushBack(const T& val)
+    {
+        if (IsFull())
+            Reserve(Capacity() * 2);
+        buffer_[rear_] = val;
+        IncreaseRear();
+    }
+
+    void PopFront()
+    {
+        IncreaseFront();
+    }
+
+    const T& Front() const
+    {
+        return buffer_[front_];
+    }
+
+    T& Front()
+    {
+        return buffer_[front_];
+    }
+
+    const T& Back() const
+    {
+        return buffer_[ClampCursor(rear_, 1)];
+    }
+
+    T& Back()
+    {
+        return buffer_[ClampCursor(rear_, 1)];
+    }
+
+    bool IsEmpty() const noexcept
+    {
+        return front_ = rear_;
+    }
+
+    bool IsFull() const noexcept
+    {
+        return front_ == (rear_ + 1) % Capacity();
+    }
+
+    size_t Size() const
+    {
+        return ClampCursor(rear_, front_);
+    }
+
+    size_t Capacity() const
+    {
+        return buffer_.size();
+    }
+
+    void Reserve(size_t capacity)
+    {
+        buffer_.resize(capacity);
+    }
+
+private:
+    void IncreaseFront()
+    {
+        if (buffer_.empty())
+            return;
+        front_ = (front_ + 1) % Capacity();
+    }
+
+    void IncreaseRear()
+    {
+        rear_ = (rear_ + 1) % Capacity();
+    }
+
+    size_t ClampCursor(size_t cursor, size_t off) const
+    {
+        return (cursor + Capacity() - off) % Capacity();
+    }
+
+private:
+    Vector<T> buffer_;
+    size_t    front_ = 0;
+    size_t    rear_  = 0;
+};
+
+
 /**
  * \addtogroup Actors
  * @{
@@ -52,7 +145,8 @@ private:
     BrushPtr    background_brush_;
     TextStyle   debug_text_style_;
     TextLayout  debug_text_;
-    List<Time>  frame_time_;
+
+    SimpleRingBuffer<Time> frame_buffer_;
 };
 
 /** @} */