implement settings

3 files changed, 55 insertions, 1 deletions

diff --git a/lib/nes/common/CMakeLists.txt b/lib/nes/common/CMakeLists.txt
index 3920d36..9a7cc6b 100644
--- a/lib/nes/common/CMakeLists.txt
+++ b/lib/nes/common/CMakeLists.txt
@@ -5,6 +5,8 @@ target_sources(
 		debug.hh
 		rgb.hh
 		display.hh
-		status.hh)
+		status.hh
+		fps-counter.hh
+		fps-counter.cc)
 
 add_subdirectory(containers)
\ No newline at end of file
diff --git a/lib/nes/common/fps-counter.cc b/lib/nes/common/fps-counter.cc
new file mode 100644
index 0000000..ef6169b
--- /dev/null
+++ b/lib/nes/common/fps-counter.cc
@@ -0,0 +1,29 @@
+#include "nes/common/fps-counter.hh"
+
+namespace nes
+{
+	auto fps_counter::frame(std::chrono::microseconds const elapsed_time) -> void
+	{
+		if (elapsed_time.count() <= 0) { return; }
+
+		if (buffer_position_ == 0)
+		{
+			// Update fps count.
+			auto sum = u32{ 0 };
+			for (auto i = u32{ 0 }; i < buffer_size; ++i) { sum += frame_times_[i]; }
+			if (sum > 0)
+			{
+				buffered_fps_ = (buffer_size * 1000000) / sum;
+			}
+			else
+			{
+				buffered_fps_ = 0;
+			}
+		}
+
+		// Add the frame time to the buffer, replacing any existing content in the ring buffer.
+		auto const frame_time = static_cast<u32>(elapsed_time.count());
+		frame_times_[buffer_position_] = frame_time;
+		buffer_position_ = (buffer_position_ + 1) % buffer_size;
+	}
+} // namespace nes
\ No newline at end of file
diff --git a/lib/nes/common/fps-counter.hh b/lib/nes/common/fps-counter.hh
new file mode 100644
index 0000000..96db98c
--- /dev/null
+++ b/lib/nes/common/fps-counter.hh
@@ -0,0 +1,23 @@
+#pragma once
+
+#include "nes/common/types.hh"
+#include <chrono>
+
+namespace nes
+{
+	/// Counts frames.
+	class fps_counter
+	{
+		static constexpr auto buffer_size = u32{ 20 };
+
+		u32 frame_times_[buffer_size]{}; // The time until the next frame for the last <buffer_size> frames.
+		u32 buffer_position_{ 0 }; // Position in the ring buffer.
+		u32 buffered_fps_{ 0 }; // Delay updates to FPS to one update per round in the ring buffer.
+
+	public:
+		explicit fps_counter() = default;
+
+		auto frame(std::chrono::microseconds elapsed_time) -> void;
+		auto get_fps() const -> u32 { return buffered_fps_; }
+	};
+} // namespace nes
\ No newline at end of file