From 1fe9578b3a67781d421fdc6fdc734d17df31b662 Mon Sep 17 00:00:00 2001
From: a dinosaur <dino@a-dinosaur.com>
Date: Mon, 5 Aug 2024 16:44:32 +1000
Subject: [PATCH] add fps counter

---
 Sources/Voxelotl/Application.swift   |  9 ++++++++-
 Sources/Voxelotl/CMakeLists.txt      |  1 +
 Sources/Voxelotl/FPSCalculator.swift | 18 ++++++++++++++++++
 3 files changed, 27 insertions(+), 1 deletion(-)
 create mode 100644 Sources/Voxelotl/FPSCalculator.swift

diff --git a/Sources/Voxelotl/Application.swift b/Sources/Voxelotl/Application.swift
index 76c7c82..d43d0ca 100644
--- a/Sources/Voxelotl/Application.swift
+++ b/Sources/Voxelotl/Application.swift
@@ -9,6 +9,7 @@ public class Application {
   private var view: SDL_MetalView? = nil
   private var renderer: Renderer? = nil
   private var lastCounter: UInt64 = 0
+  private var fpsCalculator = FPSCalculator()
 
   private var stderr = FileHandle.standardError
 
@@ -40,6 +41,7 @@ public class Application {
     view = SDL_Metal_CreateView(window)
     do {
       let layer = unsafeBitCast(SDL_Metal_GetLayer(view), to: CAMetalLayer.self)
+      layer.displaySyncEnabled = cfg.vsyncMode == .off ? false : true
       self.renderer = try Renderer(layer: layer)
     } catch RendererError.initFailure(let message) {
       print("Renderer init error: \(message)", to: &stderr)
@@ -92,6 +94,10 @@ public class Application {
   }
 
   private func update(_ deltaTime: Double) -> ApplicationExecutionState {
+    fpsCalculator.frame(deltaTime: deltaTime) { fps in
+      print("FPS: \(fps)", to: &stderr)
+    }
+
     do {
       try renderer!.paint()
     } catch RendererError.drawFailure(let message) {
@@ -99,6 +105,7 @@ public class Application {
     } catch {
       print("Renderer draw error: unexpected error", to: &stderr)
     }
+
     return .running
   }
 
@@ -140,7 +147,7 @@ public struct ApplicationConfiguration {
     static let highDPI = Flags(rawValue: 1 << 1)
   }
 
-  public enum VSyncMode {
+  public enum VSyncMode: Equatable {
     case off
     case on(interval: UInt)
     case adaptive
diff --git a/Sources/Voxelotl/CMakeLists.txt b/Sources/Voxelotl/CMakeLists.txt
index 146117b..475d7f5 100644
--- a/Sources/Voxelotl/CMakeLists.txt
+++ b/Sources/Voxelotl/CMakeLists.txt
@@ -1,6 +1,7 @@
 add_executable(Voxelotl MACOSX_BUNDLE
   Assets.xcassets
   Renderer.swift
+  FPSCalculator.swift
   Application.swift
   main.swift)
 
diff --git a/Sources/Voxelotl/FPSCalculator.swift b/Sources/Voxelotl/FPSCalculator.swift
new file mode 100644
index 0000000..812765d
--- /dev/null
+++ b/Sources/Voxelotl/FPSCalculator.swift
@@ -0,0 +1,18 @@
+import Foundation
+
+public struct FPSCalculator {
+  private var _accumulator = 0.0
+  private var _framesCount = 0
+
+  public mutating func frame(deltaTime: Double, result: (_ fps: Int) -> Void) {
+    _framesCount += 1
+    _accumulator += deltaTime
+
+    if (_accumulator >= 1.0) {
+      result(_framesCount)
+
+      _framesCount = 0
+      _accumulator = fmod(_accumulator, 1.0)
+    }
+  }
+}