From 6a58b4a8ba878281f7bddba60c8092843d9574fa Mon Sep 17 00:00:00 2001
From: Ritchie Cunningham <ritchie@ritchiecunningham.co.uk>
Date: Thu, 11 Sep 2025 23:21:37 +0100
Subject: [PATCH] feat(engine): Implement delta time calculation.

---
 src/main.cpp | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/src/main.cpp b/src/main.cpp
index c448ce5..6a98fbf 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1,6 +1,9 @@
 #include <SDL3/SDL.h>
 #include <GL/glew.h>
 #include <SDL3/SDL_error.h>
+#include <SDL3/SDL_stdinc.h>
+#include <SDL3/SDL_timer.h>
+#include <SDL3/SDL_video.h>
 #include <cstdio>
 
 const int SCREEN_WIDTH  = 800;
@@ -59,7 +62,21 @@ int main(int argc, char* argv[]) {
   bool is_running = true;
   SDL_Event event;
 
+  /* Delta time calculations. */
+  Uint64 perf_frequency = SDL_GetPerformanceFrequency();
+  Uint64 last_counter   = SDL_GetPerformanceCounter();
+  double delta_time     = 0;
+
+  /* FPS counter for window title. */
+  char window_title[256];
+  double time_since_title_update = 0.0;
+
   while(is_running) {
+    /* Calc delta time. */
+    Uint64 current_counter = SDL_GetPerformanceCounter();
+    delta_time = (double)(current_counter-last_counter) / (double)perf_frequency;
+    last_counter = current_counter;
+
     /* Event handling. */
     while(SDL_PollEvent(&event)) {
       if(event.type == SDL_EVENT_QUIT) {
@@ -67,6 +84,14 @@ int main(int argc, char* argv[]) {
       }
     }
 
+    /* Update window title with FPS counter. */
+    time_since_title_update += delta_time;
+    if(time_since_title_update > 0.25) {
+      snprintf(window_title, 256, "Bettola - FPS: %.2f", 1.0/delta_time);
+      SDL_SetWindowTitle(window, window_title);
+      time_since_title_update = 0.0;
+    }
+
     /* Render that b*tch. */
     glClearColor(0.1f, 0.1f, 0.3f, 1.0f); /* Dark blue or something. */
     glClear(GL_COLOR_BUFFER_BIT);