Add game loop to Application

Implements fixed and variable time steps.

Might be a moved to a separate class later.

cpp/Application.cpp

@@ -1,10 +1,31 @@
 #include "Gedeng/Application.h"
+#include "Gedeng/Time.h"
+#include "Gedeng/Logger.h"
 
 namespace Gedeng {
 
 void Application::run() {
+    unsigned long previous_time_ms = Time::get_time_ms();
+    unsigned long time_until_fixed_update_ms = 0.0;
+
     while (true) {
-        // TODO: Implement
+        unsigned long current_time_ms = Time::get_time_ms();
+        unsigned long elapsed_time_ms = current_time_ms - previous_time_ms;
+
+        previous_time_ms = current_time_ms;
+        time_until_fixed_update_ms += elapsed_time_ms;
+
+        // Process Input
+
+        // Update fixed time step
+        while (time_until_fixed_update_ms >= MS_PER_UPDATE) {
+            // Fixed Update
+            GG_CORE_INFO("Fixed Update");
+            time_until_fixed_update_ms -= MS_PER_UPDATE;
+        }
+
+        // Variable update
+        GG_CORE_INFO("Variable Update");
     }
 }
 

include/Gedeng/Application.h

@@ -10,6 +10,9 @@ class Application {
     virtual ~Application() = default;
 
     void run();
+
+  private:
+    const unsigned long MS_PER_UPDATE = 20;
 };
 
 // To be defined in client applications