Update render.cpp

Improve accuracy & Decrease framerate when focus is lost.

src/engine/render.cpp

@@ -64,11 +64,18 @@ void Render::render_loop() {
         auto stop = std::chrono::high_resolution_clock::now();
         float dT = (std::chrono::duration_cast<std::chrono::microseconds>(stop - start).count());
 
+
         //If we have more than 1000 fps.
-        if (dT < 1000) {
+        if (dT < 1000 && engine->window->getFlag(RWindowFlags::IN_FOCUS)) {
             int remaining = 1000 - dT;
             std::this_thread::sleep_for(std::chrono::microseconds(remaining));
-            dT = 1000;
+            dT += remaining;
+        }
+
+        //Decrease framerate when focus is lost.
+        if (!engine->window->getFlag(RWindowFlags::IN_FOCUS)) {
+            dT = 41666.67f - dT;
+            std::this_thread::sleep_for(std::chrono::microseconds((int) dT));
         }
         engine->frameDelta = (dT / 1000000);
     }