Add a countdown so it's easier to record the screen

simucene/glut_grapher.cpp

 #include "glut_grapher.h"
 #include <iostream>
 #include <iomanip>
+#include <thread>
 
 namespace simucene {
 
@@ -77,6 +78,17 @@ void GlutGrapher::display() const {
 
 //..................................................................................................
 void GlutGrapher::idle() {
+    bool const wait_to_start = true;
+    if (wait_to_start && frame_ == 0) {
+        std::cout << "Press enter to start a 5 second countdown" << std::endl;
+        do {} while (std::cin.get() != '\n');
+        for (uint32_t i = 5; i > 0; --i) {
+            std::cout << i << "... " << std::flush;
+            std::this_thread::sleep_for(std::chrono::seconds(1));
+        }
+        std::cout << 0 << "... " << std::endl;
+    }
+
     //std::cout << frame_ << ": ";
     //print_vector(state_);
     for (uint32_t i = 0; i < 100; ++i) {