implement main loop stopping condition

examples/example00.rs

@@ -11,6 +11,9 @@ impl Callbacks for Example {
     fn update(&mut self) {}
     fn draw(&self, graphics: &mut Graphics) {}
     fn clean_up(self) {}
+    fn do_next_step(&self) -> bool {
+        true
+    }
 }
 
 pub fn main() {

src/lib.rs

@@ -23,6 +23,7 @@ pub trait Callbacks {
     fn update(&mut self);
     fn draw(&self, graphics: &mut Graphics);
     fn clean_up(self);
+    fn do_next_step(&self) -> bool;
 }
 
 pub fn run<C: Callbacks>(config: Config) {
@@ -30,7 +31,7 @@ pub fn run<C: Callbacks>(config: Config) {
 
     let mut state = C::load_state();
     state.pre_loop();
-    loop {
+    while state.do_next_step() {
         state.update();
         for ev in graphics.get_events() {
             state.handle_event(ev);
@@ -46,22 +47,28 @@ mod tests {
     use crate::run;
 
     struct TestCallbacks {
+        stepper: u32,
     }
 
     impl Callbacks for TestCallbacks {
         fn load_state() -> Self {
             TestCallbacks{
+                stepper: 0,
             }
         }
         //fn preLoop(&mut self){}
         fn handle_event(&mut self, ev: Event){
         }
         fn update(&mut self){
+            self.stepper = self.stepper + 1;
         }
         fn draw(&self, graphics: &mut Graphics){
         }
         fn clean_up(self){
         }
+        fn do_next_step(&self) -> bool{
+            self.stepper < 999999
+        }
     }
 
     #[test]