Merge branch '6-stop-simulation-if-all-cells-are-empty' into 'master'

Resolve "Stop Simulation if all cells are empty"

Closes #6

See merge request webdevexp/rules-of-living!1

lib/src/App.dart

@@ -56,7 +56,7 @@ class App {
 
   void update() {
 //    print("updating");
-    grid.update();
+    if(!grid.update()) running = false;
   }
 
   void render([num interp]) {

lib/src/Cell.dart

@@ -11,11 +11,15 @@ class Cell {
 
   Cell([bool state = false]) : this.state = state;
 
-  void advanceState() {
+  // Sets the actual state to what it should be next update
+  // Returns the newly assumed actual state of the cell.
+  bool advanceState() {
     this.state = this.nextState;
     this.nextState = false;
 
     this.dirty = true;
+
+    return this.state;
   }
 
   void update(int neighbors) {

lib/src/Grid.dart

@@ -143,7 +143,8 @@ class Grid {
     return grid;
   }
 
-  void update() {
+  bool update() {
+    bool stateChanges = false;
     for (int y = 0; y < h; y++) {
       for (int x = 0; x < w; x++) {
         // DEFAULTS TO CONWAY GAME OF LIFE RANGE OF ONE
@@ -152,11 +153,14 @@ class Grid {
     }
     for (int y = 0; y < h; y++) {
       for (int x = 0; x < w; x++) {
-        // DEFAULTS TO CONWAY GAME OF LIFE RANGE OF ONE
+        Cell c = map[y][x];
-        map[y][x].advanceState();
+        if(c.state != c.nextState) stateChanges = true;
+        c.advanceState();
+
         if (!_dirty && map[y][x].dirty) _dirty = true;
       }
     }
+    return stateChanges;
   }
 
   int getSurroundingNeighbors(int x, int y, int range) {