[#1418] Fix freeze when actor width or height is 0 and tilemap is sho…

…wn (#1491)

Closes #1418 

TileMapImpl.collides() got stuck infinitely on the `trace points for overlap` loop when the actor's size is zero.

## Changes:

- Check size of actor before deciding whether to run the collision logic
- Return null when actor width or height is 0

Co-authored-by: Vincent Beers <vincent.beers@sogeti.com>

CHANGELOG.md

@@ -36,6 +36,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Fixed
 
+- Fixed Excalibur crashing when displaying both a tilemap and a zero-size actor ([#1418](https://github.com/excaliburjs/Excalibur/issues/1418))
 - Fixed animation flipping behavior ([#1172](https://github.com/excaliburjs/Excalibur/issues/1172))
 - Fixed actors being drawn when their opacity is 0 ([#875](https://github.com/excaliburjs/Excalibur/issues/875))
 - Fixed iframe event handling, excalibur will respond to keyboard events from the top window ([#1294](https://github.com/excaliburjs/Excalibur/issues/1294))

src/engine/TileMap.ts

@@ -86,6 +86,9 @@ export class TileMapImpl extends Class {
     const height = actor.pos.y + actor.height;
     const actorBounds = actor.body.collider.bounds;
     const overlaps: Vector[] = [];
+    if (actor.width <= 0 || actor.height <= 0) {
+      return null;
+    }
     // trace points for overlap
     for (let x = actorBounds.left; x <= width; x += Math.min(actor.width / 2, this.cellWidth / 2)) {
       for (let y = actorBounds.top; y <= height; y += Math.min(actor.height / 2, this.cellHeight / 2)) {
@@ -232,10 +235,10 @@ export class TileMapImpl extends Class {
     const solid = Color.Red;
     solid.a = 0.3;
     this.data
-      .filter(function(cell) {
+      .filter(function (cell) {
         return cell.solid;
       })
-      .forEach(function(cell) {
+      .forEach(function (cell) {
         ctx.fillStyle = solid.toString();
         ctx.fillRect(cell.x, cell.y, cell.width, cell.height);
       });

src/spec/TileMapSpec.ts

@@ -54,7 +54,7 @@ describe('A TileMap', () => {
       });
       const spriteTiles = new ex.SpriteSheet(texture, 1, 1, 64, 48);
       tm.registerSpriteSheet('default', spriteTiles);
-      tm.data.forEach(function(cell: ex.Cell) {
+      tm.data.forEach(function (cell: ex.Cell) {
         cell.solid = true;
         cell.pushSprite(new ex.TileSprite('default', 0));
       });
@@ -80,7 +80,7 @@ describe('A TileMap', () => {
       });
       const spriteTiles = new ex.SpriteSheet(texture, 1, 1, 64, 48);
       tm.registerSpriteSheet('default', spriteTiles);
-      tm.data.forEach(function(cell: ex.Cell) {
+      tm.data.forEach(function (cell: ex.Cell) {
         cell.solid = true;
         cell.pushSprite(new ex.TileSprite('default', 0));
       });
@@ -94,4 +94,38 @@ describe('A TileMap', () => {
       });
     });
   });
+
+  describe('with an actor', () => {
+    let tm: ex.TileMap;
+    beforeEach(() => {
+      tm = new ex.TileMap({
+        x: 0,
+        y: 0,
+        cellWidth: 64,
+        cellHeight: 48,
+        rows: 10,
+        cols: 10
+      });
+      tm.data.forEach(function (cell: ex.Cell) {
+        cell.solid = true;
+      });
+    });
+
+    it('should collide when the actor is on a solid cell', () => {
+      const actor = new ex.Actor(0, 0, 20, 20);
+
+      const collision = tm.collides(actor);
+
+      expect(collision).not.toBeNull();
+      expect(collision).toBeTruthy();
+    });
+
+    it('should not collide when the actor has zero size dimensions', () => {
+      const actor = new ex.Actor(0, 0, 0, 0);
+
+      const collision = tm.collides(actor);
+
+      expect(collision).toBeNull();
+    });
+  });
 });