Player: track position with a Vector2.

Fixes #10 (mostly).

Shared/Camera.cs

@@ -21,8 +21,8 @@ namespace SemiColinGames {
       get => Matrix.CreateOrthographicOffCenter(Left, Left + Width, Height, 0, -1, 1);
     }
 
-    public void Update(float modelTime, Point player, int worldWidth) {
-      int diff = player.X - bbox.Center.X;
+    public void Update(float modelTime, Vector2 player, int worldWidth) {
+      float diff = player.X - bbox.Center.X;
       if (Math.Abs(diff) > 16) {
         bbox.Offset((int) (diff * 0.1), 0);
       }

Shared/Player.cs

@@ -22,18 +22,20 @@ namespace SemiColinGames {
 
     // Position is tracked at the Player's center. The Player's bounding box is a rectangle
     // centered at that point and extending out by halfSize.X and halfSize.Y.
-    private Point position;
+    private Vector2 position;
     private Vector2 halfSize = new Vector2(11, 24);
+    // Fractional-pixel movement that was left over from a previous frame's movement.
+    // Useful so that we can run at a slow time-step and still get non-zero motion.
+    private Vector2 residual = Vector2.Zero;
 
     private int jumps = 0;
     private Pose pose = Pose.Jumping;
     private double swordSwingTime = 0;
     private int swordSwingNum = 0;
-    private const int swordSwingMax = 6;
     private float ySpeed = 0;
     private float invincibilityTime = 0;
 
-    public Player(Point position, int facing) {
+    public Player(Vector2 position, int facing) {
       this.position = position;
       Facing = facing;
       Health = MaxHealth;
@@ -45,20 +47,22 @@ namespace SemiColinGames {
 
     public int Facing { get; private set; }
 
-    public Point Position { get { return position; } }
+    public Vector2 Position { get { return position; } }
 
     public void Update(float modelTime, World world, History<Input> input) {
-      AABB BoxOffset(Point position, int yOffset) {
+      AABB BoxOffset(Vector2 position, int yOffset) {
         return new AABB(new Vector2(position.X, position.Y + yOffset), halfSize);
       }
 
-      AABB Box(Point position) {
+      AABB Box(Vector2 position) {
         return BoxOffset(position, 0);
       }
 
       invincibilityTime -= modelTime;
 
-      Vector2 movement = HandleInput(modelTime, input);
+      Vector2 inputMovement = HandleInput(modelTime, input);
+      Vector2 movement = Vector2.Add(residual, inputMovement);
+      residual = new Vector2(movement.X - (int) movement.X, movement.Y - (int) movement.Y);
 
       // Broad test: remove all collision targets nowhere near the player.
       // TODO: don't allocate a list here.
@@ -69,8 +73,8 @@ namespace SemiColinGames {
       // sure (the only downside is a small number of false-positive AABBs, which should be
       // discarded by later tests anyhow.)
       AABB largeBox = new AABB(
-        new Vector2(position.X + movement.X / 2, position.Y + movement.Y / 2),
-        new Vector2(halfSize.X + Math.Abs(movement.X) + 1, halfSize.Y + Math.Abs(movement.Y) + 1));
+        Vector2.Add(position, Vector2.Divide(movement, 2)),
+        Vector2.Add(halfSize, new Vector2(Math.Abs(movement.X) + 1, Math.Abs(movement.Y) + 1)));
       foreach (var box in world.CollisionTargets) {
         if (box.Intersect(largeBox) != null) {
           // Debug.AddRect(box, Color.Green);
@@ -84,7 +88,7 @@ namespace SemiColinGames {
         int dx = movePoints[i].X - movePoints[i - 1].X;
         int dy = movePoints[i].Y - movePoints[i - 1].Y;
         if (dy != 0) {
-          Point newPosition = new Point(position.X, position.Y + dy);
+          Vector2 newPosition = new Vector2(position.X, position.Y + dy);
           AABB player = Box(newPosition);
           bool reject = false;
           foreach (var box in candidates) {
@@ -102,7 +106,7 @@ namespace SemiColinGames {
           }
         }
         if (dx != 0) {
-          Point newPosition = new Point(position.X + dx, position.Y);
+          Vector2 newPosition = new Vector2(position.X + dx, position.Y);
           AABB player = Box(newPosition);
           bool reject = false;
           foreach (var box in candidates) {
@@ -149,16 +153,16 @@ namespace SemiColinGames {
         invincibilityTime = 0.6f;
       }
 
-      if (movement.X > 0) {
+      if (inputMovement.X > 0) {
         Facing = 1;
-      } else if (movement.X < 0) {
+      } else if (inputMovement.X < 0) {
         Facing = -1;
       }
       if (swordSwingTime > 0) {
         pose = Pose.SwordSwing;
       } else if (jumps == 0) {
         pose = Pose.Jumping;
-      } else if (movement.X != 0) {
+      } else if (inputMovement.X != 0) {
         pose = Pose.Walking;
       } else if (input[0].Motion.Y > 0) {
         pose = Pose.Stretching;
@@ -172,7 +176,7 @@ namespace SemiColinGames {
     // Returns the desired (dx, dy) for the player to move this frame.
     Vector2 HandleInput(float modelTime, History<Input> input) {
       Vector2 result = new Vector2() {
-        X = (int) (input[0].Motion.X * moveSpeed * modelTime)
+        X = input[0].Motion.X * moveSpeed * modelTime
       };
 
       if (input[0].Jump && !input[1].Jump && jumps > 0) {
@@ -182,7 +186,7 @@ namespace SemiColinGames {
 
       if (input[0].Attack && !input[1].Attack && swordSwingTime <= 0) {
         swordSwingTime = 0.3;
-        swordSwingNum = (swordSwingNum + 1) % swordSwingMax;
+        swordSwingNum++;
         SoundEffects.SwordSwings[swordSwingNum % SoundEffects.SwordSwings.Length].Play();
       }
 
@@ -219,7 +223,7 @@ namespace SemiColinGames {
       if (invincibilityTime > 0 && invincibilityTime % 0.2f > 0.1f) {
         color = new Color(0.5f, 0.5f, 0.5f, 0.5f);
       }
-      spriteBatch.Draw(Textures.Ninja.Get, position.ToVector2(), textureSource, color, 0f,
+      spriteBatch.Draw(Textures.Ninja.Get, Vector2.Floor(position), textureSource, color, 0f,
         spriteCenter, Vector2.One, effect, 0f);
     }
   }

Shared/World.cs

@@ -141,7 +141,7 @@ namespace SemiColinGames {
         int y = entity.SelectToken("y").Value<int>();
         int facing = entity.SelectToken("flippedX").Value<bool>() ? -1 : 1;
         if (name == "player") {
-          player = new Player(new Point(x, y), facing);
+          player = new Player(new Vector2(x, y), facing);
         } else if (name == "executioner") {
           npcs.Add(new NPC(new Vector2(x, y), facing));
         }