From bb82c46f8abb360f895cc88e2283996899b6aa68 Mon Sep 17 00:00:00 2001
From: Katie Broida <kbroida@gmail.com>
Date: Thu, 15 Nov 2018 15:50:56 -0500
Subject: [PATCH] Handle coordinate precision the same as Scratch 2 (#1722)

---
 src/blocks/scratch3_motion.js  | 13 +++++++++++--
 src/sprites/rendered-target.js | 17 ++---------------
 test/unit/blocks_motion.js     | 26 ++++++++++++++++++++++++++
 3 files changed, 39 insertions(+), 17 deletions(-)
 create mode 100644 test/unit/blocks_motion.js

diff --git a/src/blocks/scratch3_motion.js b/src/blocks/scratch3_motion.js
index a33a62905..9571e5ef1 100644
--- a/src/blocks/scratch3_motion.js
+++ b/src/blocks/scratch3_motion.js
@@ -262,16 +262,25 @@ class Scratch3MotionBlocks {
     }
 
     getX (args, util) {
-        return util.target.x;
+        return this.limitPrecision(util.target.x);
     }
 
     getY (args, util) {
-        return util.target.y;
+        return this.limitPrecision(util.target.y);
     }
 
     getDirection (args, util) {
         return util.target.direction;
     }
+
+    // This corresponds to snapToInteger in Scratch 2
+    limitPrecision (coordinate) {
+        const rounded = Math.round(coordinate);
+        const delta = coordinate - rounded;
+        const limitedCoord = (Math.abs(delta) < 1e-9) ? rounded : coordinate;
+
+        return limitedCoord;
+    }
 }
 
 module.exports = Scratch3MotionBlocks;
diff --git a/src/sprites/rendered-target.js b/src/sprites/rendered-target.js
index e4ec58d84..4c14b013e 100644
--- a/src/sprites/rendered-target.js
+++ b/src/sprites/rendered-target.js
@@ -256,17 +256,6 @@ class RenderedTarget extends Target {
         };
     }
 
-    /**
-     * Round a number to n digits
-     * @param {number} value The number to be rounded
-     * @param {number} places The number of decimal places to round to
-     * @return {number} The rounded number
-     */
-    _roundCoord (value, places) {
-        const power = Math.pow(10, places);
-        return Math.round(value * power) / power;
-    }
-
     /**
      * Set the X and Y coordinates.
      * @param {!number} x New X coordinate, in Scratch coordinates.
@@ -280,8 +269,6 @@ class RenderedTarget extends Target {
         const oldY = this.y;
         if (this.renderer) {
             const position = this.renderer.getFencedPositionOfDrawable(this.drawableID, [x, y]);
-            position[0] = this._roundCoord(position[0], 8);
-            position[1] = this._roundCoord(position[1], 8);
             this.x = position[0];
             this.y = position[1];
 
@@ -293,8 +280,8 @@ class RenderedTarget extends Target {
                 this.runtime.requestRedraw();
             }
         } else {
-            this.x = this._roundCoord(x, 8);
-            this.y = this._roundCoord(y, 8);
+            this.x = x;
+            this.y = y;
         }
         this.emit(RenderedTarget.EVENT_TARGET_MOVED, this, oldX, oldY, force);
         this.runtime.requestTargetsUpdate(this);
diff --git a/test/unit/blocks_motion.js b/test/unit/blocks_motion.js
new file mode 100644
index 000000000..09bcd22bb
--- /dev/null
+++ b/test/unit/blocks_motion.js
@@ -0,0 +1,26 @@
+const test = require('tap').test;
+const Motion = require('../../src/blocks/scratch3_motion');
+const Runtime = require('../../src/engine/runtime');
+const Sprite = require('../../src/sprites/sprite.js');
+const RenderedTarget = require('../../src/sprites/rendered-target.js');
+
+test('getPrimitives', t => {
+    const rt = new Runtime();
+    const motion = new Motion(rt);
+    t.type(motion.getPrimitives(), 'object');
+    t.end();
+});
+
+test('Coordinates have limited precision', t => {
+    const rt = new Runtime();
+    const motion = new Motion(rt);
+    const sprite = new Sprite(null, rt);
+    const target = new RenderedTarget(sprite, rt);
+    const util = {target};
+
+    motion.goToXY({X: 0.999999999, Y: 0.999999999}, util);
+
+    t.equals(motion.getX({}, util), 1);
+    t.equals(motion.getY({}, util), 1);
+    t.end();
+});