Revert "Switch from Chromeless to Playwright for tests"

Switch from Chromeless to Playwright for tests

package.json

@@ -53,7 +53,7 @@
     "minilog": "3.1.0",
     "raw-loader": "^0.5.1",
     "scratch-storage": "^1.0.0",
-    "scratch-svg-renderer": "0.2.0-prerelease.20200205003400",
+    "scratch-svg-renderer": "0.2.0-prerelease.20200507183648",
     "twgl.js": "4.4.0"
   }
 }

src/BitmapSkin.js

@@ -56,16 +56,6 @@ class BitmapSkin extends Skin {
         return this._texture || super.getTexture();
     }
 
-    /**
-     * Get the bounds of the drawable for determining its fenced position.
-     * @param {Array<number>} drawable - The Drawable instance this skin is using.
-     * @param {?Rectangle} result - Optional destination for bounds calculation.
-     * @return {!Rectangle} The drawable's bounds. For compatibility with Scratch 2, we always use getAABB for bitmaps.
-     */
-    getFenceBounds (drawable, result) {
-        return drawable.getAABB(result);
-    }
-
     /**
      * Set the contents of this skin to a snapshot of the provided bitmap data.
      * @param {ImageData|HTMLImageElement|HTMLCanvasElement|HTMLVideoElement} bitmapData - new contents for this skin.

src/RenderWebGL.js

@@ -1765,9 +1765,7 @@ class RenderWebGL extends EventEmitter {
 
     /**
      * Get the convex hull points for a particular Drawable.
-     * To do this, draw the Drawable unrotated, unscaled, and untranslated.
-     * Read back the pixels and find all boundary points.
-     * Finally, apply a convex hull algorithm to simplify the set.
+     * To do this, calculate it based on the drawable's Silhouette.
      * @param {int} drawableID The Drawable IDs calculate convex hull for.
      * @return {Array<Array<number>>} points Convex hull points, as [[x, y], ...]
      */
@@ -1784,110 +1782,120 @@ class RenderWebGL extends EventEmitter {
         }
 
         /**
-         * Return the determinant of two vectors, the vector from A to B and
-         * the vector from A to C.
+         * Return the determinant of two vectors, the vector from A to B and the vector from A to C.
          *
-         * The determinant is useful in this case to know if AC is counter
-         * clockwise from AB. A positive value means the AC is counter
-         * clockwise from AC. A negative value menas AC is clockwise from AB.
+         * The determinant is useful in this case to know if AC is counter-clockwise from AB.
+         * A positive value means that AC is counter-clockwise from AB. A negative value means AC is clockwise from AB.
          *
          * @param {Float32Array} A A 2d vector in space.
          * @param {Float32Array} B A 2d vector in space.
          * @param {Float32Array} C A 2d vector in space.
-         * @return {number} Greater than 0 if counter clockwise, less than if
-         * clockwise, 0 if all points are on a line.
+         * @return {number} Greater than 0 if counter clockwise, less than if clockwise, 0 if all points are on a line.
          */
-        const CCW = function (A, B, C) {
+        const determinant = function (A, B, C) {
             // AB = B - A
             // AC = C - A
             // det (AB BC) = AB0 * AC1 - AB1 * AC0
             return (((B[0] - A[0]) * (C[1] - A[1])) - ((B[1] - A[1]) * (C[0] - A[0])));
         };
 
-        // https://github.com/LLK/scratch-flash/blob/dcbeeb59d44c3be911545dfe54d
-        // 46a32404f8e69/src/scratch/ScratchCostume.as#L369-L413 Following
-        // RasterHull creation, compare and store left and right values that
-        // maintain a convex shape until that data can be passed to `hull` for
-        // further work.
-        const L = [];
-        const R = [];
+        // This algorithm for calculating the convex hull somewhat resembles the monotone chain algorithm.
+        // The main difference is that instead of sorting the points by x-coordinate, and y-coordinate in case of ties,
+        // it goes through them by y-coordinate in the outer loop and x-coordinate in the inner loop.
+        // This gives us "left" and "right" hulls, whereas the monotone chain algorithm gives "top" and "bottom" hulls.
+        // Adapted from https://github.com/LLK/scratch-flash/blob/dcbeeb59d44c3be911545dfe54d46a32404f8e69/src/scratch/ScratchCostume.as#L369-L413
+
+        const leftHull = [];
+        const rightHull = [];
+
+        // While convex hull algorithms usually push and pop values from the list of hull points,
+        // here, we keep indices for the "last" point in each array. Any points past these indices are ignored.
+        // This is functionally equivalent to pushing and popping from a "stack" of hull points.
+        let leftEndPointIndex = -1;
+        let rightEndPointIndex = -1;
+
         const _pixelPos = twgl.v3.create();
         const _effectPos = twgl.v3.create();
-        let ll = -1;
-        let rr = -1;
-        let Q;
+
+        let currentPoint;
+
+        // *Not* Scratch Space-- +y is bottom
+        // Loop over all rows of pixels, starting at the top
         for (let y = 0; y < height; y++) {
             _pixelPos[1] = y / height;
-            // Scan from left to right, looking for a touchable spot in the
-            // skin.
+
+            // We start at the leftmost point, then go rightwards until we hit an opaque pixel
             let x = 0;
             for (; x < width; x++) {
                 _pixelPos[0] = x / width;
                 EffectTransform.transformPoint(drawable, _pixelPos, _effectPos);
                 if (drawable.skin.isTouchingLinear(_effectPos)) {
-                    Q = [x, y];
+                    currentPoint = [x, y];
                     break;
                 }
             }
-            // If x is equal to the width there are no touchable points in the
-            // skin. Nothing we can add to L. And looping for R would find the
-            // same thing.
+
+            // If we managed to loop all the way through, there are no opaque pixels on this row. Go to the next one
             if (x >= width) {
                 continue;
             }
-            // Decrement ll until Q is clockwise (CCW returns negative) from the
-            // last two points in L.
-            while (ll > 0) {
-                if (CCW(L[ll - 1], L[ll], Q) < 0) {
+
+            // Because leftEndPointIndex is initialized to -1, this is skipped for the first two rows.
+            // It runs only when there are enough points in the left hull to make at least one line.
+            // If appending the current point to the left hull makes a counter-clockwise turn,
+            // we want to append the current point. Otherwise, we decrement the index of the "last" hull point until the
+            // current point makes a counter-clockwise turn.
+            // This decrementing has the same effect as popping from the point list, but is hopefully faster.
+            while (leftEndPointIndex > 0) {
+                if (determinant(leftHull[leftEndPointIndex], leftHull[leftEndPointIndex - 1], currentPoint) > 0) {
                     break;
                 } else {
-                    --ll;
+                    // leftHull.pop();
+                    --leftEndPointIndex;
                 }
             }
-            // Increment ll and then set L[ll] to Q. If ll was -1 before this
-            // line, this will set L[0] to Q. If ll was 0 before this line, this
-            // will set L[1] to Q.
-            L[++ll] = Q;
 
-            // Scan from right to left, looking for a touchable spot in the
-            // skin.
+            // This has the same effect as pushing to the point list.
+            // This "list head pointer" coding style leaves excess points dangling at the end of the list,
+            // but that doesn't matter; we simply won't copy them over to the final hull.
+
+            // leftHull.push(currentPoint);
+            leftHull[++leftEndPointIndex] = currentPoint;
+
+            // Now we repeat the process for the right side, looking leftwards for a pixel.
             for (x = width - 1; x >= 0; x--) {
                 _pixelPos[0] = x / width;
                 EffectTransform.transformPoint(drawable, _pixelPos, _effectPos);
                 if (drawable.skin.isTouchingLinear(_effectPos)) {
-                    Q = [x, y];
+                    currentPoint = [x, y];
                     break;
                 }
             }
-            // Decrement rr until Q is counter clockwise (CCW returns positive)
-            // from the last two points in L. L takes clockwise points and R
-            // takes counter clockwise points. if y was decremented instead of
-            // incremented R would take clockwise points. We are going in the
-            // right direction for L and the wrong direction for R, so we
-            // compare the opposite value for R from L.
-            while (rr > 0) {
-                if (CCW(R[rr - 1], R[rr], Q) > 0) {
-                    break;
-                } else {
-                    --rr;
-                }
-            }
-            // Increment rr and then set R[rr] to Q.
-            R[++rr] = Q;
-        }
 
-        // Known boundary points on left/right edges of pixels.
-        const boundaryPoints = L;
-        // Truncate boundaryPoints to the index of the last added Q to L. L may
-        // have more entries than the index for the last Q.
-        boundaryPoints.length = ll + 1;
-        // Add points in R to boundaryPoints in reverse so all points in
-        // boundaryPoints are clockwise from each other.
-        for (let j = rr; j >= 0; --j) {
-            boundaryPoints.push(R[j]);
+            // Because we're coming at this from the right, it goes clockwise this time.
+            while (rightEndPointIndex > 0) {
+                if (determinant(rightHull[rightEndPointIndex], rightHull[rightEndPointIndex - 1], currentPoint) < 0) {
+                    break;
+                } else {
+                    --rightEndPointIndex;
                 }
-        // Simplify boundary points using convex hull.
-        return hull(boundaryPoints, Infinity);
+            }
+
+            rightHull[++rightEndPointIndex] = currentPoint;
+        }
+
+        // Start off "hullPoints" with the left hull points.
+        const hullPoints = leftHull;
+        // This is where we get rid of those dangling extra points.
+        hullPoints.length = leftEndPointIndex + 1;
+        // Add points from the right side in reverse order so all points are ordered clockwise.
+        for (let j = rightEndPointIndex; j >= 0; --j) {
+            hullPoints.push(rightHull[j]);
+        }
+
+        // Simplify boundary points using hull.js.
+        // TODO: Remove this; this algorithm already generates convex hulls.
+        return hull(hullPoints, Infinity);
     }
 
     /**

src/Skin.js

@@ -143,10 +143,10 @@ class Skin extends EventEmitter {
      * Get the bounds of the drawable for determining its fenced position.
      * @param {Array<number>} drawable - The Drawable instance this skin is using.
      * @param {?Rectangle} result - Optional destination for bounds calculation.
-     * @return {!Rectangle} The drawable's bounds.
+     * @return {!Rectangle} The drawable's bounds. For compatibility with Scratch 2, we always use getAABB.
      */
     getFenceBounds (drawable, result) {
-        return drawable.getFastBounds(result);
+        return drawable.getAABB(result);
     }
 
     /**

src/shaders/sprite.frag

@@ -220,14 +220,28 @@ void main()
 	// Adapted from Inigo Quilez' 2D distance function cheat sheet
 	// https://www.iquilezles.org/www/articles/distfunctions2d/distfunctions2d.htm
 
+	// On (some?) devices with 16-bit float precision, sufficiently long lines will overflow the float's range.
+	// Avoid this by scaling these problematic values down to fit within (-1, 1) then scaling them back up later.
+	// TODO: Is this a problem on all drivers with 16-bit mediump floats, or just Mali?
+	vec2 pointDiff = abs(u_penPoints.zw - u_penPoints.xy);
+	float FLOAT_SCALING_INVERSE = max(1.0, max(pointDiff.x, pointDiff.y));
+	float FLOAT_SCALING = 1.0 / FLOAT_SCALING_INVERSE;
+
 	// The xy component of u_penPoints is the first point; the zw is the second point.
 	// This is done to minimize the number of gl.uniform calls, which can add up.
-	vec2 pa = v_texCoord - u_penPoints.xy, ba = u_penPoints.zw - u_penPoints.xy;
+	// vec2 pa = v_texCoord - u_penPoints.xy, ba = u_penPoints.zw - u_penPoints.xy;
+	vec2 pa = (v_texCoord - u_penPoints.xy) * FLOAT_SCALING, ba = (u_penPoints.zw - u_penPoints.xy) * FLOAT_SCALING;
+
+	// Avoid division by zero
+	float baDot = dot(ba, ba);
+	// the dot product of a vector and itself is always positive
+	baDot = max(baDot, epsilon);
+
 	// Magnitude of vector projection of this fragment onto the line (both relative to the line's start point).
 	// This results in a "linear gradient" which goes from 0.0 at the start point to 1.0 at the end point.
-	float projMagnitude = clamp(dot(pa, ba) / dot(ba, ba), 0.0, 1.0);
+	float projMagnitude = clamp(dot(pa, ba) / baDot, 0.0, 1.0);
 
-	float lineDistance = length(pa - (ba * projMagnitude));
+	float lineDistance = length(pa - (ba * projMagnitude)) * FLOAT_SCALING_INVERSE;
 
 	// The distance to the line allows us to create lines of any thickness.
 	// Instead of checking whether this fragment's distance < the line thickness,

src/shaders/sprite.vert

@@ -40,7 +40,13 @@ void main() {
 	position -= expandedRadius;
 
 	// Rotate quad to line angle
-	vec2 normalized = (u_penPoints.zw - u_penPoints.xy + epsilon) / (lineLength + epsilon);
+	vec2 pointDiff = u_penPoints.zw - u_penPoints.xy;
+	// Ensure line has a nonzero length so it's rendered properly
+	// As long as either component is nonzero, the line length will be nonzero
+	pointDiff.x = abs(pointDiff.x) < epsilon ? epsilon : pointDiff.x;
+	// The `normalized` vector holds rotational values equivalent to sine/cosine
+	// We're applying the standard rotation matrix formula to the position to rotate the quad to the line angle
+	vec2 normalized = pointDiff / max(lineLength, epsilon);
 	position = mat2(normalized.x, normalized.y, -normalized.y, normalized.x) * position;
 	// Translate quad
 	position += u_penPoints.xy;