Cleanups, comments [ci skip]

package.json

@@ -17,7 +17,6 @@
     "@mapbox/mapbox-gl-supported": "^1.3.0",
     "@mapbox/point-geometry": "^0.1.0",
     "@mapbox/shelf-pack": "^3.1.0",
-    "@mapbox/tilebelt": "^1.0.1",
     "@mapbox/tiny-sdf": "^1.1.0",
     "@mapbox/unitbezier": "^0.0.0",
     "@mapbox/vector-tile": "^1.3.1",

src/data/bucket/line_bucket.js

@@ -459,7 +459,7 @@ class LineBucket implements Bucket {
         const indexArray = this.indexArray;
 
         if (distancesForScaling) {
-            // Scale line from tile units to [0, 2^15)
+            // For gradient lines, scale distance from tile units to [0, 2^15)
             distance = scaleDistance(distance, distancesForScaling);
         }
 
@@ -500,7 +500,7 @@ class LineBucket implements Bucket {
      * This adds a pie slice triangle near a join to simulate round joins
      *
      * @param currentVertex the line vertex to add buffer vertices for
-     * @param distance the distance from the beggining of the line to the vertex
+     * @param distance the distance from the beginning of the line to the vertex
      * @param extrude the offset of the new vertex from the currentVertex
      * @param lineTurnsLeft whether the line is turning left or right at this angle
      * @private
@@ -532,10 +532,33 @@ class LineBucket implements Bucket {
     }
 }
 
+/**
+ * Knowing the ratio of the full linestring covered by this tiled feature, as well
+ * as the total distance (in tile units) of this tiled feature, and the distance
+ * (in tile units) of the current vertex, we can determine the relative distance
+ * of this vertex along the full linestring feature and scale it to [0, 2^15)
+ *
+ * @param {number} tileDistance the distance from the beginning of the tiled line to this vertex
+ * @param {Object} stats
+ * @param {number} stats.start the ratio (0-1) along a full original linestring feature of the start of this tiled line feature
+ * @param {number} stats.end the ratio (0-1) along a full original linestring feature of the end of this tiled line feature
+ * @param {number} stats.tileTotal the total distance, in tile units, of this tiled line feature
+ *
+ * @private
+ */
 function scaleDistance(tileDistance: number, stats: Object) {
     return ((tileDistance / stats.tileTotal) * (stats.end - stats.start) + stats.start) * (MAX_LINE_DISTANCE - 1);
 }
 
+/**
+ * Calculate the total distance, in tile units, of this tiled line feature
+ *
+ * @param {Array<Point>} vertices the full geometry of this tiled line feature
+ * @param {number} first the index in the vertices array representing the first vertex we should consider
+ * @param {number} len the count of vertices we should consider from `first`
+ *
+ * @private
+ */
 function calculateFullDistance(vertices: Array<Point>, first: number, len: number) {
     let currentVertex, nextVertex;
     let total = 0;

src/style/properties.js

@@ -620,7 +620,7 @@ class CrossFadedProperty<T> implements Property<T, ?CrossFaded<T>> {
 
 /**
  * An implementation of `Property` for `heatmap-color` and `line-gradient`. Interpolation is a no-op, and
- * evaluation returns a value in order to indicate its presence, but the real
+ * evaluation returns a boolean value in order to indicate its presence, but the real
  * evaluation happens in StyleLayer classes.
  *
  * @private
@@ -633,7 +633,7 @@ class ColorRampProperty implements Property<Color, boolean> {
     }
 
     possiblyEvaluate(value: PropertyValue<Color, boolean>, parameters: EvaluationParameters): boolean {
-        return !!value.expression.evaluate(parameters);  // ?
+        return !!value.expression.evaluate(parameters);
     }
 
     interpolate(): boolean { return false; }

test/unit/style-spec/fixture/layers.input.json

@@ -12,6 +12,11 @@
     "geojson": {
       "type": "geojson",
       "data": {}
+    },
+    "lineMetrics": {
+      "type": "geojson",
+      "data": {},
+      "lineMetrics": true
     }
   },
   "layers": [
@@ -119,7 +124,7 @@
       }
     },
     {
-      "id": "line-gradient-good",
+      "id": "line-gradient-missing-lineMetrics",
       "type": "line",
       "source": "geojson",
       "source-layer": "source-layer",
@@ -131,6 +136,20 @@
           0, "#000000"
         ]
       }
+    },
+    {
+      "id": "line-gradient-good",
+      "type": "line",
+      "source": "lineMetrics",
+      "source-layer": "source-layer",
+      "paint": {
+        "line-gradient": [
+          "interpolate",
+          ["linear"],
+          ["line-progress"],
+          0, "#000000"
+        ]
+      }
     }
   ]
 }

test/unit/style-spec/fixture/layers.output.json

@@ -1,74 +1,74 @@
 [
   {
     "message": "layers[0]: either \"type\" or \"ref\" is required",
-    "line": 18
+    "line": 23
   },
   {
     "message": "layers[1]: missing required property \"id\"",
-    "line": 23
+    "line": 28
   },
   {
     "message": "layers[3]: \"type\" is prohibited for ref layers",
-    "line": 37
+    "line": 42
   },
   {
     "message": "layers[3]: \"source\" is prohibited for ref layers",
-    "line": 38
+    "line": 43
   },
   {
     "message": "layers[3]: \"source-layer\" is prohibited for ref layers",
-    "line": 39
+    "line": 44
   },
   {
     "message": "layers[3]: \"filter\" is prohibited for ref layers",
-    "line": 40
+    "line": 45
   },
   {
     "message": "layers[3]: \"layout\" is prohibited for ref layers",
-    "line": 41
+    "line": 46
   },
   {
     "message": "layers[4]: ref layer \"not-found\" not found",
-    "line": 45
+    "line": 50
   },
   {
     "message": "layers[5]: ref cannot reference another ref layer",
-    "line": 49
+    "line": 54
   },
   {
     "message": "layers[6]: missing required property \"source\"",
-    "line": 51
+    "line": 56
   },
   {
     "message": "layers[7]: source \"not-found\" not found",
-    "line": 58
+    "line": 63
   },
   {
     "message": "layers[8]: layer \"vector-raster-mismatch\" requires a vector source",
-    "line": 63
+    "line": 68
   },
   {
     "message": "layers[9]: layer \"raster-vector-mismatch\" requires a raster source",
-    "line": 68
+    "line": 73
   },
   {
-    "message": "layers[11]: duplicate layer id \"duplicate\", previously used at line 72",
-    "line": 78
+    "message": "layers[11]: duplicate layer id \"duplicate\", previously used at line 77",
+    "line": 83
   },
   {
     "message": "layers[12].type: expected one of [fill, line, symbol, circle, heatmap, fill-extrusion, raster, hillshade, background], \"invalid\" found",
-    "line": 85
+    "line": 90
   },
   {
     "message": "layers[13]: layer \"missing-source-layer\" must specify a \"source-layer\"",
-    "line": 95
+    "line": 100
   },
   {
     "message": "layers[15]: layer \"line-gradient-bad\" specifies a line-gradient, which requires a GeoJSON source with `lineMetrics` enabled.",
-    "line": 107
+    "line": 112
   },
   {
-    "message": "layers[16]: layer \"line-gradient-good\" specifies a line-gradient, which requires a GeoJSON source with `lineMetrics` enabled.",
-    "line": 121
+    "message": "layers[16]: layer \"line-gradient-missing-lineMetrics\" specifies a line-gradient, which requires a GeoJSON source with `lineMetrics` enabled.",
+    "line": 126
   }
 ]