Optimize a transform code path.

CHANGELOG.md

@@ -8,6 +8,7 @@
 ### Improvements
 - Points with small radii or thin strokes are rendered better (#1021)
 - When only updating point styles, don't recompute geometry transforms (#1022)
+- Optimized a transform code path for pixel coordinates (#1023)
 
 ### Changes
 - Switched the default tile server to Stamen Design's toner-lite. (#1020)

src/transform.js

@@ -338,13 +338,24 @@ transform.lookup = function (projection) {
 transform.transformCoordinates = function (srcPrj, tgtPrj, coordinates, numberOfComponents) {
   'use strict';
 
-  if (srcPrj === tgtPrj) {
+  if (srcPrj === tgtPrj || (Array.isArray(coordinates) && !coordinates.length)) {
     return coordinates;
   }
 
   if (Array.isArray(coordinates) && coordinates.length >= 3 && numberOfComponents === 3 && !util.isObject(coordinates[0])) {
     return transform.transformCoordinatesFlatArray3(srcPrj, tgtPrj, coordinates);
   }
+  if (Array.isArray(coordinates) && coordinates.length && util.isObject(coordinates[0]) && 'x' in coordinates[0] && 'y' in coordinates[0]) {
+    var smatch = srcPrj.match(axisPattern),
+        tmatch = tgtPrj.match(axisPattern);
+    // if the two projections only differ in the middle axis
+    if (smatch && tmatch && smatch[1] === tmatch[1] && smatch[3] === tmatch[3]) {
+      if ('z' in coordinates[0]) {
+        return coordinates.map(p => ({x: +p.x, y: -p.y, z: +p.z || 0}));
+      }
+      return coordinates.map(p => ({x: +p.x, y: -p.y}));
+    }
+  }
   var trans = transform({source: srcPrj, target: tgtPrj}), output;
   if (util.isObject(coordinates) && 'x' in coordinates && 'y' in coordinates) {
     output = trans.forward({x: +coordinates.x, y: +coordinates.y, z: +coordinates.z || 0});

tests/cases/lineFeature.js

@@ -267,9 +267,9 @@ describe('geo.lineFeature', function () {
         line.rdpSimplifyData(testLines, 2, undefined, lineFunc);
         counts = countLines(line.data().map(line.style.get('line')));
         expect(counts).toEqual({lines: 8, vertices: 17});
-        line.rdpSimplifyData(testLines, 5, undefined, lineFunc);
+        line.rdpSimplifyData(testLines, 5.01, undefined, lineFunc);
         counts = countLines(line.data().map(line.style.get('line')));
-        expect(counts).toEqual({lines: 8, vertices: 11});
+        expect(counts).toEqual({lines: 8, vertices: 9});
         line.rdpSimplifyData(testLines, 20, undefined, lineFunc);
         counts = countLines(line.data().map(line.style.get('line')));
         expect(counts).toEqual({lines: 8, vertices: 0});