feat(fabric.util) add transformPath and joinPath to support text on a path

CHANGELOG.md

@@ -1,7 +1,9 @@
 # Changelog
 
-## [next]
+## [4.6.0]
 
+- feat(fabric.util): added fabric.util.transformPath to add transformations to path points [#7300](https://github.com/fabricjs/fabric.js/pull/7300)
+- feat(fabric.util): added fabric.util.joinPath, the opposite of fabric.util.parsePath [#7300](https://github.com/fabricjs/fabric.js/pull/7300)
 - fix(fabric.util): use integers iterators [#7233](https://github.com/fabricjs/fabric.js/pull/7233)
 - feat(fabric.Text) add path rendering to text on path [#7328](https://github.com/fabricjs/fabric.js/pull/7328)
 - feat(fabric.iText): Add optional hiddenTextareaContainer to contain hiddenTextarea [#7314](https://github.com/fabricjs/fabric.js/pull/7314)

src/brushes/pencil_brush.class.js

@@ -192,7 +192,7 @@
      * @returns {boolean}
      */
     _isEmptySVGPath: function (pathData) {
-      var pathString = pathData.map(function (segment) { return segment.join(' '); }).join(' ');
+      var pathString = fabric.util.joinPath(pathData);
       return pathString === 'M 0 0 Q 0 0 0 0 L 0 0';
     },
 

src/shapes/path.class.js

@@ -56,12 +56,9 @@
 
       var fromArray = _toString.call(path) === '[object Array]';
 
-      this.path = fromArray
-        ? fabric.util.makePathSimpler(path)
-
-        : fabric.util.makePathSimpler(
-          fabric.util.parsePath(path)
-        );
+      this.path = fabric.util.makePathSimpler(
+        fromArray ? path : fabric.util.parsePath(path)
+      );
 
       if (!this.path) {
         return;
@@ -193,9 +190,7 @@
      * of the instance
      */
     _toSVG: function() {
-      var path = this.path.map(function(path) {
-        return path.join(' ');
-      }).join(' ');
+      var path = fabric.util.joinPath(this.path);
       return [
         '<path ', 'COMMON_PARTS',
         'd="', path,

src/util/path.js

@@ -780,6 +780,36 @@
     path.push(['L', p1.x + multSignX * correction, p1.y + multSignY * correction]);
     return path;
   }
+  /**
+   * Transform a path by transforming each segment.
+   * it has to be a simplified path or it won't work.
+   * WARNING: this depends from pathOffset for correct operation
+   * @param {Array} path fabricJS parsed and simplified path commands
+   * @param {Array} transform matrix that represent the transformation
+   * @param {Object} [pathOffset] the fabric.Path pathOffset
+   * @param {Number} pathOffset.x
+   * @param {Number} pathOffset.y
+   * @returns {Array} the transformed path
+   */
+  function transformPath(path, transform, pathOffset) {
+    if (pathOffset) {
+      transform = fabric.util.multiplyTransformMatrices(
+        transform,
+        [1, 0, 0, 1, -pathOffset.x, -pathOffset.y]
+      );
+    }
+    return path.map(function(pathSegment) {
+      var newSegment = pathSegment.slice(0), point = {};
+      for (var i = 1; i < pathSegment.length - 1; i += 2) {
+        point.x = pathSegment[i];
+        point.y = pathSegment[i + 1];
+        point = fabric.util.transformPoint(point, transform);
+        newSegment[i] = point.x;
+        newSegment[i + 1] = point.y;
+      }
+      return newSegment;
+    });
+  }
 
   /**
    * Calculate bounding box of a elliptic-arc
@@ -825,19 +855,27 @@
     });
   };
 
+  /**
+   * Join path commands to go back to svg format
+   * @param {Array} pathData fabricJS parsed path commands
+   * @return {String} joined path 'M 0 0 L 20 30'
+   */
+  fabric.util.joinPath = function(pathData) {
+    return pathData.map(function (segment) { return segment.join(' '); }).join(' ');
+  };
   fabric.util.parsePath = parsePath;
   fabric.util.makePathSimpler = makePathSimpler;
   fabric.util.getSmoothPathFromPoints = getSmoothPathFromPoints;
   fabric.util.getPathSegmentsInfo = getPathSegmentsInfo;
-  fabric.util.fromArcToBeziers = fromArcToBeziers;
+  fabric.util.getBoundsOfCurve = getBoundsOfCurve;
+  fabric.util.getPointOnPath = getPointOnPath;
+  fabric.util.transformPath = transformPath;
   /**
    * Typo of `fromArcToBeziers` kept for not breaking the api once corrected.
    * Will be removed in fabric 5.0
    * @deprecated
    */
   fabric.util.fromArcToBeizers = fromArcToBeziers;
-  fabric.util.getBoundsOfCurve = getBoundsOfCurve;
-  fabric.util.getPointOnPath = getPointOnPath;
   // kept because we do not want to make breaking changes.
   // but useless and deprecated.
   fabric.util.getBoundsOfArc = getBoundsOfArc;

test/unit/util.js

@@ -1090,4 +1090,20 @@
     assert.notOk(fabric.util.isTouchEvent({ type: 'mousedown' }));
     assert.notOk(fabric.util.isTouchEvent({ pointerType: 'mouse' }));
   });
+
+  QUnit.test('fabric.util.transformPath can scale a path by 2', function(assert) {
+    assert.ok(typeof fabric.util.transformPath === 'function');
+    var path = new fabric.Path('M 100 100 L 200 100 L 170 200 z');
+    var oldPath = path.path;
+    var newPath = fabric.util.transformPath(path.path, [2, 0, 0, 2, 0, 0]);
+    assert.equal(fabric.util.joinPath(oldPath), 'M 100 100 L 200 100 L 170 200 z');
+    assert.equal(fabric.util.joinPath(newPath), 'M 200 200 L 400 200 L 340 400 z');
+  });
+  QUnit.test('fabric.util.transformPath can apply a generic transform', function(assert) {
+    var path = new fabric.Path('M 100 100 L 200 100 L 170 200 z');
+    var oldPath = path.path;
+    var newPath = fabric.util.transformPath(path.path, [1, 2, 3, 4, 5, 6], path.pathOffset);
+    assert.equal(fabric.util.joinPath(oldPath), 'M 100 100 L 200 100 L 170 200 z');
+    assert.equal(fabric.util.joinPath(newPath), 'M -195 -294 L -95 -94 L 175 246 z');
+  });
 })();