Refactor apply transforms

- handle each command separately
- handle both relative and absolute commands
- moved into _applyTransforms.js to convert eventually into plugin
- apply transforms before converting into relative

These changes makes code independent and easy to work with.

plugins/_applyTransforms.js

@@ -0,0 +1,328 @@
+'use strict';
+
+// TODO implement as separate plugin
+
+const {
+  transformsMultiply,
+  transform2js,
+  transformArc,
+} = require('./_transforms.js');
+const { removeLeadingZero } = require('../lib/svgo/tools.js');
+const { referencesProps, attrsGroupsDefaults } = require('./_collections.js');
+
+const regNumericValues = /[-+]?(\d*\.\d+|\d+\.?)(?:[eE][-+]?\d+)?/g;
+const defaultStrokeWidth = attrsGroupsDefaults.presentation['stroke-width'];
+
+/**
+ * Apply transformation(s) to the Path data.
+ *
+ * @param {Object} elem current element
+ * @param {Array} path input path data
+ * @param {Object} params whether to apply transforms to stroked lines and transform precision (used for stroke width)
+ * @return {Array} output path data
+ */
+const applyTransforms = (elem, pathData, params) => {
+  // if there are no 'stroke' attr and references to other objects such as
+  // gradiends or clip-path which are also subjects to transform.
+  if (
+    !elem.hasAttr('transform') ||
+    !elem.attr('transform').value ||
+    // styles are not considered when applying transform
+    // can be fixed properly with new style engine
+    elem.hasAttr('style') ||
+    elem.someAttr(
+      (attr) =>
+        referencesProps.includes(attr.name) && attr.value.includes('url(')
+    )
+  ) {
+    return;
+  }
+
+  const matrix = transformsMultiply(transform2js(elem.attr('transform').value));
+  const stroke = elem.computedAttr('stroke');
+  const id = elem.computedAttr('id');
+  const transformPrecision = params.transformPrecision;
+
+  if (stroke && stroke != 'none') {
+    if (
+      !params.applyTransformsStroked ||
+      ((matrix.data[0] != matrix.data[3] ||
+        matrix.data[1] != -matrix.data[2]) &&
+        (matrix.data[0] != -matrix.data[3] || matrix.data[1] != matrix.data[2]))
+    )
+      return;
+
+    // "stroke-width" should be inside the part with ID, otherwise it can be overrided in <use>
+    if (id) {
+      let idElem = elem;
+      let hasStrokeWidth = false;
+
+      do {
+        if (idElem.hasAttr('stroke-width')) hasStrokeWidth = true;
+      } while (
+        !idElem.hasAttr('id', id) &&
+        !hasStrokeWidth &&
+        (idElem = idElem.parentNode)
+      );
+
+      if (!hasStrokeWidth) return;
+    }
+
+    const scale = +Math.sqrt(
+      matrix.data[0] * matrix.data[0] + matrix.data[1] * matrix.data[1]
+    ).toFixed(transformPrecision);
+
+    if (scale !== 1) {
+      const strokeWidth =
+        elem.computedAttr('stroke-width') || defaultStrokeWidth;
+
+      if (
+        !elem.hasAttr('vector-effect') ||
+        elem.attr('vector-effect').value !== 'non-scaling-stroke'
+      ) {
+        if (elem.hasAttr('stroke-width')) {
+          elem.attrs['stroke-width'].value = elem.attrs['stroke-width'].value
+            .trim()
+            .replace(regNumericValues, (num) => removeLeadingZero(num * scale));
+        } else {
+          elem.addAttr({
+            name: 'stroke-width',
+            value: strokeWidth.replace(regNumericValues, (num) =>
+              removeLeadingZero(num * scale)
+            ),
+          });
+        }
+
+        if (elem.hasAttr('stroke-dashoffset')) {
+          elem.attrs['stroke-dashoffset'].value = elem.attrs[
+            'stroke-dashoffset'
+          ].value
+            .trim()
+            .replace(regNumericValues, (num) => removeLeadingZero(num * scale));
+        }
+
+        if (elem.hasAttr('stroke-dasharray')) {
+          elem.attrs['stroke-dasharray'].value = elem.attrs[
+            'stroke-dasharray'
+          ].value
+            .trim()
+            .replace(regNumericValues, (num) => removeLeadingZero(num * scale));
+        }
+      }
+    }
+  } else if (id) {
+    // Stroke and stroke-width can be redefined with <use>
+    return;
+  }
+
+  applyMatrixToPathData(pathData, matrix.data);
+
+  // remove transform attr
+  elem.removeAttr('transform');
+
+  return;
+};
+
+const transformAbsolutePoint = (matrix, x, y) => {
+  const newX = matrix[0] * x + matrix[2] * y + matrix[4];
+  const newY = matrix[1] * x + matrix[3] * y + matrix[5];
+  return [newX, newY];
+};
+
+const transformRelativePoint = (matrix, x, y) => {
+  const newX = matrix[0] * x + matrix[2] * y;
+  const newY = matrix[1] * x + matrix[3] * y;
+  return [newX, newY];
+};
+
+const applyMatrixToPathData = (pathData, matrix) => {
+  let start = [0, 0];
+  let cursor = [0, 0];
+
+  for (const pathItem of pathData) {
+    let { instruction: command, data: args } = pathItem;
+    // moveto (x y)
+    if (command === 'M') {
+      cursor[0] = args[0];
+      cursor[1] = args[1];
+      start[0] = cursor[0];
+      start[1] = cursor[1];
+      const [x, y] = transformAbsolutePoint(matrix, args[0], args[1]);
+      args[0] = x;
+      args[1] = y;
+    }
+    if (command === 'm') {
+      cursor[0] += args[0];
+      cursor[1] += args[1];
+      start[0] = cursor[0];
+      start[1] = cursor[1];
+      const [x, y] = transformRelativePoint(matrix, args[0], args[1]);
+      args[0] = x;
+      args[1] = y;
+    }
+
+    // horizontal lineto (x)
+    // convert to lineto to handle two-dimentional transforms
+    if (command === 'H') {
+      command = 'L';
+      args = [args[0], cursor[1]];
+    }
+    if (command === 'h') {
+      command = 'l';
+      args = [args[0], 0];
+    }
+
+    // vertical lineto (y)
+    // convert to lineto to handle two-dimentional transforms
+    if (command === 'V') {
+      command = 'L';
+      args = [cursor[0], args[0]];
+    }
+    if (command === 'v') {
+      command = 'l';
+      args = [0, args[0]];
+    }
+
+    // lineto (x y)
+    if (command === 'L') {
+      cursor[0] = args[0];
+      cursor[1] = args[1];
+      const [x, y] = transformAbsolutePoint(matrix, args[0], args[1]);
+      args[0] = x;
+      args[1] = y;
+    }
+    if (command === 'l') {
+      cursor[0] += args[0];
+      cursor[1] += args[1];
+      const [x, y] = transformRelativePoint(matrix, args[0], args[1]);
+      args[0] = x;
+      args[1] = y;
+    }
+
+    // curveto (x1 y1 x2 y2 x y)
+    if (command === 'C') {
+      cursor[0] = args[4];
+      cursor[1] = args[5];
+      const [x1, y1] = transformAbsolutePoint(matrix, args[0], args[1]);
+      const [x2, y2] = transformAbsolutePoint(matrix, args[2], args[3]);
+      const [x, y] = transformAbsolutePoint(matrix, args[4], args[5]);
+      args[0] = x1;
+      args[1] = y1;
+      args[2] = x2;
+      args[3] = y2;
+      args[4] = x;
+      args[5] = y;
+    }
+    if (command === 'c') {
+      cursor[0] += args[4];
+      cursor[1] += args[5];
+      const [x1, y1] = transformRelativePoint(matrix, args[0], args[1]);
+      const [x2, y2] = transformRelativePoint(matrix, args[2], args[3]);
+      const [x, y] = transformRelativePoint(matrix, args[4], args[5]);
+      args[0] = x1;
+      args[1] = y1;
+      args[2] = x2;
+      args[3] = y2;
+      args[4] = x;
+      args[5] = y;
+    }
+
+    // smooth curveto (x2 y2 x y)
+    if (command === 'S') {
+      cursor[0] = args[2];
+      cursor[1] = args[3];
+      const [x2, y2] = transformAbsolutePoint(matrix, args[0], args[1]);
+      const [x, y] = transformAbsolutePoint(matrix, args[2], args[3]);
+      args[0] = x2;
+      args[1] = y2;
+      args[2] = x;
+      args[3] = y;
+    }
+    if (command === 's') {
+      cursor[0] += args[2];
+      cursor[1] += args[3];
+      const [x2, y2] = transformRelativePoint(matrix, args[0], args[1]);
+      const [x, y] = transformRelativePoint(matrix, args[2], args[3]);
+      args[0] = x2;
+      args[1] = y2;
+      args[2] = x;
+      args[3] = y;
+    }
+
+    // quadratic Bézier curveto (x1 y1 x y)
+    if (command === 'Q') {
+      cursor[0] = args[2];
+      cursor[1] = args[3];
+      const [x1, y1] = transformAbsolutePoint(matrix, args[0], args[1]);
+      const [x, y] = transformAbsolutePoint(matrix, args[2], args[3]);
+      args[0] = x1;
+      args[1] = y1;
+      args[2] = x;
+      args[3] = y;
+    }
+    if (command === 'q') {
+      cursor[0] += args[2];
+      cursor[1] += args[3];
+      const [x1, y1] = transformRelativePoint(matrix, args[0], args[1]);
+      const [x, y] = transformRelativePoint(matrix, args[2], args[3]);
+      args[0] = x1;
+      args[1] = y1;
+      args[2] = x;
+      args[3] = y;
+    }
+
+    // smooth quadratic Bézier curveto (x y)
+    if (command === 'T') {
+      cursor[0] = args[0];
+      cursor[1] = args[1];
+      const [x, y] = transformAbsolutePoint(matrix, args[0], args[1]);
+      args[0] = x;
+      args[1] = y;
+    }
+    if (command === 't') {
+      cursor[0] += args[0];
+      cursor[1] += args[1];
+      const [x, y] = transformRelativePoint(matrix, args[0], args[1]);
+      args[0] = x;
+      args[1] = y;
+    }
+
+    // elliptical arc (rx ry x-axis-rotation large-arc-flag sweep-flag x y)
+    if (command === 'A') {
+      transformArc(cursor, args, matrix);
+      cursor[0] = args[5];
+      cursor[1] = args[6];
+      // reduce number of digits in rotation angle
+      if (Math.abs(args[2]) > 80) {
+        const a = args[0];
+        const rotation = args[2];
+        args[0] = args[1];
+        args[1] = a;
+        args[2] = rotation + (rotation > 0 ? -90 : 90);
+      }
+      const [x, y] = transformAbsolutePoint(matrix, args[5], args[6]);
+      args[5] = x;
+      args[6] = y;
+    }
+    if (command === 'a') {
+      transformArc([0, 0], args, matrix);
+      cursor[0] += args[5];
+      cursor[1] += args[6];
+      // reduce number of digits in rotation angle
+      if (Math.abs(args[2]) > 80) {
+        const a = args[0];
+        const rotation = args[2];
+        args[0] = args[1];
+        args[1] = a;
+        args[2] = rotation + (rotation > 0 ? -90 : 90);
+      }
+      const [x, y] = transformRelativePoint(matrix, args[5], args[6]);
+      args[5] = x;
+      args[6] = y;
+    }
+
+    pathItem.instruction = command;
+    pathItem.data = args;
+  }
+};
+exports.applyTransforms = applyTransforms;