Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1357 insertions, 0 deletions

diff --git a/dom/svg/SVGPathData.cpp b/dom/svg/SVGPathData.cpp
new file mode 100644
index 0000000000..4dde07fcbe
--- /dev/null
+++ b/dom/svg/SVGPathData.cpp
@@ -0,0 +1,1357 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "SVGPathData.h"
+
+#include "gfx2DGlue.h"
+#include "gfxPlatform.h"
+#include "mozilla/gfx/2D.h"
+#include "mozilla/gfx/Types.h"
+#include "mozilla/gfx/Point.h"
+#include "mozilla/RefPtr.h"
+#include "nsError.h"
+#include "nsString.h"
+#include "SVGPathDataParser.h"
+#include <stdarg.h>
+#include "nsStyleConsts.h"
+#include "SVGContentUtils.h"
+#include "SVGGeometryElement.h"
+#include "SVGPathSegUtils.h"
+#include <algorithm>
+
+using namespace mozilla::dom::SVGPathSeg_Binding;
+using namespace mozilla::gfx;
+
+namespace mozilla {
+
+static inline bool IsMoveto(uint16_t aSegType) {
+  return aSegType == PATHSEG_MOVETO_ABS || aSegType == PATHSEG_MOVETO_REL;
+}
+
+static inline bool IsMoveto(StylePathCommand::Tag aSegType) {
+  return aSegType == StylePathCommand::Tag::MoveTo;
+}
+
+static inline bool IsValidType(uint16_t aSegType) {
+  return SVGPathSegUtils::IsValidType(aSegType);
+}
+
+static inline bool IsValidType(StylePathCommand::Tag aSegType) {
+  return aSegType != StylePathCommand::Tag::Unknown;
+}
+
+static inline bool IsClosePath(uint16_t aSegType) {
+  return aSegType == PATHSEG_CLOSEPATH;
+}
+
+static inline bool IsClosePath(StylePathCommand::Tag aSegType) {
+  return aSegType == StylePathCommand::Tag::ClosePath;
+}
+
+static inline bool IsCubicType(StylePathCommand::Tag aType) {
+  return aType == StylePathCommand::Tag::CurveTo ||
+         aType == StylePathCommand::Tag::SmoothCurveTo;
+}
+
+static inline bool IsQuadraticType(StylePathCommand::Tag aType) {
+  return aType == StylePathCommand::Tag::QuadBezierCurveTo ||
+         aType == StylePathCommand::Tag::SmoothQuadBezierCurveTo;
+}
+
+nsresult SVGPathData::CopyFrom(const SVGPathData& rhs) {
+  if (!mData.Assign(rhs.mData, fallible)) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+  return NS_OK;
+}
+
+void SVGPathData::GetValueAsString(nsAString& aValue) const {
+  // we need this function in DidChangePathSegList
+  aValue.Truncate();
+  if (!Length()) {
+    return;
+  }
+  uint32_t i = 0;
+  for (;;) {
+    nsAutoString segAsString;
+    SVGPathSegUtils::GetValueAsString(&mData[i], segAsString);
+    // We ignore OOM, since it's not useful for us to return an error.
+    aValue.Append(segAsString);
+    i += 1 + SVGPathSegUtils::ArgCountForType(mData[i]);
+    if (i >= mData.Length()) {
+      MOZ_ASSERT(i == mData.Length(), "Very, very bad - mData corrupt");
+      return;
+    }
+    aValue.Append(' ');
+  }
+}
+
+nsresult SVGPathData::SetValueFromString(const nsAString& aValue) {
+  // We don't use a temp variable since the spec says to parse everything up to
+  // the first error. We still return any error though so that callers know if
+  // there's a problem.
+
+  SVGPathDataParser pathParser(aValue, this);
+  return pathParser.Parse() ? NS_OK : NS_ERROR_DOM_SYNTAX_ERR;
+}
+
+nsresult SVGPathData::AppendSeg(uint32_t aType, ...) {
+  uint32_t oldLength = mData.Length();
+  uint32_t newLength = oldLength + 1 + SVGPathSegUtils::ArgCountForType(aType);
+  if (!mData.SetLength(newLength, fallible)) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+
+  mData[oldLength] = SVGPathSegUtils::EncodeType(aType);
+  va_list args;
+  va_start(args, aType);
+  for (uint32_t i = oldLength + 1; i < newLength; ++i) {
+    // NOTE! 'float' is promoted to 'double' when passed through '...'!
+    mData[i] = float(va_arg(args, double));
+  }
+  va_end(args);
+  return NS_OK;
+}
+
+float SVGPathData::GetPathLength() const {
+  SVGPathTraversalState state;
+
+  uint32_t i = 0;
+  while (i < mData.Length()) {
+    SVGPathSegUtils::TraversePathSegment(&mData[i], state);
+    i += 1 + SVGPathSegUtils::ArgCountForType(mData[i]);
+  }
+
+  MOZ_ASSERT(i == mData.Length(), "Very, very bad - mData corrupt");
+
+  return state.length;
+}
+
+#ifdef DEBUG
+uint32_t SVGPathData::CountItems() const {
+  uint32_t i = 0, count = 0;
+
+  while (i < mData.Length()) {
+    i += 1 + SVGPathSegUtils::ArgCountForType(mData[i]);
+    count++;
+  }
+
+  MOZ_ASSERT(i == mData.Length(), "Very, very bad - mData corrupt");
+
+  return count;
+}
+#endif
+
+bool SVGPathData::GetDistancesFromOriginToEndsOfVisibleSegments(
+    FallibleTArray<double>* aOutput) const {
+  SVGPathTraversalState state;
+
+  aOutput->Clear();
+
+  uint32_t i = 0;
+  while (i < mData.Length()) {
+    uint32_t segType = SVGPathSegUtils::DecodeType(mData[i]);
+    SVGPathSegUtils::TraversePathSegment(&mData[i], state);
+
+    // With degenerately large point coordinates, TraversePathSegment can fail
+    // and end up producing NaNs.
+    if (!std::isfinite(state.length)) {
+      return false;
+    }
+
+    // We skip all moveto commands except an initial moveto. See the text 'A
+    // "move to" command does not count as an additional point when dividing up
+    // the duration...':
+    //
+    // http://www.w3.org/TR/SVG11/animate.html#AnimateMotionElement
+    //
+    // This is important in the non-default case of calcMode="linear". In
+    // this case an equal amount of time is spent on each path segment,
+    // except on moveto segments which are jumped over immediately.
+
+    if (i == 0 || !IsMoveto(segType)) {
+      if (!aOutput->AppendElement(state.length, fallible)) {
+        return false;
+      }
+    }
+    i += 1 + SVGPathSegUtils::ArgCountForType(segType);
+  }
+
+  MOZ_ASSERT(i == mData.Length(), "Very, very bad - mData corrupt?");
+
+  return true;
+}
+
+/* static */
+bool SVGPathData::GetDistancesFromOriginToEndsOfVisibleSegments(
+    Span<const StylePathCommand> aPath, FallibleTArray<double>* aOutput) {
+  SVGPathTraversalState state;
+
+  aOutput->Clear();
+
+  bool firstMoveToIsChecked = false;
+  for (const auto& cmd : aPath) {
+    SVGPathSegUtils::TraversePathSegment(cmd, state);
+    if (!std::isfinite(state.length)) {
+      return false;
+    }
+
+    // We skip all moveto commands except for the initial moveto.
+    if (!cmd.IsMoveTo() || !firstMoveToIsChecked) {
+      if (!aOutput->AppendElement(state.length, fallible)) {
+        return false;
+      }
+    }
+
+    if (cmd.IsMoveTo() && !firstMoveToIsChecked) {
+      firstMoveToIsChecked = true;
+    }
+  }
+
+  return true;
+}
+
+uint32_t SVGPathData::GetPathSegAtLength(float aDistance) const {
+  // TODO [SVGWG issue] get specified what happen if 'aDistance' < 0, or
+  // 'aDistance' > the length of the path, or the seg list is empty.
+  // Return -1? Throwing would better help authors avoid tricky bugs (DOM
+  // could do that if we return -1).
+
+  uint32_t i = 0, segIndex = 0;
+  SVGPathTraversalState state;
+
+  while (i < mData.Length()) {
+    SVGPathSegUtils::TraversePathSegment(&mData[i], state);
+    if (state.length >= aDistance) {
+      return segIndex;
+    }
+    i += 1 + SVGPathSegUtils::ArgCountForType(mData[i]);
+    segIndex++;
+  }
+
+  MOZ_ASSERT(i == mData.Length(), "Very, very bad - mData corrupt");
+
+  return std::max(1U, segIndex) -
+         1;  // -1 because while loop takes us 1 too far
+}
+
+/* static */
+uint32_t SVGPathData::GetPathSegAtLength(Span<const StylePathCommand> aPath,
+                                         float aDistance) {
+  uint32_t segIndex = 0;
+  SVGPathTraversalState state;
+
+  for (const auto& cmd : aPath) {
+    SVGPathSegUtils::TraversePathSegment(cmd, state);
+    if (state.length >= aDistance) {
+      return segIndex;
+    }
+    segIndex++;
+  }
+
+  return std::max(1U, segIndex) - 1;
+}
+
+/**
+ * The SVG spec says we have to paint stroke caps for zero length subpaths:
+ *
+ *   http://www.w3.org/TR/SVG11/implnote.html#PathElementImplementationNotes
+ *
+ * Cairo only does this for |stroke-linecap: round| and not for
+ * |stroke-linecap: square| (since that's what Adobe Acrobat has always done).
+ * Most likely the other backends that DrawTarget uses have the same behavior.
+ *
+ * To help us conform to the SVG spec we have this helper function to draw an
+ * approximation of square caps for zero length subpaths. It does this by
+ * inserting a subpath containing a single user space axis aligned straight
+ * line that is as small as it can be while minimizing the risk of it being
+ * thrown away by the DrawTarget's backend for being too small to affect
+ * rendering. The idea is that we'll then get stroke caps drawn for this axis
+ * aligned line, creating an axis aligned rectangle that approximates the
+ * square that would ideally be drawn.
+ *
+ * Since we don't have any information about transforms from user space to
+ * device space, we choose the length of the small line that we insert by
+ * making it a small percentage of the stroke width of the path. This should
+ * hopefully allow us to make the line as long as possible (to avoid rounding
+ * issues in the backend resulting in the backend seeing it as having zero
+ * length) while still avoiding the small rectangle being noticeably different
+ * from a square.
+ *
+ * Note that this function inserts a subpath into the current gfx path that
+ * will be present during both fill and stroke operations.
+ */
+static void ApproximateZeroLengthSubpathSquareCaps(PathBuilder* aPB,
+                                                   const Point& aPoint,
+                                                   Float aStrokeWidth) {
+  // Note that caps are proportional to stroke width, so if stroke width is
+  // zero it's actually fine for |tinyLength| below to end up being zero.
+  // However, it would be a waste to inserting a LineTo in that case, so better
+  // not to.
+  MOZ_ASSERT(aStrokeWidth > 0.0f,
+             "Make the caller check for this, or check it here");
+
+  // The fraction of the stroke width that we choose for the length of the
+  // line is rather arbitrary, other than being chosen to meet the requirements
+  // described in the comment above.
+
+  Float tinyLength = aStrokeWidth / SVG_ZERO_LENGTH_PATH_FIX_FACTOR;
+
+  aPB->LineTo(aPoint + Point(tinyLength, 0));
+  aPB->MoveTo(aPoint);
+}
+
+#define MAYBE_APPROXIMATE_ZERO_LENGTH_SUBPATH_SQUARE_CAPS_TO_DT  \
+  do {                                                           \
+    if (!subpathHasLength && hasLineCaps && aStrokeWidth > 0 &&  \
+        subpathContainsNonMoveTo && IsValidType(prevSegType) &&  \
+        (!IsMoveto(prevSegType) || IsClosePath(segType))) {      \
+      ApproximateZeroLengthSubpathSquareCaps(aBuilder, segStart, \
+                                             aStrokeWidth);      \
+    }                                                            \
+  } while (0)
+
+already_AddRefed<Path> SVGPathData::BuildPath(PathBuilder* aBuilder,
+                                              StyleStrokeLinecap aStrokeLineCap,
+                                              Float aStrokeWidth) const {
+  if (mData.IsEmpty() || !IsMoveto(SVGPathSegUtils::DecodeType(mData[0]))) {
+    return nullptr;  // paths without an initial moveto are invalid
+  }
+
+  bool hasLineCaps = aStrokeLineCap != StyleStrokeLinecap::Butt;
+  bool subpathHasLength = false;  // visual length
+  bool subpathContainsNonMoveTo = false;
+
+  uint32_t segType = PATHSEG_UNKNOWN;
+  uint32_t prevSegType = PATHSEG_UNKNOWN;
+  Point pathStart(0.0, 0.0);  // start point of [sub]path
+  Point segStart(0.0, 0.0);
+  Point segEnd;
+  Point cp1, cp2;    // previous bezier's control points
+  Point tcp1, tcp2;  // temporaries
+
+  // Regarding cp1 and cp2: If the previous segment was a cubic bezier curve,
+  // then cp2 is its second control point. If the previous segment was a
+  // quadratic curve, then cp1 is its (only) control point.
+
+  uint32_t i = 0;
+  while (i < mData.Length()) {
+    segType = SVGPathSegUtils::DecodeType(mData[i++]);
+    uint32_t argCount = SVGPathSegUtils::ArgCountForType(segType);
+
+    switch (segType) {
+      case PATHSEG_CLOSEPATH:
+        // set this early to allow drawing of square caps for "M{x},{y} Z":
+        subpathContainsNonMoveTo = true;
+        MAYBE_APPROXIMATE_ZERO_LENGTH_SUBPATH_SQUARE_CAPS_TO_DT;
+        segEnd = pathStart;
+        aBuilder->Close();
+        break;
+
+      case PATHSEG_MOVETO_ABS:
+        MAYBE_APPROXIMATE_ZERO_LENGTH_SUBPATH_SQUARE_CAPS_TO_DT;
+        pathStart = segEnd = Point(mData[i], mData[i + 1]);
+        aBuilder->MoveTo(segEnd);
+        subpathHasLength = false;
+        break;
+
+      case PATHSEG_MOVETO_REL:
+        MAYBE_APPROXIMATE_ZERO_LENGTH_SUBPATH_SQUARE_CAPS_TO_DT;
+        pathStart = segEnd = segStart + Point(mData[i], mData[i + 1]);
+        aBuilder->MoveTo(segEnd);
+        subpathHasLength = false;
+        break;
+
+      case PATHSEG_LINETO_ABS:
+        segEnd = Point(mData[i], mData[i + 1]);
+        if (segEnd != segStart) {
+          subpathHasLength = true;
+          aBuilder->LineTo(segEnd);
+        }
+        break;
+
+      case PATHSEG_LINETO_REL:
+        segEnd = segStart + Point(mData[i], mData[i + 1]);
+        if (segEnd != segStart) {
+          subpathHasLength = true;
+          aBuilder->LineTo(segEnd);
+        }
+        break;
+
+      case PATHSEG_CURVETO_CUBIC_ABS:
+        cp1 = Point(mData[i], mData[i + 1]);
+        cp2 = Point(mData[i + 2], mData[i + 3]);
+        segEnd = Point(mData[i + 4], mData[i + 5]);
+        if (segEnd != segStart || segEnd != cp1 || segEnd != cp2) {
+          subpathHasLength = true;
+          aBuilder->BezierTo(cp1, cp2, segEnd);
+        }
+        break;
+
+      case PATHSEG_CURVETO_CUBIC_REL:
+        cp1 = segStart + Point(mData[i], mData[i + 1]);
+        cp2 = segStart + Point(mData[i + 2], mData[i + 3]);
+        segEnd = segStart + Point(mData[i + 4], mData[i + 5]);
+        if (segEnd != segStart || segEnd != cp1 || segEnd != cp2) {
+          subpathHasLength = true;
+          aBuilder->BezierTo(cp1, cp2, segEnd);
+        }
+        break;
+
+      case PATHSEG_CURVETO_QUADRATIC_ABS:
+        cp1 = Point(mData[i], mData[i + 1]);
+        // Convert quadratic curve to cubic curve:
+        tcp1 = segStart + (cp1 - segStart) * 2 / 3;
+        segEnd = Point(mData[i + 2], mData[i + 3]);  // set before setting tcp2!
+        tcp2 = cp1 + (segEnd - cp1) / 3;
+        if (segEnd != segStart || segEnd != cp1) {
+          subpathHasLength = true;
+          aBuilder->BezierTo(tcp1, tcp2, segEnd);
+        }
+        break;
+
+      case PATHSEG_CURVETO_QUADRATIC_REL:
+        cp1 = segStart + Point(mData[i], mData[i + 1]);
+        // Convert quadratic curve to cubic curve:
+        tcp1 = segStart + (cp1 - segStart) * 2 / 3;
+        segEnd = segStart +
+                 Point(mData[i + 2], mData[i + 3]);  // set before setting tcp2!
+        tcp2 = cp1 + (segEnd - cp1) / 3;
+        if (segEnd != segStart || segEnd != cp1) {
+          subpathHasLength = true;
+          aBuilder->BezierTo(tcp1, tcp2, segEnd);
+        }
+        break;
+
+      case PATHSEG_ARC_ABS:
+      case PATHSEG_ARC_REL: {
+        Point radii(mData[i], mData[i + 1]);
+        segEnd = Point(mData[i + 5], mData[i + 6]);
+        if (segType == PATHSEG_ARC_REL) {
+          segEnd += segStart;
+        }
+        if (segEnd != segStart) {
+          subpathHasLength = true;
+          if (radii.x == 0.0f || radii.y == 0.0f) {
+            aBuilder->LineTo(segEnd);
+          } else {
+            SVGArcConverter converter(segStart, segEnd, radii, mData[i + 2],
+                                      mData[i + 3] != 0, mData[i + 4] != 0);
+            while (converter.GetNextSegment(&cp1, &cp2, &segEnd)) {
+              aBuilder->BezierTo(cp1, cp2, segEnd);
+            }
+          }
+        }
+        break;
+      }
+
+      case PATHSEG_LINETO_HORIZONTAL_ABS:
+        segEnd = Point(mData[i], segStart.y);
+        if (segEnd != segStart) {
+          subpathHasLength = true;
+          aBuilder->LineTo(segEnd);
+        }
+        break;
+
+      case PATHSEG_LINETO_HORIZONTAL_REL:
+        segEnd = segStart + Point(mData[i], 0.0f);
+        if (segEnd != segStart) {
+          subpathHasLength = true;
+          aBuilder->LineTo(segEnd);
+        }
+        break;
+
+      case PATHSEG_LINETO_VERTICAL_ABS:
+        segEnd = Point(segStart.x, mData[i]);
+        if (segEnd != segStart) {
+          subpathHasLength = true;
+          aBuilder->LineTo(segEnd);
+        }
+        break;
+
+      case PATHSEG_LINETO_VERTICAL_REL:
+        segEnd = segStart + Point(0.0f, mData[i]);
+        if (segEnd != segStart) {
+          subpathHasLength = true;
+          aBuilder->LineTo(segEnd);
+        }
+        break;
+
+      case PATHSEG_CURVETO_CUBIC_SMOOTH_ABS:
+        cp1 = SVGPathSegUtils::IsCubicType(prevSegType) ? segStart * 2 - cp2
+                                                        : segStart;
+        cp2 = Point(mData[i], mData[i + 1]);
+        segEnd = Point(mData[i + 2], mData[i + 3]);
+        if (segEnd != segStart || segEnd != cp1 || segEnd != cp2) {
+          subpathHasLength = true;
+          aBuilder->BezierTo(cp1, cp2, segEnd);
+        }
+        break;
+
+      case PATHSEG_CURVETO_CUBIC_SMOOTH_REL:
+        cp1 = SVGPathSegUtils::IsCubicType(prevSegType) ? segStart * 2 - cp2
+                                                        : segStart;
+        cp2 = segStart + Point(mData[i], mData[i + 1]);
+        segEnd = segStart + Point(mData[i + 2], mData[i + 3]);
+        if (segEnd != segStart || segEnd != cp1 || segEnd != cp2) {
+          subpathHasLength = true;
+          aBuilder->BezierTo(cp1, cp2, segEnd);
+        }
+        break;
+
+      case PATHSEG_CURVETO_QUADRATIC_SMOOTH_ABS:
+        cp1 = SVGPathSegUtils::IsQuadraticType(prevSegType) ? segStart * 2 - cp1
+                                                            : segStart;
+        // Convert quadratic curve to cubic curve:
+        tcp1 = segStart + (cp1 - segStart) * 2 / 3;
+        segEnd = Point(mData[i], mData[i + 1]);  // set before setting tcp2!
+        tcp2 = cp1 + (segEnd - cp1) / 3;
+        if (segEnd != segStart || segEnd != cp1) {
+          subpathHasLength = true;
+          aBuilder->BezierTo(tcp1, tcp2, segEnd);
+        }
+        break;
+
+      case PATHSEG_CURVETO_QUADRATIC_SMOOTH_REL:
+        cp1 = SVGPathSegUtils::IsQuadraticType(prevSegType) ? segStart * 2 - cp1
+                                                            : segStart;
+        // Convert quadratic curve to cubic curve:
+        tcp1 = segStart + (cp1 - segStart) * 2 / 3;
+        segEnd = segStart +
+                 Point(mData[i], mData[i + 1]);  // changed before setting tcp2!
+        tcp2 = cp1 + (segEnd - cp1) / 3;
+        if (segEnd != segStart || segEnd != cp1) {
+          subpathHasLength = true;
+          aBuilder->BezierTo(tcp1, tcp2, segEnd);
+        }
+        break;
+
+      default:
+        MOZ_ASSERT_UNREACHABLE("Bad path segment type");
+        return nullptr;  // according to spec we'd use everything up to the bad
+                         // seg anyway
+    }
+
+    subpathContainsNonMoveTo = !IsMoveto(segType);
+    i += argCount;
+    prevSegType = segType;
+    segStart = segEnd;
+  }
+
+  MOZ_ASSERT(i == mData.Length(), "Very, very bad - mData corrupt");
+  MOZ_ASSERT(prevSegType == segType,
+             "prevSegType should be left at the final segType");
+
+  MAYBE_APPROXIMATE_ZERO_LENGTH_SUBPATH_SQUARE_CAPS_TO_DT;
+
+  return aBuilder->Finish();
+}
+
+already_AddRefed<Path> SVGPathData::BuildPathForMeasuring() const {
+  // Since the path that we return will not be used for painting it doesn't
+  // matter what we pass to CreatePathBuilder as aFillRule. Hawever, we do want
+  // to pass something other than NS_STYLE_STROKE_LINECAP_SQUARE as
+  // aStrokeLineCap to avoid the insertion of extra little lines (by
+  // ApproximateZeroLengthSubpathSquareCaps), in which case the value that we
+  // pass as aStrokeWidth doesn't matter (since it's only used to determine the
+  // length of those extra little lines).
+
+  RefPtr<DrawTarget> drawTarget =
+      gfxPlatform::GetPlatform()->ScreenReferenceDrawTarget();
+  RefPtr<PathBuilder> builder =
+      drawTarget->CreatePathBuilder(FillRule::FILL_WINDING);
+  return BuildPath(builder, StyleStrokeLinecap::Butt, 0);
+}
+
+/* static */
+already_AddRefed<Path> SVGPathData::BuildPathForMeasuring(
+    Span<const StylePathCommand> aPath) {
+  RefPtr<DrawTarget> drawTarget =
+      gfxPlatform::GetPlatform()->ScreenReferenceDrawTarget();
+  RefPtr<PathBuilder> builder =
+      drawTarget->CreatePathBuilder(FillRule::FILL_WINDING);
+  return BuildPath(aPath, builder, StyleStrokeLinecap::Butt, 0);
+}
+
+// We could simplify this function because this is only used by CSS motion path
+// and clip-path, which don't render the SVG Path. i.e. The returned path is
+// used as a reference.
+/* static */
+already_AddRefed<Path> SVGPathData::BuildPath(
+    Span<const StylePathCommand> aPath, PathBuilder* aBuilder,
+    StyleStrokeLinecap aStrokeLineCap, Float aStrokeWidth, float aZoomFactor) {
+  if (aPath.IsEmpty() || !aPath[0].IsMoveTo()) {
+    return nullptr;  // paths without an initial moveto are invalid
+  }
+
+  bool hasLineCaps = aStrokeLineCap != StyleStrokeLinecap::Butt;
+  bool subpathHasLength = false;  // visual length
+  bool subpathContainsNonMoveTo = false;
+
+  StylePathCommand::Tag segType = StylePathCommand::Tag::Unknown;
+  StylePathCommand::Tag prevSegType = StylePathCommand::Tag::Unknown;
+  Point pathStart(0.0, 0.0);  // start point of [sub]path
+  Point segStart(0.0, 0.0);
+  Point segEnd;
+  Point cp1, cp2;    // previous bezier's control points
+  Point tcp1, tcp2;  // temporaries
+
+  auto scale = [aZoomFactor](const Point& p) {
+    return Point(p.x * aZoomFactor, p.y * aZoomFactor);
+  };
+
+  // Regarding cp1 and cp2: If the previous segment was a cubic bezier curve,
+  // then cp2 is its second control point. If the previous segment was a
+  // quadratic curve, then cp1 is its (only) control point.
+
+  for (const StylePathCommand& cmd : aPath) {
+    segType = cmd.tag;
+    switch (segType) {
+      case StylePathCommand::Tag::ClosePath:
+        // set this early to allow drawing of square caps for "M{x},{y} Z":
+        subpathContainsNonMoveTo = true;
+        MAYBE_APPROXIMATE_ZERO_LENGTH_SUBPATH_SQUARE_CAPS_TO_DT;
+        segEnd = pathStart;
+        aBuilder->Close();
+        break;
+      case StylePathCommand::Tag::MoveTo: {
+        MAYBE_APPROXIMATE_ZERO_LENGTH_SUBPATH_SQUARE_CAPS_TO_DT;
+        const Point& p = cmd.move_to.point.ConvertsToGfxPoint();
+        pathStart = segEnd =
+            cmd.move_to.absolute == StyleIsAbsolute::Yes ? p : segStart + p;
+        aBuilder->MoveTo(scale(segEnd));
+        subpathHasLength = false;
+        break;
+      }
+      case StylePathCommand::Tag::LineTo: {
+        const Point& p = cmd.line_to.point.ConvertsToGfxPoint();
+        segEnd =
+            cmd.line_to.absolute == StyleIsAbsolute::Yes ? p : segStart + p;
+        if (segEnd != segStart) {
+          subpathHasLength = true;
+          aBuilder->LineTo(scale(segEnd));
+        }
+        break;
+      }
+      case StylePathCommand::Tag::CurveTo:
+        cp1 = cmd.curve_to.control1.ConvertsToGfxPoint();
+        cp2 = cmd.curve_to.control2.ConvertsToGfxPoint();
+        segEnd = cmd.curve_to.point.ConvertsToGfxPoint();
+
+        if (cmd.curve_to.absolute == StyleIsAbsolute::No) {
+          cp1 += segStart;
+          cp2 += segStart;
+          segEnd += segStart;
+        }
+
+        if (segEnd != segStart || segEnd != cp1 || segEnd != cp2) {
+          subpathHasLength = true;
+          aBuilder->BezierTo(scale(cp1), scale(cp2), scale(segEnd));
+        }
+        break;
+
+      case StylePathCommand::Tag::QuadBezierCurveTo:
+        cp1 = cmd.quad_bezier_curve_to.control1.ConvertsToGfxPoint();
+        segEnd = cmd.quad_bezier_curve_to.point.ConvertsToGfxPoint();
+
+        if (cmd.quad_bezier_curve_to.absolute == StyleIsAbsolute::No) {
+          cp1 += segStart;
+          segEnd += segStart;  // set before setting tcp2!
+        }
+
+        // Convert quadratic curve to cubic curve:
+        tcp1 = segStart + (cp1 - segStart) * 2 / 3;
+        tcp2 = cp1 + (segEnd - cp1) / 3;
+
+        if (segEnd != segStart || segEnd != cp1) {
+          subpathHasLength = true;
+          aBuilder->BezierTo(scale(tcp1), scale(tcp2), scale(segEnd));
+        }
+        break;
+
+      case StylePathCommand::Tag::EllipticalArc: {
+        const auto& arc = cmd.elliptical_arc;
+        Point radii(arc.rx, arc.ry);
+        segEnd = arc.point.ConvertsToGfxPoint();
+        if (arc.absolute == StyleIsAbsolute::No) {
+          segEnd += segStart;
+        }
+        if (segEnd != segStart) {
+          subpathHasLength = true;
+          if (radii.x == 0.0f || radii.y == 0.0f) {
+            aBuilder->LineTo(scale(segEnd));
+          } else {
+            SVGArcConverter converter(segStart, segEnd, radii, arc.angle,
+                                      arc.large_arc_flag._0, arc.sweep_flag._0);
+            while (converter.GetNextSegment(&cp1, &cp2, &segEnd)) {
+              aBuilder->BezierTo(scale(cp1), scale(cp2), scale(segEnd));
+            }
+          }
+        }
+        break;
+      }
+      case StylePathCommand::Tag::HorizontalLineTo:
+        if (cmd.horizontal_line_to.absolute == StyleIsAbsolute::Yes) {
+          segEnd = Point(cmd.horizontal_line_to.x, segStart.y);
+        } else {
+          segEnd = segStart + Point(cmd.horizontal_line_to.x, 0.0f);
+        }
+
+        if (segEnd != segStart) {
+          subpathHasLength = true;
+          aBuilder->LineTo(scale(segEnd));
+        }
+        break;
+
+      case StylePathCommand::Tag::VerticalLineTo:
+        if (cmd.vertical_line_to.absolute == StyleIsAbsolute::Yes) {
+          segEnd = Point(segStart.x, cmd.vertical_line_to.y);
+        } else {
+          segEnd = segStart + Point(0.0f, cmd.vertical_line_to.y);
+        }
+
+        if (segEnd != segStart) {
+          subpathHasLength = true;
+          aBuilder->LineTo(scale(segEnd));
+        }
+        break;
+
+      case StylePathCommand::Tag::SmoothCurveTo:
+        cp1 = IsCubicType(prevSegType) ? segStart * 2 - cp2 : segStart;
+        cp2 = cmd.smooth_curve_to.control2.ConvertsToGfxPoint();
+        segEnd = cmd.smooth_curve_to.point.ConvertsToGfxPoint();
+
+        if (cmd.smooth_curve_to.absolute == StyleIsAbsolute::No) {
+          cp2 += segStart;
+          segEnd += segStart;
+        }
+
+        if (segEnd != segStart || segEnd != cp1 || segEnd != cp2) {
+          subpathHasLength = true;
+          aBuilder->BezierTo(scale(cp1), scale(cp2), scale(segEnd));
+        }
+        break;
+
+      case StylePathCommand::Tag::SmoothQuadBezierCurveTo: {
+        cp1 = IsQuadraticType(prevSegType) ? segStart * 2 - cp1 : segStart;
+        // Convert quadratic curve to cubic curve:
+        tcp1 = segStart + (cp1 - segStart) * 2 / 3;
+
+        const Point& p =
+            cmd.smooth_quad_bezier_curve_to.point.ConvertsToGfxPoint();
+        // set before setting tcp2!
+        segEnd =
+            cmd.smooth_quad_bezier_curve_to.absolute == StyleIsAbsolute::Yes
+                ? p
+                : segStart + p;
+        tcp2 = cp1 + (segEnd - cp1) / 3;
+
+        if (segEnd != segStart || segEnd != cp1) {
+          subpathHasLength = true;
+          aBuilder->BezierTo(scale(tcp1), scale(tcp2), scale(segEnd));
+        }
+        break;
+      }
+      case StylePathCommand::Tag::Unknown:
+        MOZ_ASSERT_UNREACHABLE("Unacceptable path segment type");
+        return nullptr;
+    }
+
+    subpathContainsNonMoveTo = !IsMoveto(segType);
+    prevSegType = segType;
+    segStart = segEnd;
+  }
+
+  MOZ_ASSERT(prevSegType == segType,
+             "prevSegType should be left at the final segType");
+
+  MAYBE_APPROXIMATE_ZERO_LENGTH_SUBPATH_SQUARE_CAPS_TO_DT;
+
+  return aBuilder->Finish();
+}
+
+static double AngleOfVector(const Point& aVector) {
+  // C99 says about atan2 "A domain error may occur if both arguments are
+  // zero" and "On a domain error, the function returns an implementation-
+  // defined value". In the case of atan2 the implementation-defined value
+  // seems to commonly be zero, but it could just as easily be a NaN value.
+  // We specifically want zero in this case, hence the check:
+
+  return (aVector != Point(0.0, 0.0)) ? atan2(aVector.y, aVector.x) : 0.0;
+}
+
+static float AngleOfVector(const Point& cp1, const Point& cp2) {
+  return static_cast<float>(AngleOfVector(cp1 - cp2));
+}
+
+// This implements F.6.5 and F.6.6 of
+// http://www.w3.org/TR/SVG11/implnote.html#ArcImplementationNotes
+static std::tuple<float, float, float, float>
+/* rx, ry, segStartAngle, segEndAngle */
+ComputeSegAnglesAndCorrectRadii(const Point& aSegStart, const Point& aSegEnd,
+                                const float aAngle, const bool aLargeArcFlag,
+                                const bool aSweepFlag, const float aRx,
+                                const float aRy) {
+  float rx = fabs(aRx);  // F.6.6.1
+  float ry = fabs(aRy);
+
+  // F.6.5.1:
+  const float angle = static_cast<float>(aAngle * M_PI / 180.0);
+  double x1p = cos(angle) * (aSegStart.x - aSegEnd.x) / 2.0 +
+               sin(angle) * (aSegStart.y - aSegEnd.y) / 2.0;
+  double y1p = -sin(angle) * (aSegStart.x - aSegEnd.x) / 2.0 +
+               cos(angle) * (aSegStart.y - aSegEnd.y) / 2.0;
+
+  // This is the root in F.6.5.2 and the numerator under that root:
+  double root;
+  double numerator =
+      rx * rx * ry * ry - rx * rx * y1p * y1p - ry * ry * x1p * x1p;
+
+  if (numerator >= 0.0) {
+    root = sqrt(numerator / (rx * rx * y1p * y1p + ry * ry * x1p * x1p));
+    if (aLargeArcFlag == aSweepFlag) root = -root;
+  } else {
+    // F.6.6 step 3 - |numerator < 0.0|. This is equivalent to the result
+    // of F.6.6.2 (lamedh) being greater than one. What we have here is
+    // ellipse radii that are too small for the ellipse to reach between
+    // segStart and segEnd. We scale the radii up uniformly so that the
+    // ellipse is just big enough to fit (i.e. to the point where there is
+    // exactly one solution).
+
+    double lamedh =
+        1.0 - numerator / (rx * rx * ry * ry);  // equiv to eqn F.6.6.2
+    double s = sqrt(lamedh);
+    rx = static_cast<float>((double)rx * s);  // F.6.6.3
+    ry = static_cast<float>((double)ry * s);
+    root = 0.0;
+  }
+
+  double cxp = root * rx * y1p / ry;  // F.6.5.2
+  double cyp = -root * ry * x1p / rx;
+
+  double theta =
+      AngleOfVector(Point(static_cast<float>((x1p - cxp) / rx),
+                          static_cast<float>((y1p - cyp) / ry)));  // F.6.5.5
+  double delta =
+      AngleOfVector(Point(static_cast<float>((-x1p - cxp) / rx),
+                          static_cast<float>((-y1p - cyp) / ry))) -  // F.6.5.6
+      theta;
+  if (!aSweepFlag && delta > 0) {
+    delta -= 2.0 * M_PI;
+  } else if (aSweepFlag && delta < 0) {
+    delta += 2.0 * M_PI;
+  }
+
+  double tx1, ty1, tx2, ty2;
+  tx1 = -cos(angle) * rx * sin(theta) - sin(angle) * ry * cos(theta);
+  ty1 = -sin(angle) * rx * sin(theta) + cos(angle) * ry * cos(theta);
+  tx2 = -cos(angle) * rx * sin(theta + delta) -
+        sin(angle) * ry * cos(theta + delta);
+  ty2 = -sin(angle) * rx * sin(theta + delta) +
+        cos(angle) * ry * cos(theta + delta);
+
+  if (delta < 0.0f) {
+    tx1 = -tx1;
+    ty1 = -ty1;
+    tx2 = -tx2;
+    ty2 = -ty2;
+  }
+
+  return {rx, ry, static_cast<float>(atan2(ty1, tx1)),
+          static_cast<float>(atan2(ty2, tx2))};
+}
+
+void SVGPathData::GetMarkerPositioningData(nsTArray<SVGMark>* aMarks) const {
+  // This code should assume that ANY type of segment can appear at ANY index.
+  // It should also assume that segments such as M and Z can appear in weird
+  // places, and repeat multiple times consecutively.
+
+  // info on current [sub]path (reset every M command):
+  Point pathStart(0.0, 0.0);
+  float pathStartAngle = 0.0f;
+  uint32_t pathStartIndex = 0;
+
+  // info on previous segment:
+  uint16_t prevSegType = PATHSEG_UNKNOWN;
+  Point prevSegEnd(0.0, 0.0);
+  float prevSegEndAngle = 0.0f;
+  Point prevCP;  // if prev seg was a bezier, this was its last control point
+
+  uint32_t i = 0;
+  while (i < mData.Length()) {
+    // info on current segment:
+    uint16_t segType =
+        SVGPathSegUtils::DecodeType(mData[i++]);  // advances i to args
+    Point& segStart = prevSegEnd;
+    Point segEnd;
+    float segStartAngle, segEndAngle;
+
+    switch (segType)  // to find segStartAngle, segEnd and segEndAngle
+    {
+      case PATHSEG_CLOSEPATH:
+        segEnd = pathStart;
+        segStartAngle = segEndAngle = AngleOfVector(segEnd, segStart);
+        break;
+
+      case PATHSEG_MOVETO_ABS:
+      case PATHSEG_MOVETO_REL:
+        if (segType == PATHSEG_MOVETO_ABS) {
+          segEnd = Point(mData[i], mData[i + 1]);
+        } else {
+          segEnd = segStart + Point(mData[i], mData[i + 1]);
+        }
+        pathStart = segEnd;
+        pathStartIndex = aMarks->Length();
+        // If authors are going to specify multiple consecutive moveto commands
+        // with markers, me might as well make the angle do something useful:
+        segStartAngle = segEndAngle = AngleOfVector(segEnd, segStart);
+        i += 2;
+        break;
+
+      case PATHSEG_LINETO_ABS:
+      case PATHSEG_LINETO_REL:
+        if (segType == PATHSEG_LINETO_ABS) {
+          segEnd = Point(mData[i], mData[i + 1]);
+        } else {
+          segEnd = segStart + Point(mData[i], mData[i + 1]);
+        }
+        segStartAngle = segEndAngle = AngleOfVector(segEnd, segStart);
+        i += 2;
+        break;
+
+      case PATHSEG_CURVETO_CUBIC_ABS:
+      case PATHSEG_CURVETO_CUBIC_REL: {
+        Point cp1, cp2;  // control points
+        if (segType == PATHSEG_CURVETO_CUBIC_ABS) {
+          cp1 = Point(mData[i], mData[i + 1]);
+          cp2 = Point(mData[i + 2], mData[i + 3]);
+          segEnd = Point(mData[i + 4], mData[i + 5]);
+        } else {
+          cp1 = segStart + Point(mData[i], mData[i + 1]);
+          cp2 = segStart + Point(mData[i + 2], mData[i + 3]);
+          segEnd = segStart + Point(mData[i + 4], mData[i + 5]);
+        }
+        prevCP = cp2;
+        segStartAngle = AngleOfVector(
+            cp1 == segStart ? (cp1 == cp2 ? segEnd : cp2) : cp1, segStart);
+        segEndAngle = AngleOfVector(
+            segEnd, cp2 == segEnd ? (cp1 == cp2 ? segStart : cp1) : cp2);
+        i += 6;
+        break;
+      }
+
+      case PATHSEG_CURVETO_QUADRATIC_ABS:
+      case PATHSEG_CURVETO_QUADRATIC_REL: {
+        Point cp1;  // control point
+        if (segType == PATHSEG_CURVETO_QUADRATIC_ABS) {
+          cp1 = Point(mData[i], mData[i + 1]);
+          segEnd = Point(mData[i + 2], mData[i + 3]);
+        } else {
+          cp1 = segStart + Point(mData[i], mData[i + 1]);
+          segEnd = segStart + Point(mData[i + 2], mData[i + 3]);
+        }
+        prevCP = cp1;
+        segStartAngle = AngleOfVector(cp1 == segStart ? segEnd : cp1, segStart);
+        segEndAngle = AngleOfVector(segEnd, cp1 == segEnd ? segStart : cp1);
+        i += 4;
+        break;
+      }
+
+      case PATHSEG_ARC_ABS:
+      case PATHSEG_ARC_REL: {
+        float rx = mData[i];
+        float ry = mData[i + 1];
+        float angle = mData[i + 2];
+        bool largeArcFlag = mData[i + 3] != 0.0f;
+        bool sweepFlag = mData[i + 4] != 0.0f;
+        if (segType == PATHSEG_ARC_ABS) {
+          segEnd = Point(mData[i + 5], mData[i + 6]);
+        } else {
+          segEnd = segStart + Point(mData[i + 5], mData[i + 6]);
+        }
+
+        // See section F.6 of SVG 1.1 for details on what we're doing here:
+        // http://www.w3.org/TR/SVG11/implnote.html#ArcImplementationNotes
+
+        if (segStart == segEnd) {
+          // F.6.2 says "If the endpoints (x1, y1) and (x2, y2) are identical,
+          // then this is equivalent to omitting the elliptical arc segment
+          // entirely." We take that very literally here, not adding a mark, and
+          // not even setting any of the 'prev' variables so that it's as if
+          // this arc had never existed; note the difference this will make e.g.
+          // if the arc is proceeded by a bezier curve and followed by a
+          // "smooth" bezier curve of the same degree!
+          i += 7;
+          continue;
+        }
+
+        // Below we have funny interleaving of F.6.6 (Correction of out-of-range
+        // radii) and F.6.5 (Conversion from endpoint to center
+        // parameterization) which is designed to avoid some unnecessary
+        // calculations.
+
+        if (rx == 0.0 || ry == 0.0) {
+          // F.6.6 step 1 - straight line or coincidental points
+          segStartAngle = segEndAngle = AngleOfVector(segEnd, segStart);
+          i += 7;
+          break;
+        }
+
+        std::tie(rx, ry, segStartAngle, segEndAngle) =
+            ComputeSegAnglesAndCorrectRadii(segStart, segEnd, angle,
+                                            largeArcFlag, sweepFlag, rx, ry);
+        i += 7;
+        break;
+      }
+
+      case PATHSEG_LINETO_HORIZONTAL_ABS:
+      case PATHSEG_LINETO_HORIZONTAL_REL:
+        if (segType == PATHSEG_LINETO_HORIZONTAL_ABS) {
+          segEnd = Point(mData[i++], segStart.y);
+        } else {
+          segEnd = segStart + Point(mData[i++], 0.0f);
+        }
+        segStartAngle = segEndAngle = AngleOfVector(segEnd, segStart);
+        break;
+
+      case PATHSEG_LINETO_VERTICAL_ABS:
+      case PATHSEG_LINETO_VERTICAL_REL:
+        if (segType == PATHSEG_LINETO_VERTICAL_ABS) {
+          segEnd = Point(segStart.x, mData[i++]);
+        } else {
+          segEnd = segStart + Point(0.0f, mData[i++]);
+        }
+        segStartAngle = segEndAngle = AngleOfVector(segEnd, segStart);
+        break;
+
+      case PATHSEG_CURVETO_CUBIC_SMOOTH_ABS:
+      case PATHSEG_CURVETO_CUBIC_SMOOTH_REL: {
+        Point cp1 = SVGPathSegUtils::IsCubicType(prevSegType)
+                        ? segStart * 2 - prevCP
+                        : segStart;
+        Point cp2;
+        if (segType == PATHSEG_CURVETO_CUBIC_SMOOTH_ABS) {
+          cp2 = Point(mData[i], mData[i + 1]);
+          segEnd = Point(mData[i + 2], mData[i + 3]);
+        } else {
+          cp2 = segStart + Point(mData[i], mData[i + 1]);
+          segEnd = segStart + Point(mData[i + 2], mData[i + 3]);
+        }
+        prevCP = cp2;
+        segStartAngle = AngleOfVector(
+            cp1 == segStart ? (cp1 == cp2 ? segEnd : cp2) : cp1, segStart);
+        segEndAngle = AngleOfVector(
+            segEnd, cp2 == segEnd ? (cp1 == cp2 ? segStart : cp1) : cp2);
+        i += 4;
+        break;
+      }
+
+      case PATHSEG_CURVETO_QUADRATIC_SMOOTH_ABS:
+      case PATHSEG_CURVETO_QUADRATIC_SMOOTH_REL: {
+        Point cp1 = SVGPathSegUtils::IsQuadraticType(prevSegType)
+                        ? segStart * 2 - prevCP
+                        : segStart;
+        if (segType == PATHSEG_CURVETO_QUADRATIC_SMOOTH_ABS) {
+          segEnd = Point(mData[i], mData[i + 1]);
+        } else {
+          segEnd = segStart + Point(mData[i], mData[i + 1]);
+        }
+        prevCP = cp1;
+        segStartAngle = AngleOfVector(cp1 == segStart ? segEnd : cp1, segStart);
+        segEndAngle = AngleOfVector(segEnd, cp1 == segEnd ? segStart : cp1);
+        i += 2;
+        break;
+      }
+
+      default:
+        // Leave any existing marks in aMarks so we have a visual indication of
+        // when things went wrong.
+        MOZ_ASSERT(false, "Unknown segment type - path corruption?");
+        return;
+    }
+
+    // Set the angle of the mark at the start of this segment:
+    if (aMarks->Length()) {
+      SVGMark& mark = aMarks->LastElement();
+      if (!IsMoveto(segType) && IsMoveto(prevSegType)) {
+        // start of new subpath
+        pathStartAngle = mark.angle = segStartAngle;
+      } else if (IsMoveto(segType) && !IsMoveto(prevSegType)) {
+        // end of a subpath
+        if (prevSegType != PATHSEG_CLOSEPATH) mark.angle = prevSegEndAngle;
+      } else {
+        if (!(segType == PATHSEG_CLOSEPATH && prevSegType == PATHSEG_CLOSEPATH))
+          mark.angle =
+              SVGContentUtils::AngleBisect(prevSegEndAngle, segStartAngle);
+      }
+    }
+
+    // Add the mark at the end of this segment, and set its position:
+    // XXX(Bug 1631371) Check if this should use a fallible operation as it
+    // pretended earlier.
+    aMarks->AppendElement(SVGMark(static_cast<float>(segEnd.x),
+                                  static_cast<float>(segEnd.y), 0.0f,
+                                  SVGMark::eMid));
+
+    if (segType == PATHSEG_CLOSEPATH && prevSegType != PATHSEG_CLOSEPATH) {
+      aMarks->LastElement().angle = aMarks->ElementAt(pathStartIndex).angle =
+          SVGContentUtils::AngleBisect(segEndAngle, pathStartAngle);
+    }
+
+    prevSegType = segType;
+    prevSegEnd = segEnd;
+    prevSegEndAngle = segEndAngle;
+  }
+
+  MOZ_ASSERT(i == mData.Length(), "Very, very bad - mData corrupt");
+
+  if (aMarks->Length()) {
+    if (prevSegType != PATHSEG_CLOSEPATH) {
+      aMarks->LastElement().angle = prevSegEndAngle;
+    }
+    aMarks->LastElement().type = SVGMark::eEnd;
+    aMarks->ElementAt(0).type = SVGMark::eStart;
+  }
+}
+
+// Basically, this is identical to the above function, but replace |mData| with
+// |aPath|. We probably can factor out some identical calculation, but I believe
+// the above one will be removed because we will use any kind of array of
+// StylePathCommand for SVG d attribute in the future.
+/* static */
+void SVGPathData::GetMarkerPositioningData(Span<const StylePathCommand> aPath,
+                                           nsTArray<SVGMark>* aMarks) {
+  if (aPath.IsEmpty()) {
+    return;
+  }
+
+  // info on current [sub]path (reset every M command):
+  Point pathStart(0.0, 0.0);
+  float pathStartAngle = 0.0f;
+  uint32_t pathStartIndex = 0;
+
+  // info on previous segment:
+  StylePathCommand::Tag prevSegType = StylePathCommand::Tag::Unknown;
+  Point prevSegEnd(0.0, 0.0);
+  float prevSegEndAngle = 0.0f;
+  Point prevCP;  // if prev seg was a bezier, this was its last control point
+
+  StylePathCommand::Tag segType = StylePathCommand::Tag::Unknown;
+  for (const StylePathCommand& cmd : aPath) {
+    segType = cmd.tag;
+    Point& segStart = prevSegEnd;
+    Point segEnd;
+    float segStartAngle, segEndAngle;
+
+    switch (segType)  // to find segStartAngle, segEnd and segEndAngle
+    {
+      case StylePathCommand::Tag::ClosePath:
+        segEnd = pathStart;
+        segStartAngle = segEndAngle = AngleOfVector(segEnd, segStart);
+        break;
+
+      case StylePathCommand::Tag::MoveTo: {
+        const Point& p = cmd.move_to.point.ConvertsToGfxPoint();
+        pathStart = segEnd =
+            cmd.move_to.absolute == StyleIsAbsolute::Yes ? p : segStart + p;
+        pathStartIndex = aMarks->Length();
+        // If authors are going to specify multiple consecutive moveto commands
+        // with markers, me might as well make the angle do something useful:
+        segStartAngle = segEndAngle = AngleOfVector(segEnd, segStart);
+        break;
+      }
+      case StylePathCommand::Tag::LineTo: {
+        const Point& p = cmd.line_to.point.ConvertsToGfxPoint();
+        segEnd =
+            cmd.line_to.absolute == StyleIsAbsolute::Yes ? p : segStart + p;
+        segStartAngle = segEndAngle = AngleOfVector(segEnd, segStart);
+        break;
+      }
+      case StylePathCommand::Tag::CurveTo: {
+        Point cp1 = cmd.curve_to.control1.ConvertsToGfxPoint();
+        Point cp2 = cmd.curve_to.control2.ConvertsToGfxPoint();
+        segEnd = cmd.curve_to.point.ConvertsToGfxPoint();
+
+        if (cmd.curve_to.absolute == StyleIsAbsolute::No) {
+          cp1 += segStart;
+          cp2 += segStart;
+          segEnd += segStart;
+        }
+
+        prevCP = cp2;
+        segStartAngle = AngleOfVector(
+            cp1 == segStart ? (cp1 == cp2 ? segEnd : cp2) : cp1, segStart);
+        segEndAngle = AngleOfVector(
+            segEnd, cp2 == segEnd ? (cp1 == cp2 ? segStart : cp1) : cp2);
+        break;
+      }
+      case StylePathCommand::Tag::QuadBezierCurveTo: {
+        Point cp1 = cmd.quad_bezier_curve_to.control1.ConvertsToGfxPoint();
+        segEnd = cmd.quad_bezier_curve_to.point.ConvertsToGfxPoint();
+
+        if (cmd.quad_bezier_curve_to.absolute == StyleIsAbsolute::No) {
+          cp1 += segStart;
+          segEnd += segStart;  // set before setting tcp2!
+        }
+
+        prevCP = cp1;
+        segStartAngle = AngleOfVector(cp1 == segStart ? segEnd : cp1, segStart);
+        segEndAngle = AngleOfVector(segEnd, cp1 == segEnd ? segStart : cp1);
+        break;
+      }
+      case StylePathCommand::Tag::EllipticalArc: {
+        const auto& arc = cmd.elliptical_arc;
+        float rx = arc.rx;
+        float ry = arc.ry;
+        float angle = arc.angle;
+        bool largeArcFlag = arc.large_arc_flag._0;
+        bool sweepFlag = arc.sweep_flag._0;
+        Point radii(arc.rx, arc.ry);
+        segEnd = arc.point.ConvertsToGfxPoint();
+        if (arc.absolute == StyleIsAbsolute::No) {
+          segEnd += segStart;
+        }
+
+        // See section F.6 of SVG 1.1 for details on what we're doing here:
+        // http://www.w3.org/TR/SVG11/implnote.html#ArcImplementationNotes
+
+        if (segStart == segEnd) {
+          // F.6.2 says "If the endpoints (x1, y1) and (x2, y2) are identical,
+          // then this is equivalent to omitting the elliptical arc segment
+          // entirely." We take that very literally here, not adding a mark, and
+          // not even setting any of the 'prev' variables so that it's as if
+          // this arc had never existed; note the difference this will make e.g.
+          // if the arc is proceeded by a bezier curve and followed by a
+          // "smooth" bezier curve of the same degree!
+          continue;
+        }
+
+        // Below we have funny interleaving of F.6.6 (Correction of out-of-range
+        // radii) and F.6.5 (Conversion from endpoint to center
+        // parameterization) which is designed to avoid some unnecessary
+        // calculations.
+
+        if (rx == 0.0 || ry == 0.0) {
+          // F.6.6 step 1 - straight line or coincidental points
+          segStartAngle = segEndAngle = AngleOfVector(segEnd, segStart);
+          break;
+        }
+
+        std::tie(rx, ry, segStartAngle, segEndAngle) =
+            ComputeSegAnglesAndCorrectRadii(segStart, segEnd, angle,
+                                            largeArcFlag, sweepFlag, rx, ry);
+        break;
+      }
+      case StylePathCommand::Tag::HorizontalLineTo: {
+        if (cmd.horizontal_line_to.absolute == StyleIsAbsolute::Yes) {
+          segEnd = Point(cmd.horizontal_line_to.x, segStart.y);
+        } else {
+          segEnd = segStart + Point(cmd.horizontal_line_to.x, 0.0f);
+        }
+        segStartAngle = segEndAngle = AngleOfVector(segEnd, segStart);
+        break;
+      }
+      case StylePathCommand::Tag::VerticalLineTo: {
+        if (cmd.vertical_line_to.absolute == StyleIsAbsolute::Yes) {
+          segEnd = Point(segStart.x, cmd.vertical_line_to.y);
+        } else {
+          segEnd = segStart + Point(0.0f, cmd.vertical_line_to.y);
+        }
+        segStartAngle = segEndAngle = AngleOfVector(segEnd, segStart);
+        break;
+      }
+      case StylePathCommand::Tag::SmoothCurveTo: {
+        Point cp1 = IsCubicType(prevSegType) ? segStart * 2 - prevCP : segStart;
+        Point cp2 = cmd.smooth_curve_to.control2.ConvertsToGfxPoint();
+        segEnd = cmd.smooth_curve_to.point.ConvertsToGfxPoint();
+
+        if (cmd.smooth_curve_to.absolute == StyleIsAbsolute::No) {
+          cp2 += segStart;
+          segEnd += segStart;
+        }
+
+        prevCP = cp2;
+        segStartAngle = AngleOfVector(
+            cp1 == segStart ? (cp1 == cp2 ? segEnd : cp2) : cp1, segStart);
+        segEndAngle = AngleOfVector(
+            segEnd, cp2 == segEnd ? (cp1 == cp2 ? segStart : cp1) : cp2);
+        break;
+      }
+      case StylePathCommand::Tag::SmoothQuadBezierCurveTo: {
+        Point cp1 =
+            IsQuadraticType(prevSegType) ? segStart * 2 - prevCP : segStart;
+        segEnd =
+            cmd.smooth_quad_bezier_curve_to.absolute == StyleIsAbsolute::Yes
+                ? cmd.smooth_quad_bezier_curve_to.point.ConvertsToGfxPoint()
+                : segStart + cmd.smooth_quad_bezier_curve_to.point
+                                 .ConvertsToGfxPoint();
+
+        prevCP = cp1;
+        segStartAngle = AngleOfVector(cp1 == segStart ? segEnd : cp1, segStart);
+        segEndAngle = AngleOfVector(segEnd, cp1 == segEnd ? segStart : cp1);
+        break;
+      }
+      case StylePathCommand::Tag::Unknown:
+        // Leave any existing marks in aMarks so we have a visual indication of
+        // when things went wrong.
+        MOZ_ASSERT_UNREACHABLE("Unknown segment type - path corruption?");
+        return;
+    }
+
+    // Set the angle of the mark at the start of this segment:
+    if (aMarks->Length()) {
+      SVGMark& mark = aMarks->LastElement();
+      if (!IsMoveto(segType) && IsMoveto(prevSegType)) {
+        // start of new subpath
+        pathStartAngle = mark.angle = segStartAngle;
+      } else if (IsMoveto(segType) && !IsMoveto(prevSegType)) {
+        // end of a subpath
+        if (prevSegType != StylePathCommand::Tag::ClosePath) {
+          mark.angle = prevSegEndAngle;
+        }
+      } else if (!(segType == StylePathCommand::Tag::ClosePath &&
+                   prevSegType == StylePathCommand::Tag::ClosePath)) {
+        mark.angle =
+            SVGContentUtils::AngleBisect(prevSegEndAngle, segStartAngle);
+      }
+    }
+
+    // Add the mark at the end of this segment, and set its position:
+    // XXX(Bug 1631371) Check if this should use a fallible operation as it
+    // pretended earlier.
+    aMarks->AppendElement(SVGMark(static_cast<float>(segEnd.x),
+                                  static_cast<float>(segEnd.y), 0.0f,
+                                  SVGMark::eMid));
+
+    if (segType == StylePathCommand::Tag::ClosePath &&
+        prevSegType != StylePathCommand::Tag::ClosePath) {
+      aMarks->LastElement().angle = aMarks->ElementAt(pathStartIndex).angle =
+          SVGContentUtils::AngleBisect(segEndAngle, pathStartAngle);
+    }
+
+    prevSegType = segType;
+    prevSegEnd = segEnd;
+    prevSegEndAngle = segEndAngle;
+  }
+
+  if (aMarks->Length()) {
+    if (prevSegType != StylePathCommand::Tag::ClosePath) {
+      aMarks->LastElement().angle = prevSegEndAngle;
+    }
+    aMarks->LastElement().type = SVGMark::eEnd;
+    aMarks->ElementAt(0).type = SVGMark::eStart;
+  }
+}
+
+size_t SVGPathData::SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const {
+  return mData.ShallowSizeOfExcludingThis(aMallocSizeOf);
+}
+
+size_t SVGPathData::SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const {
+  return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);
+}
+
+}  // namespace mozilla