gecko-dev/dom/svg/SVGGeometryElement.h

/* -*- 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/. */

#ifndef DOM_SVG_SVGGEOMETRYELEMENT_H_
#define DOM_SVG_SVGGEOMETRYELEMENT_H_

#include "mozilla/dom/SVGGraphicsElement.h"
#include "mozilla/gfx/2D.h"
#include "mozilla/dom/SVGAnimatedNumber.h"

namespace mozilla {

struct SVGMark {
  enum Type {
    eStart,
    eMid,
    eEnd,

    eTypeCount
  };

  float x, y, angle;
  Type type;
  SVGMark(float aX, float aY, float aAngle, Type aType)
      : x(aX), y(aY), angle(aAngle), type(aType) {}
};

namespace dom {

class DOMSVGAnimatedNumber;
class DOMSVGPoint;

using SVGGeometryElementBase = mozilla::dom::SVGGraphicsElement;

class SVGGeometryElement : public SVGGeometryElementBase {
 protected:
  using CapStyle = mozilla::gfx::CapStyle;
  using DrawTarget = mozilla::gfx::DrawTarget;
  using FillRule = mozilla::gfx::FillRule;
  using Float = mozilla::gfx::Float;
  using Matrix = mozilla::gfx::Matrix;
  using Path = mozilla::gfx::Path;
  using Point = mozilla::gfx::Point;
  using PathBuilder = mozilla::gfx::PathBuilder;
  using Rect = mozilla::gfx::Rect;
  using StrokeOptions = mozilla::gfx::StrokeOptions;

 public:
  explicit SVGGeometryElement(
      already_AddRefed<mozilla::dom::NodeInfo>&& aNodeInfo);

  nsresult AfterSetAttr(int32_t aNamespaceID, nsAtom* aName,
                        const nsAttrValue* aValue, const nsAttrValue* aOldValue,
                        nsIPrincipal* aSubjectPrincipal, bool aNotify) override;
  bool IsNodeOfType(uint32_t aFlags) const override;

  /**
   * Causes this element to discard any Path object that GetOrBuildPath may
   * have cached.
   */
  void ClearAnyCachedPath() final { mCachedPath = nullptr; }

  virtual bool AttributeDefinesGeometry(const nsAtom* aName);

  /**
   * Returns true if this element's geometry depends on the width or height of
   * its coordinate context (typically the viewport established by its nearest
   * <svg> ancestor). In other words, returns true if one of the attributes for
   * which AttributeDefinesGeometry returns true has a percentage value.
   *
   * This could be moved up to a more general class so it can be used for
   * non-leaf elements, but that would require care and for now there's no need.
   */
  bool GeometryDependsOnCoordCtx();

  virtual bool IsMarkable();
  virtual void GetMarkPoints(nsTArray<SVGMark>* aMarks);

  /**
   * A method that can be faster than using a Moz2D Path and calling GetBounds/
   * GetStrokedBounds on it.  It also helps us avoid rounding error for simple
   * shapes and simple transforms where the Moz2D Path backends can fail to
   * produce the clean integer bounds that content authors expect in some cases.
   *
   * If |aToNonScalingStrokeSpace| is non-null then |aBounds|, which is computed
   * in bounds space, has the property that it's the smallest (axis-aligned)
   * rectangular bound containing the image of this shape as stroked in
   * non-scaling-stroke space.  (When all transforms involved are rectilinear
   * the bounds of the image of |aBounds| in non-scaling-stroke space will be
   * tight, but if there are non-rectilinear transforms involved then that may
   * be impossible and this method will return false).
   *
   * If |aToNonScalingStrokeSpace| is non-null then |*aToNonScalingStrokeSpace|
   * must be non-singular.
   */
  virtual bool GetGeometryBounds(
      Rect* aBounds, const StrokeOptions& aStrokeOptions,
      const Matrix& aToBoundsSpace,
      const Matrix* aToNonScalingStrokeSpace = nullptr) {
    return false;
  }

  /**
   * For use with GetAsSimplePath.
   */
  class SimplePath {
   public:
    SimplePath()
        : mX(0.0), mY(0.0), mWidthOrX2(0.0), mHeightOrY2(0.0), mType(NONE) {}
    bool IsPath() const { return mType != NONE; }
    void SetRect(Float x, Float y, Float width, Float height) {
      mX = x;
      mY = y;
      mWidthOrX2 = width;
      mHeightOrY2 = height;
      mType = RECT;
    }
    Rect AsRect() const {
      MOZ_ASSERT(mType == RECT);
      return Rect(mX, mY, mWidthOrX2, mHeightOrY2);
    }
    bool IsRect() const { return mType == RECT; }
    void SetLine(Float x1, Float y1, Float x2, Float y2) {
      mX = x1;
      mY = y1;
      mWidthOrX2 = x2;
      mHeightOrY2 = y2;
      mType = LINE;
    }
    Point Point1() const {
      MOZ_ASSERT(mType == LINE);
      return Point(mX, mY);
    }
    Point Point2() const {
      MOZ_ASSERT(mType == LINE);
      return Point(mWidthOrX2, mHeightOrY2);
    }
    bool IsLine() const { return mType == LINE; }
    void Reset() { mType = NONE; }

   private:
    enum Type { NONE, RECT, LINE };
    Float mX, mY, mWidthOrX2, mHeightOrY2;
    Type mType;
  };

  /**
   * For some platforms there is significant overhead to creating and painting
   * a Moz2D Path object. For Rects and lines it is better to get the path data
   * using this method and then use the optimized DrawTarget methods for
   * filling/stroking rects and lines.
   */
  virtual void GetAsSimplePath(SimplePath* aSimplePath) {
    aSimplePath->Reset();
  }

  /**
   * Returns a Path that can be used to paint, hit-test or calculate bounds for
   * this element. May return nullptr if there is no [valid] path. The path
   * that is created may be cached and returned on subsequent calls.
   */
  virtual already_AddRefed<Path> GetOrBuildPath(const DrawTarget* aDrawTarget,
                                                FillRule fillRule);

  /**
   * The same as GetOrBuildPath, but bypasses the cache (neither returns any
   * previously cached Path, nor caches the Path that in does return).
   * this element. May return nullptr if there is no [valid] path.
   */
  virtual already_AddRefed<Path> BuildPath(PathBuilder* aBuilder) = 0;

  /**
   * Get the distances from the origin of the path segments.
   * For non-path elements that's just 0 and the total length of the shape.
   */
  virtual bool GetDistancesFromOriginToEndsOfVisibleSegments(
      FallibleTArray<double>* aOutput) {
    aOutput->Clear();
    double distances[] = {0.0, GetTotalLength()};
    return aOutput->AppendElements(Span<double>(distances), fallible);
  }

  /**
   * Returns a Path that can be used to measure the length of this elements
   * path, or to find the position at a given distance along it.
   *
   * This is currently equivalent to calling GetOrBuildPath, but it may not be
   * in the future. The reason for this function to be separate from
   * GetOrBuildPath is because SVGPathData::BuildPath inserts small lines into
   * the path if zero length subpaths are encountered, in order to implement
   * the SVG specifications requirements that zero length subpaths should
   * render circles/squares if stroke-linecap is round/square, respectively.
   * In principle these inserted lines could interfere with path measurement,
   * so we keep callers that are looking to do measurement separate in case we
   * run into problems with the inserted lines negatively affecting measuring
   * for content.
   */
  virtual already_AddRefed<Path> GetOrBuildPathForMeasuring();

  /**
   * Return |true| if some geometry properties (|x|, |y|, etc) are changed
   * because of CSS change.
   */
  bool IsGeometryChangedViaCSS(ComputedStyle const& aNewStyle,
                               ComputedStyle const& aOldStyle) const;

  /**
   * Returns the current computed value of the CSS property 'fill-rule' for
   * this element.
   */
  FillRule GetFillRule();

  enum PathLengthScaleForType { eForTextPath, eForStroking };

  /**
   * Gets the ratio of the actual element's length to the content author's
   * estimated length (as provided by the element's 'pathLength' attribute).
   * This is used to scale stroke dashing, and to scale offsets along a
   * textPath.
   */
  float GetPathLengthScale(PathLengthScaleForType aFor);

  // WebIDL
  already_AddRefed<DOMSVGAnimatedNumber> PathLength();
  MOZ_CAN_RUN_SCRIPT bool IsPointInFill(const DOMPointInit& aPoint);
  MOZ_CAN_RUN_SCRIPT bool IsPointInStroke(const DOMPointInit& aPoint);
  MOZ_CAN_RUN_SCRIPT float GetTotalLengthForBinding();
  MOZ_CAN_RUN_SCRIPT already_AddRefed<DOMSVGPoint> GetPointAtLength(
      float distance, ErrorResult& rv);

 protected:
  // SVGElement method
  NumberAttributesInfo GetNumberInfo() override;

  // d is a presentation attribute, so we would like to make sure style is
  // up-to-date. This function flushes the style if the path attribute is d.
  MOZ_CAN_RUN_SCRIPT void FlushStyleIfNeeded();

  SVGAnimatedNumber mPathLength;
  static NumberInfo sNumberInfo;
  mutable RefPtr<Path> mCachedPath;

 private:
  already_AddRefed<Path> GetOrBuildPathForHitTest();

  float GetTotalLength();
};

}  // namespace dom
}  // namespace mozilla

#endif  // DOM_SVG_SVGGEOMETRYELEMENT_H_