layout/style/nsStyleTransformMatrix.h
author Boris Chiou <boris.chiou@gmail.com>
Wed, 07 Jun 2017 11:25:14 +0800
changeset 413263 ab49fc64a4bf9271d2b33575907f7d5e6827a1f7
parent 390312 72d2c783f673c71ab1011e185a10f672a9b8220d
child 415707 37c332642a18ce4c89f359a46ae014ce92044ef2
permissions -rw-r--r--
Bug 1335998 - Part 2: Delegate matrix decomposition/interpolation/recomposition to Servo. r=birtles,manishearth Use Servo backend to decompose/interpolate/recompose matrices on both main thread and compositor thread. Note: Due there may be differences in precision used to represent the components, and the computation of matrix interpolation are not exactly same (still following the formulas in spec). There are some tiny differences between the interpolation results of 2d/3d matrices on Gecko and Servo, especially if there is skew() or any 3d transform function. MozReview-Commit-ID: 6T8vlR4MJGr

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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/. */

/*
 * A class representing three matrices that can be used for style transforms.
 */

#ifndef nsStyleTransformMatrix_h_
#define nsStyleTransformMatrix_h_

#include "mozilla/EnumeratedArray.h"
#include "nsCSSValue.h"

#include <limits>

class nsIFrame;
class nsStyleContext;
class nsPresContext;
struct gfxQuaternion;
struct nsRect;
namespace mozilla {
class RuleNodeCacheConditions;
} // namespace mozilla

/**
 * A helper to generate gfxMatrixes from css transform functions.
 */
namespace nsStyleTransformMatrix {
  // The operator passed to Servo backend.
  enum class MatrixTransformOperator: uint8_t {
    Interpolate,
    Accumulate
  };

  // Function for applying perspective() transform function. We treat
  // any value smaller than epsilon as perspective(infinity), which
  // follows CSSWG's resolution on perspective(0). See bug 1316236.
  inline void ApplyPerspectiveToMatrix(mozilla::gfx::Matrix4x4& aMatrix,
                                       float aDepth)
  {
    if (aDepth >= std::numeric_limits<float>::epsilon()) {
      aMatrix.Perspective(aDepth);
    }
  }

  /**
   * This class provides on-demand access to the 'reference box' for CSS
   * transforms (needed to resolve percentage values in 'transform',
   * 'transform-origin', etc.):
   *
   *    http://dev.w3.org/csswg/css-transforms/#reference-box
   *
   * This class helps us to avoid calculating the reference box unless and
   * until it is actually needed. This is important for performance when
   * transforms are applied to SVG elements since the reference box for SVG is
   * much more expensive to calculate (than for elements with a CSS layout box
   * where we can use the nsIFrame's cached mRect), much more common (than on
   * HTML), and yet very rarely have percentage values that require the
   * reference box to be resolved. We also don't want to cause SVG frames to
   * cache lots of ObjectBoundingBoxProperty objects that aren't needed.
   *
   * If UNIFIED_CONTINUATIONS (experimental, and currently broke) is defined,
   * we consider the reference box for non-SVG frames to be the smallest
   * rectangle containing a frame and all of its continuations.  For example,
   * if there is a <span> element with several continuations split over
   * several lines, this function will return the rectangle containing all of
   * those continuations. (This behavior is not currently in a spec.)
   */
  class MOZ_STACK_CLASS TransformReferenceBox final {
  public:
    typedef nscoord (TransformReferenceBox::*DimensionGetter)();

    explicit TransformReferenceBox()
      : mFrame(nullptr)
      , mIsCached(false)
    {}

    explicit TransformReferenceBox(const nsIFrame* aFrame)
      : mFrame(aFrame)
      , mIsCached(false)
    {
      MOZ_ASSERT(mFrame);
    }

    explicit TransformReferenceBox(const nsIFrame* aFrame,
                                   const nsSize& aFallbackDimensions)
    {
      mFrame = aFrame;
      mIsCached = false;
      if (!mFrame) {
        Init(aFallbackDimensions);
      }
    }

    void Init(const nsIFrame* aFrame) {
      MOZ_ASSERT(!mFrame && !mIsCached);
      mFrame = aFrame;
    }

    void Init(const nsSize& aDimensions);

    /**
     * The offset of the reference box from the nsIFrame's TopLeft(). This
     * is non-zero only in the case of SVG content. If we can successfully
     * implement UNIFIED_CONTINUATIONS at some point in the future then it
     * may also be non-zero for non-SVG content.
     */
    nscoord X() {
      EnsureDimensionsAreCached();
      return mX;
    }
    nscoord Y() {
      EnsureDimensionsAreCached();
      return mY;
    }

    /**
     * The size of the reference box.
     */
    nscoord Width() {
      EnsureDimensionsAreCached();
      return mWidth;
    }
    nscoord Height() {
      EnsureDimensionsAreCached();
      return mHeight;
    }

    bool IsEmpty() {
      return !mFrame;
    }

  private:
    // We don't really need to prevent copying, but since none of our consumers
    // currently need to copy, preventing copying may allow us to catch some
    // cases where we use pass-by-value instead of pass-by-reference.
    TransformReferenceBox(const TransformReferenceBox&) = delete;

    void EnsureDimensionsAreCached();

    const nsIFrame* mFrame;
    nscoord mX, mY, mWidth, mHeight;
    bool mIsCached;
  };

  /**
   * Return the transform function, as an nsCSSKeyword, for the given
   * nsCSSValue::Array from a transform list.
   */
  nsCSSKeyword TransformFunctionOf(const nsCSSValue::Array* aData);

  void SetIdentityMatrix(nsCSSValue::Array* aMatrix);

  float ProcessTranslatePart(const nsCSSValue& aValue,
                             nsStyleContext* aContext,
                             nsPresContext* aPresContext,
                             mozilla::RuleNodeCacheConditions& aConditions,
                             TransformReferenceBox* aRefBox,
                             TransformReferenceBox::DimensionGetter aDimensionGetter = nullptr);

  void
  ProcessInterpolateMatrix(mozilla::gfx::Matrix4x4& aMatrix,
                           const nsCSSValue::Array* aData,
                           nsStyleContext* aContext,
                           nsPresContext* aPresContext,
                           mozilla::RuleNodeCacheConditions& aConditions,
                           TransformReferenceBox& aBounds,
                           bool* aContains3dTransform);

  void
  ProcessAccumulateMatrix(mozilla::gfx::Matrix4x4& aMatrix,
                          const nsCSSValue::Array* aData,
                          nsStyleContext* aContext,
                          nsPresContext* aPresContext,
                          mozilla::RuleNodeCacheConditions& aConditions,
                          TransformReferenceBox& aBounds,
                          bool* aContains3dTransform);

  /**
   * Given an nsCSSValueList containing -moz-transform functions,
   * returns a matrix containing the value of those functions.
   *
   * @param aData The nsCSSValueList containing the transform functions
   * @param aContext The style context, used for unit conversion.
   * @param aPresContext The presentation context, used for unit conversion.
   * @param aConditions Set to uncachable (by calling SetUncacheable()) if the
   *   result cannot be cached in the rule tree, otherwise untouched.
   * @param aBounds The frame's bounding rectangle.
   * @param aAppUnitsPerMatrixUnit The number of app units per device pixel.
   * @param aContains3dTransform [out] Set to true if aList contains at least
   *   one 3d transform function (as defined in the CSS transforms
   *   specification), false otherwise.
   *
   * aContext and aPresContext may be null if all of the (non-percent)
   * length values in aData are already known to have been converted to
   * eCSSUnit_Pixel (as they are in an StyleAnimationValue)
   */
  mozilla::gfx::Matrix4x4 ReadTransforms(const nsCSSValueList* aList,
                                         nsStyleContext* aContext,
                                         nsPresContext* aPresContext,
                                         mozilla::RuleNodeCacheConditions& aConditions,
                                         TransformReferenceBox& aBounds,
                                         float aAppUnitsPerMatrixUnit,
                                         bool* aContains3dTransform);

  // Shear type for decomposition.
  enum class ShearType {
    XYSHEAR,
    XZSHEAR,
    YZSHEAR,
    Count
  };
  using ShearArray =
    mozilla::EnumeratedArray<ShearType, ShearType::Count, float>;

  /*
   * Implements the 2d transform matrix decomposition algorithm.
   */
  bool Decompose2DMatrix(const mozilla::gfx::Matrix& aMatrix,
                         mozilla::gfx::Point3D& aScale,
                         ShearArray& aShear,
                         gfxQuaternion& aRotate,
                         mozilla::gfx::Point3D& aTranslate);
  /*
   * Implements the 3d transform matrix decomposition algorithm.
   */
  bool Decompose3DMatrix(const mozilla::gfx::Matrix4x4& aMatrix,
                         mozilla::gfx::Point3D& aScale,
                         ShearArray& aShear,
                         gfxQuaternion& aRotate,
                         mozilla::gfx::Point3D& aTranslate,
                         mozilla::gfx::Point4D& aPerspective);

  mozilla::gfx::Matrix CSSValueArrayTo2DMatrix(nsCSSValue::Array* aArray);
  mozilla::gfx::Matrix4x4 CSSValueArrayTo3DMatrix(nsCSSValue::Array* aArray);

  gfxSize GetScaleValue(const nsCSSValueSharedList* aList,
                        const nsIFrame* aForFrame);
} // namespace nsStyleTransformMatrix

#endif