tor-browser

nsStyleTransformMatrix.h (6783B)

---

/* -*- 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/. */

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

#ifndef nsStyleTransformMatrix_h_
#define nsStyleTransformMatrix_h_

#include "Units.h"  // for CSSPoint
#include "mozilla/ServoStyleConsts.h"
#include "mozilla/gfx/Matrix.h"
#include "nsSize.h"

class nsIFrame;
class nsPresContext;
struct gfxQuaternion;
struct nsRect;

namespace mozilla {
struct ResolvedMotionPathData;
}  // 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 };

/**
* 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)();

 TransformReferenceBox() = default;

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

 TransformReferenceBox(const nsIFrame* aFrame,
                       const nsRect& aFallbackDimensions) {
   mFrame = aFrame;
   if (!mFrame) {
     Init(aFallbackDimensions);
   }
 }

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

 void Init(const nsRect& aDimensions) {
   MOZ_ASSERT(!mFrame && !mIsCached);
   mBox = aDimensions;
   mIsCached = true;
 }

 /**
  * 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 mBox.X();
 }
 nscoord Y() {
   EnsureDimensionsAreCached();
   return mBox.Y();
 }

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

 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 = nullptr;
 nsRect mBox;
 bool mIsCached = false;
};

float ProcessTranslatePart(
   const mozilla::LengthPercentage& aValue, TransformReferenceBox* aRefBox,
   TransformReferenceBox::DimensionGetter aDimensionGetter = nullptr);

void ProcessInterpolateMatrix(mozilla::gfx::Matrix4x4& aMatrix,
                             const mozilla::StyleTransformOperation& aOp,
                             TransformReferenceBox& aBounds);

void ProcessAccumulateMatrix(mozilla::gfx::Matrix4x4& aMatrix,
                            const mozilla::StyleTransformOperation& aOp,
                            TransformReferenceBox& aBounds);

/**
* Given a StyleTransform containing transform functions, returns a matrix
* containing the value of those functions.
*
* @param aList the transform operation list.
* @param aBounds The frame's bounding rectangle.
* @param aAppUnitsPerMatrixUnit The number of app units per device pixel.
*/
mozilla::gfx::Matrix4x4 ReadTransforms(const mozilla::StyleTransform& aList,
                                      TransformReferenceBox& aBounds,
                                      float aAppUnitsPerMatrixUnit);

// Generate the gfx::Matrix for CSS Transform Module Level 2.
// https://drafts.csswg.org/css-transforms-2/#ctm
mozilla::gfx::Matrix4x4 ReadTransforms(
   const mozilla::StyleTranslate&, const mozilla::StyleRotate&,
   const mozilla::StyleScale&, const mozilla::ResolvedMotionPathData* aMotion,
   const mozilla::StyleTransform&, TransformReferenceBox& aRefBox,
   float aAppUnitsPerMatrixUnit);

/**
* Given the x and y values, compute the 2d position with respect to the given
* a reference box size that these values describe, in CSS pixels.
*/
mozilla::CSSPoint Convert2DPosition(const mozilla::LengthPercentage& aX,
                                   const mozilla::LengthPercentage& aY,
                                   const mozilla::CSSSize& aSize);

/**
* Given the x and y values, compute the 2d position with respect to the given
* TransformReferenceBox that these values describe, in CSS pixels.
*/
mozilla::CSSPoint Convert2DPosition(const mozilla::LengthPercentage& aX,
                                   const mozilla::LengthPercentage& aY,
                                   TransformReferenceBox& aRefBox);

/**
* Given the x and y values, compute the 2d position with respect to the given
* TransformReferenceBox that these values describe, in device pixels.
*/
mozilla::gfx::Point Convert2DPosition(const mozilla::LengthPercentage& aX,
                                     const mozilla::LengthPercentage& aY,
                                     TransformReferenceBox& aRefBox,
                                     int32_t aAppUnitsPerDevPixel);

}  // namespace nsStyleTransformMatrix

#endif