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gecko-dev/layout/base/MotionPathUtils.cpp

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/* -*- 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 "mozilla/MotionPathUtils.h"
#include "gfxPlatform.h"
#include "mozilla/dom/SVGPathData.h"
#include "mozilla/gfx/2D.h"
#include "mozilla/gfx/Matrix.h"
#include "mozilla/layers/LayersMessages.h"
#include "mozilla/RefPtr.h"
#include "nsIFrame.h"
#include "nsStyleTransformMatrix.h"
#include <math.h>
namespace mozilla {
using nsStyleTransformMatrix::TransformReferenceBox;
RayReferenceData::RayReferenceData(const nsIFrame* aFrame) {
// We use GetContainingBlock() for now. TYLin said this function is buggy in
// modern CSS layout, but is ok for most cases.
// FIXME: Bug 1581237: This is still not clear that which box we should use
// for calculating the path length. We may need to update this.
// https://github.com/w3c/fxtf-drafts/issues/369
// FIXME: Bug 1579294: SVG layout may get a |container| with empty mRect
// (e.g. nsSVGOuterSVGAnonChildFrame), which makes the path length zero.
const nsIFrame* container = aFrame->GetContainingBlock();
if (!container) {
// If there is no parent frame, it's impossible to calculate the path
// length, so does the path.
return;
}
// The initial position is (0, 0) in |aFrame|, and we have to transform it
// into the space of |container|, so use GetOffsetsTo() to get the delta
// value.
// FIXME: Bug 1559232: The initial position will be adjusted after
// supporting `offset-position`.
mInitialPosition = CSSPoint::FromAppUnits(aFrame->GetOffsetTo(container));
// FIXME: We need a better definition for containing box in the spec. For now,
// we use border box for calculation.
// https://github.com/w3c/fxtf-drafts/issues/369
mContainingBlockRect =
CSSRect::FromAppUnits(container->GetRectRelativeToSelf());
}
// The distance is measured between the initial position and the intersection of
// the ray with the box
// https://drafts.fxtf.org/motion-1/#size-sides
static CSSCoord ComputeSides(const CSSPoint& aInitialPosition,
const CSSSize& aContainerSize,
const StyleAngle& aAngle) {
// Given an acute angle |theta| (i.e. |t|) of a right-angled triangle, the
// hypotenuse |h| is the side that connects the two acute angles. The side
// |b| adjacent to |theta| is the side of the triangle that connects |theta|
// to the right angle.
//
// e.g. if the angle |t| is 0 ~ 90 degrees, and b * tan(theta) <= b',
// h = b / cos(t):
// b*tan(t)
// (0, 0) #--------*-----*--# (aContainerSize.width, 0)
// | | / |
// | | / |
// | b h |
// | |t/ |
// | |/ |
// (aInitialPosition) *---b'---* (aContainerSize.width, aInitialPosition.y)
// | | |
// | | |
// | | |
// | | |
// | | |
// #-----------------# (aContainerSize.width,
// (0, aContainerSize.height) aContainerSize.height)
double theta = aAngle.ToRadians();
double sint = std::sin(theta);
double cost = std::cos(theta);
double b = cost >= 0 ? aInitialPosition.y
: aContainerSize.height - aInitialPosition.y;
double bPrime = sint >= 0 ? aContainerSize.width - aInitialPosition.x
: aInitialPosition.x;
sint = std::fabs(sint);
cost = std::fabs(cost);
// If |b * tan(theta)| is larger than |bPrime|, the intersection is
// on the other side, and |b'| is the opposite side of angle |theta| in this
// case.
//
// e.g. If b * tan(theta) > b', h = b' / sin(theta):
// *----*
// | |
// | /|
// b /t|
// |t/ |
// |/ |
// *-b'-*
if (b * sint > bPrime * cost) {
return bPrime / sint;
}
return b / cost;
}
static CSSCoord ComputeRayPathLength(const StyleRaySize aRaySizeType,
const StyleAngle& aAngle,
const RayReferenceData& aRayData) {
if (aRaySizeType == StyleRaySize::Sides) {
// If the initial position is not within the box, the distance is 0.
if (!aRayData.mContainingBlockRect.Contains(aRayData.mInitialPosition)) {
return 0.0;
}
return ComputeSides(aRayData.mInitialPosition,
aRayData.mContainingBlockRect.Size(), aAngle);
}
// left: the length between the initial point and the left side.
// right: the length between the initial point and the right side.
// top: the length between the initial point and the top side.
// bottom: the lenght between the initial point and the bottom side.
CSSCoord left = std::abs(aRayData.mInitialPosition.x);
CSSCoord right = std::abs(aRayData.mContainingBlockRect.width -
aRayData.mInitialPosition.x);
CSSCoord top = std::abs(aRayData.mInitialPosition.y);
CSSCoord bottom = std::abs(aRayData.mContainingBlockRect.height -
aRayData.mInitialPosition.y);
switch (aRaySizeType) {
case StyleRaySize::ClosestSide:
return std::min({left, right, top, bottom});
case StyleRaySize::FarthestSide:
return std::max({left, right, top, bottom});
case StyleRaySize::ClosestCorner:
case StyleRaySize::FarthestCorner: {
CSSCoord h = 0;
CSSCoord v = 0;
if (aRaySizeType == StyleRaySize::ClosestCorner) {
h = std::min(left, right);
v = std::min(top, bottom);
} else {
h = std::max(left, right);
v = std::max(top, bottom);
}
return sqrt(h.value * h.value + v.value * v.value);
}
default:
MOZ_ASSERT_UNREACHABLE("Unsupported ray size");
}
return 0.0;
}
static void ApplyRotationAndMoveRayToXAxis(
const StyleOffsetRotate& aOffsetRotate, const StyleAngle& aRayAngle,
AutoTArray<gfx::Point, 4>& aVertices) {
const StyleAngle directionAngle = aRayAngle - StyleAngle{90.0f};
// Get the final rotation which includes the direction angle and
// offset-rotate.
const StyleAngle rotateAngle =
(aOffsetRotate.auto_ ? directionAngle : StyleAngle{0.0f}) +
aOffsetRotate.angle;
// This is the rotation to rotate ray to positive x-axis (i.e. 90deg).
const StyleAngle rayToXAxis = StyleAngle{90.0} - aRayAngle;
gfx::Matrix m;
m.PreRotate((rotateAngle + rayToXAxis).ToRadians());
for (gfx::Point& p : aVertices) {
p = m.TransformPoint(p);
}
}
class RayPointComparator {
public:
bool Equals(const gfx::Point& a, const gfx::Point& b) const {
return std::fabs(a.y) == std::fabs(b.y);
}
bool LessThan(const gfx::Point& a, const gfx::Point& b) const {
return std::fabs(a.y) > std::fabs(b.y);
}
};
// Note: the calculation of contain doesn't take other transform-like properties
// into account. The spec doesn't mention the co-operation for this, so for now,
// we assume we only need to take motion-path into account.
static CSSCoord ComputeRayUsedDistance(const RayFunction& aRay,
const LengthPercentage& aDistance,
const StyleOffsetRotate& aRotate,
const StylePositionOrAuto& aAnchor,
const CSSPoint& aTransformOrigin,
TransformReferenceBox& aRefBox,
const CSSCoord& aPathLength) {
CSSCoord usedDistance = aDistance.ResolveToCSSPixels(aPathLength);
if (!aRay.contain) {
return usedDistance;
}
// We have to simulate the 4 vertices to check if any of them is outside the
// path circle. Here, we create a 2D Cartesian coordinate system and its
// origin is at the anchor point of the box. And then apply the rotation on
// these 4 vertices, calculate the range of |usedDistance| which makes the box
// entirely contained within the path.
// Note:
// "Contained within the path" means the rectangle is inside a circle whose
// radius is |aPathLength|.
CSSPoint usedAnchor = aTransformOrigin;
CSSSize size =
CSSPixel::FromAppUnits(nsSize(aRefBox.Width(), aRefBox.Height()));
if (!aAnchor.IsAuto()) {
const StylePosition& anchor = aAnchor.AsPosition();
usedAnchor.x = anchor.horizontal.ResolveToCSSPixels(size.width);
usedAnchor.y = anchor.vertical.ResolveToCSSPixels(size.height);
}
AutoTArray<gfx::Point, 4> vertices = {
{-usedAnchor.x, -usedAnchor.y},
{size.width - usedAnchor.x, -usedAnchor.y},
{size.width - usedAnchor.x, size.height - usedAnchor.y},
{-usedAnchor.x, size.height - usedAnchor.y}};
ApplyRotationAndMoveRayToXAxis(aRotate, aRay.angle, vertices);
// We have to check if all 4 vertices are inside the circle with radius |r|.
// Assume the position of the vertex is (x, y), and the box is moved by
// |usedDistance| along the path:
//
// (usedDistance + x)^2 + y^2 <= r^2
// ==> (usedDistance + x)^2 <= r^2 - y^2 = d
// ==> -x - sqrt(d) <= used distance <= -x + sqrt(d)
//
// Note: |usedDistance| is added into |x| because we convert the ray function
// to 90deg, x-axis):
float upperMin = std::numeric_limits<float>::max();
float lowerMax = std::numeric_limits<float>::min();
bool shouldIncreasePathLength = false;
for (const gfx::Point& p : vertices) {
float d = aPathLength.value * aPathLength.value - p.y * p.y;
if (d < 0) {
// Impossible to make the box inside the path circle. Need to increase
// the path length.
shouldIncreasePathLength = true;
break;
}
float sqrtD = sqrt(d);
upperMin = std::min(upperMin, -p.x + sqrtD);
lowerMax = std::max(lowerMax, -p.x - sqrtD);
}
if (!shouldIncreasePathLength) {
return std::max(lowerMax, std::min(upperMin, (float)usedDistance));
}
// Sort by the absolute value of y, so the first vertex of the each pair of
// vertices we check has a larger y value. (i.e. |yi| is always larger than or
// equal to |yj|.)
vertices.Sort(RayPointComparator());
// Assume we set |usedDistance| to |-vertices[0].x|, so the current radius is
// fabs(vertices[0].y). This is a possible solution.
double radius = std::fabs(vertices[0].y);
usedDistance = -vertices[0].x;
const double epsilon = 1e-5;
for (size_t i = 0; i < 3; ++i) {
for (size_t j = i + 1; j < 4; ++j) {
double xi = vertices[i].x;
double yi = vertices[i].y;
double xj = vertices[j].x;
double yj = vertices[j].y;
double dx = xi - xj;
// Check if any path that enclosed vertices[i] would also enclose
// vertices[j].
//
// For example, the initial setup:
// * (0, yi)
// |
// r
// | * (xj - xi, yj)
// xi | dx
// ----*-----------*----------*---
// (anchor point) | (0, 0)
//
// Assuming (0, yi) is on the path and (xj - xi, yj) is inside the path
// circle, we should use the inequality to check this:
// (xj - xi)^2 + yj^2 <= yi^2
//
// After the first iterations, the updated inequality is:
// (dx + d)^2 + yj^2 <= yi^2 + d^2
// ==> dx^2 + 2dx*d + yj^2 <= yi^2
// ==> dx^2 + yj^2 <= yi^2 - 2dx*d <= yi^2
// , |d| is the difference (or offset) between the old |usedDistance| and
// new |usedDistance|.
//
// Note: `2dx * d` must be positive because
// 1. if |xj| is larger than |xi|, only negative |d| could be used to get
// a new path length which encloses both vertices.
// 2. if |xj| is smaller than |xi|, only positive |d| could be used to get
// a new path length which encloses both vertices.
if (dx * dx + yj * yj <= yi * yi + epsilon) {
continue;
}
// We have to find a new usedDistance which let both vertices[i] and
// vertices[j] be on the path.
// (usedDistance + xi)^2 + yi^2 = (usedDistance + xj)^2 + yj^2
// = radius^2
// ==> usedDistance = (xj^2 + yj^2 - xi^2 - yi^2) / 2(xi-xj)
//
// Note: it's impossible to have a "divide by zero" problem here.
// If |dx| is zero, the if-condition above should always be true and so
// we skip the calculation.
double newUsedDistance =
(xj * xj + yj * yj - xi * xi - yi * yi) / dx / 2.0;
// Then, move vertices[i] and vertices[j] by |newUsedDistance|.
xi += newUsedDistance; // or xj += newUsedDistance; if we use |xj| to get
// |newRadius|.
double newRadius = sqrt(xi * xi + yi * yi);
if (newRadius > radius) {
// We have to increase the path length to make sure both vertices[i] and
// vertices[j] are contained by this new path length.
radius = newRadius;
usedDistance = (float)newUsedDistance;
}
}
}
return usedDistance;
}
/* static */
CSSPoint MotionPathUtils::ComputeAnchorPointAdjustment(const nsIFrame& aFrame) {
if (!aFrame.HasAnyStateBits(NS_FRAME_SVG_LAYOUT)) {
return {};
}
auto transformBox = aFrame.StyleDisplay()->mTransformBox;
if (transformBox == StyleGeometryBox::ViewBox ||
transformBox == StyleGeometryBox::BorderBox) {
return {};
}
if (aFrame.IsFrameOfType(nsIFrame::eSVGContainer)) {
nsRect boxRect = nsLayoutUtils::ComputeGeometryBox(
const_cast<nsIFrame*>(&aFrame), StyleGeometryBox::FillBox);
return CSSPoint::FromAppUnits(boxRect.TopLeft());
}
return CSSPoint::FromAppUnits(aFrame.GetPosition());
}
/* static */
Maybe<ResolvedMotionPathData> MotionPathUtils::ResolveMotionPath(
const OffsetPathData& aPath, const LengthPercentage& aDistance,
const StyleOffsetRotate& aRotate, const StylePositionOrAuto& aAnchor,
const CSSPoint& aTransformOrigin, TransformReferenceBox& aRefBox,
const CSSPoint& aAnchorPointAdjustment) {
if (aPath.IsNone()) {
return Nothing();
}
// Compute the point and angle for creating the equivalent translate and
// rotate.
double directionAngle = 0.0;
gfx::Point point;
if (aPath.IsPath()) {
const auto& path = aPath.AsPath();
if (!path.mGfxPath) {
// Empty gfx::Path means it is path('') (i.e. empty path string).
return Nothing();
}
// Per the spec, we have to convert offset distance to pixels, with 100%
// being converted to total length. So here |gfxPath| is built with CSS
// pixel, and we calculate |pathLength| and |computedDistance| with CSS
// pixel as well.
gfx::Float pathLength = path.mGfxPath->ComputeLength();
gfx::Float usedDistance =
aDistance.ResolveToCSSPixels(CSSCoord(pathLength));
if (path.mIsClosedIntervals) {
// Per the spec, let used offset distance be equal to offset distance
// modulus the total length of the path. If the total length of the path
// is 0, used offset distance is also 0.
usedDistance = pathLength > 0.0 ? fmod(usedDistance, pathLength) : 0.0;
// We make sure |usedDistance| is 0.0 or a positive value.
// https://github.com/w3c/fxtf-drafts/issues/339
if (usedDistance < 0.0) {
usedDistance += pathLength;
}
} else {
// Per the spec, for unclosed interval, let used offset distance be equal
// to offset distance clamped by 0 and the total length of the path.
usedDistance = clamped(usedDistance, 0.0f, pathLength);
}
gfx::Point tangent;
point = path.mGfxPath->ComputePointAtLength(usedDistance, &tangent);
directionAngle = (double)atan2(tangent.y, tangent.x); // In Radian.
} else if (aPath.IsRay()) {
const auto& ray = aPath.AsRay();
MOZ_ASSERT(ray.mRay);
CSSCoord pathLength =
ComputeRayPathLength(ray.mRay->size, ray.mRay->angle, ray.mData);
CSSCoord usedDistance =
ComputeRayUsedDistance(*ray.mRay, aDistance, aRotate, aAnchor,
aTransformOrigin, aRefBox, pathLength);
// 0deg pointing up and positive angles representing clockwise rotation.
directionAngle =
StyleAngle{ray.mRay->angle.ToDegrees() - 90.0f}.ToRadians();
point.x = usedDistance * cos(directionAngle);
point.y = usedDistance * sin(directionAngle);
} else {
MOZ_ASSERT_UNREACHABLE("Unsupported offset-path value");
return Nothing();
}
// If |rotate.auto_| is true, the element should be rotated by the angle of
// the direction (i.e. directional tangent vector) of the offset-path, and the
// computed value of <angle> is added to this.
// Otherwise, the element has a constant clockwise rotation transformation
// applied to it by the specified rotation angle. (i.e. Don't need to
// consider the direction of the path.)
gfx::Float angle = static_cast<gfx::Float>(
(aRotate.auto_ ? directionAngle : 0.0) + aRotate.angle.ToRadians());
// Compute the offset for motion path translate.
// Bug 1559232: the translate parameters will be adjusted more after we
// support offset-position.
// Per the spec, the default offset-anchor is `auto`, so initialize the anchor
// point to transform-origin.
CSSPoint anchorPoint(aTransformOrigin);
gfx::Point shift;
if (!aAnchor.IsAuto()) {
const auto& pos = aAnchor.AsPosition();
anchorPoint = nsStyleTransformMatrix::Convert2DPosition(
pos.horizontal, pos.vertical, aRefBox);
// We need this value to shift the origin from transform-origin to
// offset-anchor (and vice versa).
// See nsStyleTransformMatrix::ReadTransform for more details.
shift = (anchorPoint - aTransformOrigin).ToUnknownPoint();
}
anchorPoint += aAnchorPointAdjustment;
return Some(ResolvedMotionPathData{point - anchorPoint.ToUnknownPoint(),
angle, shift});
}
static OffsetPathData GenerateOffsetPathData(const nsIFrame* aFrame) {
const StyleOffsetPath& path = aFrame->StyleDisplay()->mOffsetPath;
switch (path.tag) {
case StyleOffsetPath::Tag::Path: {
const StyleSVGPathData& pathData = path.AsPath();
RefPtr<gfx::Path> gfxPath =
aFrame->GetProperty(nsIFrame::OffsetPathCache());
MOZ_ASSERT(
gfxPath || pathData._0.IsEmpty(),
"Should have a valid cached gfx::Path or an empty path string");
return OffsetPathData::Path(pathData, gfxPath.forget());
}
case StyleOffsetPath::Tag::Ray:
return OffsetPathData::Ray(path.AsRay(), RayReferenceData(aFrame));
case StyleOffsetPath::Tag::None:
return OffsetPathData::None();
default:
MOZ_ASSERT_UNREACHABLE("Unknown offset-path");
return OffsetPathData::None();
}
}
/* static*/
Maybe<ResolvedMotionPathData> MotionPathUtils::ResolveMotionPath(
const nsIFrame* aFrame, TransformReferenceBox& aRefBox) {
MOZ_ASSERT(aFrame);
const nsStyleDisplay* display = aFrame->StyleDisplay();
// FIXME: It's possible to refactor the calculation of transform-origin, so we
// could calculate from the caller, and reuse the value in nsDisplayList.cpp.
CSSPoint transformOrigin = nsStyleTransformMatrix::Convert2DPosition(
display->mTransformOrigin.horizontal, display->mTransformOrigin.vertical,
aRefBox);
return ResolveMotionPath(GenerateOffsetPathData(aFrame),
display->mOffsetDistance, display->mOffsetRotate,
display->mOffsetAnchor, transformOrigin, aRefBox,
ComputeAnchorPointAdjustment(*aFrame));
}
static OffsetPathData GenerateOffsetPathData(
const StyleOffsetPath& aPath, const RayReferenceData& aRayReferenceData,
gfx::Path* aCachedMotionPath) {
switch (aPath.tag) {
case StyleOffsetPath::Tag::Path: {
const StyleSVGPathData& pathData = aPath.AsPath();
// If aCachedMotionPath is valid, we have a fixed path.
// This means we have pre-built it already and no need to update.
RefPtr<gfx::Path> path = aCachedMotionPath;
if (!path) {
RefPtr<gfx::PathBuilder> builder =
MotionPathUtils::GetCompositorPathBuilder();
path = MotionPathUtils::BuildPath(pathData, builder);
}
return OffsetPathData::Path(pathData, path.forget());
}
case StyleOffsetPath::Tag::Ray:
return OffsetPathData::Ray(aPath.AsRay(), aRayReferenceData);
case StyleOffsetPath::Tag::None:
default:
return OffsetPathData::None();
}
}
/* static */
Maybe<ResolvedMotionPathData> MotionPathUtils::ResolveMotionPath(
const StyleOffsetPath* aPath, const StyleLengthPercentage* aDistance,
const StyleOffsetRotate* aRotate, const StylePositionOrAuto* aAnchor,
const Maybe<layers::MotionPathData>& aMotionPathData,
TransformReferenceBox& aRefBox, gfx::Path* aCachedMotionPath) {
if (!aPath) {
return Nothing();
}
MOZ_ASSERT(aMotionPathData);
auto zeroOffsetDistance = LengthPercentage::Zero();
auto autoOffsetRotate = StyleOffsetRotate{true, StyleAngle::Zero()};
auto autoOffsetAnchor = StylePositionOrAuto::Auto();
return ResolveMotionPath(
GenerateOffsetPathData(*aPath, aMotionPathData->rayReferenceData(),
aCachedMotionPath),
aDistance ? *aDistance : zeroOffsetDistance,
aRotate ? *aRotate : autoOffsetRotate,
aAnchor ? *aAnchor : autoOffsetAnchor, aMotionPathData->origin(), aRefBox,
aMotionPathData->anchorAdjustment());
}
/* static */
StyleSVGPathData MotionPathUtils::NormalizeSVGPathData(
const StyleSVGPathData& aPath) {
StyleSVGPathData n;
Servo_SVGPathData_Normalize(&aPath, &n);
return n;
}
/* static */
already_AddRefed<gfx::Path> MotionPathUtils::BuildPath(
const StyleSVGPathData& aPath, gfx::PathBuilder* aPathBuilder) {
if (!aPathBuilder) {
return nullptr;
}
const Span<const StylePathCommand>& path = aPath._0.AsSpan();
return SVGPathData::BuildPath(path, aPathBuilder, StyleStrokeLinecap::Butt,
0.0);
}
/* static */
already_AddRefed<gfx::PathBuilder> MotionPathUtils::GetCompositorPathBuilder() {
// FIXME: Perhaps we need a PathBuilder which is independent on the backend.
RefPtr<gfx::PathBuilder> builder =
gfxPlatform::Initialized()
? gfxPlatform::GetPlatform()
->ScreenReferenceDrawTarget()
->CreatePathBuilder(gfx::FillRule::FILL_WINDING)
: gfx::Factory::CreateSimplePathBuilder();
return builder.forget();
}
} // namespace mozilla
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