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gecko-dev/layout/painting/nsCSSRenderingGradients.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/. */
/* utility functions for drawing borders and backgrounds */
#include "nsCSSRenderingGradients.h"
#include <tuple>
#include "gfx2DGlue.h"
#include "mozilla/ArrayUtils.h"
#include "mozilla/ComputedStyle.h"
#include "mozilla/DebugOnly.h"
#include "mozilla/gfx/2D.h"
#include "mozilla/gfx/Helpers.h"
#include "mozilla/MathAlgorithms.h"
#include "mozilla/ProfilerLabels.h"
#include "nsLayoutUtils.h"
#include "nsStyleConsts.h"
#include "nsPresContext.h"
#include "nsPoint.h"
#include "nsRect.h"
#include "nsCSSColorUtils.h"
#include "gfxContext.h"
#include "nsStyleStructInlines.h"
#include "nsCSSProps.h"
#include "gfxUtils.h"
#include "gfxGradientCache.h"
#include "mozilla/layers/StackingContextHelper.h"
#include "mozilla/layers/WebRenderLayerManager.h"
#include "mozilla/webrender/WebRenderTypes.h"
#include "mozilla/webrender/WebRenderAPI.h"
#include "Units.h"
#include "mozilla/StaticPrefs_layout.h"
using namespace mozilla;
using namespace mozilla::gfx;
static CSSPoint ResolvePosition(const Position& aPos, const CSSSize& aSize) {
CSSCoord h = aPos.horizontal.ResolveToCSSPixels(aSize.width);
CSSCoord v = aPos.vertical.ResolveToCSSPixels(aSize.height);
return CSSPoint(h, v);
}
// Given a box with size aBoxSize and origin (0,0), and an angle aAngle,
// and a starting point for the gradient line aStart, find the endpoint of
// the gradient line --- the intersection of the gradient line with a line
// perpendicular to aAngle that passes through the farthest corner in the
// direction aAngle.
static CSSPoint ComputeGradientLineEndFromAngle(const CSSPoint& aStart,
double aAngle,
const CSSSize& aBoxSize) {
double dx = cos(-aAngle);
double dy = sin(-aAngle);
CSSPoint farthestCorner(dx > 0 ? aBoxSize.width : 0,
dy > 0 ? aBoxSize.height : 0);
CSSPoint delta = farthestCorner - aStart;
double u = delta.x * dy - delta.y * dx;
return farthestCorner + CSSPoint(-u * dy, u * dx);
}
// Compute the start and end points of the gradient line for a linear gradient.
static std::tuple<CSSPoint, CSSPoint> ComputeLinearGradientLine(
nsPresContext* aPresContext, const StyleGradient& aGradient,
const CSSSize& aBoxSize) {
using X = StyleHorizontalPositionKeyword;
using Y = StyleVerticalPositionKeyword;
const StyleLineDirection& direction = aGradient.AsLinear().direction;
const bool isModern =
aGradient.AsLinear().compat_mode == StyleGradientCompatMode::Modern;
CSSPoint center(aBoxSize.width / 2, aBoxSize.height / 2);
switch (direction.tag) {
case StyleLineDirection::Tag::Angle: {
double angle = direction.AsAngle().ToRadians();
if (isModern) {
angle = M_PI_2 - angle;
}
CSSPoint end = ComputeGradientLineEndFromAngle(center, angle, aBoxSize);
CSSPoint start = CSSPoint(aBoxSize.width, aBoxSize.height) - end;
return {start, end};
}
case StyleLineDirection::Tag::Vertical: {
CSSPoint start(center.x, 0);
CSSPoint end(center.x, aBoxSize.height);
if (isModern == (direction.AsVertical() == Y::Top)) {
std::swap(start.y, end.y);
}
return {start, end};
}
case StyleLineDirection::Tag::Horizontal: {
CSSPoint start(0, center.y);
CSSPoint end(aBoxSize.width, center.y);
if (isModern == (direction.AsHorizontal() == X::Left)) {
std::swap(start.x, end.x);
}
return {start, end};
}
case StyleLineDirection::Tag::Corner: {
const auto& corner = direction.AsCorner();
const X& h = corner._0;
const Y& v = corner._1;
if (isModern) {
float xSign = h == X::Right ? 1.0 : -1.0;
float ySign = v == Y::Top ? 1.0 : -1.0;
double angle = atan2(ySign * aBoxSize.width, xSign * aBoxSize.height);
CSSPoint end = ComputeGradientLineEndFromAngle(center, angle, aBoxSize);
CSSPoint start = CSSPoint(aBoxSize.width, aBoxSize.height) - end;
return {start, end};
}
CSSCoord startX = h == X::Left ? 0.0 : aBoxSize.width;
CSSCoord startY = v == Y::Top ? 0.0 : aBoxSize.height;
CSSPoint start(startX, startY);
CSSPoint end = CSSPoint(aBoxSize.width, aBoxSize.height) - start;
return {start, end};
}
default:
break;
}
MOZ_ASSERT_UNREACHABLE("Unknown line direction");
return {CSSPoint(), CSSPoint()};
}
using EndingShape = StyleGenericEndingShape<Length, LengthPercentage>;
using RadialGradientRadii =
Variant<StyleShapeExtent, std::pair<CSSCoord, CSSCoord>>;
static RadialGradientRadii ComputeRadialGradientRadii(const EndingShape& aShape,
const CSSSize& aSize) {
if (aShape.IsCircle()) {
auto& circle = aShape.AsCircle();
if (circle.IsExtent()) {
return RadialGradientRadii(circle.AsExtent());
}
CSSCoord radius = circle.AsRadius().ToCSSPixels();
return RadialGradientRadii(std::make_pair(radius, radius));
}
auto& ellipse = aShape.AsEllipse();
if (ellipse.IsExtent()) {
return RadialGradientRadii(ellipse.AsExtent());
}
auto& radii = ellipse.AsRadii();
return RadialGradientRadii(
std::make_pair(radii._0.ResolveToCSSPixels(aSize.width),
radii._1.ResolveToCSSPixels(aSize.height)));
}
// Compute the start and end points of the gradient line for a radial gradient.
// Also returns the horizontal and vertical radii defining the circle or
// ellipse to use.
static std::tuple<CSSPoint, CSSPoint, CSSCoord, CSSCoord>
ComputeRadialGradientLine(const StyleGradient& aGradient,
const CSSSize& aBoxSize) {
const auto& radial = aGradient.AsRadial();
const EndingShape& endingShape = radial.shape;
const Position& position = radial.position;
CSSPoint start = ResolvePosition(position, aBoxSize);
// Compute gradient shape: the x and y radii of an ellipse.
CSSCoord radiusX, radiusY;
CSSCoord leftDistance = Abs(start.x);
CSSCoord rightDistance = Abs(aBoxSize.width - start.x);
CSSCoord topDistance = Abs(start.y);
CSSCoord bottomDistance = Abs(aBoxSize.height - start.y);
auto radii = ComputeRadialGradientRadii(endingShape, aBoxSize);
if (radii.is<StyleShapeExtent>()) {
switch (radii.as<StyleShapeExtent>()) {
case StyleShapeExtent::ClosestSide:
radiusX = std::min(leftDistance, rightDistance);
radiusY = std::min(topDistance, bottomDistance);
if (endingShape.IsCircle()) {
radiusX = radiusY = std::min(radiusX, radiusY);
}
break;
case StyleShapeExtent::ClosestCorner: {
// Compute x and y distances to nearest corner
CSSCoord offsetX = std::min(leftDistance, rightDistance);
CSSCoord offsetY = std::min(topDistance, bottomDistance);
if (endingShape.IsCircle()) {
radiusX = radiusY = NS_hypot(offsetX, offsetY);
} else {
// maintain aspect ratio
radiusX = offsetX * M_SQRT2;
radiusY = offsetY * M_SQRT2;
}
break;
}
case StyleShapeExtent::FarthestSide:
radiusX = std::max(leftDistance, rightDistance);
radiusY = std::max(topDistance, bottomDistance);
if (endingShape.IsCircle()) {
radiusX = radiusY = std::max(radiusX, radiusY);
}
break;
case StyleShapeExtent::FarthestCorner: {
// Compute x and y distances to nearest corner
CSSCoord offsetX = std::max(leftDistance, rightDistance);
CSSCoord offsetY = std::max(topDistance, bottomDistance);
if (endingShape.IsCircle()) {
radiusX = radiusY = NS_hypot(offsetX, offsetY);
} else {
// maintain aspect ratio
radiusX = offsetX * M_SQRT2;
radiusY = offsetY * M_SQRT2;
}
break;
}
default:
MOZ_ASSERT_UNREACHABLE("Unknown shape extent keyword?");
radiusX = radiusY = 0;
}
} else {
auto pair = radii.as<std::pair<CSSCoord, CSSCoord>>();
radiusX = pair.first;
radiusY = pair.second;
}
// The gradient line end point is where the gradient line intersects
// the ellipse.
CSSPoint end = start + CSSPoint(radiusX, 0);
return {start, end, radiusX, radiusY};
}
// Compute the center and the start angle of the conic gradient.
static std::tuple<CSSPoint, float> ComputeConicGradientProperties(
const StyleGradient& aGradient, const CSSSize& aBoxSize) {
const auto& conic = aGradient.AsConic();
const Position& position = conic.position;
float angle = static_cast<float>(conic.angle.ToRadians());
CSSPoint center = ResolvePosition(position, aBoxSize);
return {center, angle};
}
static float Interpolate(float aF1, float aF2, float aFrac) {
return aF1 + aFrac * (aF2 - aF1);
}
static StyleAbsoluteColor Interpolate(const StyleAbsoluteColor& aLeft,
const StyleAbsoluteColor& aRight,
float aFrac) {
// NOTE: This has to match the interpolation method that WebRender uses which
// right now is sRGB. In the future we should implement interpolation in more
// gradient color-spaces.
static constexpr auto kMethod = StyleColorInterpolationMethod{
StyleColorSpace::Srgb,
StyleHueInterpolationMethod::Shorter,
};
return Servo_InterpolateColor(kMethod, &aRight, &aLeft, aFrac);
}
static nscoord FindTileStart(nscoord aDirtyCoord, nscoord aTilePos,
nscoord aTileDim) {
NS_ASSERTION(aTileDim > 0, "Non-positive tile dimension");
double multiples = floor(double(aDirtyCoord - aTilePos) / aTileDim);
return NSToCoordRound(multiples * aTileDim + aTilePos);
}
static gfxFloat LinearGradientStopPositionForPoint(
const gfxPoint& aGradientStart, const gfxPoint& aGradientEnd,
const gfxPoint& aPoint) {
gfxPoint d = aGradientEnd - aGradientStart;
gfxPoint p = aPoint - aGradientStart;
/**
* Compute a parameter t such that a line perpendicular to the
* d vector, passing through aGradientStart + d*t, also
* passes through aPoint.
*
* t is given by
* (p.x - d.x*t)*d.x + (p.y - d.y*t)*d.y = 0
*
* Solving for t we get
* numerator = d.x*p.x + d.y*p.y
* denominator = d.x^2 + d.y^2
* t = numerator/denominator
*
* In nsCSSRendering::PaintGradient we know the length of d
* is not zero.
*/
double numerator = d.x.value * p.x.value + d.y.value * p.y.value;
double denominator = d.x.value * d.x.value + d.y.value * d.y.value;
return numerator / denominator;
}
static bool RectIsBeyondLinearGradientEdge(const gfxRect& aRect,
const gfxMatrix& aPatternMatrix,
const nsTArray<ColorStop>& aStops,
const gfxPoint& aGradientStart,
const gfxPoint& aGradientEnd,
StyleAbsoluteColor* aOutEdgeColor) {
gfxFloat topLeft = LinearGradientStopPositionForPoint(
aGradientStart, aGradientEnd,
aPatternMatrix.TransformPoint(aRect.TopLeft()));
gfxFloat topRight = LinearGradientStopPositionForPoint(
aGradientStart, aGradientEnd,
aPatternMatrix.TransformPoint(aRect.TopRight()));
gfxFloat bottomLeft = LinearGradientStopPositionForPoint(
aGradientStart, aGradientEnd,
aPatternMatrix.TransformPoint(aRect.BottomLeft()));
gfxFloat bottomRight = LinearGradientStopPositionForPoint(
aGradientStart, aGradientEnd,
aPatternMatrix.TransformPoint(aRect.BottomRight()));
const ColorStop& firstStop = aStops[0];
if (topLeft < firstStop.mPosition && topRight < firstStop.mPosition &&
bottomLeft < firstStop.mPosition && bottomRight < firstStop.mPosition) {
*aOutEdgeColor = firstStop.mColor;
return true;
}
const ColorStop& lastStop = aStops.LastElement();
if (topLeft >= lastStop.mPosition && topRight >= lastStop.mPosition &&
bottomLeft >= lastStop.mPosition && bottomRight >= lastStop.mPosition) {
*aOutEdgeColor = lastStop.mColor;
return true;
}
return false;
}
static void ResolveMidpoints(nsTArray<ColorStop>& stops) {
for (size_t x = 1; x < stops.Length() - 1;) {
if (!stops[x].mIsMidpoint) {
x++;
continue;
}
const auto& color1 = stops[x - 1].mColor;
const auto& color2 = stops[x + 1].mColor;
float offset1 = stops[x - 1].mPosition;
float offset2 = stops[x + 1].mPosition;
float offset = stops[x].mPosition;
// check if everything coincides. If so, ignore the midpoint.
if (offset - offset1 == offset2 - offset) {
stops.RemoveElementAt(x);
continue;
}
// Check if we coincide with the left colorstop.
if (offset1 == offset) {
// Morph the midpoint to a regular stop with the color of the next
// color stop.
stops[x].mColor = color2;
stops[x].mIsMidpoint = false;
continue;
}
// Check if we coincide with the right colorstop.
if (offset2 == offset) {
// Morph the midpoint to a regular stop with the color of the previous
// color stop.
stops[x].mColor = color1;
stops[x].mIsMidpoint = false;
continue;
}
float midpoint = (offset - offset1) / (offset2 - offset1);
ColorStop newStops[9];
if (midpoint > .5f) {
for (size_t y = 0; y < 7; y++) {
newStops[y].mPosition = offset1 + (offset - offset1) * (7 + y) / 13;
}
newStops[7].mPosition = offset + (offset2 - offset) / 3;
newStops[8].mPosition = offset + (offset2 - offset) * 2 / 3;
} else {
newStops[0].mPosition = offset1 + (offset - offset1) / 3;
newStops[1].mPosition = offset1 + (offset - offset1) * 2 / 3;
for (size_t y = 0; y < 7; y++) {
newStops[y + 2].mPosition = offset + (offset2 - offset) * y / 13;
}
}
// calculate colors
for (auto& newStop : newStops) {
// Calculate the intermediate color stops per the formula of the CSS
// images spec. http://dev.w3.org/csswg/css-images/#color-stop-syntax 9
// points were chosen since it is the minimum number of stops that always
// give the smoothest appearace regardless of midpoint position and
// difference in luminance of the end points.
const float relativeOffset =
(newStop.mPosition - offset1) / (offset2 - offset1);
const float multiplier = powf(relativeOffset, logf(.5f) / logf(midpoint));
auto srgb1 = color1.ToColorSpace(StyleColorSpace::Srgb);
auto srgb2 = color2.ToColorSpace(StyleColorSpace::Srgb);
const float red =
srgb1.components._0 +
multiplier * (srgb2.components._0 - srgb1.components._0);
const float green =
srgb1.components._1 +
multiplier * (srgb2.components._1 - srgb1.components._1);
const float blue =
srgb1.components._2 +
multiplier * (srgb2.components._2 - srgb1.components._2);
const float alpha =
srgb1.alpha + multiplier * (srgb2.alpha - srgb1.alpha);
newStop.mColor = StyleAbsoluteColor::SrgbLegacy(red, green, blue, alpha);
}
stops.ReplaceElementsAt(x, 1, newStops, 9);
x += 9;
}
}
static StyleAbsoluteColor TransparentColor(const StyleAbsoluteColor& aColor) {
auto color = aColor;
color.alpha = 0.0f;
return color;
}
// Adjusts and adds color stops in such a way that drawing the gradient with
// unpremultiplied interpolation looks nearly the same as if it were drawn with
// premultiplied interpolation.
static const float kAlphaIncrementPerGradientStep = 0.1f;
static void ResolvePremultipliedAlpha(nsTArray<ColorStop>& aStops) {
for (size_t x = 1; x < aStops.Length(); x++) {
const ColorStop leftStop = aStops[x - 1];
const ColorStop rightStop = aStops[x];
// if the left and right stop have the same alpha value, we don't need
// to do anything. Hardstops should be instant, and also should never
// require dealing with interpolation.
if (leftStop.mColor.alpha == rightStop.mColor.alpha ||
leftStop.mPosition == rightStop.mPosition) {
continue;
}
// Is the stop on the left 100% transparent? If so, have it adopt the color
// of the right stop
if (leftStop.mColor.alpha == 0) {
aStops[x - 1].mColor = TransparentColor(rightStop.mColor);
continue;
}
// Is the stop on the right completely transparent?
// If so, duplicate it and assign it the color on the left.
if (rightStop.mColor.alpha == 0) {
ColorStop newStop = rightStop;
newStop.mColor = TransparentColor(leftStop.mColor);
aStops.InsertElementAt(x, newStop);
x++;
continue;
}
// Now handle cases where one or both of the stops are partially
// transparent.
if (leftStop.mColor.alpha != 1.0f || rightStop.mColor.alpha != 1.0f) {
// Calculate how many extra steps. We do a step per 10% transparency.
size_t stepCount =
NSToIntFloor(fabsf(leftStop.mColor.alpha - rightStop.mColor.alpha) /
kAlphaIncrementPerGradientStep);
for (size_t y = 1; y < stepCount; y++) {
float frac = static_cast<float>(y) / stepCount;
ColorStop newStop(
Interpolate(leftStop.mPosition, rightStop.mPosition, frac), false,
Interpolate(leftStop.mColor, rightStop.mColor, frac));
aStops.InsertElementAt(x, newStop);
x++;
}
}
}
}
static ColorStop InterpolateColorStop(const ColorStop& aFirst,
const ColorStop& aSecond,
double aPosition,
const StyleAbsoluteColor& aDefault) {
MOZ_ASSERT(aFirst.mPosition <= aPosition);
MOZ_ASSERT(aPosition <= aSecond.mPosition);
double delta = aSecond.mPosition - aFirst.mPosition;
if (delta < 1e-6) {
return ColorStop(aPosition, false, aDefault);
}
return ColorStop(aPosition, false,
Interpolate(aFirst.mColor, aSecond.mColor,
(aPosition - aFirst.mPosition) / delta));
}
// Clamp and extend the given ColorStop array in-place to fit exactly into the
// range [0, 1].
static void ClampColorStops(nsTArray<ColorStop>& aStops) {
MOZ_ASSERT(aStops.Length() > 0);
// If all stops are outside the range, then get rid of everything and replace
// with a single colour.
if (aStops.Length() < 2 || aStops[0].mPosition > 1 ||
aStops.LastElement().mPosition < 0) {
const auto c = aStops[0].mPosition > 1 ? aStops[0].mColor
: aStops.LastElement().mColor;
aStops.Clear();
aStops.AppendElement(ColorStop(0, false, c));
return;
}
// Create the 0 and 1 points if they fall in the range of |aStops|, and
// discard all stops outside the range [0, 1].
// XXX: If we have stops positioned at 0 or 1, we only keep the innermost of
// those stops. This should be fine for the current user(s) of this function.
for (size_t i = aStops.Length() - 1; i > 0; i--) {
if (aStops[i - 1].mPosition < 1 && aStops[i].mPosition >= 1) {
// Add a point to position 1.
aStops[i] =
InterpolateColorStop(aStops[i - 1], aStops[i],
/* aPosition = */ 1, aStops[i - 1].mColor);
// Remove all the elements whose position is greater than 1.
aStops.RemoveLastElements(aStops.Length() - (i + 1));
}
if (aStops[i - 1].mPosition <= 0 && aStops[i].mPosition > 0) {
// Add a point to position 0.
aStops[i - 1] =
InterpolateColorStop(aStops[i - 1], aStops[i],
/* aPosition = */ 0, aStops[i].mColor);
// Remove all of the preceding stops -- they are all negative.
aStops.RemoveElementsAt(0, i - 1);
break;
}
}
MOZ_ASSERT(aStops[0].mPosition >= -1e6);
MOZ_ASSERT(aStops.LastElement().mPosition - 1 <= 1e6);
// The end points won't exist yet if they don't fall in the original range of
// |aStops|. Create them if needed.
if (aStops[0].mPosition > 0) {
aStops.InsertElementAt(0, ColorStop(0, false, aStops[0].mColor));
}
if (aStops.LastElement().mPosition < 1) {
aStops.AppendElement(ColorStop(1, false, aStops.LastElement().mColor));
}
}
namespace mozilla {
template <typename T>
static StyleAbsoluteColor GetSpecifiedColor(
const StyleGenericGradientItem<StyleColor, T>& aItem,
const ComputedStyle& aStyle) {
if (aItem.IsInterpolationHint()) {
return StyleAbsoluteColor::TRANSPARENT_BLACK;
}
const StyleColor& c = aItem.IsSimpleColorStop()
? aItem.AsSimpleColorStop()
: aItem.AsComplexColorStop().color;
return c.ResolveColor(aStyle.StyleText()->mColor);
}
static Maybe<double> GetSpecifiedGradientPosition(
const StyleGenericGradientItem<StyleColor, StyleLengthPercentage>& aItem,
CSSCoord aLineLength) {
if (aItem.IsSimpleColorStop()) {
return Nothing();
}
const LengthPercentage& pos = aItem.IsComplexColorStop()
? aItem.AsComplexColorStop().position
: aItem.AsInterpolationHint();
if (pos.ConvertsToPercentage()) {
return Some(pos.ToPercentage());
}
if (aLineLength < 1e-6) {
return Some(0.0);
}
return Some(pos.ResolveToCSSPixels(aLineLength) / aLineLength);
}
// aLineLength argument is unused for conic-gradients.
static Maybe<double> GetSpecifiedGradientPosition(
const StyleGenericGradientItem<StyleColor, StyleAngleOrPercentage>& aItem,
CSSCoord aLineLength) {
if (aItem.IsSimpleColorStop()) {
return Nothing();
}
const StyleAngleOrPercentage& pos = aItem.IsComplexColorStop()
? aItem.AsComplexColorStop().position
: aItem.AsInterpolationHint();
if (pos.IsPercentage()) {
return Some(pos.AsPercentage()._0);
}
return Some(pos.AsAngle().ToRadians() / (2 * M_PI));
}
template <typename T>
static nsTArray<ColorStop> ComputeColorStopsForItems(
ComputedStyle* aComputedStyle,
Span<const StyleGenericGradientItem<StyleColor, T>> aItems,
CSSCoord aLineLength) {
MOZ_ASSERT(aItems.Length() >= 2,
"The parser should reject gradients with less than two stops");
nsTArray<ColorStop> stops(aItems.Length());
// If there is a run of stops before stop i that did not have specified
// positions, then this is the index of the first stop in that run.
Maybe<size_t> firstUnsetPosition;
for (size_t i = 0; i < aItems.Length(); ++i) {
const auto& stop = aItems[i];
double position;
Maybe<double> specifiedPosition =
GetSpecifiedGradientPosition(stop, aLineLength);
if (specifiedPosition) {
position = *specifiedPosition;
} else if (i == 0) {
// First stop defaults to position 0.0
position = 0.0;
} else if (i == aItems.Length() - 1) {
// Last stop defaults to position 1.0
position = 1.0;
} else {
// Other stops with no specified position get their position assigned
// later by interpolation, see below.
// Remember where the run of stops with no specified position starts,
// if it starts here.
if (firstUnsetPosition.isNothing()) {
firstUnsetPosition.emplace(i);
}
MOZ_ASSERT(!stop.IsInterpolationHint(),
"Interpolation hints always specify position");
auto color = GetSpecifiedColor(stop, *aComputedStyle);
stops.AppendElement(ColorStop(0, false, color));
continue;
}
if (i > 0) {
// Prevent decreasing stop positions by advancing this position
// to the previous stop position, if necessary
double previousPosition = firstUnsetPosition
? stops[*firstUnsetPosition - 1].mPosition
: stops[i - 1].mPosition;
position = std::max(position, previousPosition);
}
auto stopColor = GetSpecifiedColor(stop, *aComputedStyle);
stops.AppendElement(
ColorStop(position, stop.IsInterpolationHint(), stopColor));
if (firstUnsetPosition) {
// Interpolate positions for all stops that didn't have a specified
// position
double p = stops[*firstUnsetPosition - 1].mPosition;
double d = (stops[i].mPosition - p) / (i - *firstUnsetPosition + 1);
for (size_t j = *firstUnsetPosition; j < i; ++j) {
p += d;
stops[j].mPosition = p;
}
firstUnsetPosition.reset();
}
}
return stops;
}
static nsTArray<ColorStop> ComputeColorStops(ComputedStyle* aComputedStyle,
const StyleGradient& aGradient,
CSSCoord aLineLength) {
if (aGradient.IsLinear()) {
return ComputeColorStopsForItems(
aComputedStyle, aGradient.AsLinear().items.AsSpan(), aLineLength);
}
if (aGradient.IsRadial()) {
return ComputeColorStopsForItems(
aComputedStyle, aGradient.AsRadial().items.AsSpan(), aLineLength);
}
return ComputeColorStopsForItems(
aComputedStyle, aGradient.AsConic().items.AsSpan(), aLineLength);
}
nsCSSGradientRenderer nsCSSGradientRenderer::Create(
nsPresContext* aPresContext, ComputedStyle* aComputedStyle,
const StyleGradient& aGradient, const nsSize& aIntrinsicSize) {
auto srcSize = CSSSize::FromAppUnits(aIntrinsicSize);
// Compute "gradient line" start and end relative to the intrinsic size of
// the gradient.
CSSPoint lineStart, lineEnd, center; // center is for conic gradients only
CSSCoord radiusX = 0, radiusY = 0; // for radial gradients only
float angle = 0.0; // for conic gradients only
if (aGradient.IsLinear()) {
std::tie(lineStart, lineEnd) =
ComputeLinearGradientLine(aPresContext, aGradient, srcSize);
} else if (aGradient.IsRadial()) {
std::tie(lineStart, lineEnd, radiusX, radiusY) =
ComputeRadialGradientLine(aGradient, srcSize);
} else {
MOZ_ASSERT(aGradient.IsConic());
std::tie(center, angle) =
ComputeConicGradientProperties(aGradient, srcSize);
}
// Avoid sending Infs or Nans to downwind draw targets.
if (!lineStart.IsFinite() || !lineEnd.IsFinite()) {
lineStart = lineEnd = CSSPoint(0, 0);
}
if (!center.IsFinite()) {
center = CSSPoint(0, 0);
}
CSSCoord lineLength =
NS_hypot(lineEnd.x - lineStart.x, lineEnd.y - lineStart.y);
// Build color stop array and compute stop positions
nsTArray<ColorStop> stops =
ComputeColorStops(aComputedStyle, aGradient, lineLength);
ResolveMidpoints(stops);
nsCSSGradientRenderer renderer;
renderer.mPresContext = aPresContext;
renderer.mGradient = &aGradient;
renderer.mStops = std::move(stops);
renderer.mLineStart = {
aPresContext->CSSPixelsToDevPixels(lineStart.x),
aPresContext->CSSPixelsToDevPixels(lineStart.y),
};
renderer.mLineEnd = {
aPresContext->CSSPixelsToDevPixels(lineEnd.x),
aPresContext->CSSPixelsToDevPixels(lineEnd.y),
};
renderer.mRadiusX = aPresContext->CSSPixelsToDevPixels(radiusX);
renderer.mRadiusY = aPresContext->CSSPixelsToDevPixels(radiusY);
renderer.mCenter = {
aPresContext->CSSPixelsToDevPixels(center.x),
aPresContext->CSSPixelsToDevPixels(center.y),
};
renderer.mAngle = angle;
return renderer;
}
void nsCSSGradientRenderer::Paint(gfxContext& aContext, const nsRect& aDest,
const nsRect& aFillArea,
const nsSize& aRepeatSize,
const CSSIntRect& aSrc,
const nsRect& aDirtyRect, float aOpacity) {
AUTO_PROFILER_LABEL("nsCSSGradientRenderer::Paint", GRAPHICS);
if (aDest.IsEmpty() || aFillArea.IsEmpty()) {
return;
}
nscoord appUnitsPerDevPixel = mPresContext->AppUnitsPerDevPixel();
gfxFloat lineLength =
NS_hypot(mLineEnd.x - mLineStart.x, mLineEnd.y - mLineStart.y);
bool cellContainsFill = aDest.Contains(aFillArea);
// If a non-repeating linear gradient is axis-aligned and there are no gaps
// between tiles, we can optimise away most of the work by converting to a
// repeating linear gradient and filling the whole destination rect at once.
bool forceRepeatToCoverTiles =
mGradient->IsLinear() &&
(mLineStart.x == mLineEnd.x) != (mLineStart.y == mLineEnd.y) &&
aRepeatSize.width == aDest.width && aRepeatSize.height == aDest.height &&
!(mGradient->Repeating()) && !aSrc.IsEmpty() && !cellContainsFill;
gfxMatrix matrix;
if (forceRepeatToCoverTiles) {
// Length of the source rectangle along the gradient axis.
double rectLen;
// The position of the start of the rectangle along the gradient.
double offset;
// The gradient line is "backwards". Flip the line upside down to make
// things easier, and then rotate the matrix to turn everything back the
// right way up.
if (mLineStart.x > mLineEnd.x || mLineStart.y > mLineEnd.y) {
std::swap(mLineStart, mLineEnd);
matrix.PreScale(-1, -1);
}
// Fit the gradient line exactly into the source rect.
// aSrc is relative to aIntrinsincSize.
// srcRectDev will be relative to srcSize, so in the same coordinate space
// as lineStart / lineEnd.
gfxRect srcRectDev = nsLayoutUtils::RectToGfxRect(
CSSPixel::ToAppUnits(aSrc), appUnitsPerDevPixel);
if (mLineStart.x != mLineEnd.x) {
rectLen = srcRectDev.width;
offset = (srcRectDev.x - mLineStart.x) / lineLength;
mLineStart.x = srcRectDev.x;
mLineEnd.x = srcRectDev.XMost();
} else {
rectLen = srcRectDev.height;
offset = (srcRectDev.y - mLineStart.y) / lineLength;
mLineStart.y = srcRectDev.y;
mLineEnd.y = srcRectDev.YMost();
}
// Adjust gradient stop positions for the new gradient line.
double scale = lineLength / rectLen;
for (size_t i = 0; i < mStops.Length(); i++) {
mStops[i].mPosition = (mStops[i].mPosition - offset) * fabs(scale);
}
// Clamp or extrapolate gradient stops to exactly [0, 1].
ClampColorStops(mStops);
lineLength = rectLen;
}
// Eliminate negative-position stops if the gradient is radial.
double firstStop = mStops[0].mPosition;
if (mGradient->IsRadial() && firstStop < 0.0) {
if (mGradient->AsRadial().flags & StyleGradientFlags::REPEATING) {
// Choose an instance of the repeated pattern that gives us all positive
// stop-offsets.
double lastStop = mStops[mStops.Length() - 1].mPosition;
double stopDelta = lastStop - firstStop;
// If all the stops are in approximately the same place then logic below
// will kick in that makes us draw just the last stop color, so don't
// try to do anything in that case. We certainly need to avoid
// dividing by zero.
if (stopDelta >= 1e-6) {
double instanceCount = ceil(-firstStop / stopDelta);
// Advance stops by instanceCount multiples of the period of the
// repeating gradient.
double offset = instanceCount * stopDelta;
for (uint32_t i = 0; i < mStops.Length(); i++) {
mStops[i].mPosition += offset;
}
}
} else {
// Move negative-position stops to position 0.0. We may also need
// to set the color of the stop to the color the gradient should have
// at the center of the ellipse.
for (uint32_t i = 0; i < mStops.Length(); i++) {
double pos = mStops[i].mPosition;
if (pos < 0.0) {
mStops[i].mPosition = 0.0;
// If this is the last stop, we don't need to adjust the color,
// it will fill the entire area.
if (i < mStops.Length() - 1) {
double nextPos = mStops[i + 1].mPosition;
// If nextPos is approximately equal to pos, then we don't
// need to adjust the color of this stop because it's
// not going to be displayed.
// If nextPos is negative, we don't need to adjust the color of
// this stop since it's not going to be displayed because
// nextPos will also be moved to 0.0.
if (nextPos >= 0.0 && nextPos - pos >= 1e-6) {
// Compute how far the new position 0.0 is along the interval
// between pos and nextPos.
// XXX Color interpolation (in cairo, too) should use the
// CSS 'color-interpolation' property!
float frac = float((0.0 - pos) / (nextPos - pos));
mStops[i].mColor =
Interpolate(mStops[i].mColor, mStops[i + 1].mColor, frac);
}
}
}
}
}
firstStop = mStops[0].mPosition;
MOZ_ASSERT(firstStop >= 0.0, "Failed to fix stop offsets");
}
if (mGradient->IsRadial() &&
!(mGradient->AsRadial().flags & StyleGradientFlags::REPEATING)) {
// Direct2D can only handle a particular class of radial gradients because
// of the way the it specifies gradients. Setting firstStop to 0, when we
// can, will help us stay on the fast path. Currently we don't do this
// for repeating gradients but we could by adjusting the stop collection
// to start at 0
firstStop = 0;
}
double lastStop = mStops[mStops.Length() - 1].mPosition;
// Cairo gradients must have stop positions in the range [0, 1]. So,
// stop positions will be normalized below by subtracting firstStop and then
// multiplying by stopScale.
double stopScale;
double stopOrigin = firstStop;
double stopEnd = lastStop;
double stopDelta = lastStop - firstStop;
bool zeroRadius =
mGradient->IsRadial() && (mRadiusX < 1e-6 || mRadiusY < 1e-6);
if (stopDelta < 1e-6 || (!mGradient->IsConic() && lineLength < 1e-6) ||
zeroRadius) {
// Stops are all at the same place. Map all stops to 0.0.
// For repeating radial gradients, or for any radial gradients with
// a zero radius, we need to fill with the last stop color, so just set
// both radii to 0.
if (mGradient->Repeating() || zeroRadius) {
mRadiusX = mRadiusY = 0.0;
}
stopDelta = 0.0;
}
// Don't normalize non-repeating or degenerate gradients below 0..1
// This keeps the gradient line as large as the box and doesn't
// lets us avoiding having to get padding correct for stops
// at 0 and 1
if (!mGradient->Repeating() || stopDelta == 0.0) {
stopOrigin = std::min(stopOrigin, 0.0);
stopEnd = std::max(stopEnd, 1.0);
}
stopScale = 1.0 / (stopEnd - stopOrigin);
// Create the gradient pattern.
RefPtr<gfxPattern> gradientPattern;
gfxPoint gradientStart;
gfxPoint gradientEnd;
if (mGradient->IsLinear()) {
// Compute the actual gradient line ends we need to pass to cairo after
// stops have been normalized.
gradientStart = mLineStart + (mLineEnd - mLineStart) * stopOrigin;
gradientEnd = mLineStart + (mLineEnd - mLineStart) * stopEnd;
if (stopDelta == 0.0) {
// Stops are all at the same place. For repeating gradients, this will
// just paint the last stop color. We don't need to do anything.
// For non-repeating gradients, this should render as two colors, one
// on each "side" of the gradient line segment, which is a point. All
// our stops will be at 0.0; we just need to set the direction vector
// correctly.
gradientEnd = gradientStart + (mLineEnd - mLineStart);
}
gradientPattern = new gfxPattern(gradientStart.x, gradientStart.y,
gradientEnd.x, gradientEnd.y);
} else if (mGradient->IsRadial()) {
NS_ASSERTION(firstStop >= 0.0,
"Negative stops not allowed for radial gradients");
// To form an ellipse, we'll stretch a circle vertically, if necessary.
// So our radii are based on radiusX.
double innerRadius = mRadiusX * stopOrigin;
double outerRadius = mRadiusX * stopEnd;
if (stopDelta == 0.0) {
// Stops are all at the same place. See above (except we now have
// the inside vs. outside of an ellipse).
outerRadius = innerRadius + 1;
}
gradientPattern = new gfxPattern(mLineStart.x, mLineStart.y, innerRadius,
mLineStart.x, mLineStart.y, outerRadius);
if (mRadiusX != mRadiusY) {
// Stretch the circles into ellipses vertically by setting a transform
// in the pattern.
// Recall that this is the transform from user space to pattern space.
// So to stretch the ellipse by factor of P vertically, we scale
// user coordinates by 1/P.
matrix.PreTranslate(mLineStart);
matrix.PreScale(1.0, mRadiusX / mRadiusY);
matrix.PreTranslate(-mLineStart);
}
} else {
gradientPattern =
new gfxPattern(mCenter.x, mCenter.y, mAngle, stopOrigin, stopEnd);
}
// Use a pattern transform to take account of source and dest rects
matrix.PreTranslate(gfxPoint(mPresContext->CSSPixelsToDevPixels(aSrc.x),
mPresContext->CSSPixelsToDevPixels(aSrc.y)));
matrix.PreScale(
gfxFloat(nsPresContext::CSSPixelsToAppUnits(aSrc.width)) / aDest.width,
gfxFloat(nsPresContext::CSSPixelsToAppUnits(aSrc.height)) / aDest.height);
gradientPattern->SetMatrix(matrix);
if (stopDelta == 0.0) {
// Non-repeating gradient with all stops in same place -> just add
// first stop and last stop, both at position 0.
// Repeating gradient with all stops in the same place, or radial
// gradient with radius of 0 -> just paint the last stop color.
// We use firstStop offset to keep |stops| with same units (will later
// normalize to 0).
auto firstColor(mStops[0].mColor);
auto lastColor(mStops.LastElement().mColor);
mStops.Clear();
if (!mGradient->Repeating() && !zeroRadius) {
mStops.AppendElement(ColorStop(firstStop, false, firstColor));
}
mStops.AppendElement(ColorStop(firstStop, false, lastColor));
}
ResolvePremultipliedAlpha(mStops);
bool isRepeat = mGradient->Repeating() || forceRepeatToCoverTiles;
// Now set normalized color stops in pattern.
// Offscreen gradient surface cache (not a tile):
// On some backends (e.g. D2D), the GradientStops object holds an offscreen
// surface which is a lookup table used to evaluate the gradient. This surface
// can use much memory (ram and/or GPU ram) and can be expensive to create. So
// we cache it. The cache key correlates 1:1 with the arguments for
// CreateGradientStops (also the implied backend type) Note that GradientStop
// is a simple struct with a stop value (while GradientStops has the surface).
nsTArray<gfx::GradientStop> rawStops(mStops.Length());
rawStops.SetLength(mStops.Length());
for (uint32_t i = 0; i < mStops.Length(); i++) {
rawStops[i].color = ToDeviceColor(mStops[i].mColor);
rawStops[i].color.a *= aOpacity;
rawStops[i].offset = stopScale * (mStops[i].mPosition - stopOrigin);
}
RefPtr<mozilla::gfx::GradientStops> gs =
gfxGradientCache::GetOrCreateGradientStops(
aContext.GetDrawTarget(), rawStops,
isRepeat ? gfx::ExtendMode::REPEAT : gfx::ExtendMode::CLAMP);
gradientPattern->SetColorStops(gs);
// Paint gradient tiles. This isn't terribly efficient, but doing it this
// way is simple and sure to get pixel-snapping right. We could speed things
// up by drawing tiles into temporary surfaces and copying those to the
// destination, but after pixel-snapping tiles may not all be the same size.
nsRect dirty;
if (!dirty.IntersectRect(aDirtyRect, aFillArea)) return;
gfxRect areaToFill =
nsLayoutUtils::RectToGfxRect(aFillArea, appUnitsPerDevPixel);
gfxRect dirtyAreaToFill =
nsLayoutUtils::RectToGfxRect(dirty, appUnitsPerDevPixel);
dirtyAreaToFill.RoundOut();
Matrix ctm = aContext.CurrentMatrix();
bool isCTMPreservingAxisAlignedRectangles =
ctm.PreservesAxisAlignedRectangles();
// xStart/yStart are the top-left corner of the top-left tile.
nscoord xStart = FindTileStart(dirty.x, aDest.x, aRepeatSize.width);
nscoord yStart = FindTileStart(dirty.y, aDest.y, aRepeatSize.height);
nscoord xEnd = forceRepeatToCoverTiles ? xStart + aDest.width : dirty.XMost();
nscoord yEnd =
forceRepeatToCoverTiles ? yStart + aDest.height : dirty.YMost();
if (TryPaintTilesWithExtendMode(aContext, gradientPattern, xStart, yStart,
dirtyAreaToFill, aDest, aRepeatSize,
forceRepeatToCoverTiles)) {
return;
}
// x and y are the top-left corner of the tile to draw
for (nscoord y = yStart; y < yEnd; y += aRepeatSize.height) {
for (nscoord x = xStart; x < xEnd; x += aRepeatSize.width) {
// The coordinates of the tile
gfxRect tileRect = nsLayoutUtils::RectToGfxRect(
nsRect(x, y, aDest.width, aDest.height), appUnitsPerDevPixel);
// The actual area to fill with this tile is the intersection of this
// tile with the overall area we're supposed to be filling
gfxRect fillRect =
forceRepeatToCoverTiles ? areaToFill : tileRect.Intersect(areaToFill);
// Try snapping the fill rect. Snap its top-left and bottom-right
// independently to preserve the orientation.
gfxPoint snappedFillRectTopLeft = fillRect.TopLeft();
gfxPoint snappedFillRectTopRight = fillRect.TopRight();
gfxPoint snappedFillRectBottomRight = fillRect.BottomRight();
// Snap three points instead of just two to ensure we choose the
// correct orientation if there's a reflection.
if (isCTMPreservingAxisAlignedRectangles &&
aContext.UserToDevicePixelSnapped(snappedFillRectTopLeft, true) &&
aContext.UserToDevicePixelSnapped(snappedFillRectBottomRight, true) &&
aContext.UserToDevicePixelSnapped(snappedFillRectTopRight, true)) {
if (snappedFillRectTopLeft.x == snappedFillRectBottomRight.x ||
snappedFillRectTopLeft.y == snappedFillRectBottomRight.y) {
// Nothing to draw; avoid scaling by zero and other weirdness that
// could put the context in an error state.
continue;
}
// Set the context's transform to the transform that maps fillRect to
// snappedFillRect. The part of the gradient that was going to
// exactly fill fillRect will fill snappedFillRect instead.
gfxMatrix transform = gfxUtils::TransformRectToRect(
fillRect, snappedFillRectTopLeft, snappedFillRectTopRight,
snappedFillRectBottomRight);
aContext.SetMatrixDouble(transform);
}
aContext.NewPath();
aContext.Rectangle(fillRect);
gfxRect dirtyFillRect = fillRect.Intersect(dirtyAreaToFill);
gfxRect fillRectRelativeToTile = dirtyFillRect - tileRect.TopLeft();
auto edgeColor = StyleAbsoluteColor::TRANSPARENT_BLACK;
if (mGradient->IsLinear() && !isRepeat &&
RectIsBeyondLinearGradientEdge(fillRectRelativeToTile, matrix, mStops,
gradientStart, gradientEnd,
&edgeColor)) {
edgeColor.alpha *= aOpacity;
aContext.SetColor(ToSRGBColor(edgeColor));
} else {
aContext.SetMatrixDouble(
aContext.CurrentMatrixDouble().Copy().PreTranslate(
tileRect.TopLeft()));
aContext.SetPattern(gradientPattern);
}
aContext.Fill();
aContext.SetMatrix(ctm);
}
}
}
bool nsCSSGradientRenderer::TryPaintTilesWithExtendMode(
gfxContext& aContext, gfxPattern* aGradientPattern, nscoord aXStart,
nscoord aYStart, const gfxRect& aDirtyAreaToFill, const nsRect& aDest,
const nsSize& aRepeatSize, bool aForceRepeatToCoverTiles) {
// If we have forced a non-repeating gradient to repeat to cover tiles,
// then it will be faster to just paint it once using that optimization
if (aForceRepeatToCoverTiles) {
return false;
}
nscoord appUnitsPerDevPixel = mPresContext->AppUnitsPerDevPixel();
// We can only use this fast path if we don't have to worry about pixel
// snapping, and there is no spacing between tiles. We could handle spacing
// by increasing the size of tileSurface and leaving it transparent, but I'm
// not sure it's worth it
bool canUseExtendModeForTiling = (aXStart % appUnitsPerDevPixel == 0) &&
(aYStart % appUnitsPerDevPixel == 0) &&
(aDest.width % appUnitsPerDevPixel == 0) &&
(aDest.height % appUnitsPerDevPixel == 0) &&
(aRepeatSize.width == aDest.width) &&
(aRepeatSize.height == aDest.height);
if (!canUseExtendModeForTiling) {
return false;
}
IntSize tileSize{
NSAppUnitsToIntPixels(aDest.width, appUnitsPerDevPixel),
NSAppUnitsToIntPixels(aDest.height, appUnitsPerDevPixel),
};
// Check whether this is a reasonable surface size and doesn't overflow
// before doing calculations with the tile size
if (!Factory::ReasonableSurfaceSize(tileSize)) {
return false;
}
// We only want to do this when there are enough tiles to justify the
// overhead of painting to an offscreen surface. The heuristic here
// is when we will be painting at least 16 tiles or more, this is kind
// of arbitrary
bool shouldUseExtendModeForTiling =
aDirtyAreaToFill.Area() > (tileSize.width * tileSize.height) * 16.0;
if (!shouldUseExtendModeForTiling) {
return false;
}
// Draw the gradient pattern into a surface for our single tile
RefPtr<gfx::SourceSurface> tileSurface;
{
RefPtr<gfx::DrawTarget> tileTarget =
aContext.GetDrawTarget()->CreateSimilarDrawTarget(
tileSize, gfx::SurfaceFormat::B8G8R8A8);
if (!tileTarget || !tileTarget->IsValid()) {
return false;
}
{
gfxContext tileContext(tileTarget);
tileContext.SetPattern(aGradientPattern);
tileContext.Paint();
}
tileSurface = tileTarget->Snapshot();
tileTarget = nullptr;
}
// Draw the gradient using tileSurface as a repeating pattern masked by
// the dirtyRect
Matrix tileTransform = Matrix::Translation(
NSAppUnitsToFloatPixels(aXStart, appUnitsPerDevPixel),
NSAppUnitsToFloatPixels(aYStart, appUnitsPerDevPixel));
aContext.NewPath();
aContext.Rectangle(aDirtyAreaToFill);
aContext.Fill(SurfacePattern(tileSurface, ExtendMode::REPEAT, tileTransform));
return true;
}
class MOZ_STACK_CLASS WrColorStopInterpolator
: public ColorStopInterpolator<WrColorStopInterpolator> {
public:
WrColorStopInterpolator(
const nsTArray<ColorStop>& aStops,
const StyleColorInterpolationMethod& aStyleColorInterpolationMethod,
float aOpacity, nsTArray<wr::GradientStop>& aResult, bool aExtendLastStop)
: ColorStopInterpolator(aStops, aStyleColorInterpolationMethod,
aExtendLastStop),
mResult(aResult),
mOpacity(aOpacity),
mOutputStop(0) {}
void CreateStops() {
mResult.SetLengthAndRetainStorage(0);
// We always emit at least two stops (start and end) for each input stop,
// which avoids ambiguity with incomplete oklch/lch/hsv/hsb color stops for
// the last stop pair, where the last color stop can't be interpreted on its
// own because it actually depends on the previous stop.
mResult.SetLength(mStops.Length() * 2 + kFullRangeExtraStops);
mOutputStop = 0;
ColorStopInterpolator::CreateStops();
mResult.SetLength(mOutputStop);
}
void CreateStop(float aPosition, DeviceColor aColor) {
if (mOutputStop < mResult.Capacity()) {
mResult[mOutputStop].color = wr::ToColorF(aColor);
mResult[mOutputStop].color.a *= mOpacity;
mResult[mOutputStop].offset = aPosition;
mOutputStop++;
}
}
private:
nsTArray<wr::GradientStop>& mResult;
float mOpacity;
uint32_t mOutputStop;
};
void nsCSSGradientRenderer::BuildWebRenderParameters(
float aOpacity, wr::ExtendMode& aMode, nsTArray<wr::GradientStop>& aStops,
LayoutDevicePoint& aLineStart, LayoutDevicePoint& aLineEnd,
LayoutDeviceSize& aGradientRadius, LayoutDevicePoint& aGradientCenter,
float& aGradientAngle) {
aMode =
mGradient->Repeating() ? wr::ExtendMode::Repeat : wr::ExtendMode::Clamp;
// If the interpolation space is not sRGB, or if color management is active,
// we need to add additional stops so that the sRGB interpolation in WebRender
// still closely approximates the correct curves. We prefer avoiding this if
// the gradient is simple because WebRender has fast rendering of linear
// gradients with 2 stops (which represent >99% of all gradients on the web).
//
// WebRender doesn't have easy access to StyleAbsoluteColor and CMS display
// color correction, so we just expand the gradient stop table significantly
// so that gamma and hue interpolation errors become imperceptible.
//
// This always turns into 128 pairs of stops inside WebRender as an
// implementation detail, so the number of stops we generate here should have
// very little impact on performance as the texture upload is always the same,
// except for the special linear gradient 2-stop case, and it is gpucache so
// if it does not change it is not re-uploaded.
//
// Color management bugs that this addresses:
// * https://bugzilla.mozilla.org/show_bug.cgi?id=939387
// * https://bugzilla.mozilla.org/show_bug.cgi?id=1248178
StyleColorInterpolationMethod styleColorInterpolationMethod =
mGradient->ColorInterpolationMethod();
// For colorspaces supported by WebRender (Srgb, Hsl, Hwb) we technically do
// not need to add extra stops, but the only one of those colorspaces that
// appears frequently is Srgb, and Srgb still needs extra stops if CMS is
// enabled. Hsl/Hwb need extra stops if StyleHueInterpolationMethod is not
// Shorter, or if CMS is enabled.
//
// It's probably best to keep this logic as simple as possible, see
// https://bugzilla.mozilla.org/show_bug.cgi?id=1885716 for an example of
// what can happen if we try to be clever here.
if (styleColorInterpolationMethod.space != StyleColorSpace::Srgb ||
gfxPlatform::GetCMSMode() == CMSMode::All) {
// For the specific case of longer hue interpolation on a CSS non-repeating
// gradient, we have to pretend there is another stop at position=1.0 that
// duplicates the last stop, this is probably only used for things like a
// color wheel. No such problem for SVG as it doesn't have that complexity.
bool extendLastStop = aMode == wr::ExtendMode::Clamp &&
styleColorInterpolationMethod.hue ==
StyleHueInterpolationMethod::Longer;
WrColorStopInterpolator interpolator(mStops, styleColorInterpolationMethod,
aOpacity, aStops, extendLastStop);
interpolator.CreateStops();
} else {
aStops.SetLength(mStops.Length());
for (uint32_t i = 0; i < mStops.Length(); i++) {
aStops[i].color = wr::ToColorF(ToDeviceColor(mStops[i].mColor));
aStops[i].color.a *= aOpacity;
aStops[i].offset = (float)mStops[i].mPosition;
}
}
aLineStart = LayoutDevicePoint(mLineStart.x, mLineStart.y);
aLineEnd = LayoutDevicePoint(mLineEnd.x, mLineEnd.y);
aGradientRadius = LayoutDeviceSize(mRadiusX, mRadiusY);
aGradientCenter = LayoutDevicePoint(mCenter.x, mCenter.y);
aGradientAngle = mAngle;
}
void nsCSSGradientRenderer::BuildWebRenderDisplayItems(
wr::DisplayListBuilder& aBuilder, const layers::StackingContextHelper& aSc,
const nsRect& aDest, const nsRect& aFillArea, const nsSize& aRepeatSize,
const CSSIntRect& aSrc, bool aIsBackfaceVisible, float aOpacity) {
if (aDest.IsEmpty() || aFillArea.IsEmpty()) {
return;
}
wr::ExtendMode extendMode;
nsTArray<wr::GradientStop> stops;
LayoutDevicePoint lineStart;
LayoutDevicePoint lineEnd;
LayoutDeviceSize gradientRadius;
LayoutDevicePoint gradientCenter;
float gradientAngle;
BuildWebRenderParameters(aOpacity, extendMode, stops, lineStart, lineEnd,
gradientRadius, gradientCenter, gradientAngle);
nscoord appUnitsPerDevPixel = mPresContext->AppUnitsPerDevPixel();
nsPoint firstTile =
nsPoint(FindTileStart(aFillArea.x, aDest.x, aRepeatSize.width),
FindTileStart(aFillArea.y, aDest.y, aRepeatSize.height));
// Translate the parameters into device coordinates
LayoutDeviceRect clipBounds =
LayoutDevicePixel::FromAppUnits(aFillArea, appUnitsPerDevPixel);
LayoutDeviceRect firstTileBounds = LayoutDevicePixel::FromAppUnits(
nsRect(firstTile, aDest.Size()), appUnitsPerDevPixel);
LayoutDeviceSize tileRepeat =
LayoutDevicePixel::FromAppUnits(aRepeatSize, appUnitsPerDevPixel);
// Calculate the bounds of the gradient display item, which starts at the
// first tile and extends to the end of clip bounds
LayoutDevicePoint tileToClip =
clipBounds.BottomRight() - firstTileBounds.TopLeft();
LayoutDeviceRect gradientBounds = LayoutDeviceRect(
firstTileBounds.TopLeft(), LayoutDeviceSize(tileToClip.x, tileToClip.y));
// Calculate the tile spacing, which is the repeat size minus the tile size
LayoutDeviceSize tileSpacing = tileRepeat - firstTileBounds.Size();
// srcTransform is used for scaling the gradient to match aSrc
LayoutDeviceRect srcTransform = LayoutDeviceRect(
nsPresContext::CSSPixelsToAppUnits(aSrc.x),
nsPresContext::CSSPixelsToAppUnits(aSrc.y),
aDest.width / ((float)nsPresContext::CSSPixelsToAppUnits(aSrc.width)),
aDest.height / ((float)nsPresContext::CSSPixelsToAppUnits(aSrc.height)));
lineStart.x = (lineStart.x - srcTransform.x) * srcTransform.width;
lineStart.y = (lineStart.y - srcTransform.y) * srcTransform.height;
gradientCenter.x = (gradientCenter.x - srcTransform.x) * srcTransform.width;
gradientCenter.y = (gradientCenter.y - srcTransform.y) * srcTransform.height;
if (mGradient->IsLinear()) {
lineEnd.x = (lineEnd.x - srcTransform.x) * srcTransform.width;
lineEnd.y = (lineEnd.y - srcTransform.y) * srcTransform.height;
aBuilder.PushLinearGradient(
mozilla::wr::ToLayoutRect(gradientBounds),
mozilla::wr::ToLayoutRect(clipBounds), aIsBackfaceVisible,
mozilla::wr::ToLayoutPoint(lineStart),
mozilla::wr::ToLayoutPoint(lineEnd), stops, extendMode,
mozilla::wr::ToLayoutSize(firstTileBounds.Size()),
mozilla::wr::ToLayoutSize(tileSpacing));
} else if (mGradient->IsRadial()) {
gradientRadius.width *= srcTransform.width;
gradientRadius.height *= srcTransform.height;
aBuilder.PushRadialGradient(
mozilla::wr::ToLayoutRect(gradientBounds),
mozilla::wr::ToLayoutRect(clipBounds), aIsBackfaceVisible,
mozilla::wr::ToLayoutPoint(lineStart),
mozilla::wr::ToLayoutSize(gradientRadius), stops, extendMode,
mozilla::wr::ToLayoutSize(firstTileBounds.Size()),
mozilla::wr::ToLayoutSize(tileSpacing));
} else {
MOZ_ASSERT(mGradient->IsConic());
aBuilder.PushConicGradient(
mozilla::wr::ToLayoutRect(gradientBounds),
mozilla::wr::ToLayoutRect(clipBounds), aIsBackfaceVisible,
mozilla::wr::ToLayoutPoint(gradientCenter), gradientAngle, stops,
extendMode, mozilla::wr::ToLayoutSize(firstTileBounds.Size()),
mozilla::wr::ToLayoutSize(tileSpacing));
}
}
} // namespace mozilla
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