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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 "gfx2DGlue.h"
#include "mozilla/ArrayUtils.h"
#include "mozilla/DebugOnly.h"
#include "mozilla/gfx/2D.h"
#include "mozilla/gfx/Helpers.h"
#include "mozilla/MathAlgorithms.h"
#include "nsStyleConsts.h"
#include "nsPresContext.h"
#include "nsPoint.h"
#include "nsRect.h"
#include "nsStyleContext.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"
using namespace mozilla;
using namespace mozilla::gfx;
static gfxFloat
ConvertGradientValueToPixels(const nsStyleCoord& aCoord,
gfxFloat aFillLength,
int32_t aAppUnitsPerPixel)
{
switch (aCoord.GetUnit()) {
case eStyleUnit_Percent:
return aCoord.GetPercentValue() * aFillLength;
case eStyleUnit_Coord:
return NSAppUnitsToFloatPixels(aCoord.GetCoordValue(), aAppUnitsPerPixel);
case eStyleUnit_Calc: {
const nsStyleCoord::Calc *calc = aCoord.GetCalcValue();
return calc->mPercent * aFillLength +
NSAppUnitsToFloatPixels(calc->mLength, aAppUnitsPerPixel);
}
default:
NS_WARNING("Unexpected coord unit");
return 0;
}
}
// 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 gfxPoint
ComputeGradientLineEndFromAngle(const gfxPoint& aStart,
double aAngle,
const gfxSize& aBoxSize)
{
double dx = cos(-aAngle);
double dy = sin(-aAngle);
gfxPoint farthestCorner(dx > 0 ? aBoxSize.width : 0,
dy > 0 ? aBoxSize.height : 0);
gfxPoint delta = farthestCorner - aStart;
double u = delta.x*dy - delta.y*dx;
return farthestCorner + gfxPoint(-u*dy, u*dx);
}
// Compute the start and end points of the gradient line for a linear gradient.
static void
ComputeLinearGradientLine(nsPresContext* aPresContext,
nsStyleGradient* aGradient,
const gfxSize& aBoxSize,
gfxPoint* aLineStart,
gfxPoint* aLineEnd)
{
if (aGradient->mBgPosX.GetUnit() == eStyleUnit_None) {
double angle;
if (aGradient->mAngle.IsAngleValue()) {
angle = aGradient->mAngle.GetAngleValueInRadians();
if (!aGradient->mLegacySyntax) {
angle = M_PI_2 - angle;
}
} else {
angle = -M_PI_2; // defaults to vertical gradient starting from top
}
gfxPoint center(aBoxSize.width/2, aBoxSize.height/2);
*aLineEnd = ComputeGradientLineEndFromAngle(center, angle, aBoxSize);
*aLineStart = gfxPoint(aBoxSize.width, aBoxSize.height) - *aLineEnd;
} else if (!aGradient->mLegacySyntax) {
float xSign = aGradient->mBgPosX.GetPercentValue() * 2 - 1;
float ySign = 1 - aGradient->mBgPosY.GetPercentValue() * 2;
double angle = atan2(ySign * aBoxSize.width, xSign * aBoxSize.height);
gfxPoint center(aBoxSize.width/2, aBoxSize.height/2);
*aLineEnd = ComputeGradientLineEndFromAngle(center, angle, aBoxSize);
*aLineStart = gfxPoint(aBoxSize.width, aBoxSize.height) - *aLineEnd;
} else {
int32_t appUnitsPerPixel = aPresContext->AppUnitsPerDevPixel();
*aLineStart = gfxPoint(
ConvertGradientValueToPixels(aGradient->mBgPosX, aBoxSize.width,
appUnitsPerPixel),
ConvertGradientValueToPixels(aGradient->mBgPosY, aBoxSize.height,
appUnitsPerPixel));
if (aGradient->mAngle.IsAngleValue()) {
MOZ_ASSERT(aGradient->mLegacySyntax);
double angle = aGradient->mAngle.GetAngleValueInRadians();
*aLineEnd = ComputeGradientLineEndFromAngle(*aLineStart, angle, aBoxSize);
} else {
// No angle, the line end is just the reflection of the start point
// through the center of the box
*aLineEnd = gfxPoint(aBoxSize.width, aBoxSize.height) - *aLineStart;
}
}
}
// 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 void
ComputeRadialGradientLine(nsPresContext* aPresContext,
nsStyleGradient* aGradient,
const gfxSize& aBoxSize,
gfxPoint* aLineStart,
gfxPoint* aLineEnd,
double* aRadiusX,
double* aRadiusY)
{
if (aGradient->mBgPosX.GetUnit() == eStyleUnit_None) {
// Default line start point is the center of the box
*aLineStart = gfxPoint(aBoxSize.width/2, aBoxSize.height/2);
} else {
int32_t appUnitsPerPixel = aPresContext->AppUnitsPerDevPixel();
*aLineStart = gfxPoint(
ConvertGradientValueToPixels(aGradient->mBgPosX, aBoxSize.width,
appUnitsPerPixel),
ConvertGradientValueToPixels(aGradient->mBgPosY, aBoxSize.height,
appUnitsPerPixel));
}
// Compute gradient shape: the x and y radii of an ellipse.
double radiusX, radiusY;
double leftDistance = Abs(aLineStart->x);
double rightDistance = Abs(aBoxSize.width - aLineStart->x);
double topDistance = Abs(aLineStart->y);
double bottomDistance = Abs(aBoxSize.height - aLineStart->y);
switch (aGradient->mSize) {
case NS_STYLE_GRADIENT_SIZE_CLOSEST_SIDE:
radiusX = std::min(leftDistance, rightDistance);
radiusY = std::min(topDistance, bottomDistance);
if (aGradient->mShape == NS_STYLE_GRADIENT_SHAPE_CIRCULAR) {
radiusX = radiusY = std::min(radiusX, radiusY);
}
break;
case NS_STYLE_GRADIENT_SIZE_CLOSEST_CORNER: {
// Compute x and y distances to nearest corner
double offsetX = std::min(leftDistance, rightDistance);
double offsetY = std::min(topDistance, bottomDistance);
if (aGradient->mShape == NS_STYLE_GRADIENT_SHAPE_CIRCULAR) {
radiusX = radiusY = NS_hypot(offsetX, offsetY);
} else {
// maintain aspect ratio
radiusX = offsetX*M_SQRT2;
radiusY = offsetY*M_SQRT2;
}
break;
}
case NS_STYLE_GRADIENT_SIZE_FARTHEST_SIDE:
radiusX = std::max(leftDistance, rightDistance);
radiusY = std::max(topDistance, bottomDistance);
if (aGradient->mShape == NS_STYLE_GRADIENT_SHAPE_CIRCULAR) {
radiusX = radiusY = std::max(radiusX, radiusY);
}
break;
case NS_STYLE_GRADIENT_SIZE_FARTHEST_CORNER: {
// Compute x and y distances to nearest corner
double offsetX = std::max(leftDistance, rightDistance);
double offsetY = std::max(topDistance, bottomDistance);
if (aGradient->mShape == NS_STYLE_GRADIENT_SHAPE_CIRCULAR) {
radiusX = radiusY = NS_hypot(offsetX, offsetY);
} else {
// maintain aspect ratio
radiusX = offsetX*M_SQRT2;
radiusY = offsetY*M_SQRT2;
}
break;
}
case NS_STYLE_GRADIENT_SIZE_EXPLICIT_SIZE: {
int32_t appUnitsPerPixel = aPresContext->AppUnitsPerDevPixel();
radiusX = ConvertGradientValueToPixels(aGradient->mRadiusX,
aBoxSize.width, appUnitsPerPixel);
radiusY = ConvertGradientValueToPixels(aGradient->mRadiusY,
aBoxSize.height, appUnitsPerPixel);
break;
}
default:
radiusX = radiusY = 0;
MOZ_ASSERT(false, "unknown radial gradient sizing method");
}
*aRadiusX = radiusX;
*aRadiusY = radiusY;
double angle;
if (aGradient->mAngle.IsAngleValue()) {
angle = aGradient->mAngle.GetAngleValueInRadians();
} else {
// Default angle is 0deg
angle = 0.0;
}
// The gradient line end point is where the gradient line intersects
// the ellipse.
*aLineEnd = *aLineStart + gfxPoint(radiusX*cos(-angle), radiusY*sin(-angle));
}
static float Interpolate(float aF1, float aF2, float aFrac)
{
return aF1 + aFrac * (aF2 - aF1);
}
// Returns aFrac*aC2 + (1 - aFrac)*C1. The interpolation is done
// in unpremultiplied space, which is what SVG gradients and cairo
// gradients expect.
static Color
InterpolateColor(const Color& aC1, const Color& aC2, float aFrac)
{
double other = 1 - aFrac;
return Color(aC2.r*aFrac + aC1.r*other,
aC2.g*aFrac + aC1.g*other,
aC2.b*aFrac + aC1.b*other,
aC2.a*aFrac + aC1.a*other);
}
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 * p.x + d.y * p.y;
double denominator = d.x * d.x + d.y * d.y;
return numerator / denominator;
}
static bool
RectIsBeyondLinearGradientEdge(const gfxRect& aRect,
const gfxMatrix& aPatternMatrix,
const nsTArray<ColorStop>& aStops,
const gfxPoint& aGradientStart,
const gfxPoint& aGradientEnd,
Color* 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;
}
Color color1 = stops[x-1].mColor;
Color 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 (size_t y = 0; y < 9; y++) {
// 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.
float relativeOffset = (newStops[y].mPosition - offset1) / (offset2 - offset1);
float multiplier = powf(relativeOffset, logf(.5f) / logf(midpoint));
gfx::Float red = color1.r + multiplier * (color2.r - color1.r);
gfx::Float green = color1.g + multiplier * (color2.g - color1.g);
gfx::Float blue = color1.b + multiplier * (color2.b - color1.b);
gfx::Float alpha = color1.a + multiplier * (color2.a - color1.a);
newStops[y].mColor = Color(red, green, blue, alpha);
}
stops.ReplaceElementsAt(x, 1, newStops, 9);
x += 9;
}
}
static Color
Premultiply(const Color& aColor)
{
gfx::Float a = aColor.a;
return Color(aColor.r * a, aColor.g * a, aColor.b * a, a);
}
static Color
Unpremultiply(const Color& aColor)
{
gfx::Float a = aColor.a;
return (a > 0.f)
? Color(aColor.r / a, aColor.g / a, aColor.b / a, a)
: aColor;
}
static Color
TransparentColor(Color aColor) {
aColor.a = 0;
return aColor;
}
// 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
if (leftStop.mColor.a == rightStop.mColor.a) {
continue;
}
// Is the stop on the left 100% transparent? If so, have it adopt the color
// of the right stop
if (leftStop.mColor.a == 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.a == 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.a != 1.0f || rightStop.mColor.a != 1.0f) {
Color premulLeftColor = Premultiply(leftStop.mColor);
Color premulRightColor = Premultiply(rightStop.mColor);
// Calculate how many extra steps. We do a step per 10% transparency.
size_t stepCount = NSToIntFloor(fabsf(leftStop.mColor.a - rightStop.mColor.a) / 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,
Unpremultiply(InterpolateColor(premulLeftColor, premulRightColor, frac)));
aStops.InsertElementAt(x, newStop);
x++;
}
}
}
}
static ColorStop
InterpolateColorStop(const ColorStop& aFirst, const ColorStop& aSecond,
double aPosition, const Color& 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,
Unpremultiply(InterpolateColor(Premultiply(aFirst.mColor),
Premultiply(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) {
Color 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.RemoveElementsAt(i + 1, 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 {
nsCSSGradientRenderer
nsCSSGradientRenderer::Create(nsPresContext* aPresContext,
nsStyleGradient* aGradient,
const nsSize& aIntrinsicSize)
{
nscoord appUnitsPerDevPixel = aPresContext->AppUnitsPerDevPixel();
gfxSize srcSize = gfxSize(gfxFloat(aIntrinsicSize.width)/appUnitsPerDevPixel,
gfxFloat(aIntrinsicSize.height)/appUnitsPerDevPixel);
// Compute "gradient line" start and end relative to the intrinsic size of
// the gradient.
gfxPoint lineStart, lineEnd;
double radiusX = 0, radiusY = 0; // for radial gradients only
if (aGradient->mShape == NS_STYLE_GRADIENT_SHAPE_LINEAR) {
ComputeLinearGradientLine(aPresContext, aGradient, srcSize,
&lineStart, &lineEnd);
} else {
ComputeRadialGradientLine(aPresContext, aGradient, srcSize,
&lineStart, &lineEnd, &radiusX, &radiusY);
}
// Avoid sending Infs or Nans to downwind draw targets.
if (!lineStart.IsFinite() || !lineEnd.IsFinite()) {
lineStart = lineEnd = gfxPoint(0, 0);
}
gfxFloat lineLength = NS_hypot(lineEnd.x - lineStart.x,
lineEnd.y - lineStart.y);
MOZ_ASSERT(aGradient->mStops.Length() >= 2,
"The parser should reject gradients with less than two stops");
// Build color stop array and compute stop positions
nsTArray<ColorStop> stops;
// 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, otherwise
// it's -1.
int32_t firstUnsetPosition = -1;
for (uint32_t i = 0; i < aGradient->mStops.Length(); ++i) {
const nsStyleGradientStop& stop = aGradient->mStops[i];
double position;
switch (stop.mLocation.GetUnit()) {
case eStyleUnit_None:
if (i == 0) {
// First stop defaults to position 0.0
position = 0.0;
} else if (i == aGradient->mStops.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.
// Remeber where the run of stops with no specified position starts,
// if it starts here.
if (firstUnsetPosition < 0) {
firstUnsetPosition = i;
}
stops.AppendElement(ColorStop(0, stop.mIsInterpolationHint,
Color::FromABGR(stop.mColor)));
continue;
}
break;
case eStyleUnit_Percent:
position = stop.mLocation.GetPercentValue();
break;
case eStyleUnit_Coord:
position = lineLength < 1e-6 ? 0.0 :
stop.mLocation.GetCoordValue() / appUnitsPerDevPixel / lineLength;
break;
case eStyleUnit_Calc:
nsStyleCoord::Calc *calc;
calc = stop.mLocation.GetCalcValue();
position = calc->mPercent +
((lineLength < 1e-6) ? 0.0 :
(NSAppUnitsToFloatPixels(calc->mLength, appUnitsPerDevPixel) / lineLength));
break;
default:
MOZ_ASSERT(false, "Unknown stop position type");
}
if (i > 0) {
// Prevent decreasing stop positions by advancing this position
// to the previous stop position, if necessary
double previousPosition = firstUnsetPosition > 0
? stops[firstUnsetPosition - 1].mPosition
: stops[i - 1].mPosition;
position = std::max(position, previousPosition);
}
stops.AppendElement(ColorStop(position, stop.mIsInterpolationHint,
Color::FromABGR(stop.mColor)));
if (firstUnsetPosition > 0) {
// 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 (uint32_t j = firstUnsetPosition; j < i; ++j) {
p += d;
stops[j].mPosition = p;
}
firstUnsetPosition = -1;
}
}
ResolveMidpoints(stops);
nsCSSGradientRenderer renderer;
renderer.mPresContext = aPresContext;
renderer.mGradient = aGradient;
renderer.mStops = std::move(stops);
renderer.mLineStart = lineStart;
renderer.mLineEnd = lineEnd;
renderer.mRadiusX = radiusX;
renderer.mRadiusY = radiusY;
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->mShape == NS_STYLE_GRADIENT_SHAPE_LINEAR &&
(mLineStart.x == mLineEnd.x) != (mLineStart.y == mLineEnd.y) &&
aRepeatSize.width == aDest.width && aRepeatSize.height == aDest.height &&
!mGradient->mRepeating && !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->mShape != NS_STYLE_GRADIENT_SHAPE_LINEAR && firstStop < 0.0) {
if (mGradient->mRepeating) {
// 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 =
InterpolateColor(mStops[i].mColor, mStops[i + 1].mColor, frac);
}
}
}
}
}
firstStop = mStops[0].mPosition;
MOZ_ASSERT(firstStop >= 0.0, "Failed to fix stop offsets");
}
if (mGradient->mShape != NS_STYLE_GRADIENT_SHAPE_LINEAR && !mGradient->mRepeating) {
// 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->mShape != NS_STYLE_GRADIENT_SHAPE_LINEAR &&
(mRadiusX < 1e-6 || mRadiusY < 1e-6);
if (stopDelta < 1e-6 || 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->mRepeating || zeroRadius) {
mRadiusX = mRadiusY = 0.0;
}
stopDelta = 0.0;
lastStop = firstStop;
}
// 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->mRepeating || 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->mShape == NS_STYLE_GRADIENT_SHAPE_LINEAR) {
// 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 {
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);
}
}
// 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(mPresContext->CSSPixelsToAppUnits(aSrc.width))/aDest.width,
gfxFloat(mPresContext->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).
Color firstColor(mStops[0].mColor);
Color lastColor(mStops.LastElement().mColor);
mStops.Clear();
if (!mGradient->mRepeating && !zeroRadius) {
mStops.AppendElement(ColorStop(firstStop, false, firstColor));
}
mStops.AppendElement(ColorStop(firstStop, false, lastColor));
}
ResolvePremultipliedAlpha(mStops);
bool isRepeat = mGradient->mRepeating || 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 = 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();
// 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();
Color edgeColor;
if (mGradient->mShape == NS_STYLE_GRADIENT_SHAPE_LINEAR && !isRepeat &&
RectIsBeyondLinearGradientEdge(fillRectRelativeToTile, matrix, mStops,
gradientStart, gradientEnd, &edgeColor)) {
edgeColor.a *= aOpacity;
aContext.SetColor(edgeColor);
} else {
aContext.SetMatrixDouble(
aContext.CurrentMatrixDouble().Copy().PreTranslate(tileRect.TopLeft()));
aContext.SetPattern(gradientPattern);
}
aContext.Fill();
aContext.SetMatrix(ctm);
}
}
}
void
nsCSSGradientRenderer::BuildWebRenderParameters(float aOpacity,
wr::ExtendMode& aMode,
nsTArray<wr::GradientStop>& aStops,
LayoutDevicePoint& aLineStart,
LayoutDevicePoint& aLineEnd,
LayoutDeviceSize& aGradientRadius)
{
aMode = mGradient->mRepeating ? wr::ExtendMode::Repeat : wr::ExtendMode::Clamp;
aStops.SetLength(mStops.Length());
for(uint32_t i = 0; i < mStops.Length(); i++) {
aStops[i].color.r = mStops[i].mColor.r;
aStops[i].color.g = mStops[i].mColor.g;
aStops[i].color.b = mStops[i].mColor.b;
aStops[i].color.a = mStops[i].mColor.a * aOpacity;
aStops[i].offset = mStops[i].mPosition;
}
aLineStart = LayoutDevicePoint(mLineStart.x, mLineStart.y);
aLineEnd = LayoutDevicePoint(mLineEnd.x, mLineEnd.y);
aGradientRadius = LayoutDeviceSize(mRadiusX, mRadiusY);
}
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;
BuildWebRenderParameters(aOpacity, extendMode, stops, lineStart, lineEnd, gradientRadius);
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();
// Make the rects relative to the parent stacking context
wr::LayoutRect wrClipBounds = aSc.ToRelativeLayoutRect(clipBounds);
wr::LayoutRect wrGradientBounds = aSc.ToRelativeLayoutRect(gradientBounds);
// srcTransform is used for scaling the gradient to match aSrc
LayoutDeviceRect srcTransform = LayoutDeviceRect(mPresContext->CSSPixelsToAppUnits(aSrc.x),
mPresContext->CSSPixelsToAppUnits(aSrc.y),
aDest.width / ((float)mPresContext->CSSPixelsToAppUnits(aSrc.width)),
aDest.height / ((float)mPresContext->CSSPixelsToAppUnits(aSrc.height)));
lineStart.x = (lineStart.x - srcTransform.x) * srcTransform.width;
lineStart.y = (lineStart.y - srcTransform.y) * srcTransform.height;
if (mGradient->mShape == NS_STYLE_GRADIENT_SHAPE_LINEAR) {
lineEnd.x = (lineEnd.x - srcTransform.x) * srcTransform.width;
lineEnd.y = (lineEnd.y - srcTransform.y) * srcTransform.height;
aBuilder.PushLinearGradient(
wrGradientBounds,
wrClipBounds,
aIsBackfaceVisible,
mozilla::wr::ToLayoutPoint(lineStart),
mozilla::wr::ToLayoutPoint(lineEnd),
stops,
extendMode,
mozilla::wr::ToLayoutSize(firstTileBounds.Size()),
mozilla::wr::ToLayoutSize(tileSpacing));
} else {
gradientRadius.width *= srcTransform.width;
gradientRadius.height *= srcTransform.height;
aBuilder.PushRadialGradient(
wrGradientBounds,
wrClipBounds,
aIsBackfaceVisible,
mozilla::wr::ToLayoutPoint(lineStart),
mozilla::wr::ToLayoutSize(gradientRadius),
stops,
extendMode,
mozilla::wr::ToLayoutSize(firstTileBounds.Size()),
mozilla::wr::ToLayoutSize(tileSpacing));
}
}
} // namespace mozilla
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