Source/core/rendering/shapes/Shape.cpp

/*
 * Copyright (C) 2012 Adobe Systems Incorporated. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above
 *    copyright notice, this list of conditions and the following
 *    disclaimer.
 * 2. Redistributions in binary form must reproduce the above
 *    copyright notice, this list of conditions and the following
 *    disclaimer in the documentation and/or other materials
 *    provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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#include "config.h"
#include "core/rendering/shapes/Shape.h"

#include "core/fetch/ImageResource.h"
#include "core/platform/graphics/ImageBuffer.h"
#include "core/rendering/shapes/PolygonShape.h"
#include "core/rendering/shapes/RasterShape.h"
#include "core/rendering/shapes/RectangleShape.h"
#include "platform/LengthFunctions.h"
#include "platform/geometry/FloatSize.h"
#include "platform/graphics/WindRule.h"
#include "wtf/MathExtras.h"
#include "wtf/OwnPtr.h"
#include "wtf/PassOwnPtr.h"

namespace WebCore {

static PassOwnPtr<Shape> createRectangleShape(const FloatRect& bounds, const FloatSize& radii)
{
    ASSERT(bounds.width() >= 0 && bounds.height() >= 0 && radii.width() >= 0 && radii.height() >= 0);
    return adoptPtr(new RectangleShape(bounds, radii));
}

static PassOwnPtr<Shape> createCircleShape(const FloatPoint& center, float radius)
{
    ASSERT(radius >= 0);
    return adoptPtr(new RectangleShape(FloatRect(center.x() - radius, center.y() - radius, radius*2, radius*2), FloatSize(radius, radius)));
}

static PassOwnPtr<Shape> createEllipseShape(const FloatPoint& center, const FloatSize& radii)
{
    ASSERT(radii.width() >= 0 && radii.height() >= 0);
    return adoptPtr(new RectangleShape(FloatRect(center.x() - radii.width(), center.y() - radii.height(), radii.width()*2, radii.height()*2), radii));
}

static PassOwnPtr<Shape> createPolygonShape(PassOwnPtr<Vector<FloatPoint> > vertices, WindRule fillRule)
{
    return adoptPtr(new PolygonShape(vertices, fillRule));
}

static inline FloatRect physicalRectToLogical(const FloatRect& rect, float logicalBoxHeight, WritingMode writingMode)
{
    if (isHorizontalWritingMode(writingMode))
        return rect;
    if (isFlippedBlocksWritingMode(writingMode))
        return FloatRect(rect.y(), logicalBoxHeight - rect.maxX(), rect.height(), rect.width());
    return rect.transposedRect();
}

static inline FloatPoint physicalPointToLogical(const FloatPoint& point, float logicalBoxHeight, WritingMode writingMode)
{
    if (isHorizontalWritingMode(writingMode))
        return point;
    if (isFlippedBlocksWritingMode(writingMode))
        return FloatPoint(point.y(), logicalBoxHeight - point.x());
    return point.transposedPoint();
}

static inline FloatSize physicalSizeToLogical(const FloatSize& size, WritingMode writingMode)
{
    if (isHorizontalWritingMode(writingMode))
        return size;
    return size.transposedSize();
}

static inline void ensureRadiiDoNotOverlap(FloatRect &bounds, FloatSize &radii)
{
    float widthRatio = bounds.width() / (2 * radii.width());
    float heightRatio = bounds.height() / (2 * radii.height());
    float reductionRatio = std::min<float>(widthRatio, heightRatio);
    if (reductionRatio < 1) {
        radii.setWidth(reductionRatio * radii.width());
        radii.setHeight(reductionRatio * radii.height());
    }
}

PassOwnPtr<Shape> Shape::createShape(const BasicShape* basicShape, const LayoutSize& logicalBoxSize, WritingMode writingMode, Length margin, Length padding)
{
    ASSERT(basicShape);

    bool horizontalWritingMode = isHorizontalWritingMode(writingMode);
    float boxWidth = horizontalWritingMode ? logicalBoxSize.width() : logicalBoxSize.height();
    float boxHeight = horizontalWritingMode ? logicalBoxSize.height() : logicalBoxSize.width();
    OwnPtr<Shape> shape;

    switch (basicShape->type()) {

    case BasicShape::BasicShapeRectangleType: {
        const BasicShapeRectangle* rectangle = static_cast<const BasicShapeRectangle*>(basicShape);
        FloatRect bounds(
            floatValueForLength(rectangle->x(), boxWidth),
            floatValueForLength(rectangle->y(), boxHeight),
            floatValueForLength(rectangle->width(), boxWidth),
            floatValueForLength(rectangle->height(), boxHeight));
        FloatSize cornerRadii(
            floatValueForLength(rectangle->cornerRadiusX(), boxWidth),
            floatValueForLength(rectangle->cornerRadiusY(), boxHeight));
        ensureRadiiDoNotOverlap(bounds, cornerRadii);
        FloatRect logicalBounds = physicalRectToLogical(bounds, logicalBoxSize.height(), writingMode);

        shape = createRectangleShape(logicalBounds, physicalSizeToLogical(cornerRadii, writingMode));
        break;
    }

    case BasicShape::BasicShapeCircleType: {
        const BasicShapeCircle* circle = static_cast<const BasicShapeCircle*>(basicShape);
        float centerX = floatValueForLength(circle->centerX(), boxWidth);
        float centerY = floatValueForLength(circle->centerY(), boxHeight);
        // This method of computing the radius is as defined in SVG
        // (http://www.w3.org/TR/SVG/coords.html#Units). It bases the radius
        // off of the diagonal of the box and ensures that if the box is
        // square, the radius is equal to half the diagonal.
        float radius = floatValueForLength(circle->radius(), sqrtf((boxWidth * boxWidth + boxHeight * boxHeight) / 2));
        FloatPoint logicalCenter = physicalPointToLogical(FloatPoint(centerX, centerY), logicalBoxSize.height(), writingMode);

        shape = createCircleShape(logicalCenter, radius);
        break;
    }

    case BasicShape::BasicShapeEllipseType: {
        const BasicShapeEllipse* ellipse = static_cast<const BasicShapeEllipse*>(basicShape);
        float centerX = floatValueForLength(ellipse->centerX(), boxWidth);
        float centerY = floatValueForLength(ellipse->centerY(), boxHeight);
        float radiusX = floatValueForLength(ellipse->radiusX(), boxWidth);
        float radiusY = floatValueForLength(ellipse->radiusY(), boxHeight);
        FloatPoint logicalCenter = physicalPointToLogical(FloatPoint(centerX, centerY), logicalBoxSize.height(), writingMode);
        FloatSize logicalRadii = physicalSizeToLogical(FloatSize(radiusX, radiusY), writingMode);

        shape = createEllipseShape(logicalCenter, logicalRadii);
        break;
    }

    case BasicShape::BasicShapePolygonType: {
        const BasicShapePolygon* polygon = static_cast<const BasicShapePolygon*>(basicShape);
        const Vector<Length>& values = polygon->values();
        size_t valuesSize = values.size();
        ASSERT(!(valuesSize % 2));
        OwnPtr<Vector<FloatPoint> > vertices = adoptPtr(new Vector<FloatPoint>(valuesSize / 2));
        for (unsigned i = 0; i < valuesSize; i += 2) {
            FloatPoint vertex(
                floatValueForLength(values.at(i), boxWidth),
                floatValueForLength(values.at(i + 1), boxHeight));
            (*vertices)[i / 2] = physicalPointToLogical(vertex, logicalBoxSize.height(), writingMode);
        }
        shape = createPolygonShape(vertices.release(), polygon->windRule());
        break;
    }

    case BasicShape::BasicShapeInsetRectangleType: {
        const BasicShapeInsetRectangle* rectangle = static_cast<const BasicShapeInsetRectangle*>(basicShape);
        float left = floatValueForLength(rectangle->left(), boxWidth);
        float top = floatValueForLength(rectangle->top(), boxHeight);
        FloatRect bounds(
            left,
            top,
            boxWidth - left - floatValueForLength(rectangle->right(), boxWidth),
            boxHeight - top - floatValueForLength(rectangle->bottom(), boxHeight));
        FloatSize cornerRadii(
            floatValueForLength(rectangle->cornerRadiusX(), boxWidth),
            floatValueForLength(rectangle->cornerRadiusY(), boxHeight));
        ensureRadiiDoNotOverlap(bounds, cornerRadii);
        FloatRect logicalBounds = physicalRectToLogical(bounds, logicalBoxSize.height(), writingMode);

        shape = createRectangleShape(logicalBounds, physicalSizeToLogical(cornerRadii, writingMode));
        break;
    }

    default:
        ASSERT_NOT_REACHED();
    }

    shape->m_writingMode = writingMode;
    shape->m_margin = floatValueForLength(margin, 0);
    shape->m_padding = floatValueForLength(padding, 0);

    return shape.release();
}

PassOwnPtr<Shape> Shape::createShape(const StyleImage* styleImage, float threshold, const LayoutSize&, WritingMode writingMode, Length margin, Length padding)
{
    ASSERT(styleImage && styleImage->isImageResource() && styleImage->cachedImage() && styleImage->cachedImage()->image());

    Image* image = styleImage->cachedImage()->image();
    const IntSize& imageSize = image->size();
    OwnPtr<ImageBuffer> imageBuffer = ImageBuffer::create(imageSize);

    OwnPtr<RasterShapeIntervals> intervals = adoptPtr(new RasterShapeIntervals(imageSize.height()));

    if (imageBuffer) {
        GraphicsContext* graphicsContext = imageBuffer->context();
        graphicsContext->drawImage(image, IntPoint());

        RefPtr<Uint8ClampedArray> pixelArray = imageBuffer->getUnmultipliedImageData(IntRect(IntPoint(), imageSize));
        unsigned pixelArrayLength = pixelArray->length();
        unsigned pixelArrayOffset = 3; // Each pixel is four bytes: RGBA.
        uint8_t alphaPixelThreshold = threshold * 255;

        ASSERT(static_cast<unsigned>(imageSize.width() * imageSize.height() * 4) == pixelArrayLength);

        for (int y = 0; y < imageSize.height(); ++y) {
            int startX = -1;
            for (int x = 0; x < imageSize.width() && pixelArrayOffset < pixelArrayLength; ++x, pixelArrayOffset += 4) {
                uint8_t alpha = pixelArray->item(pixelArrayOffset);
                if ((startX == -1) && alpha > alphaPixelThreshold) {
                    startX = x;
                } else if (startX != -1 && (alpha <= alphaPixelThreshold || x == imageSize.width() - 1)) {
                    intervals->appendInterval(y, startX, x);
                    startX = -1;
                }
            }
        }
    }

    OwnPtr<RasterShape> rasterShape = adoptPtr(new RasterShape(intervals.release(), imageSize));
    rasterShape->m_writingMode = writingMode;
    rasterShape->m_margin = floatValueForLength(margin, 0);
    rasterShape->m_padding = floatValueForLength(padding, 0);
    return rasterShape.release();
}

} // namespace WebCore