third_party/WebKit/Source/core/paint/BoxReflectionUtils.cpp

// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "core/paint/BoxReflectionUtils.h"

#include "core/layout/LayoutBox.h"
#include "core/paint/NinePieceImagePainter.h"
#include "core/paint/PaintLayer.h"
#include "platform/LengthFunctions.h"
#include "platform/geometry/FloatRect.h"
#include "platform/geometry/LayoutPoint.h"
#include "platform/geometry/LayoutRect.h"
#include "platform/graphics/BoxReflection.h"
#include "platform/graphics/paint/DrawingRecorder.h"
#include "platform/graphics/paint/SkPictureBuilder.h"

namespace blink {

BoxReflection boxReflectionForPaintLayer(const PaintLayer& layer, const ComputedStyle& style)
{
    const StyleReflection* reflectStyle = style.boxReflect();

    LayoutRect frameLayoutRect = toLayoutBox(layer.layoutObject())->frameRect();
    FloatRect frameRect(frameLayoutRect);
    BoxReflection::ReflectionDirection direction = BoxReflection::VerticalReflection;
    float offset = 0;
    switch (reflectStyle->direction()) {
    case ReflectionAbove:
        direction = BoxReflection::VerticalReflection;
        offset = -floatValueForLength(reflectStyle->offset(), frameRect.height());
        break;
    case ReflectionBelow:
        direction = BoxReflection::VerticalReflection;
        offset = 2 * frameRect.height() + floatValueForLength(reflectStyle->offset(), frameRect.height());
        break;
    case ReflectionLeft:
        direction = BoxReflection::HorizontalReflection;
        offset = -floatValueForLength(reflectStyle->offset(), frameRect.width());
        break;
    case ReflectionRight:
        direction = BoxReflection::HorizontalReflection;
        offset = 2 * frameRect.width() + floatValueForLength(reflectStyle->offset(), frameRect.width());
        break;
    }

    // Since the filter origin is the corner of the input bounds, which may
    // include visual overflow (e.g. due to box-shadow), we must adjust the
    // offset to also account for this offset (this is equivalent to using
    // SkLocalMatrixImageFilter, but simpler).
    // The rect used here should match the one used in FilterPainter.
    LayoutRect filterInputBounds = layer.physicalBoundingBoxIncludingReflectionAndStackingChildren(LayoutPoint());
    offset -= 2 * (direction == BoxReflection::VerticalReflection ? filterInputBounds.y() : filterInputBounds.x()).toFloat();

    RefPtr<SkPicture> mask;
    const NinePieceImage& maskNinePiece = reflectStyle->mask();
    if (maskNinePiece.hasImage()) {
        LayoutRect maskRect(LayoutPoint(), frameLayoutRect.size());
        maskRect.moveBy(-filterInputBounds.location());

        LayoutRect maskBoundingRect(maskRect);
        maskBoundingRect.expand(style.imageOutsets(maskNinePiece));
        FloatRect maskBoundingFloatRect(maskBoundingRect);

        // TODO(jbroman): SkPictureBuilder + DrawingRecorder seems excessive.
        // If NinePieceImagePainter operated on SkCanvas, we'd only need an
        // SkPictureRecorder here.
        SkPictureBuilder recorder(maskBoundingFloatRect);
        {
            GraphicsContext& context = recorder.context();
            DrawingRecorder drawingRecorder(context, *layer.layoutObject(), DisplayItem::ReflectionMask, maskBoundingFloatRect);
            NinePieceImagePainter(*layer.layoutObject()).paint(
                recorder.context(), maskRect, style, maskNinePiece, SkXfermode::kSrcOver_Mode);
        }
        mask = recorder.endRecording();
    }

    return BoxReflection(direction, offset, mask);
}

} // namespace blink