SkiaUtils.cpp   [plain text]

/*
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 * in the documentation and/or other materials provided with the
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 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 * 
 * 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
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 */

#include "config.h"

#include "SkiaUtils.h"

#include "ImageBuffer.h"
#include "SharedBuffer.h"
#include "SkCanvas.h"
#include "SkColorPriv.h"
#include "SkMatrix.h"
#include "SkRegion.h"

namespace WebCore {

static const struct CompositOpToXfermodeMode {
    uint8_t mCompositOp;
    uint8_t m_xfermodeMode;
} gMapCompositOpsToXfermodeModes[] = {
    { CompositeClear,           SkXfermode::kClear_Mode },
    { CompositeCopy,            SkXfermode::kSrc_Mode },
    { CompositeSourceOver,      SkXfermode::kSrcOver_Mode },
    { CompositeSourceIn,        SkXfermode::kSrcIn_Mode },
    { CompositeSourceOut,       SkXfermode::kSrcOut_Mode },
    { CompositeSourceAtop,      SkXfermode::kSrcATop_Mode },
    { CompositeDestinationOver, SkXfermode::kDstOver_Mode },
    { CompositeDestinationIn,   SkXfermode::kDstIn_Mode },
    { CompositeDestinationOut,  SkXfermode::kDstOut_Mode },
    { CompositeDestinationAtop, SkXfermode::kDstATop_Mode },
    { CompositeXOR,             SkXfermode::kXor_Mode },
    { CompositePlusDarker,      SkXfermode::kDarken_Mode },
    { CompositePlusLighter,     SkXfermode::kPlus_Mode }
};

SkXfermode::Mode WebCoreCompositeToSkiaComposite(CompositeOperator op)
{
    const CompositOpToXfermodeMode* table = gMapCompositOpsToXfermodeModes;
    
    for (unsigned i = 0; i < SK_ARRAY_COUNT(gMapCompositOpsToXfermodeModes); i++) {
        if (table[i].mCompositOp == op)
            return (SkXfermode::Mode)table[i].m_xfermodeMode;
    }

    SkDEBUGF(("GraphicsContext::setPlatformCompositeOperation unknown CompositeOperator %d\n", op));
    return SkXfermode::kSrcOver_Mode; // fall-back
}

static U8CPU InvScaleByte(U8CPU component, uint32_t scale)
{
    SkASSERT(component == (uint8_t)component);
    return (component * scale + 0x8000) >> 16;
}

SkColor SkPMColorToColor(SkPMColor pm)
{
    if (!pm)
        return 0;
    unsigned a = SkGetPackedA32(pm);
    if (!a) {
        // A zero alpha value when there are non-zero R, G, or B channels is an
        // invalid premultiplied color (since all channels should have been
        // multiplied by 0 if a=0).
        SkASSERT(false); 
        // In production, return 0 to protect against division by zero.
        return 0;
    }
    
    uint32_t scale = (255 << 16) / a;
    
    return SkColorSetARGB(a,
                          InvScaleByte(SkGetPackedR32(pm), scale),
                          InvScaleByte(SkGetPackedG32(pm), scale),
                          InvScaleByte(SkGetPackedB32(pm), scale));
}

Color SkPMColorToWebCoreColor(SkPMColor pm)
{
    return SkPMColorToColor(pm);
}

void ClipRectToCanvas(const SkCanvas& canvas, const SkRect& srcRect, SkRect* destRect)
{
    if (!canvas.getClipBounds(destRect) || !destRect->intersect(srcRect))
        destRect->setEmpty();
}

bool SkPathContainsPoint(SkPath* originalPath, const FloatPoint& point, SkPath::FillType ft)
{
    SkRect bounds = originalPath->getBounds();

    // We can immediately return false if the point is outside the bounding
    // rect.  We don't use bounds.contains() here, since it would exclude
    // points on the right and bottom edges of the bounding rect, and we want
    // to include them.
    SkScalar fX = SkFloatToScalar(point.x());
    SkScalar fY = SkFloatToScalar(point.y());
    if (fX < bounds.fLeft || fX > bounds.fRight || fY < bounds.fTop || fY > bounds.fBottom)
        return false;

    // Scale the path to a large size before hit testing for two reasons:
    // 1) Skia has trouble with coordinates close to the max signed 16-bit values, so we scale larger paths down.
    //    TODO: when Skia is patched to work properly with large values, this will not be necessary.
    // 2) Skia does not support analytic hit testing, so we scale paths up to do raster hit testing with subpixel accuracy.
    SkScalar biggestCoord = std::max(std::max(std::max(bounds.fRight, bounds.fBottom), -bounds.fLeft), -bounds.fTop);
    if (SkScalarNearlyZero(biggestCoord))
        return false;
    biggestCoord = std::max(std::max(biggestCoord, fX + 1), fY + 1);

    const SkScalar kMaxCoordinate = SkIntToScalar(1 << 15);
    SkScalar scale = SkScalarDiv(kMaxCoordinate, biggestCoord);

    SkRegion rgn;  
    SkRegion clip;
    SkMatrix m;
    SkPath scaledPath;

    SkPath::FillType originalFillType = originalPath->getFillType();
    originalPath->setFillType(ft);

    m.setScale(scale, scale);
    originalPath->transform(m, &scaledPath);

    int x = static_cast<int>(floorf(0.5f + point.x() * scale));
    int y = static_cast<int>(floorf(0.5f + point.y() * scale));
    clip.setRect(x - 1, y - 1, x + 1, y + 1);

    bool contains = rgn.setPath(scaledPath, clip);
    originalPath->setFillType(originalFillType);
    return contains;
}

GraphicsContext* scratchContext()
{
    static ImageBuffer* scratch = ImageBuffer::create(IntSize(1, 1)).leakPtr();
    // We don't bother checking for failure creating the ImageBuffer, since our
    // ImageBuffer initializer won't fail.
    return scratch->context();
}

}  // namespace WebCore