third_party/WebKit/Source/platform/graphics/skia/SkiaUtils.h

/*
 * Copyright (c) 2006,2007,2008, Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * 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.
 *     * Neither the name of Google Inc. nor the names of its
 * 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
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER 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,
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 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

// All of the functions in this file should move to new homes and this file should be deleted.

#ifndef SkiaUtils_h
#define SkiaUtils_h

#include "platform/PlatformExport.h"
#include "platform/graphics/GraphicsTypes.h"
#include "platform/graphics/Image.h"
#include "platform/transforms/AffineTransform.h"
#include "third_party/skia/include/core/SkCanvas.h"
#include "third_party/skia/include/core/SkColor.h"
#include "third_party/skia/include/core/SkRefCnt.h"
#include "third_party/skia/include/core/SkScalar.h"
#include "third_party/skia/include/core/SkXfermode.h"
#include "wtf/MathExtras.h"

namespace blink {

class GraphicsContext;

/**** constants ****/

enum {
    // Firefox limits width/height to 32767 pixels, but slows down dramatically before it
    // reaches that limit. We limit by area instead, giving us larger maximum dimensions,
    // in exchange for a smaller maximum canvas size.
    kMaxCanvasArea = 32768 * 8192, // Maximum canvas area in CSS pixels

    // In Skia, we will also limit width/height to 32767.
    kMaxSkiaDim = 32767 // Maximum width/height in CSS pixels.
};

SkXfermode::Mode PLATFORM_EXPORT WebCoreCompositeToSkiaComposite(CompositeOperator, WebBlendMode = WebBlendModeNormal);
CompositeOperator PLATFORM_EXPORT compositeOperatorFromSkia(SkXfermode::Mode);
WebBlendMode PLATFORM_EXPORT blendModeFromSkia(SkXfermode::Mode);

// Map alpha values from [0, 1] to [0, 256] for alpha blending.
int PLATFORM_EXPORT clampedAlphaForBlending(float);

// Multiply a color's alpha channel by an additional alpha factor where
// alpha is in the range [0, 1].
SkColor PLATFORM_EXPORT scaleAlpha(SkColor, float);

// Multiply a color's alpha channel by an additional alpha factor where
// alpha is in the range [0, 256].
SkColor PLATFORM_EXPORT scaleAlpha(SkColor, int);

// Skia has problems when passed infinite, etc floats, filter them to 0.
inline SkScalar WebCoreFloatToSkScalar(float f)
{
    return SkFloatToScalar(std::isfinite(f) ? f : 0);
}

inline SkScalar WebCoreDoubleToSkScalar(double d)
{
    return SkDoubleToScalar(std::isfinite(d) ? d : 0);
}

inline bool WebCoreFloatNearlyEqual(float a, float b)
{
    return SkScalarNearlyEqual(WebCoreFloatToSkScalar(a), WebCoreFloatToSkScalar(b));
}

inline SkPath::FillType WebCoreWindRuleToSkFillType(WindRule rule)
{
    return static_cast<SkPath::FillType>(rule);
}

inline WindRule SkFillTypeToWindRule(SkPath::FillType fillType)
{
    switch (fillType) {
    case SkPath::kWinding_FillType:
    case SkPath::kEvenOdd_FillType:
        return static_cast<WindRule>(fillType);
    default:
        ASSERT_NOT_REACHED();
        break;
    }
    return RULE_NONZERO;
}

SkMatrix PLATFORM_EXPORT affineTransformToSkMatrix(const AffineTransform&);

bool nearlyIntegral(float value);

InterpolationQuality limitInterpolationQuality(const GraphicsContext&, InterpolationQuality resampling);

InterpolationQuality computeInterpolationQuality(
    float srcWidth,
    float srcHeight,
    float destWidth,
    float destHeight,
    bool isDataComplete = true);

// This replicates the old skia behavior when it used to take radius for blur. Now it takes sigma.
inline SkScalar skBlurRadiusToSigma(SkScalar radius)
{
    SkASSERT(radius >= 0);
    if (radius == 0)
        return 0.0f;
    return 0.288675f * radius + 0.5f;
}

template<typename PrimitiveType>
void drawPlatformFocusRing(const PrimitiveType&, SkCanvas*, SkColor, int width);

// TODO(fmalita): remove in favor of direct SrcRectConstraint use.
inline SkCanvas::SrcRectConstraint WebCoreClampingModeToSkiaRectConstraint(Image::ImageClampingMode clampMode)
{
    return clampMode == Image::ClampImageToSourceRect
        ? SkCanvas::kStrict_SrcRectConstraint
        : SkCanvas::kFast_SrcRectConstraint;
}

// Skia's smart pointer APIs are preferable over their legacy raw pointer counterparts.
// The following helpers ensure interoperability between Skia's SkRefCnt wrapper sk_sp<T> and
// Blink's RefPtr<T>/PassRefPtr<T>.
//
//   - fromSkSp(sk_sp<T>):       adopts an sk_sp into a PassRefPtr (to be used when transferring
//                               ownership from Skia to Blink).
//   - toSkSp(PassRefPtr<T>):    releases a PassRefPtr into a sk_sp (to be used when transferring
//                               ownership from Blink to Skia).
//   - toSkSp(const RefPtr<T>&): shares a RefPtr as a new sk_sp (to be used when sharing
//                               ownership).
//
// General guidelines
//
// When receiving ref counted objects from Skia:
//
//   1) use sk_sp-based Skia factories if available (e.g. SkShader::MakeFoo() instead of
//      SkShader::CreateFoo())
//
//   2) use sk_sp<T> locals for temporary objects (to be immediately transferred back to Skia)
//
//   3) use RefPtr<T>/PassRefPtr<T> for objects to be retained in Blink, use
//      fromSkSp(sk_sp<T>) to convert
//
// When passing ref counted objects to Skia:
//
//   1) use sk_sk-based Skia APIs when available (e.g. SkPaint::setShader(sk_sp<SkShader>)
//      instead of SkPaint::setShader(SkShader*))
//
//   2) if the object ownership is being passed to Skia, use std::move(sk_sp<T>) or
//      toSkSp(PassRefPtr<T>) to transfer without refcount churn
//
//   3) if the object ownership is shared with Skia (Blink retains a reference), use
//      toSkSp(const RefPtr<T>&)
//
// Example (creating a SkShader and setting it on SkPaint):
//
// a) legacy/old style
//
//     RefPtr<SkShader> shader = adoptRef(SkShader::CreateFoo(...));
//     paint.setShader(shader.get());
//
//  (Note: the legacy approach introduces refcount churn as Skia grabs a ref while Blink is
//   temporarily holding on to its own)
//
// b) new style, ownership transferred
//
//     // using Skia smart pointer locals
//     sk_sp<SkShader> shader = SkShader::MakeFoo(...);
//     paint.setShader(std::move(shader));
//
//     // using Blink smart pointer locals
//     RefPtr<SkShader> shader = fromSkSp(SkShader::MakeFoo(...));
//     paint.setShader(toSkSp(shader.release());
//
//     // using no locals
//     paint.setShader(SkShader::MakeFoo(...));
//
// c) new style, shared ownership
//
//     RefPtr<SkShader> shader = fromSkSp(SkShader::MakeFoo(...));
//     paint.setShader(toSkSp(shader));
//
template <typename T> PassRefPtr<T> fromSkSp(sk_sp<T> sp)
{
    return adoptRef(sp.release());
}

template <typename T> sk_sp<T> toSkSp(PassRefPtr<T> ref)
{
    return sk_sp<T>(ref.leakRef());
}

template <typename T> sk_sp<T> toSkSp(const RefPtr<T>& ref)
{
    return toSkSp(PassRefPtr<T>(ref));
}

} // namespace blink

#endif  // SkiaUtils_h