Source/core/platform/graphics/GraphicsContextState.h

// Copyright (C) 2013 Google Inc. All rights reserved.
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#ifndef GraphicsContextState_h
#define GraphicsContextState_h

#include "core/platform/graphics/ColorSpace.h"
#include "core/platform/graphics/Gradient.h"
#include "core/platform/graphics/GraphicsTypes.h"
#include "core/platform/graphics/Path.h"
#include "core/platform/graphics/Pattern.h"

#include "third_party/skia/include/core/SkColorPriv.h"
#include "third_party/skia/include/core/SkDrawLooper.h"
#include "third_party/skia/include/effects/SkDashPathEffect.h"

#include "wtf/PassOwnPtr.h"

namespace WebCore {

// Encapsulates the state information we store for each pushed graphics state.
// Only GraphicsContext can use this class.
class GraphicsContextState {
public:
    ~GraphicsContextState()
    {
        SkSafeUnref(m_looper);
        SkSafeUnref(m_dash);
    }

private:
    friend class GraphicsContext;

    GraphicsContextState()
        : m_strokeStyle(SolidStroke)
        , m_strokeThickness(0)
        , m_strokeColor(Color::black)
        , m_strokeColorSpace(ColorSpaceDeviceRGB)
        , m_miterLimit(4)
        , m_lineCap(SkPaint::kDefault_Cap)
        , m_lineJoin(SkPaint::kDefault_Join)
        , m_dash(0)
        , m_fillColor(Color::black)
        , m_fillColorSpace(ColorSpaceDeviceRGB)
        , m_fillRule(RULE_NONZERO)
        , m_looper(0)
        , m_textDrawingMode(TextModeFill)
        , m_alpha(1)
        , m_xferMode(SkXfermode::kSrcOver_Mode)
        , m_compositeOperator(CompositeSourceOver)
        , m_blendMode(BlendModeNormal)
        , m_clip(SkRect::MakeEmpty())
#if USE(LOW_QUALITY_IMAGE_INTERPOLATION)
        , m_interpolationQuality(InterpolationLow)
#else
        , m_interpolationQuality(InterpolationHigh)
#endif
        , m_shouldAntialias(true)
        , m_shouldSmoothFonts(true)
        , m_shadowsIgnoreTransforms(false)
    {
    }

    GraphicsContextState(const GraphicsContextState& other)
        : m_strokeStyle(other.m_strokeStyle)
        , m_strokeThickness(other.m_strokeThickness)
        , m_strokeColor(other.m_strokeColor)
        , m_strokeColorSpace(other.m_strokeColorSpace)
        , m_strokeGradient(other.m_strokeGradient)
        , m_strokePattern(other.m_strokePattern)
        , m_miterLimit(other.m_miterLimit)
        , m_lineCap(other.m_lineCap)
        , m_lineJoin(other.m_lineJoin)
        , m_dash(other.m_dash)
        , m_fillColor(other.m_fillColor)
        , m_fillColorSpace(other.m_fillColorSpace)
        , m_fillRule(other.m_fillRule)
        , m_fillGradient(other.m_fillGradient)
        , m_fillPattern(other.m_fillPattern)
        , m_looper(other.m_looper)
        , m_textDrawingMode(other.m_textDrawingMode)
        , m_alpha(other.m_alpha)
        , m_xferMode(other.m_xferMode)
        , m_compositeOperator(other.m_compositeOperator)
        , m_blendMode(other.m_blendMode)
        , m_imageBufferClip(other.m_imageBufferClip)
        , m_clip(other.m_clip)
        , m_interpolationQuality(other.m_interpolationQuality)
        , m_shouldAntialias(other.m_shouldAntialias)
        , m_shouldSmoothFonts(other.m_shouldSmoothFonts)
        , m_shadowsIgnoreTransforms(other.m_shadowsIgnoreTransforms)
    {
        // Up the ref count of these. SkSafeRef does nothing if its argument is 0.
        SkSafeRef(m_looper);
        SkSafeRef(m_dash);

        // The clip image only needs to be applied once. Reset the image so that we
        // don't attempt to clip multiple times.
        m_imageBufferClip.reset();
    }

    // Helper function for applying the state's alpha value to the given input
    // color to produce a new output color.
    SkColor applyAlpha(SkColor c) const
    {
        int s = roundf(m_alpha * 256);
        if (s >= 256)
            return c;
        if (s < 0)
            return 0;

        int a = SkAlphaMul(SkColorGetA(c), s);
        return (c & 0x00FFFFFF) | (a << 24);
    }

    // Returns a new State with all of this object's inherited properties copied.
    PassOwnPtr<GraphicsContextState> clone() { return adoptPtr(new GraphicsContextState(*this)); }

    // Not supported. No implementations.
    void operator=(const GraphicsContextState&);

    // Stroke.
    StrokeStyle m_strokeStyle;
    float m_strokeThickness;
    Color m_strokeColor;
    ColorSpace m_strokeColorSpace;
    RefPtr<Gradient> m_strokeGradient;
    RefPtr<Pattern> m_strokePattern;
    float m_miterLimit;
    SkPaint::Cap m_lineCap;
    SkPaint::Join m_lineJoin;
    SkDashPathEffect* m_dash;

    // Fill.
    Color m_fillColor;
    ColorSpace m_fillColorSpace;
    WindRule m_fillRule;
    RefPtr<Gradient> m_fillGradient;
    RefPtr<Pattern> m_fillPattern;

    // Shadow. (This will need tweaking if we use draw loopers for other things.)
    SkDrawLooper* m_looper;

    // Text. (See TextModeFill & friends.)
    TextDrawingModeFlags m_textDrawingMode;

    // Common shader state.
    float m_alpha;
    SkXfermode::Mode m_xferMode;

    // Compositing control, for the CSS and Canvas compositing spec.
    CompositeOperator m_compositeOperator;
    BlendMode m_blendMode;

    // If non-empty, the current State is clipped to this image.
    SkBitmap m_imageBufferClip;

    // If m_imageBufferClip is non-empty, this is the region the image is clipped to.
    SkRect m_clip;

    // Image interpolation control.
    InterpolationQuality m_interpolationQuality;

    bool m_shouldAntialias : 1;
    bool m_shouldSmoothFonts : 1;
    bool m_shadowsIgnoreTransforms : 1;
};

} // namespace WebCore

#endif // GraphicsContextState_h