sky/engine/platform/graphics/GraphicsContextState.h

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

#include "sky/engine/platform/graphics/DrawLooperBuilder.h"
#include "sky/engine/platform/graphics/Gradient.h"
#include "sky/engine/platform/graphics/GraphicsTypes.h"
#include "sky/engine/platform/graphics/Path.h"
#include "sky/engine/platform/graphics/Pattern.h"
#include "sky/engine/platform/graphics/StrokeData.h"
#include "sky/engine/wtf/PassOwnPtr.h"
#include "sky/engine/wtf/RefPtr.h"
#include "third_party/skia/include/core/SkColorFilter.h"
#include "third_party/skia/include/core/SkPaint.h"

namespace blink {

// Encapsulates the state information we store for each pushed graphics state.
// Only GraphicsContext can use this class.
class PLATFORM_EXPORT GraphicsContextState final {
public:
    static PassOwnPtr<GraphicsContextState> create()
    {
        return adoptPtr(new GraphicsContextState());
    }

    static PassOwnPtr<GraphicsContextState> createAndCopy(const GraphicsContextState& other)
    {
        return adoptPtr(new GraphicsContextState(other));
    }

    void copy(const GraphicsContextState&);

    // SkPaint objects that reflect the current state. If the length of the
    // path to be stroked is known, pass it in for correct dash or dot placement.
    const SkPaint& strokePaint(int strokedPathLength = 0) const;
    const SkPaint& fillPaint() const;

    uint16_t saveCount() const { return m_saveCount; }
    void incrementSaveCount() { ++m_saveCount; }
    void decrementSaveCount() { --m_saveCount; }

    // Stroke data
    const StrokeData& strokeData() const { return m_strokeData; }

    void setStrokeStyle(StrokeStyle);

    void setStrokeThickness(float);

    SkColor effectiveStrokeColor() const { return applyAlpha(m_strokeData.color().rgb()); }
    void setStrokeColor(const Color&);

    void setStrokeGradient(const PassRefPtr<Gradient>);
    void clearStrokeGradient();

    void setStrokePattern(const PassRefPtr<Pattern>);
    void clearStrokePattern();

    void setLineCap(LineCap);

    void setLineJoin(LineJoin);

    void setMiterLimit(float);

    void setLineDash(const DashArray&, float);

    // Fill data
    Color fillColor() const { return m_fillColor; }
    SkColor effectiveFillColor() const { return applyAlpha(m_fillColor.rgb()); }
    void setFillColor(const Color&);

    Gradient* fillGradient() const { return m_fillGradient.get(); }
    void setFillGradient(const PassRefPtr<Gradient>);
    void clearFillGradient();

    Pattern* fillPattern() const { return m_fillPattern.get(); }
    void setFillPattern(const PassRefPtr<Pattern>);
    void clearFillPattern();

    // Path fill rule
    WindRule fillRule() const { return m_fillRule; }
    void setFillRule(WindRule rule) { m_fillRule = rule; }

    // Shadow. (This will need tweaking if we use draw loopers for other things.)
    SkDrawLooper* drawLooper() const { return m_looper.get(); }
    void setDrawLooper(PassRefPtr<SkDrawLooper>);
    void clearDrawLooper();

    // Text. (See TextModeFill & friends.)
    TextDrawingModeFlags textDrawingMode() const { return m_textDrawingMode; }
    void setTextDrawingMode(TextDrawingModeFlags mode) { m_textDrawingMode = mode; }

    // Common shader state.
    int alpha() const { return m_alpha; }
    void setAlphaAsFloat(float);

    SkColorFilter* colorFilter() const { return m_colorFilter.get(); }
    void setColorFilter(PassRefPtr<SkColorFilter>);

    // Compositing control, for the CSS and Canvas compositing spec.
    void setCompositeOperation(CompositeOperator, WebBlendMode);
    CompositeOperator compositeOperator() const { return m_compositeOperator; }
    WebBlendMode blendMode() const { return m_blendMode; }

    // Image interpolation control.
    InterpolationQuality interpolationQuality() const { return m_interpolationQuality; }
    void setInterpolationQuality(InterpolationQuality);

    bool shouldAntialias() const { return m_shouldAntialias; }
    void setShouldAntialias(bool);

    bool shouldClampToSourceRect() const { return m_shouldClampToSourceRect; }
    void setShouldClampToSourceRect(bool shouldClampToSourceRect) { m_shouldClampToSourceRect = shouldClampToSourceRect; }

private:
    GraphicsContextState();
    explicit GraphicsContextState(const GraphicsContextState&);
    GraphicsContextState& operator=(const GraphicsContextState&);

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

    // These are mutbale to enable gradient updates when the paints are fetched for use.
    mutable SkPaint m_strokePaint;
    mutable SkPaint m_fillPaint;

    StrokeData m_strokeData;

    Color m_fillColor;
    WindRule m_fillRule;
    RefPtr<Gradient> m_fillGradient;
    RefPtr<Pattern> m_fillPattern;

    RefPtr<SkDrawLooper> m_looper;

    TextDrawingModeFlags m_textDrawingMode;

    int m_alpha;
    RefPtr<SkColorFilter> m_colorFilter;

    CompositeOperator m_compositeOperator;
    WebBlendMode m_blendMode;

    InterpolationQuality m_interpolationQuality;

    uint16_t m_saveCount;

    bool m_shouldAntialias : 1;
    bool m_shouldClampToSourceRect : 1;
};

} // namespace blink

#endif  // SKY_ENGINE_PLATFORM_GRAPHICS_GRAPHICSCONTEXTSTATE_H_