src/core/SkPaintPriv.h

/*
 * Copyright 2013 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef SkPaintPriv_DEFINED
#define SkPaintPriv_DEFINED

#include "include/core/SkPaint.h"

class SkFont;
class SkReadBuffer;
class SkWriteBuffer;

enum SkReadPaintResult {
    kFailed_ReadPaint,
    kSuccess_JustPaint,
    kSuccess_PaintAndFont,
};

class SkPaintPriv {
public:
    enum ShaderOverrideOpacity {
        kNone_ShaderOverrideOpacity,        //!< there is no overriding shader (bitmap or image)
        kOpaque_ShaderOverrideOpacity,      //!< the overriding shader is opaque
        kNotOpaque_ShaderOverrideOpacity,   //!< the overriding shader may not be opaque
    };

    /**
     *  Returns true if drawing with this paint (or nullptr) will ovewrite all affected pixels.
     *
     *  Note: returns conservative true, meaning it may return false even though the paint might
     *        in fact overwrite its pixels.
     */
    static bool Overwrites(const SkPaint* paint, ShaderOverrideOpacity);

    static bool ShouldDither(const SkPaint&, SkColorType);

    /*
     * The luminance color is used to determine which Gamma Canonical color to map to.  This is
     * really only used by backends which want to cache glyph masks, and need some way to know if
     * they need to generate new masks based off a given color.
     */
    static SkColor ComputeLuminanceColor(const SkPaint&);

    /** Serializes SkPaint into a buffer. A companion unflatten() call
    can reconstitute the paint at a later time.

    @param buffer  SkWriteBuffer receiving the flattened SkPaint data
    */
    static void Flatten(const SkPaint& paint, SkWriteBuffer& buffer);

    /** Populates SkPaint, typically from a serialized stream, created by calling
        flatten() at an earlier time.

        SkReadBuffer class is not public, so unflatten() cannot be meaningfully called
        by the client.

        Older formats also stored font info in the serialized data. On success, this
        returns if it deserialized just a paint, or both a font and paint. The font
        param is optional.

        @param buffer  serialized data describing SkPaint content
        @return        false if the buffer contains invalid data
    */
    static SkReadPaintResult Unflatten(SkPaint* paint, SkReadBuffer& buffer, SkFont* font);

    // If this paint has any color filter, fold it into the shader and/or paint color
    // so that it draws the same but getColorFilter() returns nullptr.
    //
    // Since we may be filtering now, we need to know what color space to filter in,
    // typically the color space of the device we're drawing into.
    static void RemoveColorFilter(SkPaint*, SkColorSpace* dstCS);

    static SkScalar ComputeResScaleForStroking(const SkMatrix&);
};

#endif