include/utils/SkShadowUtils.h

/*
 * Copyright 2017 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
#ifndef SkShadowUtils_DEFINED
#define SkShadowUtils_DEFINED

#include "SkColor.h"
#include "SkScalar.h"
#include "../private/SkShadowFlags.h"

class SkCanvas;
class SkPath;
class SkResourceCache;

class SkShadowUtils {
public:
    /**
     * Draw an offset spot shadow and outlining ambient shadow for the given path using a disc
     * light.
     *
     * @param canvas  The canvas on which to draw the shadows.
     * @param path  The occluder used to generate the shadows.
     * @param occluderHeight  The vertical offset of the occluder from the canvas. This is
     *  indepdendent of the canvas's current matrix.
     * @param lightPos  The 3D position of the light relative to the canvas plane. This is
     *  independent of the canvas's current matrix.
     * @param lightRadius  The radius of the disc light.
     * @param ambientAlpha  The maximum alpha of the ambient shadow.
     * @param spotAlpha  The maxium alpha of the spot shadow.
     * @param color  The shadow color.
     * @param flags  Options controlling opaque occluder optimizations and shadow appearance. See
     *               SkShadowFlags.
     * @param cache  Used for testing purposes. Clients should pass nullptr (default).
     */
    static void DrawShadow(SkCanvas* canvas, const SkPath& path, SkScalar occluderHeight,
                           const SkPoint3& lightPos, SkScalar lightRadius, SkScalar ambientAlpha,
                           SkScalar spotAlpha, SkColor color,
                           uint32_t flags = SkShadowFlags::kNone_ShadowFlag,
                           SkResourceCache* cache = nullptr);
};

#endif