SkCanvasStack.h

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/*
 * 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 SkCanvasStack_DEFINED
#define SkCanvasStack_DEFINED
 
#include "include/core/SkCanvas.h"
#include "include/core/SkM44.h"
#include "include/core/SkPoint.h"
#include "include/core/SkRefCnt.h"
#include "include/core/SkRegion.h"
#include "include/core/SkTypes.h"
#include "include/private/base/SkTArray.h"
#include "include/private/base/SkTypeTraits.h"
#include "include/utils/SkNWayCanvas.h"
 
#include <memory>
#include <type_traits>
 
class SkPath;
class SkRRect;
class SkShader;
enum class SkClipOp;
struct SkRect;
 
/**
 *  Like NWayCanvas, in that it forwards all canvas methods to each sub-canvas that is "pushed".
 *
 *  Unlike NWayCanvas, this takes ownership of each subcanvas, and deletes them when this canvas
 *  is deleted.
 */
class SkCanvasStack : public SkNWayCanvas {
public:
    SkCanvasStack(int width, int height);
    ~SkCanvasStack() override;
 
    void pushCanvas(std::unique_ptr<SkCanvas>, const SkIPoint& origin);
    void removeAll() override;
 
    /*
     * The following add/remove canvas methods are overrides from SkNWayCanvas
     * that do not make sense in the context of our CanvasStack, but since we
     * can share most of the other implementation of NWay we override those
     * methods to be no-ops.
     */
    void addCanvas(SkCanvas*) override { SkDEBUGFAIL("Invalid Op"); }
    void removeCanvas(SkCanvas*) override { SkDEBUGFAIL("Invalid Op"); }
 
protected:
    void didSetM44(const SkM44&) override;
 
    void onClipRect(const SkRect&, SkClipOp, ClipEdgeStyle) override;
    void onClipRRect(const SkRRect&, SkClipOp, ClipEdgeStyle) override;
    void onClipPath(const SkPath&, SkClipOp, ClipEdgeStyle) override;
    void onClipShader(sk_sp<SkShader>, SkClipOp) override;
    void onClipRegion(const SkRegion&, SkClipOp) override;
 
private:
    void clipToZOrderedBounds();
 
    struct CanvasData {
        SkIPoint origin;
        SkRegion requiredClip;
        std::unique_ptr<SkCanvas> ownedCanvas;
 
        static_assert(::sk_is_trivially_relocatable<decltype(origin)>::value);
        static_assert(::sk_is_trivially_relocatable<decltype(requiredClip)>::value);
        static_assert(::sk_is_trivially_relocatable<decltype(ownedCanvas)>::value);
 
        using sk_is_trivially_relocatable = std::true_type;
    };
 
    skia_private::TArray<CanvasData> fCanvasData;
 
    using INHERITED = SkNWayCanvas;
};
 
#endif