experimental/xform/XContext.cpp

/*
 * Copyright 2019 Google LLC.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "experimental/xform/SkShape.h"
#include "experimental/xform/SkXform.h"
#include "include/core/SkCanvas.h"

#include "src/core/SkRasterClip.h"

class RasterClipCache : public ClipCache {
public:
    RasterClipCache(const SkRasterClip& rc) : fRC(std::move(rc)) {}

    SkRasterClip fRC;
};

static const SkRasterClip& peek_rasterclip(ClipCache* clip) {
    return ((RasterClipCache*)clip)->fRC;
}

class RasterXformResolver : public XformResolver {
public:
    RasterXformResolver(const SkIRect& bounds)
        : fBounds(bounds)
        , fCTM(SkMatrix::I())
        , fRC(bounds)
    {}

    RasterXformResolver(Xform* parent) {
        const SkRasterClip& rc = peek_rasterclip(parent->clip());
        fBounds = rc.getBounds();
        fCTM = parent->ctm();
        fRC = rc;
    }

    void concat(const SkMatrix& m) override {
        fCTM.preConcat(m);
    }

    void clipRect(const SkRect& r, SkClipOp op) override {
        fRC.op(r, fCTM, fBounds, (SkRegion::Op)op, false);
        fCache.reset(nullptr);
    }

    void clipRRect(const SkRRect& rr, SkClipOp op) override {
        fRC.op(rr, fCTM, fBounds, (SkRegion::Op)op, false);
        fCache.reset(nullptr);
    }
    void clipPath(const SkPath& p, SkClipOp op) override {
        fRC.op(p, fCTM, fBounds, (SkRegion::Op)op, false);
        fCache.reset(nullptr);
    }

    const SkMatrix& ctm() const { return fCTM; }

    sk_sp<ClipCache> snapCache() {
        if (!fCache) {
            fCache = sk_sp<ClipCache>(new RasterClipCache(fRC));
        }
        return fCache;
    }

private:
    SkIRect         fBounds;
    SkMatrix        fCTM;
    SkRasterClip    fRC;
    sk_sp<ClipCache> fCache;
};

void XContext::drawRect(const SkRect& r, const SkPaint& p, Xform* x) {
    this->onDrawRect(r, p, x);
}

class CanvasXContext : public XContext {
public:
    CanvasXContext(SkCanvas* canvas) : fCanvas(canvas) {
        fBounds = {
            0, 0, canvas->getBaseLayerSize().width(), canvas->getBaseLayerSize().height()
        };
    }

protected:
    static int count_nodes(const Xform* x) {
        int n = 0;
        for (; x; x = x->parent()) {
            n += 1;
        }
        return n;
    }

    void onPush(Xform* x) override {
        int n = count_nodes(x);
        fCounts.push_back(n);
        if (n) {
            int prevCount = fStack.count();
            // now push the x tree such that we get [... grandparent, parent, x] in the array
            Xform** ptr = fStack.append(n) + n;
            Xform* xx = x;
            while (n --> 0) {
                *--ptr = xx;
                xx = xx->parent();
            }
            // init with the old tail
            if (prevCount > 0) {
                RasterXformResolver res(fStack[prevCount - 1]);
                for (int i = prevCount; i < fStack.count(); ++i) {
                    fStack[i]->visit(&res);
                    fStack[i]->setCache(res.ctm(), res.snapCache());
                }
            } else if (!x->genID()) {
                RasterXformResolver res(fBounds);
                for (int i = 0; i < fStack.count(); ++i) {
                    fStack[i]->visit(&res);
                    fStack[i]->setCache(res.ctm(), res.snapCache());
                }
                SkASSERT(x->genID());
            }
        }
    }

    void onPop() override {
        int n = fCounts.top();
        fCounts.pop();
        if (n) {
            fStack.setCount(fStack.count() - n);
        }
    }

    void onDrawRect(const SkRect& r, const SkPaint& p, Xform* x) override {
        Xform* parent = this->parentOrNull();
        Xform::GenID parentID = parent ? parent->genID() : 0;
        SkASSERT(parent == nullptr || parentID != 0);

        if (x) {
            SkASSERT(x->genID() != parentID || (x->genID() == 0 && parentID == 0));
            if (x->genID() <= parentID) {    // x is out of date
                this->push(x);              // will update caches
                this->pop();
            }
            SkASSERT(x->genID() > parentID);
        } else {
            x = parent;
        }

        SkAutoCanvasRestore acr(fCanvas, false);
        if (x) {
            fCanvas->save();
            fCanvas->concat(x->ctm());
            fCanvas->clipRegion(peek_rasterclip(x->clip()).bwRgn());
        }
        fCanvas->drawRect(r, p);
    }

private:
    SkTDArray<Xform*> fStack;
    SkTDArray<int>    fCounts;

    SkCanvas* fCanvas;    // bare pointer
    SkIRect   fBounds;

    Xform* parentOrNull() {
        return fStack.count() > 0 ? fStack.top() : nullptr;
    }
};

std::unique_ptr<XContext> XContext::Make(SkCanvas* canvas) {
    return std::unique_ptr<XContext>(new CanvasXContext(canvas));
}