modules/sksg/src/SkSGRenderNode.cpp

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

#include "SkSGRenderNode.h"

#include "SkCanvas.h"
#include "SkPaint.h"

namespace sksg {

RenderNode::RenderNode() : INHERITED(0) {}

void RenderNode::render(SkCanvas* canvas, const RenderContext* ctx) const {
    SkASSERT(!this->hasInval());
    this->onRender(canvas, ctx);
}

bool RenderNode::RenderContext::modulatePaint(SkPaint* paint) const {
    const auto initial_alpha = paint->getAlpha(),
                       alpha = SkToU8(sk_float_round2int(initial_alpha * fOpacity));

    if (alpha != initial_alpha) {
        paint->setAlpha(alpha);
        return true;
    }

    return false;
}

RenderNode::ScopedRenderContext::ScopedRenderContext(SkCanvas* canvas, const RenderContext* ctx)
    : fCanvas(canvas)
    , fCtx(ctx)
    , fRestoreCount(canvas->getSaveCount()) {}

RenderNode::ScopedRenderContext::~ScopedRenderContext() {
    if (fRestoreCount >= 0) {
        fCanvas->restoreToCount(fRestoreCount);
    }
}

RenderNode::RenderContext* RenderNode::ScopedRenderContext::writableContext() {
    // If no inherited context is present, allocate one in local storage.
    if (!fCtx.get()) {
        // N.B.: we have to force a copy while the default source is in scope.
        // TODO: add SkTCopyOnWrite::init_copy() to simplify this
        RenderContext default_ctx;
        fCtx.init(default_ctx);
        return fCtx.writable();
    }
    return fCtx.writable();
}

RenderNode::ScopedRenderContext&&
RenderNode::ScopedRenderContext::modulateOpacity(float opacity) {
    SkASSERT(opacity >= 0 && opacity <= 1);
    if (opacity < 1) {
        this->writableContext()->fOpacity *= opacity;
    }
    return std::move(*this);
}

RenderNode::ScopedRenderContext&&
RenderNode::ScopedRenderContext::setIsolation(const SkRect& bounds, bool isolation) {
    if (isolation && fCtx.get()) {
        SkPaint layer_paint;
        if (fCtx->modulatePaint(&layer_paint)) {
            fCanvas->saveLayer(bounds, &layer_paint);
            *fCtx.writable() = RenderContext();
        }
    }
    return std::move(*this);
}

} // namespace sksg