android_frameworks_base/libs/hwui/pipeline/skia/ReorderBarrierDrawables.cpp

/*
 * Copyright (C) 2016 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "ReorderBarrierDrawables.h"
#include "RenderNode.h"
#include "SkiaDisplayList.h"
#include "SkiaPipeline.h"

#include <SkBlurMask.h>
#include <SkBlurMaskFilter.h>
#include <SkGaussianEdgeShader.h>
#include <SkPathOps.h>
#include <SkRRectsGaussianEdgeMaskFilter.h>
#include <SkShadowUtils.h>

namespace android {
namespace uirenderer {
namespace skiapipeline {

StartReorderBarrierDrawable::StartReorderBarrierDrawable(SkiaDisplayList* data)
        : mEndChildIndex(0)
        , mBeginChildIndex(data->mChildNodes.size())
        , mDisplayList(data) {
}

void StartReorderBarrierDrawable::onDraw(SkCanvas* canvas) {
    if (mChildren.empty()) {
        //mChildren is allocated and initialized only the first time onDraw is called and cached for
        //subsequent calls
        mChildren.reserve(mEndChildIndex - mBeginChildIndex + 1);
        for (int i = mBeginChildIndex; i <= mEndChildIndex; i++) {
            mChildren.push_back(const_cast<RenderNodeDrawable*>(&mDisplayList->mChildNodes[i]));
        }
    }
    std::stable_sort(mChildren.begin(), mChildren.end(),
        [](RenderNodeDrawable* a, RenderNodeDrawable* b) {
            const float aZValue = a->getNodeProperties().getZ();
            const float bZValue = b->getNodeProperties().getZ();
            return aZValue < bZValue;
        });

    SkASSERT(!mChildren.empty());

    size_t drawIndex = 0;
    const size_t endIndex = mChildren.size();
    while (drawIndex < endIndex) {
        RenderNodeDrawable* childNode = mChildren[drawIndex];
        SkASSERT(childNode);
        const float casterZ = childNode->getNodeProperties().getZ();
        if (casterZ >= -NON_ZERO_EPSILON) { //draw only children with negative Z
            return;
        }
        childNode->forceDraw(canvas);
        drawIndex++;
    }
}

EndReorderBarrierDrawable::EndReorderBarrierDrawable(StartReorderBarrierDrawable* startBarrier)
        : mStartBarrier(startBarrier) {
    mStartBarrier->mEndChildIndex = mStartBarrier->mDisplayList->mChildNodes.size() - 1;
}

#define SHADOW_DELTA 0.1f

void EndReorderBarrierDrawable::onDraw(SkCanvas* canvas) {
    auto& zChildren = mStartBarrier->mChildren;
    SkASSERT(!zChildren.empty());

    /**
     * Draw shadows and (potential) casters mostly in order, but allow the shadows of casters
     * with very similar Z heights to draw together.
     *
     * This way, if Views A & B have the same Z height and are both casting shadows, the shadows are
     * underneath both, and neither's shadow is drawn on top of the other.
     */
    size_t drawIndex = 0;

    const size_t endIndex = zChildren.size();
    while (drawIndex < endIndex     //draw only children with positive Z
            && zChildren[drawIndex]->getNodeProperties().getZ() <= NON_ZERO_EPSILON) drawIndex++;
    size_t shadowIndex = drawIndex;

    float lastCasterZ = 0.0f;
    while (shadowIndex < endIndex || drawIndex < endIndex) {
        if (shadowIndex < endIndex) {
            const float casterZ = zChildren[shadowIndex]->getNodeProperties().getZ();

            // attempt to render the shadow if the caster about to be drawn is its caster,
            // OR if its caster's Z value is similar to the previous potential caster
            if (shadowIndex == drawIndex || casterZ - lastCasterZ < SHADOW_DELTA) {
                this->drawShadow(canvas, zChildren[shadowIndex]);
                lastCasterZ = casterZ; // must do this even if current caster not casting a shadow
                shadowIndex++;
                continue;
            }
        }

        RenderNodeDrawable* childNode = zChildren[drawIndex];
        SkASSERT(childNode);
        childNode->forceDraw(canvas);

        drawIndex++;
    }
}

// copied from FrameBuilder::deferShadow
void EndReorderBarrierDrawable::drawShadow(SkCanvas* canvas, RenderNodeDrawable* caster) {
    const RenderProperties& casterProperties = caster->getNodeProperties();

    if (casterProperties.getAlpha() <= 0.0f
            || casterProperties.getOutline().getAlpha() <= 0.0f
            || !casterProperties.getOutline().getPath()
            || casterProperties.getScaleX() == 0
            || casterProperties.getScaleY() == 0) {
        // no shadow to draw
        return;
    }

    const SkScalar casterAlpha = casterProperties.getAlpha()
            * casterProperties.getOutline().getAlpha();
    if (casterAlpha <= 0.0f) {
        return;
    }

    float ambientAlpha = (SkiaPipeline::getAmbientShadowAlpha()/255.f)*casterAlpha;
    float spotAlpha = (SkiaPipeline::getSpotShadowAlpha()/255.f)*casterAlpha;
    const float casterZValue = casterProperties.getZ();

    const RevealClip& revealClip = casterProperties.getRevealClip();
    const SkPath* revealClipPath = revealClip.getPath();
    if (revealClipPath && revealClipPath->isEmpty()) {
        // An empty reveal clip means nothing is drawn
        return;
    }

    bool clippedToBounds = casterProperties.getClippingFlags() & CLIP_TO_CLIP_BOUNDS;

    SkRect casterClipRect = SkRect::MakeEmpty();
    if (clippedToBounds) {
        Rect clipBounds;
        casterProperties.getClippingRectForFlags(CLIP_TO_CLIP_BOUNDS, &clipBounds);
        casterClipRect = clipBounds.toSkRect();
        if (casterClipRect.isEmpty()) {
            // An empty clip rect means nothing is drawn
            return;
        }
    }

    SkAutoCanvasRestore acr(canvas, true);

    SkMatrix shadowMatrix;
    mat4 hwuiMatrix;
    // TODO we don't pass the optional boolean to treat it as a 4x4 matrix
    caster->getRenderNode()->applyViewPropertyTransforms(hwuiMatrix);
    hwuiMatrix.copyTo(shadowMatrix);
    canvas->concat(shadowMatrix);

    const SkPath* casterOutlinePath = casterProperties.getOutline().getPath();
    // holds temporary SkPath to store the result of intersections
    SkPath tmpPath;
    const SkPath* casterPath = casterOutlinePath;

    // TODO: In to following course of code that calculates the final shape, is there an optimal
    //       of doing the Op calculations?
    // intersect the shadow-casting path with the reveal, if present
    if (revealClipPath) {
        Op(*casterPath, *revealClipPath, kIntersect_SkPathOp, &tmpPath);
        casterPath = &tmpPath;
    }

    // intersect the shadow-casting path with the clipBounds, if present
    if (clippedToBounds) {
        SkPath clipBoundsPath;
        clipBoundsPath.addRect(casterClipRect);
        Op(*casterPath, clipBoundsPath, kIntersect_SkPathOp, &tmpPath);
        casterPath = &tmpPath;
    }
    const Vector3 lightPos = SkiaPipeline::getLightCenter();
    SkPoint3 skiaLightPos = SkPoint3::Make(lightPos.x, lightPos.y, lightPos.z);
    if (shadowMatrix.hasPerspective() || revealClipPath || clippedToBounds) {
        std::function<SkScalar(SkScalar, SkScalar)> casterHeightFunc;
        if (shadowMatrix.hasPerspective()) {
            // get the matrix with the full 3D transform
            mat4 zMatrix;
            caster->getRenderNode()->applyViewPropertyTransforms(zMatrix, true);
            SkScalar A = zMatrix[2];
            SkScalar B = zMatrix[6];
            SkScalar C = zMatrix[mat4::kTranslateZ];
            casterHeightFunc = [A, B, C](SkScalar x, SkScalar y) {
                return A*x + B*y + C;  // casterZValue already baked into C
            };
        } else {
            casterHeightFunc = [casterZValue] (SkScalar, SkScalar) {
                return casterZValue;
            };
        }

        SkShadowUtils::DrawUncachedShadow(canvas, *casterPath, casterHeightFunc, skiaLightPos,
            SkiaPipeline::getLightRadius(), ambientAlpha, spotAlpha, SK_ColorBLACK,
            casterAlpha < 1.0f ? SkShadowFlags::kTransparentOccluder_ShadowFlag : 0);
    } else {
        SkShadowUtils::DrawShadow(canvas, *casterPath, casterZValue, skiaLightPos,
            SkiaPipeline::getLightRadius(), ambientAlpha, spotAlpha, SK_ColorBLACK,
            casterAlpha < 1.0f ? SkShadowFlags::kTransparentOccluder_ShadowFlag : 0);
    }
}

}; // namespace skiapipeline
}; // namespace uirenderer
}; // namespace android