src/gpu/GrBlurUtils.cpp

/*
 * Copyright 2015 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "src/gpu/GrBlurUtils.h"

#include "include/private/GrRecordingContext.h"
#include "src/gpu/GrBitmapTextureMaker.h"
#include "src/gpu/GrCaps.h"
#include "src/gpu/GrFixedClip.h"
#include "src/gpu/GrProxyProvider.h"
#include "src/gpu/GrRecordingContextPriv.h"
#include "src/gpu/GrRenderTargetContext.h"
#include "src/gpu/GrRenderTargetContextPriv.h"
#include "src/gpu/GrSoftwarePathRenderer.h"
#include "src/gpu/GrStyle.h"
#include "src/gpu/GrTextureProxy.h"
#include "src/gpu/effects/GrTextureEffect.h"
#include "src/gpu/geometry/GrStyledShape.h"

#include "include/core/SkPaint.h"
#include "src/core/SkDraw.h"
#include "src/core/SkMaskFilterBase.h"
#include "src/core/SkMatrixProvider.h"
#include "src/core/SkTLazy.h"
#include "src/gpu/SkGr.h"

static bool clip_bounds_quick_reject(const SkIRect& clipBounds, const SkIRect& rect) {
    return clipBounds.isEmpty() || rect.isEmpty() || !SkIRect::Intersects(clipBounds, rect);
}

static constexpr auto kMaskOrigin = kTopLeft_GrSurfaceOrigin;

static GrSurfaceProxyView find_filtered_mask(GrProxyProvider* provider, const GrUniqueKey& key) {
    return provider->findCachedProxyWithColorTypeFallback(key, kMaskOrigin, GrColorType::kAlpha_8,
                                                          1);
}

// Draw a mask using the supplied paint. Since the coverage/geometry
// is already burnt into the mask this boils down to a rect draw.
// Return true if the mask was successfully drawn.
static bool draw_mask(GrRenderTargetContext* renderTargetContext,
                      const GrClip* clip,
                      const SkMatrix& viewMatrix,
                      const SkIRect& maskRect,
                      GrPaint&& paint,
                      GrSurfaceProxyView mask) {
    SkMatrix inverse;
    if (!viewMatrix.invert(&inverse)) {
        return false;
    }

    SkMatrix matrix = SkMatrix::Translate(-SkIntToScalar(maskRect.fLeft),
                                          -SkIntToScalar(maskRect.fTop));
    matrix.preConcat(viewMatrix);
    paint.addCoverageFragmentProcessor(
            GrTextureEffect::Make(std::move(mask), kUnknown_SkAlphaType, matrix));

    renderTargetContext->fillRectWithLocalMatrix(clip, std::move(paint), GrAA::kNo, SkMatrix::I(),
                                                 SkRect::Make(maskRect), inverse);
    return true;
}

static void mask_release_proc(void* addr, void* /*context*/) {
    SkMask::FreeImage(addr);
}

static bool sw_draw_with_mask_filter(GrRecordingContext* context,
                                     GrRenderTargetContext* renderTargetContext,
                                     const GrClip* clipData,
                                     const SkMatrix& viewMatrix,
                                     const GrStyledShape& shape,
                                     const SkMaskFilter* filter,
                                     const SkIRect& clipBounds,
                                     GrPaint&& paint,
                                     const GrUniqueKey& key) {
    SkASSERT(filter);
    SkASSERT(!shape.style().applies());

    auto proxyProvider = context->priv().proxyProvider();

    GrSurfaceProxyView filteredMaskView;

    SkStrokeRec::InitStyle fillOrHairline = shape.style().isSimpleHairline()
                                                    ? SkStrokeRec::kHairline_InitStyle
                                                    : SkStrokeRec::kFill_InitStyle;

    if (key.isValid()) {
        filteredMaskView = find_filtered_mask(proxyProvider, key);
    }

    SkIRect drawRect;
    if (filteredMaskView) {
        SkRect devBounds = shape.bounds();
        viewMatrix.mapRect(&devBounds);

        // Here we need to recompute the destination bounds in order to draw the mask correctly
        SkMask srcM, dstM;
        if (!SkDraw::ComputeMaskBounds(devBounds, &clipBounds, filter, &viewMatrix,
                                       &srcM.fBounds)) {
            return false;
        }

        srcM.fFormat = SkMask::kA8_Format;

        if (!as_MFB(filter)->filterMask(&dstM, srcM, viewMatrix, nullptr)) {
            return false;
        }

        // Unfortunately, we cannot double check that the computed bounds (i.e., dstM.fBounds)
        // match the stored bounds of the mask bc the proxy may have been recreated and,
        // when it is recreated, it just gets the bounds of the underlying GrTexture (which
        // might be a loose fit).
        drawRect = dstM.fBounds;
    } else {
        // TODO: it seems like we could create an SkDraw here and set its fMatrix field rather
        // than explicitly transforming the path to device space.
        SkPath devPath;

        shape.asPath(&devPath);

        devPath.transform(viewMatrix);

        SkMask srcM, dstM;
        if (!SkDraw::DrawToMask(devPath, &clipBounds, filter, &viewMatrix, &srcM,
                                SkMask::kComputeBoundsAndRenderImage_CreateMode, fillOrHairline)) {
            return false;
        }
        SkAutoMaskFreeImage autoSrc(srcM.fImage);

        SkASSERT(SkMask::kA8_Format == srcM.fFormat);

        if (!as_MFB(filter)->filterMask(&dstM, srcM, viewMatrix, nullptr)) {
            return false;
        }
        // this will free-up dstM when we're done (allocated in filterMask())
        SkAutoMaskFreeImage autoDst(dstM.fImage);

        if (clip_bounds_quick_reject(clipBounds, dstM.fBounds)) {
            return false;
        }

        // we now have a device-aligned 8bit mask in dstM, ready to be drawn using
        // the current clip (and identity matrix) and GrPaint settings
        SkBitmap bm;
        if (!bm.installPixels(SkImageInfo::MakeA8(dstM.fBounds.width(), dstM.fBounds.height()),
                              autoDst.release(), dstM.fRowBytes, mask_release_proc, nullptr)) {
            return false;
        }
        bm.setImmutable();

        GrBitmapTextureMaker maker(context, bm, SkBackingFit::kApprox);
        filteredMaskView = maker.view(GrMipMapped::kNo);
        if (!filteredMaskView.proxy()) {
            return false;
        }

        SkASSERT(kMaskOrigin == filteredMaskView.origin());

        drawRect = dstM.fBounds;

        if (key.isValid()) {
            proxyProvider->assignUniqueKeyToProxy(key, filteredMaskView.asTextureProxy());
        }
    }

    return draw_mask(renderTargetContext, clipData, viewMatrix, drawRect, std::move(paint),
                     std::move(filteredMaskView));
}

// Create a mask of 'shape' and return the resulting renderTargetContext
static std::unique_ptr<GrRenderTargetContext> create_mask_GPU(GrRecordingContext* context,
                                                              const SkIRect& maskRect,
                                                              const SkMatrix& origViewMatrix,
                                                              const GrStyledShape& shape,
                                                              int sampleCnt) {
    // Use GrResourceProvider::MakeApprox to implement our own approximate size matching, but demand
    // a "SkBackingFit::kExact" size match on the actual render target. We do this because the
    // filter will reach outside the src bounds, so we need to pre-clear these values to ensure a
    // "decal" sampling effect (i.e., ensure reads outside the src bounds return alpha=0).
    //
    // FIXME: Reads outside the left and top edges will actually clamp to the edge pixel. And in the
    // event that MakeApprox does not change the size, reads outside the right and/or bottom will do
    // the same. We should offset our filter within the render target and expand the size as needed
    // to guarantee at least 1px of padding on all sides.
    auto approxSize = GrResourceProvider::MakeApprox(maskRect.size());
    auto rtContext = GrRenderTargetContext::MakeWithFallback(
            context, GrColorType::kAlpha_8, nullptr, SkBackingFit::kExact, approxSize, sampleCnt,
            GrMipMapped::kNo, GrProtected::kNo, kMaskOrigin);
    if (!rtContext) {
        return nullptr;
    }

    rtContext->clear(SK_PMColor4fTRANSPARENT);

    GrPaint maskPaint;
    maskPaint.setCoverageSetOpXPFactory(SkRegion::kReplace_Op);

    // setup new clip
    GrFixedClip clip(rtContext->dimensions(), SkIRect::MakeWH(maskRect.width(), maskRect.height()));

    // Draw the mask into maskTexture with the path's integerized top-left at the origin using
    // maskPaint.
    SkMatrix viewMatrix = origViewMatrix;
    viewMatrix.postTranslate(-SkIntToScalar(maskRect.fLeft), -SkIntToScalar(maskRect.fTop));
    rtContext->drawShape(&clip, std::move(maskPaint), GrAA::kYes, viewMatrix, shape);
    return rtContext;
}

static bool get_unclipped_shape_dev_bounds(const GrStyledShape& shape, const SkMatrix& matrix,
                                           SkIRect* devBounds) {
    SkRect shapeBounds = shape.styledBounds();
    if (shapeBounds.isEmpty()) {
        return false;
    }
    SkRect shapeDevBounds;
    matrix.mapRect(&shapeDevBounds, shapeBounds);
    // Even though these are "unclipped" bounds we still clip to the int32_t range.
    // This is the largest int32_t that is representable exactly as a float. The next 63 larger ints
    // would round down to this value when cast to a float, but who really cares.
    // INT32_MIN is exactly representable.
    static constexpr int32_t kMaxInt = 2147483520;
    if (!shapeDevBounds.intersect(SkRect::MakeLTRB(INT32_MIN, INT32_MIN, kMaxInt, kMaxInt))) {
        return false;
    }
    // Make sure that the resulting SkIRect can have representable width and height
    if (SkScalarRoundToInt(shapeDevBounds.width()) > kMaxInt ||
        SkScalarRoundToInt(shapeDevBounds.height()) > kMaxInt) {
        return false;
    }
    shapeDevBounds.roundOut(devBounds);
    return true;
}

// Gets the shape bounds, the clip bounds, and the intersection (if any). Returns false if there
// is no intersection.
static bool get_shape_and_clip_bounds(GrRenderTargetContext* renderTargetContext,
                                      const GrClip* clip,
                                      const GrStyledShape& shape,
                                      const SkMatrix& matrix,
                                      SkIRect* unclippedDevShapeBounds,
                                      SkIRect* devClipBounds) {
    // compute bounds as intersection of rt size, clip, and path
    *devClipBounds = clip ? clip->getConservativeBounds()
                          : SkIRect::MakeWH(renderTargetContext->width(),
                                            renderTargetContext->height());

    if (!get_unclipped_shape_dev_bounds(shape, matrix, unclippedDevShapeBounds)) {
        *unclippedDevShapeBounds = SkIRect::MakeEmpty();
        return false;
    }

    return true;
}

static void draw_shape_with_mask_filter(GrRecordingContext* context,
                                        GrRenderTargetContext* renderTargetContext,
                                        const GrClip* clip,
                                        GrPaint&& paint,
                                        const SkMatrix& viewMatrix,
                                        const SkMaskFilterBase* maskFilter,
                                        const GrStyledShape& origShape) {
    SkASSERT(maskFilter);

    const GrStyledShape* shape = &origShape;
    SkTLazy<GrStyledShape> tmpShape;

    if (origShape.style().applies()) {
        SkScalar styleScale =  GrStyle::MatrixToScaleFactor(viewMatrix);
        if (0 == styleScale) {
            return;
        }

        tmpShape.init(origShape.applyStyle(GrStyle::Apply::kPathEffectAndStrokeRec, styleScale));
        if (tmpShape.get()->isEmpty()) {
            return;
        }

        shape = tmpShape.get();
    }

    if (maskFilter->directFilterMaskGPU(context, renderTargetContext, std::move(paint), clip,
                                        viewMatrix, *shape)) {
        // the mask filter was able to draw itself directly, so there's nothing
        // left to do.
        return;
    }
    assert_alive(paint);

    // If the path is hairline, ignore inverse fill.
    bool inverseFilled = shape->inverseFilled() &&
                         !GrPathRenderer::IsStrokeHairlineOrEquivalent(shape->style(),
                                                                       viewMatrix, nullptr);

    SkIRect unclippedDevShapeBounds, devClipBounds;
    if (!get_shape_and_clip_bounds(renderTargetContext, clip, *shape, viewMatrix,
                                   &unclippedDevShapeBounds, &devClipBounds)) {
        // TODO: just cons up an opaque mask here
        if (!inverseFilled) {
            return;
        }
    }

    // To prevent overloading the cache with entries during animations we limit the cache of masks
    // to cases where the matrix preserves axis alignment.
#ifdef SK_DISABLE_MASKFILTERED_MASK_CACHING
    bool useCache = false;
#else
    bool useCache = !inverseFilled && viewMatrix.preservesAxisAlignment() &&
                    shape->hasUnstyledKey() && as_MFB(maskFilter)->asABlur(nullptr);
#endif

    const SkIRect* boundsForClip = &devClipBounds;
    if (useCache) {
        SkIRect clippedMaskRect, unClippedMaskRect;
        maskFilter->canFilterMaskGPU(*shape, unclippedDevShapeBounds, devClipBounds,
                                     viewMatrix, &clippedMaskRect);
        maskFilter->canFilterMaskGPU(*shape, unclippedDevShapeBounds, unclippedDevShapeBounds,
                                     viewMatrix, &unClippedMaskRect);
        if (clippedMaskRect.isEmpty()) {
            return;
        }

        // Use the cache only if >50% of the filtered mask is visible.
        int unclippedWidth = unClippedMaskRect.width();
        int unclippedHeight = unClippedMaskRect.height();
        int64_t unclippedArea = sk_64_mul(unclippedWidth, unclippedHeight);
        int64_t clippedArea = sk_64_mul(clippedMaskRect.width(), clippedMaskRect.height());
        int maxTextureSize = renderTargetContext->caps()->maxTextureSize();
        if (unclippedArea > 2 * clippedArea || unclippedWidth > maxTextureSize ||
            unclippedHeight > maxTextureSize) {
            useCache = false;
        } else {
            // Make the clip not affect the mask
            boundsForClip = &unclippedDevShapeBounds;
        }
    }

    GrUniqueKey maskKey;
    if (useCache) {
        static const GrUniqueKey::Domain kDomain = GrUniqueKey::GenerateDomain();
        GrUniqueKey::Builder builder(&maskKey, kDomain, 5 + 2 + shape->unstyledKeySize(),
                                     "Mask Filtered Masks");

        // We require the upper left 2x2 of the matrix to match exactly for a cache hit.
        SkScalar sx = viewMatrix.get(SkMatrix::kMScaleX);
        SkScalar sy = viewMatrix.get(SkMatrix::kMScaleY);
        SkScalar kx = viewMatrix.get(SkMatrix::kMSkewX);
        SkScalar ky = viewMatrix.get(SkMatrix::kMSkewY);
        SkScalar tx = viewMatrix.get(SkMatrix::kMTransX);
        SkScalar ty = viewMatrix.get(SkMatrix::kMTransY);
        // Allow 8 bits each in x and y of subpixel positioning.
        SkFixed fracX = SkScalarToFixed(SkScalarFraction(tx)) & 0x0000FF00;
        SkFixed fracY = SkScalarToFixed(SkScalarFraction(ty)) & 0x0000FF00;

        builder[0] = SkFloat2Bits(sx);
        builder[1] = SkFloat2Bits(sy);
        builder[2] = SkFloat2Bits(kx);
        builder[3] = SkFloat2Bits(ky);
        // Distinguish between hairline and filled paths. For hairlines, we also need to include
        // the cap. (SW grows hairlines by 0.5 pixel with round and square caps). Note that
        // stroke-and-fill of hairlines is turned into pure fill by SkStrokeRec, so this covers
        // all cases we might see.
        uint32_t styleBits = shape->style().isSimpleHairline()
                                    ? ((shape->style().strokeRec().getCap() << 1) | 1)
                                    : 0;
        builder[4] = fracX | (fracY >> 8) | (styleBits << 16);

        SkMaskFilterBase::BlurRec rec;
        SkAssertResult(as_MFB(maskFilter)->asABlur(&rec));

        builder[5] = rec.fStyle;  // TODO: we could put this with the other style bits
        builder[6] = SkFloat2Bits(rec.fSigma);
        shape->writeUnstyledKey(&builder[7]);
    }

    SkIRect maskRect;
    if (maskFilter->canFilterMaskGPU(*shape,
                                     unclippedDevShapeBounds,
                                     *boundsForClip,
                                     viewMatrix,
                                     &maskRect)) {
        if (clip_bounds_quick_reject(*boundsForClip, maskRect)) {
            // clipped out
            return;
        }

        GrSurfaceProxyView filteredMaskView;

        GrProxyProvider* proxyProvider = context->priv().proxyProvider();

        if (maskKey.isValid()) {
            filteredMaskView = find_filtered_mask(proxyProvider, maskKey);
        }

        if (!filteredMaskView) {
            std::unique_ptr<GrRenderTargetContext> maskRTC(create_mask_GPU(
                                                           context,
                                                           maskRect,
                                                           viewMatrix,
                                                           *shape,
                                                           renderTargetContext->numSamples()));
            if (maskRTC) {
                filteredMaskView = maskFilter->filterMaskGPU(context,
                                                             maskRTC->readSurfaceView(),
                                                             maskRTC->colorInfo().colorType(),
                                                             maskRTC->colorInfo().alphaType(),
                                                             viewMatrix,
                                                             maskRect);
                if (filteredMaskView.proxy() && maskKey.isValid()) {
                    SkASSERT(filteredMaskView.asTextureProxy());
                    proxyProvider->assignUniqueKeyToProxy(maskKey,
                                                          filteredMaskView.asTextureProxy());
                }
            }
        }

        if (filteredMaskView) {
            if (draw_mask(renderTargetContext, clip, viewMatrix, maskRect, std::move(paint),
                          std::move(filteredMaskView))) {
                // This path is completely drawn
                return;
            }
            assert_alive(paint);
        }
    }

    sw_draw_with_mask_filter(context, renderTargetContext, clip, viewMatrix, *shape,
                             maskFilter, *boundsForClip, std::move(paint), maskKey);
}

void GrBlurUtils::drawShapeWithMaskFilter(GrRecordingContext* context,
                                          GrRenderTargetContext* renderTargetContext,
                                          const GrClip* clip,
                                          const GrStyledShape& shape,
                                          GrPaint&& paint,
                                          const SkMatrix& viewMatrix,
                                          const SkMaskFilter* mf) {
    draw_shape_with_mask_filter(context, renderTargetContext, clip, std::move(paint),
                                viewMatrix, as_MFB(mf), shape);
}

void GrBlurUtils::drawShapeWithMaskFilter(GrRecordingContext* context,
                                          GrRenderTargetContext* renderTargetContext,
                                          const GrClip* clip,
                                          const SkPaint& paint,
                                          const SkMatrixProvider& matrixProvider,
                                          const GrStyledShape& shape) {
    if (context->abandoned()) {
        return;
    }

    GrPaint grPaint;
    if (!SkPaintToGrPaint(context, renderTargetContext->colorInfo(), paint, matrixProvider,
                          &grPaint)) {
        return;
    }

    const SkMatrix& viewMatrix(matrixProvider.localToDevice());
    SkMaskFilterBase* mf = as_MFB(paint.getMaskFilter());
    if (mf && !mf->hasFragmentProcessor()) {
        // The MaskFilter wasn't already handled in SkPaintToGrPaint
        draw_shape_with_mask_filter(context, renderTargetContext, clip, std::move(grPaint),
                                    viewMatrix, mf, shape);
    } else {
        GrAA aa = GrAA(paint.isAntiAlias());
        renderTargetContext->drawShape(clip, std::move(grPaint), aa, viewMatrix, shape);
    }
}