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* Copyright 2016 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/GrClipStackClip.h"
#include "include/gpu/GrDirectContext.h"
#include "include/private/SkTo.h"
#include "src/core/SkClipOpPriv.h"
#include "src/core/SkTaskGroup.h"
#include "src/core/SkTraceEvent.h"
#include "src/gpu/GrAppliedClip.h"
#include "src/gpu/GrAttachment.h"
#include "src/gpu/GrDeferredProxyUploader.h"
#include "src/gpu/GrDirectContextPriv.h"
#include "src/gpu/GrDrawingManager.h"
#include "src/gpu/GrGpuResourcePriv.h"
#include "src/gpu/GrProxyProvider.h"
#include "src/gpu/GrRecordingContextPriv.h"
#include "src/gpu/GrSWMaskHelper.h"
#include "src/gpu/GrStyle.h"
#include "src/gpu/GrTextureProxy.h"
#include "src/gpu/effects/GrBlendFragmentProcessor.h"
#include "src/gpu/effects/GrRRectEffect.h"
#include "src/gpu/effects/generated/GrDeviceSpaceEffect.h"
#include "src/gpu/geometry/GrStyledShape.h"
typedef SkClipStack::Element Element;
typedef GrReducedClip::InitialState InitialState;
typedef GrReducedClip::ElementList ElementList;
const char GrClipStackClip::kMaskTestTag[] = "clip_mask";
GrClip::PreClipResult GrClipStackClip::preApply(const SkRect& drawBounds, GrAA aa) const {
SkIRect deviceRect = SkIRect::MakeSize(fDeviceSize);
SkRect rect = SkRect::Make(deviceRect);
if (!rect.intersect(drawBounds) || (fStack && fStack->isEmpty(deviceRect))) {
return Effect::kClippedOut;
} else if (!fStack || fStack->isWideOpen()) {
return Effect::kUnclipped;
PreClipResult result(Effect::kClipped);
bool isAA;
// SkClipStack does not have a way to distinguish "not a rrect" vs. "rrect that doesn't
// intersect the draw", so pass in the device bounds and then check the returned shape for
// intersection afterwards.
if (fStack->isRRect(SkRect::Make(deviceRect), &result.fRRect, &isAA)) {
if (!result.fRRect.getBounds().intersects(rect)) {
return Effect::kClippedOut;
result.fIsRRect = true;
result.fAA = GrAA(isAA);
return result;
SkIRect GrClipStackClip::getConservativeBounds() const {
if (fStack) {
SkRect devBounds;
fStack->getConservativeBounds(0, 0, fDeviceSize.fWidth, fDeviceSize.fHeight, &devBounds);
return devBounds.roundOut();
} else {
return SkIRect::MakeSize(fDeviceSize);
// set up the draw state to enable the aa clipping mask.
static std::unique_ptr<GrFragmentProcessor> create_fp_for_mask(GrSurfaceProxyView mask,
const SkIRect& devBound,
const GrCaps& caps) {
GrSamplerState samplerState(GrSamplerState::WrapMode::kClampToBorder,
auto m = SkMatrix::Translate(-devBound.fLeft, -devBound.fTop);
auto subset = SkRect::Make(devBound.size());
// We scissor to devBounds. The mask's texel centers are aligned to device space
// pixel centers. Hence this domain of texture coordinates.
auto domain = subset.makeInset(0.5, 0.5);
auto fp = GrTextureEffect::MakeSubset(std::move(mask), kPremul_SkAlphaType, m, samplerState,
subset, domain, caps);
fp = GrBlendFragmentProcessor::Make(std::move(fp), nullptr, SkBlendMode::kDstIn);
return GrDeviceSpaceEffect::Make(std::move(fp));
// Does the path in 'element' require SW rendering?
bool GrClipStackClip::PathNeedsSWRenderer(GrRecordingContext* context,
const SkIRect& scissorRect,
bool hasUserStencilSettings,
const GrSurfaceDrawContext* surfaceDrawContext,
const SkMatrix& viewMatrix,
const Element* element,
bool needsStencil) {
if (Element::DeviceSpaceType::kRect == element->getDeviceSpaceType()) {
// rects can always be drawn directly w/o using the software path
// TODO: skip rrects once we're drawing them directly.
return false;
} else {
// We shouldn't get here with an empty clip element.
SkASSERT(Element::DeviceSpaceType::kEmpty != element->getDeviceSpaceType());
// the gpu alpha mask will draw the inverse paths as non-inverse to a temp buffer
SkPath path;
if (path.isInverseFillType()) {
// We only use this method when rendering coverage clip masks.
SkASSERT(surfaceDrawContext->numSamples() <= 1);
auto aaType = (element->isAA()) ? GrAAType::kCoverage : GrAAType::kNone;
GrPathRendererChain::DrawType type =
needsStencil ? GrPathRendererChain::DrawType::kStencilAndColor
: GrPathRendererChain::DrawType::kColor;
GrStyledShape shape(path, GrStyle::SimpleFill());
GrPathRenderer::CanDrawPathArgs canDrawArgs;
canDrawArgs.fCaps = context->priv().caps();
canDrawArgs.fProxy = surfaceDrawContext->asRenderTargetProxy();
canDrawArgs.fClipConservativeBounds = &scissorRect;
canDrawArgs.fViewMatrix = &viewMatrix;
canDrawArgs.fShape = &shape;
canDrawArgs.fPaint = nullptr;
canDrawArgs.fAAType = aaType;
canDrawArgs.fTargetIsWrappedVkSecondaryCB = false;
canDrawArgs.fHasUserStencilSettings = hasUserStencilSettings;
// the 'false' parameter disallows use of the SW path renderer
GrPathRenderer* pr =
context->priv().drawingManager()->getPathRenderer(canDrawArgs, false, type);
return SkToBool(!pr);
* This method traverses the clip stack to see if the GrSoftwarePathRenderer
* will be used on any element. If so, it returns true to indicate that the
* entire clip should be rendered in SW and then uploaded en masse to the gpu.
bool GrClipStackClip::UseSWOnlyPath(GrRecordingContext* context,
bool hasUserStencilSettings,
const GrSurfaceDrawContext* surfaceDrawContext,
const GrReducedClip& reducedClip) {
// TODO: right now it appears that GPU clip masks are strictly slower than software. We may
// want to revisit this assumption once we can test with render target sorting.
return true;
// TODO: generalize this function so that when
// a clip gets complex enough it can just be done in SW regardless
// of whether it would invoke the GrSoftwarePathRenderer.
// If we're avoiding stencils, always use SW. This includes drawing into a wrapped vulkan
// secondary command buffer which can't handle stencils.
if (context->priv().caps()->avoidStencilBuffers() ||
surfaceDrawContext->wrapsVkSecondaryCB()) {
return true;
// Set the matrix so that rendered clip elements are transformed to mask space from clip
// space.
SkMatrix translate;
translate.setTranslate(SkIntToScalar(-reducedClip.left()), SkIntToScalar(;
for (ElementList::Iter iter(reducedClip.maskElements()); iter.get(); {
const Element* element = iter.get();
SkClipOp op = element->getOp();
bool invert = element->isInverseFilled();
bool needsStencil = invert ||
kIntersect_SkClipOp == op || kReverseDifference_SkClipOp == op;
if (PathNeedsSWRenderer(context, reducedClip.scissor(), hasUserStencilSettings,
surfaceDrawContext, translate, element, needsStencil)) {
return true;
return false;
// sort out what kind of clip mask needs to be created: alpha, stencil,
// scissor, or entirely software
GrClip::Effect GrClipStackClip::apply(GrRecordingContext* context,
GrSurfaceDrawContext* surfaceDrawContext,
GrAAType aa, bool hasUserStencilSettings,
GrAppliedClip* out, SkRect* bounds) const {
SkASSERT(surfaceDrawContext->width() == fDeviceSize.fWidth &&
surfaceDrawContext->height() == fDeviceSize.fHeight);
SkRect devBounds = SkRect::MakeIWH(fDeviceSize.fWidth, fDeviceSize.fHeight);
if (!devBounds.intersect(*bounds)) {
return Effect::kClippedOut;
if (!fStack || fStack->isWideOpen()) {
return Effect::kUnclipped;
// An default count of 4 was chosen because of the common pattern in Blink of:
// isect RR
// diff RR
// isect convex_poly
// isect convex_poly
// when drawing rounded div borders.
constexpr int kMaxAnalyticElements = 4;
int maxWindowRectangles = surfaceDrawContext->maxWindowRectangles();
int maxAnalyticElements = kMaxAnalyticElements;
if (surfaceDrawContext->numSamples() > 1 || aa == GrAAType::kMSAA || hasUserStencilSettings) {
// Disable analytic clips when we have MSAA. In MSAA we never conflate coverage and opacity.
maxAnalyticElements = 0;
// We disable MSAA when avoiding stencil.
auto* ccpr = context->priv().drawingManager()->getCoverageCountingPathRenderer();
GrReducedClip reducedClip(*fStack, devBounds, context->priv().caps(), maxWindowRectangles,
maxAnalyticElements, ccpr ? maxAnalyticElements : 0);
if (InitialState::kAllOut == reducedClip.initialState() &&
reducedClip.maskElements().isEmpty()) {
return Effect::kClippedOut;
Effect effect = Effect::kUnclipped;
if (reducedClip.hasScissor() && !GrClip::IsInsideClip(reducedClip.scissor(), devBounds)) {
out->hardClip().addScissor(reducedClip.scissor(), bounds);
effect = Effect::kClipped;
if (!reducedClip.windowRectangles().empty()) {
effect = Effect::kClipped;
if (!reducedClip.maskElements().isEmpty()) {
if (!this->applyClipMask(context, surfaceDrawContext, reducedClip, hasUserStencilSettings,
out)) {
return Effect::kClippedOut;
effect = Effect::kClipped;
// The opsTask ID must not be looked up until AFTER producing the clip mask (if any). That step
// can cause a flush or otherwise change which opstask our draw is going into.
uint32_t opsTaskID = surfaceDrawContext->getOpsTask()->uniqueID();
auto [success, clipFPs] = reducedClip.finishAndDetachAnalyticElements(context, *fMatrixProvider,
ccpr, opsTaskID);
if (success) {
effect = Effect::kClipped;
} else {
effect = Effect::kClippedOut;
return effect;
bool GrClipStackClip::applyClipMask(GrRecordingContext* context,
GrSurfaceDrawContext* surfaceDrawContext,
const GrReducedClip& reducedClip, bool hasUserStencilSettings,
GrAppliedClip* out) const {
#ifdef SK_DEBUG
SkIRect rtIBounds = SkIRect::MakeWH(surfaceDrawContext->width(),
const SkIRect& scissor = reducedClip.scissor();
SkASSERT(rtIBounds.contains(scissor)); // Mask shouldn't be larger than the RT.
// MIXED SAMPLES TODO: We may want to explore using the stencil buffer for AA clipping.
if ((surfaceDrawContext->numSamples() <= 1 && reducedClip.maskRequiresAA()) ||
context->priv().caps()->avoidStencilBuffers() ||
surfaceDrawContext->wrapsVkSecondaryCB()) {
GrSurfaceProxyView result;
if (UseSWOnlyPath(context, hasUserStencilSettings, surfaceDrawContext, reducedClip)) {
// The clip geometry is complex enough that it will be more efficient to create it
// entirely in software
result = this->createSoftwareClipMask(context, reducedClip, surfaceDrawContext);
} else {
result = this->createAlphaClipMask(context, reducedClip);
if (result) {
// The mask's top left coord should be pinned to the rounded-out top left corner of
// the clip's device space bounds.
out->addCoverageFP(create_fp_for_mask(std::move(result), reducedClip.scissor(),
return true;
// If alpha or software clip mask creation fails, fall through to the stencil code paths,
// unless stencils are disallowed.
if (context->priv().caps()->avoidStencilBuffers() ||
surfaceDrawContext->wrapsVkSecondaryCB()) {
SkDebugf("WARNING: Clip mask requires stencil, but stencil unavailable. "
"Clip will be ignored.\n");
return false;
reducedClip.drawStencilClipMask(context, surfaceDrawContext);
return true;
// Create a 8-bit clip mask in alpha
static void create_clip_mask_key(uint32_t clipGenID, const SkIRect& bounds, int numAnalyticElements,
GrUniqueKey* key) {
static const GrUniqueKey::Domain kDomain = GrUniqueKey::GenerateDomain();
GrUniqueKey::Builder builder(key, kDomain, 4, GrClipStackClip::kMaskTestTag);
builder[0] = clipGenID;
// SkToS16 because image filters outset layers to a size indicated by the filter, which can
// sometimes result in negative coordinates from device space.
builder[1] = SkToS16(bounds.fLeft) | (SkToS16(bounds.fRight) << 16);
builder[2] = SkToS16(bounds.fTop) | (SkToS16(bounds.fBottom) << 16);
builder[3] = numAnalyticElements;
static void add_invalidate_on_pop_message(GrRecordingContext* context,
const SkClipStack& stack, uint32_t clipGenID,
const GrUniqueKey& clipMaskKey) {
GrProxyProvider* proxyProvider = context->priv().proxyProvider();
SkClipStack::Iter iter(stack, SkClipStack::Iter::kTop_IterStart);
while (const Element* element = iter.prev()) {
if (element->getGenID() == clipGenID) {
element->addResourceInvalidationMessage(proxyProvider, clipMaskKey);
SkDEBUGFAIL("Gen ID was not found in stack.");
static constexpr auto kMaskOrigin = kTopLeft_GrSurfaceOrigin;
static GrSurfaceProxyView find_mask(GrProxyProvider* provider, const GrUniqueKey& key) {
return provider->findCachedProxyWithColorTypeFallback(key, kMaskOrigin, GrColorType::kAlpha_8,
GrSurfaceProxyView GrClipStackClip::createAlphaClipMask(GrRecordingContext* context,
const GrReducedClip& reducedClip) const {
GrProxyProvider* proxyProvider = context->priv().proxyProvider();
GrUniqueKey key;
create_clip_mask_key(reducedClip.maskGenID(), reducedClip.scissor(),
reducedClip.numAnalyticElements(), &key);
if (auto cachedView = find_mask(context->priv().proxyProvider(), key)) {
return cachedView;
auto rtc = GrSurfaceDrawContext::MakeWithFallback(
context, GrColorType::kAlpha_8, nullptr, SkBackingFit::kApprox,
{reducedClip.width(), reducedClip.height()}, 1, GrMipmapped::kNo, GrProtected::kNo,
if (!rtc) {
return {};
if (!reducedClip.drawAlphaClipMask(rtc.get())) {
return {};
GrSurfaceProxyView result = rtc->readSurfaceView();
if (!result || !result.asTextureProxy()) {
return {};
SkASSERT(result.origin() == kMaskOrigin);
proxyProvider->assignUniqueKeyToProxy(key, result.asTextureProxy());
add_invalidate_on_pop_message(context, *fStack, reducedClip.maskGenID(), key);
return result;
namespace {
* Payload class for use with GrTDeferredProxyUploader. The clip mask code renders multiple
* elements, each storing their own AA setting (and already transformed into device space). This
* stores all of the information needed by the worker thread to draw all clip elements (see below,
* in createSoftwareClipMask).
class ClipMaskData {
ClipMaskData(const GrReducedClip& reducedClip)
: fScissor(reducedClip.scissor())
, fInitialState(reducedClip.initialState()) {
for (ElementList::Iter iter(reducedClip.maskElements()); iter.get(); {
const SkIRect& scissor() const { return fScissor; }
InitialState initialState() const { return fInitialState; }
const ElementList& elements() const { return fElements; }
SkIRect fScissor;
InitialState fInitialState;
ElementList fElements;
} // namespace
static void draw_clip_elements_to_mask_helper(GrSWMaskHelper& helper, const ElementList& elements,
const SkIRect& scissor, InitialState initialState) {
// Set the matrix so that rendered clip elements are transformed to mask space from clip space.
SkMatrix translate;
translate.setTranslate(SkIntToScalar(-scissor.left()), SkIntToScalar(;
helper.clear(InitialState::kAllIn == initialState ? 0xFF : 0x00);
for (ElementList::Iter iter(elements); iter.get(); {
const Element* element = iter.get();
SkClipOp op = element->getOp();
GrAA aa = GrAA(element->isAA());
if (kIntersect_SkClipOp == op || kReverseDifference_SkClipOp == op) {
// Intersect and reverse difference require modifying pixels outside of the geometry
// that is being "drawn". In both cases we erase all the pixels outside of the geometry
// but leave the pixels inside the geometry alone. For reverse difference we invert all
// the pixels before clearing the ones outside the geometry.
if (kReverseDifference_SkClipOp == op) {
SkRect temp = SkRect::Make(scissor);
// invert the entire scene
helper.drawRect(temp, translate, SkRegion::kXOR_Op, GrAA::kNo, 0xFF);
SkPath clipPath;
helper.drawShape(GrShape(clipPath), translate, SkRegion::kReplace_Op, aa, 0x00);
// The other ops (union, xor, diff) only affect pixels inside
// the geometry so they can just be drawn normally
if (Element::DeviceSpaceType::kRect == element->getDeviceSpaceType()) {
helper.drawRect(element->getDeviceSpaceRect(), translate, (SkRegion::Op)op, aa, 0xFF);
} else if (Element::DeviceSpaceType::kRRect == element->getDeviceSpaceType()) {
helper.drawRRect(element->getDeviceSpaceRRect(), translate, (SkRegion::Op)op, aa, 0xFF);
} else {
SkPath path;
helper.drawShape(GrShape(path), translate, (SkRegion::Op)op, aa, 0xFF);
GrSurfaceProxyView GrClipStackClip::createSoftwareClipMask(
GrRecordingContext* context, const GrReducedClip& reducedClip,
GrSurfaceDrawContext* surfaceDrawContext) const {
GrUniqueKey key;
create_clip_mask_key(reducedClip.maskGenID(), reducedClip.scissor(),
reducedClip.numAnalyticElements(), &key);
GrProxyProvider* proxyProvider = context->priv().proxyProvider();
if (auto cachedView = find_mask(proxyProvider, key)) {
return cachedView;
// The mask texture may be larger than necessary. We round out the clip bounds and pin the top
// left corner of the resulting rect to the top left of the texture.
SkIRect maskSpaceIBounds = SkIRect::MakeWH(reducedClip.width(), reducedClip.height());
SkTaskGroup* taskGroup = nullptr;
if (auto direct = context->asDirectContext()) {
taskGroup = direct->priv().getTaskGroup();
GrSurfaceProxyView view;
if (taskGroup && surfaceDrawContext) {
const GrCaps* caps = context->priv().caps();
// Create our texture proxy
GrBackendFormat format = caps->getDefaultBackendFormat(GrColorType::kAlpha_8,
GrSwizzle swizzle = context->priv().caps()->getReadSwizzle(format, GrColorType::kAlpha_8);
// MDB TODO: We're going to fill this proxy with an ASAP upload (which is out of order wrt
// to ops), so it can't have any pending IO.
auto proxy = proxyProvider->createProxy(format,
auto uploader = std::make_unique<GrTDeferredProxyUploader<ClipMaskData>>(reducedClip);
GrTDeferredProxyUploader<ClipMaskData>* uploaderRaw = uploader.get();
auto drawAndUploadMask = [uploaderRaw, maskSpaceIBounds] {
TRACE_EVENT0("skia.gpu", "Threaded SW Clip Mask Render");
GrSWMaskHelper helper(uploaderRaw->getPixels());
if (helper.init(maskSpaceIBounds)) {
draw_clip_elements_to_mask_helper(helper, uploaderRaw->data().elements(),
} else {
SkDEBUGFAIL("Unable to allocate SW clip mask.");
view = {std::move(proxy), kMaskOrigin, swizzle};
} else {
GrSWMaskHelper helper;
if (!helper.init(maskSpaceIBounds)) {
return {};
draw_clip_elements_to_mask_helper(helper, reducedClip.maskElements(), reducedClip.scissor(),
view = helper.toTextureView(context, SkBackingFit::kApprox);
SkASSERT(view.origin() == kMaskOrigin);
proxyProvider->assignUniqueKeyToProxy(key, view.asTextureProxy());
add_invalidate_on_pop_message(context, *fStack, reducedClip.maskGenID(), key);
return view;