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* Copyright 2017 Google Inc.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
#ifndef SkThreadedBMPDevice_DEFINED
#define SkThreadedBMPDevice_DEFINED
#include "SkBitmapDevice.h"
#include "SkDraw.h"
#include "SkRectPriv.h"
#include "SkTaskGroup2D.h"
#include <new>
class SkThreadedBMPDevice : public SkBitmapDevice {
// When threads = 0, we make fThreadCnt = tiles. Otherwise fThreadCnt = threads.
// When executor = nullptr, we manages the thread pool. Otherwise, the caller manages it.
SkThreadedBMPDevice(const SkBitmap& bitmap, int tiles, int threads = 0,
SkExecutor* executor = nullptr);
~SkThreadedBMPDevice() override { fQueue.finish(); }
void drawPaint(const SkPaint& paint) override;
void drawPoints(SkCanvas::PointMode mode, size_t count,
const SkPoint[], const SkPaint& paint) override;
void drawRect(const SkRect& r, const SkPaint& paint) override;
void drawRRect(const SkRRect& rr, const SkPaint& paint) override;
void drawPath(const SkPath&, const SkPaint&, const SkMatrix* prePathMatrix,
bool pathIsMutable) override;
void drawSprite(const SkBitmap&, int x, int y, const SkPaint&) override;
void drawPosText(const void* text, size_t len, const SkScalar pos[],
int scalarsPerPos, const SkPoint& offset, const SkPaint& paint) override;
void drawVertices(const SkVertices*, SkBlendMode, const SkPaint&) override;
void drawBitmap(const SkBitmap&, const SkMatrix&, const SkRect* dstOrNull,
const SkPaint&) override;
void drawBitmapRect(const SkBitmap& bitmap, const SkRect* src, const SkRect& dst,
const SkPaint& paint, SkCanvas::SrcRectConstraint constraint) override;
sk_sp<SkSpecialImage> snapSpecial() override;
void flush() override;
// We store DrawState inside DrawElement because inifFn and drawFn both want to use it
struct DrawState {
SkPixmap fDst;
SkMatrix fMatrix;
SkRasterClip fRC;
DrawState() {}
explicit DrawState(SkThreadedBMPDevice* dev);
SkDraw getDraw() const;
class TileDraw : public SkDraw {
public: TileDraw(const DrawState& ds, const SkIRect& tileBounds);
private: SkRasterClip fTileRC;
class DrawElement {
using InitFn = std::function<void(SkArenaAlloc* threadAlloc, DrawElement* element)>;
using DrawFn = std::function<void(SkArenaAlloc* threadAlloc, const DrawState& ds,
const SkIRect& tileBounds)>;
DrawElement() {}
DrawElement(SkThreadedBMPDevice* device, DrawFn&& drawFn, const SkIRect& drawBounds)
: fInitialized(true)
, fDrawFn(std::move(drawFn))
, fDS(device)
, fDrawBounds(drawBounds) {}
DrawElement(SkThreadedBMPDevice* device, InitFn&& initFn, const SkIRect& drawBounds)
: fInitialized(false)
, fNeedInit(true)
, fInitFn(std::move(initFn))
, fDS(device)
, fDrawBounds(drawBounds) {}
SK_ALWAYS_INLINE bool tryInitOnce(SkArenaAlloc* alloc) {
bool t = true;
// If there are multiple threads reaching this point simutaneously,
// compare_exchange_strong ensures that only one thread can enter the if condition and
// do the initialization.
if (!fInitialized && fNeedInit && fNeedInit.compare_exchange_strong(t, false)) {
#ifdef SK_DEBUG
fDrawFn = 0; // Invalidate fDrawFn
fInitFn(alloc, this);
fInitialized = true;
SkASSERT(fDrawFn != 0); // Ensure that fInitFn does populate fDrawFn
return true;
return false;
SK_ALWAYS_INLINE bool tryDraw(const SkIRect& tileBounds, SkArenaAlloc* alloc) {
if (!SkIRect::Intersects(tileBounds, fDrawBounds)) {
return true;
if (fInitialized) {
fDrawFn(alloc, fDS, tileBounds);
return true;
return false;
SkDraw getDraw() const { return fDS.getDraw(); }
void setDrawFn(DrawFn&& fn) { fDrawFn = std::move(fn); }
std::atomic<bool> fInitialized;
std::atomic<bool> fNeedInit;
InitFn fInitFn;
DrawFn fDrawFn;
DrawState fDS;
SkIRect fDrawBounds;
class DrawQueue : public SkWorkKernel2D {
static constexpr int MAX_QUEUE_SIZE = 100000;
DrawQueue(SkThreadedBMPDevice* device) : fDevice(device) {}
void reset();
// For ~SkThreadedBMPDevice() to shutdown tasks, we use this instead of reset because reset
// will start new tasks.
void finish() { fTasks->finish(); }
// Push a draw command into the queue. If Fn is DrawFn, we're pushing an element without
// the need of initialization. If Fn is InitFn, we're pushing an element with init-once
// and the InitFn will generate the DrawFn during initialization.
template<bool useCTM = true, typename Fn>
SK_ALWAYS_INLINE void push(const SkRect& rawDrawBounds, Fn&& fn) {
if (fSize == MAX_QUEUE_SIZE) {
SkIRect drawBounds = fDevice->transformDrawBounds<useCTM>(rawDrawBounds);
fElements[fSize].~DrawElement(); // release previous resources to prevent memory leak
new (&fElements[fSize++]) DrawElement(fDevice, std::move(fn), drawBounds);
// SkWorkKernel2D
bool initColumn(int column, int thread) override;
bool work2D(int row, int column, int thread) override;
SkThreadedBMPDevice* fDevice;
std::unique_ptr<SkTaskGroup2D> fTasks;
SkTArray<SkSTArenaAlloc<8 << 10>> fThreadAllocs; // 8k stack size
DrawElement fElements[MAX_QUEUE_SIZE];
int fSize;
template<bool useCTM = true>
SkIRect transformDrawBounds(const SkRect& drawBounds) const {
if (drawBounds == SkRectPriv::MakeLargest()) {
return SkRectPriv::MakeILarge();
SkRect transformedBounds;
if (useCTM) {
this->ctm().mapRect(&transformedBounds, drawBounds);
} else {
transformedBounds = drawBounds;
return transformedBounds.roundOut();
template<typename T>
T* cloneArray(const T* array, int count) {
T* clone = fAlloc.makeArrayDefault<T>(count);
memcpy(clone, array, sizeof(T) * count);
return clone;
SkBitmap snapBitmap(const SkBitmap& bitmap);
const int fTileCnt;
const int fThreadCnt;
SkTArray<SkIRect> fTileBounds;
* This can either be
* 1. fInternalExecutor.get() which means that we're managing the thread pool's life cycle.
* 2. provided by our caller which means that our caller is managing the threads' life cycle.
* In the 2nd case, fInternalExecutor == nullptr.
SkExecutor* fExecutor = nullptr;
std::unique_ptr<SkExecutor> fInternalExecutor;
SkSTArenaAlloc<8 << 10> fAlloc; // so we can allocate memory that lives until flush
DrawQueue fQueue;
friend struct SkInitOnceData; // to access DrawElement and DrawState
friend class SkDraw; // to access DrawState
typedef SkBitmapDevice INHERITED;
// Passed to SkDraw::drawXXX to enable threaded draw with init-once. The goal is to reuse as much
// code as possible from SkDraw. (See SkDraw::drawPath and SkDraw::drawDevPath for an example.)
struct SkInitOnceData {
SkArenaAlloc* fAlloc;
SkThreadedBMPDevice::DrawElement* fElement;
void setEmptyDrawFn() {
fElement->setDrawFn([](SkArenaAlloc* threadAlloc, const SkThreadedBMPDevice::DrawState& ds,
const SkIRect& tileBounds){});
#endif // SkThreadedBMPDevice_DEFINED