src/image/SkSurface_Raster.cpp

/*
 * Copyright 2012 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "SkSurface_Base.h"
#include "SkImagePriv.h"
#include "SkCanvas.h"
#include "SkDevice.h"
#include "SkMallocPixelRef.h"

static const size_t kIgnoreRowBytesValue = (size_t)~0;

class SkSurface_Raster : public SkSurface_Base {
public:
    static bool Valid(const SkImageInfo&, size_t rb = kIgnoreRowBytesValue);

    SkSurface_Raster(const SkImageInfo&, void*, size_t rb,
                     void (*releaseProc)(void* pixels, void* context), void* context,
                     const SkSurfaceProps*);
    SkSurface_Raster(SkPixelRef*, const SkSurfaceProps*);

    SkCanvas* onNewCanvas() override;
    SkSurface* onNewSurface(const SkImageInfo&) override;
    SkImage* onNewImageSnapshot(Budgeted) override;
    void onDraw(SkCanvas*, SkScalar x, SkScalar y, const SkPaint*) override;
    void onCopyOnWrite(ContentChangeMode) override;
    void onRestoreBackingMutability() override;

private:
    SkBitmap    fBitmap;
    size_t      fRowBytes;
    bool        fWeOwnThePixels;

    typedef SkSurface_Base INHERITED;
};

///////////////////////////////////////////////////////////////////////////////

bool SkSurface_Raster::Valid(const SkImageInfo& info, size_t rowBytes) {
    if (info.isEmpty()) {
        return false;
    }

    static const size_t kMaxTotalSize = SK_MaxS32;

    int shift = 0;
    switch (info.colorType()) {
        case kAlpha_8_SkColorType:
            shift = 0;
            break;
        case kRGB_565_SkColorType:
            shift = 1;
            break;
        case kN32_SkColorType:
            shift = 2;
            break;
        case kRGBA_F16_SkColorType:
            shift = 3;
            break;
        default:
            return false;
    }

    if (kIgnoreRowBytesValue == rowBytes) {
        return true;
    }

    uint64_t minRB = (uint64_t)info.width() << shift;
    if (minRB > rowBytes) {
        return false;
    }

    size_t alignedRowBytes = rowBytes >> shift << shift;
    if (alignedRowBytes != rowBytes) {
        return false;
    }

    uint64_t size = sk_64_mul(info.height(), rowBytes);
    if (size > kMaxTotalSize) {
        return false;
    }

    return true;
}

SkSurface_Raster::SkSurface_Raster(const SkImageInfo& info, void* pixels, size_t rb,
                                   void (*releaseProc)(void* pixels, void* context), void* context,
                                   const SkSurfaceProps* props)
    : INHERITED(info, props)
{
    fBitmap.installPixels(info, pixels, rb, nullptr, releaseProc, context);
    fRowBytes = 0;              // don't need to track the rowbytes
    fWeOwnThePixels = false;    // We are "Direct"
}

SkSurface_Raster::SkSurface_Raster(SkPixelRef* pr, const SkSurfaceProps* props)
    : INHERITED(pr->info().width(), pr->info().height(), props)
{
    const SkImageInfo& info = pr->info();

    fBitmap.setInfo(info, pr->rowBytes());
    fBitmap.setPixelRef(pr);
    fRowBytes = pr->rowBytes(); // we track this, so that subsequent re-allocs will match
    fWeOwnThePixels = true;
}

SkCanvas* SkSurface_Raster::onNewCanvas() { return new SkCanvas(fBitmap, this->props()); }

SkSurface* SkSurface_Raster::onNewSurface(const SkImageInfo& info) {
    return SkSurface::NewRaster(info, &this->props());
}

void SkSurface_Raster::onDraw(SkCanvas* canvas, SkScalar x, SkScalar y,
                              const SkPaint* paint) {
    canvas->drawBitmap(fBitmap, x, y, paint);
}

SkImage* SkSurface_Raster::onNewImageSnapshot(Budgeted) {
    if (fWeOwnThePixels) {
        // SkImage_raster requires these pixels are immutable for its full lifetime.
        // We'll undo this via onRestoreBackingMutability() if we can avoid the COW.
        if (SkPixelRef* pr = fBitmap.pixelRef()) {
            pr->setTemporarilyImmutable();
        }
    }
    // Our pixels are in memory, so read access on the snapshot SkImage could be cheap.
    // Lock the shared pixel ref to ensure peekPixels() is usable.
    return SkNewImageFromRasterBitmap(fBitmap,
                                      fWeOwnThePixels ? kNo_ForceCopyMode : kYes_ForceCopyMode);
}

void SkSurface_Raster::onRestoreBackingMutability() {
    SkASSERT(!this->hasCachedImage());  // Shouldn't be any snapshots out there.
    if (SkPixelRef* pr = fBitmap.pixelRef()) {
        pr->restoreMutability();
    }
}

void SkSurface_Raster::onCopyOnWrite(ContentChangeMode mode) {
    // are we sharing pixelrefs with the image?
    SkASSERT(this->getCachedImage(kNo_Budgeted));
    if (SkBitmapImageGetPixelRef(this->getCachedImage(kNo_Budgeted)) == fBitmap.pixelRef()) {
        SkASSERT(fWeOwnThePixels);
        if (kDiscard_ContentChangeMode == mode) {
            fBitmap.allocPixels();
        } else {
            SkBitmap prev(fBitmap);
            fBitmap.allocPixels();
            prev.lockPixels();
            SkASSERT(prev.info() == fBitmap.info());
            SkASSERT(prev.rowBytes() == fBitmap.rowBytes());
            memcpy(fBitmap.getPixels(), prev.getPixels(), fBitmap.getSafeSize());
        }
        SkASSERT(fBitmap.rowBytes() == fRowBytes);  // be sure we always use the same value

        // Now fBitmap is a deep copy of itself (and therefore different from
        // what is being used by the image. Next we update the canvas to use
        // this as its backend, so we can't modify the image's pixels anymore.
        SkASSERT(this->getCachedCanvas());
        this->getCachedCanvas()->getDevice()->replaceBitmapBackendForRasterSurface(fBitmap);
    }
}

///////////////////////////////////////////////////////////////////////////////

SkSurface* SkSurface::NewRasterDirectReleaseProc(const SkImageInfo& info, void* pixels, size_t rb,
                                                 void (*releaseProc)(void* pixels, void* context),
                                                 void* context, const SkSurfaceProps* props) {
    if (nullptr == releaseProc) {
        context = nullptr;
    }
    if (!SkSurface_Raster::Valid(info, rb)) {
        return nullptr;
    }
    if (nullptr == pixels) {
        return nullptr;
    }

    return new SkSurface_Raster(info, pixels, rb, releaseProc, context, props);
}

SkSurface* SkSurface::NewRasterDirect(const SkImageInfo& info, void* pixels, size_t rowBytes,
                                      const SkSurfaceProps* props) {
    return NewRasterDirectReleaseProc(info, pixels, rowBytes, nullptr, nullptr, props);
}

SkSurface* SkSurface::NewRaster(const SkImageInfo& info, size_t rowBytes,
                                const SkSurfaceProps* props) {
    if (!SkSurface_Raster::Valid(info)) {
        return nullptr;
    }

    SkAutoTUnref<SkPixelRef> pr(SkMallocPixelRef::NewZeroed(info, rowBytes, nullptr));
    if (nullptr == pr.get()) {
        return nullptr;
    }
    if (rowBytes) {
        SkASSERT(pr->rowBytes() == rowBytes);
    }
    return new SkSurface_Raster(pr, props);
}

SkSurface* SkSurface::NewRaster(const SkImageInfo& info, const SkSurfaceProps* props) {
    return NewRaster(info, 0, props);
}