C++ GrContext::flush方法代码示例

DEF_GPUTEST_FOR_ALL_GL_CONTEXTS(VertexAttributeCount, reporter, ctxInfo) {
    GrContext* context = ctxInfo.fGrContext;
    GrTextureDesc desc;
    desc.fHeight = 1;
    desc.fWidth = 1;
    desc.fFlags = kRenderTarget_GrSurfaceFlag;
    desc.fConfig = kRGBA_8888_GrPixelConfig;
    SkAutoTUnref<GrTexture> target(context->textureProvider()->createTexture(desc,
                                                                             SkBudgeted::kYes));
    if (!target) {
        ERRORF(reporter, "Could not create render target.");
        return;
    }
    SkAutoTUnref<GrDrawContext> dc(context->drawContext(target->asRenderTarget()));
    if (!dc) {
        ERRORF(reporter, "Could not create draw context.");
        return;
    }
    int attribCnt = context->caps()->maxVertexAttributes();
    if (!attribCnt) {
        ERRORF(reporter, "No attributes allowed?!");
        return;
    }
    context->flush();
    context->resetGpuStats();
#if GR_GPU_STATS
    REPORTER_ASSERT(reporter, context->getGpu()->stats()->numDraws() == 0);
    REPORTER_ASSERT(reporter, context->getGpu()->stats()->numFailedDraws() == 0);
#endif
    SkAutoTUnref<GrDrawBatch> batch;
    GrPipelineBuilder pb;
    pb.setRenderTarget(target->asRenderTarget());
    // This one should succeed.
    batch.reset(new Batch(attribCnt));
    dc->drawContextPriv().testingOnly_drawBatch(pb, batch);
    context->flush();
#if GR_GPU_STATS
    REPORTER_ASSERT(reporter, context->getGpu()->stats()->numDraws() == 1);
    REPORTER_ASSERT(reporter, context->getGpu()->stats()->numFailedDraws() == 0);
#endif
    context->resetGpuStats();
    // This one should fail.
    batch.reset(new Batch(attribCnt+1));
    dc->drawContextPriv().testingOnly_drawBatch(pb, batch);
    context->flush();
#if GR_GPU_STATS
    REPORTER_ASSERT(reporter, context->getGpu()->stats()->numDraws() == 0);
    REPORTER_ASSERT(reporter, context->getGpu()->stats()->numFailedDraws() == 1);
#endif
}

// Tests that MIP maps are created and invalidated as expected when drawing to and from GrTextures.
DEF_GPUTEST_FOR_RENDERING_CONTEXTS(GrTextureMipMapInvalidationTest, reporter, ctxInfo) {
    GrContext* context = ctxInfo.grContext();
    if (!context->priv().caps()->mipMapSupport()) {
        return;
    }

    auto isMipped = [] (SkSurface* surf) {
        const GrTexture* texture = surf->makeImageSnapshot()->getTexture();
        return GrMipMapped::kYes == texture->texturePriv().mipMapped();
    };

    auto mipsAreDirty = [] (SkSurface* surf) {
        return surf->makeImageSnapshot()->getTexture()->texturePriv().mipMapsAreDirty();
    };

    auto info = SkImageInfo::MakeN32Premul(256, 256);
    for (auto allocateMips : {false, true}) {
        auto surf1 = SkSurface::MakeRenderTarget(context, SkBudgeted::kYes, info, 0,
                                                 kBottomLeft_GrSurfaceOrigin, nullptr,
                                                 allocateMips);
        auto surf2 = SkSurface::MakeRenderTarget(context, SkBudgeted::kYes, info);
        // Draw something just in case we ever had a solid color optimization
        surf1->getCanvas()->drawCircle(128, 128, 50, SkPaint());
        surf1->flush();

        // No mipmaps initially
        REPORTER_ASSERT(reporter, isMipped(surf1.get()) == allocateMips);

        // Painting with downscale and medium filter quality should result in mipmap creation
        // Flush the context rather than the canvas as flushing the canvas triggers MIP level
        // generation.
        SkPaint paint;
        paint.setFilterQuality(kMedium_SkFilterQuality);
        surf2->getCanvas()->scale(0.2f, 0.2f);
        surf2->getCanvas()->drawImage(surf1->makeImageSnapshot(), 0, 0, &paint);
        context->flush();
        REPORTER_ASSERT(reporter, isMipped(surf1.get()) == allocateMips);
        REPORTER_ASSERT(reporter, !allocateMips || !mipsAreDirty(surf1.get()));

        // Changing the contents of the surface should invalidate the mipmap, but not de-allocate
        surf1->getCanvas()->drawCircle(128, 128, 100, SkPaint());
        context->flush();
        REPORTER_ASSERT(reporter, isMipped(surf1.get()) == allocateMips);
        REPORTER_ASSERT(reporter, mipsAreDirty(surf1.get()));
    }
}

void GrContext::TextBlobCacheOverBudgetCB(void* data) {
    SkASSERT(data);

    // Unlike the GrResourceCache, TextBlobs are drawn at the SkGpuDevice level, therefore they
    // cannot use fFlushTorReduceCacheSize because it uses AutoCheckFlush.  The solution is to move
    // drawText calls to below the GrContext level, but this is not trivial because they call
    // drawPath on SkGpuDevice
    GrContext* context = reinterpret_cast<GrContext*>(data);
    context->flush();
}

DEF_GPUTEST_FOR_ALL_CONTEXTS(VertexAttributeCount, reporter, ctxInfo) {
    GrContext* context = ctxInfo.grContext();

    sk_sp<GrDrawContext> drawContext(context->newDrawContext(SkBackingFit::kApprox,
                                                             1, 1, kRGBA_8888_GrPixelConfig));
    if (!drawContext) {
        ERRORF(reporter, "Could not create draw context.");
        return;
    }
    int attribCnt = context->caps()->maxVertexAttributes();
    if (!attribCnt) {
        ERRORF(reporter, "No attributes allowed?!");
        return;
    }
    context->flush();
    context->resetGpuStats();
#if GR_GPU_STATS
    REPORTER_ASSERT(reporter, context->getGpu()->stats()->numDraws() == 0);
    REPORTER_ASSERT(reporter, context->getGpu()->stats()->numFailedDraws() == 0);
#endif
    SkAutoTUnref<GrDrawBatch> batch;
    GrPaint grPaint;
    // This one should succeed.
    batch.reset(new Batch(attribCnt));
    drawContext->drawContextPriv().testingOnly_drawBatch(grPaint, batch);
    context->flush();
#if GR_GPU_STATS
    REPORTER_ASSERT(reporter, context->getGpu()->stats()->numDraws() == 1);
    REPORTER_ASSERT(reporter, context->getGpu()->stats()->numFailedDraws() == 0);
#endif
    context->resetGpuStats();
    // This one should fail.
    batch.reset(new Batch(attribCnt+1));
    drawContext->drawContextPriv().testingOnly_drawBatch(grPaint, batch);
    context->flush();
#if GR_GPU_STATS
    REPORTER_ASSERT(reporter, context->getGpu()->stats()->numDraws() == 0);
    REPORTER_ASSERT(reporter, context->getGpu()->stats()->numFailedDraws() == 1);
#endif
}

RENDERTHREAD_SKIA_PIPELINE_TEST(CacheManager, trimMemory) {
    DisplayInfo displayInfo = renderThread.mainDisplayInfo();
    GrContext* grContext = renderThread.getGrContext();
    ASSERT_TRUE(grContext != nullptr);

    // create pairs of offscreen render targets and images until we exceed the
    // backgroundCacheSizeLimit
    std::vector<sk_sp<SkSurface>> surfaces;

    while (getCacheUsage(grContext) <= renderThread.cacheManager().getBackgroundCacheSize()) {
        SkImageInfo info = SkImageInfo::MakeA8(displayInfo.w, displayInfo.h);
        sk_sp<SkSurface> surface = SkSurface::MakeRenderTarget(grContext, SkBudgeted::kYes, info);
        surface->getCanvas()->drawColor(SK_AlphaTRANSPARENT);

        grContext->flush();

        surfaces.push_back(surface);
    }

    // create an image and pin it so that we have something with a unique key in the cache
    sk_sp<Bitmap> bitmap =
            Bitmap::allocateHeapBitmap(SkImageInfo::MakeA8(displayInfo.w, displayInfo.h));
    sk_sp<SkColorFilter> filter;
    sk_sp<SkImage> image = bitmap->makeImage(&filter);
    ASSERT_TRUE(SkImage_pinAsTexture(image.get(), grContext));

    // attempt to trim all memory while we still hold strong refs
    renderThread.cacheManager().trimMemory(CacheManager::TrimMemoryMode::Complete);
    ASSERT_TRUE(0 == grContext->getResourceCachePurgeableBytes());

    // free the surfaces
    for (size_t i = 0; i < surfaces.size(); i++) {
        ASSERT_TRUE(surfaces[i]->unique());
        surfaces[i].reset();
    }

    // unpin the image which should add a unique purgeable key to the cache
    SkImage_unpinAsTexture(image.get(), grContext);

    // verify that we have enough purgeable bytes
    const size_t purgeableBytes = grContext->getResourceCachePurgeableBytes();
    ASSERT_TRUE(renderThread.cacheManager().getBackgroundCacheSize() < purgeableBytes);

    // UI hidden and make sure only some got purged (unique should remain)
    renderThread.cacheManager().trimMemory(CacheManager::TrimMemoryMode::UiHidden);
    ASSERT_TRUE(0 < grContext->getResourceCachePurgeableBytes());
    ASSERT_TRUE(renderThread.cacheManager().getBackgroundCacheSize() > getCacheUsage(grContext));

    // complete and make sure all get purged
    renderThread.cacheManager().trimMemory(CacheManager::TrimMemoryMode::Complete);
    ASSERT_TRUE(0 == grContext->getResourceCachePurgeableBytes());
}

DEF_GPUTEST_FOR_ALL_CONTEXTS(VertexAttributeCount, reporter, ctxInfo) {
    GrContext* context = ctxInfo.grContext();

    sk_sp<GrRenderTargetContext> renderTargetContext(context->makeDeferredRenderTargetContext(
                                                                     SkBackingFit::kApprox,
                                                                     1, 1, kRGBA_8888_GrPixelConfig,
                                                                     nullptr));
    if (!renderTargetContext) {
        ERRORF(reporter, "Could not create render target context.");
        return;
    }
    int attribCnt = context->caps()->maxVertexAttributes();
    if (!attribCnt) {
        ERRORF(reporter, "No attributes allowed?!");
        return;
    }
    context->flush();
    context->resetGpuStats();
#if GR_GPU_STATS
    REPORTER_ASSERT(reporter, context->getGpu()->stats()->numDraws() == 0);
    REPORTER_ASSERT(reporter, context->getGpu()->stats()->numFailedDraws() == 0);
#endif
    GrPaint grPaint;
    // This one should succeed.
    renderTargetContext->priv().testingOnly_addDrawOp(Op::Make(attribCnt));
    context->flush();
#if GR_GPU_STATS
    REPORTER_ASSERT(reporter, context->getGpu()->stats()->numDraws() == 1);
    REPORTER_ASSERT(reporter, context->getGpu()->stats()->numFailedDraws() == 0);
#endif
    context->resetGpuStats();
    renderTargetContext->priv().testingOnly_addDrawOp(Op::Make(attribCnt + 1));
    context->flush();
#if GR_GPU_STATS
    REPORTER_ASSERT(reporter, context->getGpu()->stats()->numDraws() == 0);
    REPORTER_ASSERT(reporter, context->getGpu()->stats()->numFailedDraws() == 1);
#endif
}

DEF_GPUTEST_FOR_ALL_CONTEXTS(TessellatingPathRendererTests, reporter, ctxInfo) {
    GrContext* ctx = ctxInfo.grContext();
    sk_sp<GrRenderTargetContext> rtc(ctx->makeDeferredRenderTargetContext(
            SkBackingFit::kApprox, 800, 800, kRGBA_8888_GrPixelConfig, nullptr, 1, GrMipMapped::kNo,
            kTopLeft_GrSurfaceOrigin));
    if (!rtc) {
        return;
    }

    ctx->flush();
    // Adding discard to appease vulkan validation warning about loading uninitialized data on draw
    rtc->discard();

    test_path(ctx, rtc.get(), create_path_0());
    test_path(ctx, rtc.get(), create_path_1());
    test_path(ctx, rtc.get(), create_path_2());
    test_path(ctx, rtc.get(), create_path_3());
    test_path(ctx, rtc.get(), create_path_4());
    test_path(ctx, rtc.get(), create_path_5());
    test_path(ctx, rtc.get(), create_path_6());
    test_path(ctx, rtc.get(), create_path_7());
    test_path(ctx, rtc.get(), create_path_8());
    test_path(ctx, rtc.get(), create_path_9());
    test_path(ctx, rtc.get(), create_path_10());
    test_path(ctx, rtc.get(), create_path_11());
    test_path(ctx, rtc.get(), create_path_12());
    test_path(ctx, rtc.get(), create_path_13());
    test_path(ctx, rtc.get(), create_path_14());
    test_path(ctx, rtc.get(), create_path_15());
    test_path(ctx, rtc.get(), create_path_16());
    SkMatrix nonInvertibleMatrix = SkMatrix::MakeScale(0, 0);
    std::unique_ptr<GrFragmentProcessor> fp(create_linear_gradient_processor(ctx));
    test_path(ctx, rtc.get(), create_path_17(), nonInvertibleMatrix, GrAAType::kCoverage,
              std::move(fp));
    test_path(ctx, rtc.get(), create_path_18());
    test_path(ctx, rtc.get(), create_path_19());
    test_path(ctx, rtc.get(), create_path_20(), SkMatrix(), GrAAType::kCoverage);
    test_path(ctx, rtc.get(), create_path_21(), SkMatrix(), GrAAType::kCoverage);
    test_path(ctx, rtc.get(), create_path_22());
    test_path(ctx, rtc.get(), create_path_23());
    test_path(ctx, rtc.get(), create_path_24());
    test_path(ctx, rtc.get(), create_path_25(), SkMatrix(), GrAAType::kCoverage);
    test_path(ctx, rtc.get(), create_path_26(), SkMatrix(), GrAAType::kCoverage);
    test_path(ctx, rtc.get(), create_path_27(), SkMatrix(), GrAAType::kCoverage);
    test_path(ctx, rtc.get(), create_path_28(), SkMatrix(), GrAAType::kCoverage);
    test_path(ctx, rtc.get(), create_path_29());
}

void SKPBench::getGpuStats(SkCanvas* canvas, SkTArray<SkString>* keys, SkTArray<double>* values) {
#if SK_SUPPORT_GPU
    // we do a special single draw and then dump the key / value pairs
    GrContext* context = canvas->getGrContext();
    if (!context) {
        return;
    }

    // TODO refactor this out if we want to test other subclasses of skpbench
    context->flush();
    context->freeGpuResources();
    context->resetContext();
    context->getGpu()->resetShaderCacheForTesting();
    draw_pic_for_stats(canvas, context, fPic, keys, values, "first_frame");

    // draw second frame
    draw_pic_for_stats(canvas, context, fPic, keys, values, "second_frame");

#endif
}

DEF_GPUTEST_FOR_ALL_CONTEXTS(TessellatingPathRendererTests, reporter, ctxInfo) {
    GrContext* ctx = ctxInfo.grContext();

    sk_sp<GrRenderTargetContext> rtc(ctx->makeDeferredRenderTargetContext(
                                                                  SkBackingFit::kApprox,
                                                                  800, 800,
                                                                  kRGBA_8888_GrPixelConfig,
                                                                  nullptr,
                                                                  0,
                                                                  kTopLeft_GrSurfaceOrigin));
    if (!rtc) {
        return;
    }

    ctx->flush();
    test_path(ctx, rtc.get(), create_path_0());
    test_path(ctx, rtc.get(), create_path_1());
    test_path(ctx, rtc.get(), create_path_2());
    test_path(ctx, rtc.get(), create_path_3());
    test_path(ctx, rtc.get(), create_path_4());
    test_path(ctx, rtc.get(), create_path_5());
    test_path(ctx, rtc.get(), create_path_6());
    test_path(ctx, rtc.get(), create_path_7());
    test_path(ctx, rtc.get(), create_path_8());
    test_path(ctx, rtc.get(), create_path_9());
    test_path(ctx, rtc.get(), create_path_10());
    test_path(ctx, rtc.get(), create_path_11());
    test_path(ctx, rtc.get(), create_path_12());
    test_path(ctx, rtc.get(), create_path_13());
    test_path(ctx, rtc.get(), create_path_14());
    test_path(ctx, rtc.get(), create_path_15());
    test_path(ctx, rtc.get(), create_path_16());
    SkMatrix nonInvertibleMatrix = SkMatrix::MakeScale(0, 0);
    sk_sp<GrFragmentProcessor> fp(create_linear_gradient_processor(ctx));
    test_path(ctx, rtc.get(), create_path_17(), nonInvertibleMatrix, GrAAType::kCoverage, fp);
    test_path(ctx, rtc.get(), create_path_18());
    test_path(ctx, rtc.get(), create_path_19());
    test_path(ctx, rtc.get(), create_path_20(), SkMatrix(), GrAAType::kCoverage);
    test_path(ctx, rtc.get(), create_path_21(), SkMatrix(), GrAAType::kCoverage);
    test_path(ctx, rtc.get(), create_path_22());
}

void LayerTextureUpdaterSkPicture::updateTextureRect(GraphicsContext3D* compositorContext, TextureAllocator* allocator, ManagedTexture* texture, const IntRect& sourceRect, const IntRect& destRect)
{
    ASSERT(!m_context || m_context == compositorContext);
    m_context = compositorContext;

    if (m_createFrameBuffer) {
        deleteFrameBuffer();
        createFrameBuffer();
        m_createFrameBuffer = false;
    }
    if (!m_fbo)
        return;

    // Bind texture.
    context()->bindFramebuffer(GraphicsContext3D::FRAMEBUFFER, m_fbo);
    texture->framebufferTexture2D(context(), allocator);
    ASSERT(context()->checkFramebufferStatus(GraphicsContext3D::FRAMEBUFFER) == GraphicsContext3D::FRAMEBUFFER_COMPLETE);

    // Make sure SKIA uses the correct GL context.
    context()->makeContextCurrent();

    GrContext* skiaContext = m_context->grContext();
    // Notify SKIA to sync its internal GL state.
    skiaContext->resetContext();
    m_canvas->save();
    m_canvas->clipRect(SkRect(destRect));
    // Translate the origin of contentRect to that of destRect.
    // Note that destRect is defined relative to sourceRect.
    m_canvas->translate(contentRect().x() - sourceRect.x() + destRect.x(),
                        contentRect().y() - sourceRect.y() + destRect.y());
    m_canvas->drawPicture(m_picture);
    m_canvas->restore();
    // Flush SKIA context so that all the rendered stuff appears on the texture.
    skiaContext->flush();

    // Unbind texture.
    context()->framebufferTexture2D(GraphicsContext3D::FRAMEBUFFER, GraphicsContext3D::COLOR_ATTACHMENT0, GraphicsContext3D::TEXTURE_2D, 0, 0);
    context()->bindFramebuffer(GraphicsContext3D::FRAMEBUFFER, 0);
}

bool Canvas2DLayerBridge::prepareMailbox(WebExternalTextureMailbox* outMailbox, WebExternalBitmap* bitmap)
{
    ASSERT(isAccelerated());
    if (m_destructionInProgress) {
        // It can be hit in the following sequence.
        // 1. Canvas draws something.
        // 2. The compositor begins the frame.
        // 3. Javascript makes a context be lost.
        // 4. Here.
        return false;
    }
    if (bitmap) {
        // Using accelerated 2d canvas with software renderer, which
        // should only happen in tests that use fake graphics contexts
        // or in Android WebView in software mode. In this case, we do
        // not care about producing any results for this canvas.
        skipQueuedDrawCommands();
        m_lastImageId = 0;
        return false;
    }
    if (!checkSurfaceValid())
        return false;

    WebGraphicsContext3D* webContext = context();

    RefPtr<SkImage> image = newImageSnapshot(PreferAcceleration);

    // Early exit if canvas was not drawn to since last prepareMailbox
    GLenum filter = m_filterQuality == kNone_SkFilterQuality ? GL_NEAREST : GL_LINEAR;
    if (image->uniqueID() == m_lastImageId && filter == m_lastFilter)
        return false;
    m_lastImageId = image->uniqueID();
    m_lastFilter = filter;

    {
        MailboxInfo tmp;
        tmp.m_image = image;
        tmp.m_parentLayerBridge = this;
        m_mailboxes.prepend(tmp);
    }
    MailboxInfo& mailboxInfo = m_mailboxes.first();

    mailboxInfo.m_mailbox.nearestNeighbor = filter == GL_NEAREST;

    GrContext* grContext = m_contextProvider->grContext();
    if (!grContext)
        return true; // for testing: skip gl stuff when using a mock graphics context.

    // Need to flush skia's internal queue because texture is about to be accessed directly
    grContext->flush();

    ASSERT(image->getTexture());

    // Because of texture sharing with the compositor, we must invalidate
    // the state cached in skia so that the deferred copy on write
    // in SkSurface_Gpu does not make any false assumptions.
    mailboxInfo.m_image->getTexture()->textureParamsModified();

    webContext->bindTexture(GL_TEXTURE_2D, mailboxInfo.m_image->getTexture()->getTextureHandle());
    webContext->texParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, filter);
    webContext->texParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, filter);
    webContext->texParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    webContext->texParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

    // Re-use the texture's existing mailbox, if there is one.
    if (image->getTexture()->getCustomData()) {
        ASSERT(image->getTexture()->getCustomData()->size() == sizeof(mailboxInfo.m_mailbox.name));
        memcpy(&mailboxInfo.m_mailbox.name[0], image->getTexture()->getCustomData()->data(), sizeof(mailboxInfo.m_mailbox.name));
    } else {
        context()->genMailboxCHROMIUM(mailboxInfo.m_mailbox.name);
        RefPtr<SkData> mailboxNameData = adoptRef(SkData::NewWithCopy(&mailboxInfo.m_mailbox.name[0], sizeof(mailboxInfo.m_mailbox.name)));
        image->getTexture()->setCustomData(mailboxNameData.get());
        webContext->produceTextureCHROMIUM(GL_TEXTURE_2D, mailboxInfo.m_mailbox.name);
    }

    if (isHidden()) {
        // With hidden canvases, we release the SkImage immediately because
        // there is no need for animations to be double buffered.
        mailboxInfo.m_image.clear();
    } else {
        // FIXME: We'd rather insert a syncpoint than perform a flush here,
        // but currentlythe canvas will flicker if we don't flush here.
        webContext->flush();
        // mailboxInfo.m_mailbox.syncPoint = webContext->insertSyncPoint();
    }
    webContext->bindTexture(GL_TEXTURE_2D, 0);
    // Because we are changing the texture binding without going through skia,
    // we must dirty the context.
    grContext->resetContext(kTextureBinding_GrGLBackendState);

    *outMailbox = mailboxInfo.m_mailbox;
    return true;
}

//.........这里部分代码省略.........

                    if ((benchMode == kRecord_BenchMode || benchMode == kPictureRecord_BenchMode)) {
                        // Clear the recorded commands so that they do not accumulate.
                        canvas.reset(SkRef(recorderTo.beginRecording(dim.fX, dim.fY)));
                    }

                    timer.start();
                    // Inner loop that allows us to break the run into smaller
                    // chunks (e.g. frames). This is especially useful for the GPU
                    // as we can flush and/or swap buffers to keep the GPU from
                    // queuing up too much work.
                    for (int loopCount = loopsPerIter; loopCount > 0; ) {
                        // Save and restore around each call to draw() to guarantee a pristine canvas.
                        SkAutoCanvasRestore saveRestore(canvas, true/*also save*/);

                        int loops;
                        if (frameIntervalComputed && loopCount > loopsPerFrame) {
                            loops = loopsPerFrame;
                            loopCount -= loopsPerFrame;
                        } else {
                            loops = loopCount;
                            loopCount = 0;
                        }

                        if (benchMode == kPictureRecord_BenchMode) {
                            recordFrom->draw(canvas);
                        } else {
                            bench->draw(loops, canvas);
                        }

                        if (kDeferredSilent_BenchMode == benchMode) {
                            static_cast<SkDeferredCanvas*>(canvas.get())->silentFlush();
                        } else if (NULL != canvas) {
                            canvas->flush();
                        }

    #if SK_SUPPORT_GPU
                        // swap drawing buffers on each frame to prevent the GPU
                        // from queuing up too much work
                        if (NULL != glContext) {
                            glContext->swapBuffers();
                        }
    #endif
                    }



                    // Stop truncated timers before GL calls complete, and stop the full timers after.
                    timer.truncatedEnd();
    #if SK_SUPPORT_GPU
                    if (NULL != glContext) {
                        context->flush();
                        SK_GL(*glContext, Finish());
                    }
    #endif
                    timer.end();

                    // setup the frame interval for subsequent iterations
                    if (!frameIntervalComputed) {
                        frameIntervalTime += timer.fWall;
                        frameIntervalTotalLoops += loopsPerIter;
                        if (frameIntervalTime >= FLAGS_minMs) {
                            frameIntervalComputed = true;
                            loopsPerFrame =
                              (int)(((double)frameIntervalTotalLoops / frameIntervalTime) * FLAGS_minMs);
                            if (loopsPerFrame < 1) {

 void flush() {
     context->flush();
 }