gm/gmmain.cpp

/*
 * Copyright 2011 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "gm.h"
#include "GrContext.h"
#include "GrRenderTarget.h"

#include "SkColorPriv.h"
#include "SkData.h"
#include "SkDeferredCanvas.h"
#include "SkDevice.h"
#include "SkGpuCanvas.h"
#include "SkGpuDevice.h"
#include "SkGraphics.h"
#include "SkImageDecoder.h"
#include "SkImageEncoder.h"
#include "SkNativeGLContext.h"
#include "SkMesaGLContext.h"
#include "SkPicture.h"
#include "SkStream.h"
#include "SkRefCnt.h"

static bool gForceBWtext;

extern bool gSkSuppressFontCachePurgeSpew;

#ifdef SK_SUPPORT_PDF
    #include "SkPDFDevice.h"
    #include "SkPDFDocument.h"
#endif

// Until we resolve http://code.google.com/p/skia/issues/detail?id=455 ,
// stop writing out XPS-format image baselines in gm.
#undef SK_SUPPORT_XPS
#ifdef SK_SUPPORT_XPS
    #include "SkXPSDevice.h"
#endif

#ifdef SK_BUILD_FOR_MAC
    #include "SkCGUtils.h"
    #define CAN_IMAGE_PDF   1
#else
    #define CAN_IMAGE_PDF   0
#endif

typedef int ErrorBitfield;
const static ErrorBitfield ERROR_NONE                    = 0x00;
const static ErrorBitfield ERROR_NO_GPU_CONTEXT          = 0x01;
const static ErrorBitfield ERROR_PIXEL_MISMATCH          = 0x02;
const static ErrorBitfield ERROR_DIMENSION_MISMATCH      = 0x04;
const static ErrorBitfield ERROR_READING_REFERENCE_IMAGE = 0x08;
const static ErrorBitfield ERROR_WRITING_REFERENCE_IMAGE = 0x10;

using namespace skiagm;

class Iter {
public:
    Iter() {
        this->reset();
    }

    void reset() {
        fReg = GMRegistry::Head();
    }

    GM* next() {
        if (fReg) {
            GMRegistry::Factory fact = fReg->factory();
            fReg = fReg->next();
            return fact(0);
        }
        return NULL;
    }

    static int Count() {
        const GMRegistry* reg = GMRegistry::Head();
        int count = 0;
        while (reg) {
            count += 1;
            reg = reg->next();
        }
        return count;
    }

private:
    const GMRegistry* fReg;
};

static SkString make_name(const char shortName[], const char configName[]) {
    SkString name(shortName);
    name.appendf("_%s", configName);
    return name;
}

static SkString make_filename(const char path[],
                              const char pathSuffix[],
                              const SkString& name,
                              const char suffix[]) {
    SkString filename(path);
    if (filename.endsWith("/")) {
        filename.remove(filename.size() - 1, 1);
    }
    filename.append(pathSuffix);
    filename.append("/");
    filename.appendf("%s.%s", name.c_str(), suffix);
    return filename;
}

/* since PNG insists on unpremultiplying our alpha, we take no precision chances
    and force all pixels to be 100% opaque, otherwise on compare we may not get
    a perfect match.
 */
static void force_all_opaque(const SkBitmap& bitmap) {
    SkAutoLockPixels lock(bitmap);
    for (int y = 0; y < bitmap.height(); y++) {
        for (int x = 0; x < bitmap.width(); x++) {
            *bitmap.getAddr32(x, y) |= (SK_A32_MASK << SK_A32_SHIFT);
        }
    }
}

static bool write_bitmap(const SkString& path, const SkBitmap& bitmap) {
    SkBitmap copy;
    bitmap.copyTo(&copy, SkBitmap::kARGB_8888_Config);
    force_all_opaque(copy);
    return SkImageEncoder::EncodeFile(path.c_str(), copy,
                                      SkImageEncoder::kPNG_Type, 100);
}

static inline SkPMColor compute_diff_pmcolor(SkPMColor c0, SkPMColor c1) {
    int dr = SkGetPackedR32(c0) - SkGetPackedR32(c1);
    int dg = SkGetPackedG32(c0) - SkGetPackedG32(c1);
    int db = SkGetPackedB32(c0) - SkGetPackedB32(c1);
    return SkPackARGB32(0xFF, SkAbs32(dr), SkAbs32(dg), SkAbs32(db));
}

static void compute_diff(const SkBitmap& target, const SkBitmap& base,
                         SkBitmap* diff) {
    SkAutoLockPixels alp(*diff);

    const int w = target.width();
    const int h = target.height();
    for (int y = 0; y < h; y++) {
        for (int x = 0; x < w; x++) {
            SkPMColor c0 = *base.getAddr32(x, y);
            SkPMColor c1 = *target.getAddr32(x, y);
            SkPMColor d = 0;
            if (c0 != c1) {
                d = compute_diff_pmcolor(c0, c1);
            }
            *diff->getAddr32(x, y) = d;
        }
    }
}

static ErrorBitfield compare(const SkBitmap& target, const SkBitmap& base,
                             const SkString& name,
                             const char* renderModeDescriptor,
                             SkBitmap* diff) {
    SkBitmap copy;
    const SkBitmap* bm = &target;
    if (target.config() != SkBitmap::kARGB_8888_Config) {
        target.copyTo(&copy, SkBitmap::kARGB_8888_Config);
        bm = &copy;
    }
    SkBitmap baseCopy;
    const SkBitmap* bp = &base;
    if (base.config() != SkBitmap::kARGB_8888_Config) {
        base.copyTo(&baseCopy, SkBitmap::kARGB_8888_Config);
        bp = &baseCopy;
    }

    force_all_opaque(*bm);
    force_all_opaque(*bp);

    const int w = bm->width();
    const int h = bm->height();
    if (w != bp->width() || h != bp->height()) {
        SkDebugf(
"---- %s dimensions mismatch for %s base [%d %d] current [%d %d]\n",
                 renderModeDescriptor, name.c_str(),
                 bp->width(), bp->height(), w, h);
        return ERROR_DIMENSION_MISMATCH;
    }

    SkAutoLockPixels bmLock(*bm);
    SkAutoLockPixels baseLock(*bp);

    for (int y = 0; y < h; y++) {
        for (int x = 0; x < w; x++) {
            SkPMColor c0 = *bp->getAddr32(x, y);
            SkPMColor c1 = *bm->getAddr32(x, y);
            if (c0 != c1) {
                SkDebugf(
"----- %s pixel mismatch for %s at [%d %d] base 0x%08X current 0x%08X\n",
                         renderModeDescriptor, name.c_str(), x, y, c0, c1);

                if (diff) {
                    diff->setConfig(SkBitmap::kARGB_8888_Config, w, h);
                    diff->allocPixels();
                    compute_diff(*bm, *bp, diff);
                }
                return ERROR_PIXEL_MISMATCH;
            }
        }
    }

    // they're equal
    return ERROR_NONE;
}

static bool write_document(const SkString& path,
                           const SkDynamicMemoryWStream& document) {
    SkFILEWStream stream(path.c_str());
    SkAutoDataUnref data(document.copyToData());
    return stream.writeData(data.get());
}

enum Backend {
  kRaster_Backend,
  kGPU_Backend,
  kPDF_Backend,
  kXPS_Backend,
};

struct ConfigData {
    SkBitmap::Config    fConfig;
    Backend             fBackend;
    const char*         fName;
};

/// Returns true if processing should continue, false to skip the
/// remainder of this config for this GM.
//@todo thudson 22 April 2011 - could refactor this to take in
// a factory to generate the context, always call readPixels()
// (logically a noop for rasters, if wasted time), and thus collapse the
// GPU special case and also let this be used for SkPicture testing.
static void setup_bitmap(const ConfigData& gRec, SkISize& size,
                         SkBitmap* bitmap) {
    bitmap->setConfig(gRec.fConfig, size.width(), size.height());
    bitmap->allocPixels();
    bitmap->eraseColor(0);
}

#include "SkDrawFilter.h"
class BWTextDrawFilter : public SkDrawFilter {
public:
    virtual void filter(SkPaint*, Type) SK_OVERRIDE;
};
void BWTextDrawFilter::filter(SkPaint* p, Type t) {
    if (kText_Type == t) {
        p->setAntiAlias(false);
    }
}

static void installFilter(SkCanvas* canvas) {
    if (gForceBWtext) {
        canvas->setDrawFilter(new BWTextDrawFilter)->unref();
    }
}

static void invokeGM(GM* gm, SkCanvas* canvas) {
    installFilter(canvas);
    gm->draw(canvas);
    canvas->setDrawFilter(NULL);
}

static ErrorBitfield generate_image(GM* gm, const ConfigData& gRec,
                                    GrContext* context,
                                    GrRenderTarget* rt,
                                    SkBitmap* bitmap,
                                    bool deferred) {
    SkISize size (gm->getISize());
    setup_bitmap(gRec, size, bitmap);

    if (gRec.fBackend == kRaster_Backend) {
        SkCanvas* canvas;
        if (deferred) {
            canvas = new SkDeferredCanvas;
            canvas->setDevice(new SkDevice(*bitmap))->unref();
        } else {
            canvas = new SkCanvas(*bitmap);
        }
        SkAutoUnref canvasUnref(canvas);
        invokeGM(gm, canvas);
        if (deferred) {
            canvas->getDevice()->accessBitmap(false); // trigger a flush
        }
    } else {  // GPU
        if (NULL == context) {
            return ERROR_NO_GPU_CONTEXT;
        }
        SkCanvas* gc;
        if (deferred) {
            gc = new SkDeferredCanvas;
        } else {
            gc = new SkGpuCanvas(context, rt);
        }
        SkAutoUnref gcUnref(gc);
        gc->setDevice(new SkGpuDevice(context, rt))->unref();
        invokeGM(gm, gc);
        // the device is as large as the current rendertarget, so we explicitly
        // only readback the amount we expect (in size)
        // overwrite our previous allocation
        bitmap->setConfig(SkBitmap::kARGB_8888_Config, size.fWidth,
                                                       size.fHeight);
        gc->readPixels(bitmap, 0, 0);
    }
    return ERROR_NONE;
}

static void generate_image_from_picture(GM* gm, const ConfigData& gRec,
                                        SkPicture* pict, SkBitmap* bitmap) {
    SkISize size = gm->getISize();
    setup_bitmap(gRec, size, bitmap);
    SkCanvas canvas(*bitmap);
    installFilter(&canvas);
    canvas.drawPicture(*pict);
}

static void generate_pdf(GM* gm, SkDynamicMemoryWStream& pdf) {
#ifdef SK_SUPPORT_PDF
    SkISize size = gm->getISize();
    SkMatrix identity;
    identity.reset();
    SkPDFDevice* dev = new SkPDFDevice(size, size, identity);
    SkAutoUnref aur(dev);

    SkCanvas c(dev);
    invokeGM(gm, &c);

    SkPDFDocument doc;
    doc.appendPage(dev);
    doc.emitPDF(&pdf);
#endif
}

static void generate_xps(GM* gm, SkDynamicMemoryWStream& xps) {
#ifdef SK_SUPPORT_XPS
    SkISize size = gm->getISize();
    
    SkSize trimSize = SkSize::Make(SkIntToScalar(size.width()),
                                   SkIntToScalar(size.height()));
    static const SkScalar inchesPerMeter = SkScalarDiv(10000, 254);
    static const SkScalar upm = 72 * inchesPerMeter;
    SkVector unitsPerMeter = SkPoint::Make(upm, upm);
    static const SkScalar ppm = 200 * inchesPerMeter;
    SkVector pixelsPerMeter = SkPoint::Make(ppm, ppm);

    SkXPSDevice* dev = new SkXPSDevice();
    SkAutoUnref aur(dev);

    SkCanvas c(dev);
    dev->beginPortfolio(&xps);
    dev->beginSheet(unitsPerMeter, pixelsPerMeter, trimSize);
    invokeGM(gm, &c);
    dev->endSheet();
    dev->endPortfolio();

#endif
}

static ErrorBitfield write_reference_image(const ConfigData& gRec,
                                           const char writePath [],
                                           const char renderModeDescriptor [],
                                           const SkString& name,
                                           SkBitmap& bitmap,
                                           SkDynamicMemoryWStream* document) {
    SkString path;
    bool success = false;
    if (gRec.fBackend == kRaster_Backend ||
        gRec.fBackend == kGPU_Backend ||
        (gRec.fBackend == kPDF_Backend && CAN_IMAGE_PDF)) {
    
        path = make_filename(writePath, renderModeDescriptor, name, "png");
        success = write_bitmap(path, bitmap);
    }
    if (kPDF_Backend == gRec.fBackend) {
        path = make_filename(writePath, renderModeDescriptor, name, "pdf");
        success = write_document(path, *document);
    }
    if (kXPS_Backend == gRec.fBackend) {
        path = make_filename(writePath, renderModeDescriptor, name, "xps");
        success = write_document(path, *document);
    }
    if (success) {
        return ERROR_NONE;
    } else {
        fprintf(stderr, "FAILED to write %s\n", path.c_str());
        return ERROR_WRITING_REFERENCE_IMAGE;
    }
}

static ErrorBitfield compare_to_reference_image(const SkString& name,
                                                SkBitmap &bitmap,
                                                const SkBitmap& comparisonBitmap,
                                                const char diffPath [],
                                                const char renderModeDescriptor []) {
    ErrorBitfield errors;
    SkBitmap diffBitmap;
    errors = compare(bitmap, comparisonBitmap, name, renderModeDescriptor,
                     diffPath ? &diffBitmap : NULL);
    if ((ERROR_NONE == errors) && diffPath) {
        SkString diffName = make_filename(diffPath, "", name, ".diff.png");
        if (!write_bitmap(diffName, diffBitmap)) {
            errors |= ERROR_WRITING_REFERENCE_IMAGE;
        }
    }
    return errors;
}

static ErrorBitfield compare_to_reference_image(const char readPath [],
                                                const SkString& name,
                                                SkBitmap &bitmap,
                                                const char diffPath [],
                                                const char renderModeDescriptor []) {
    SkString path = make_filename(readPath, "", name, "png");
    SkBitmap orig;
    if (SkImageDecoder::DecodeFile(path.c_str(), &orig,
                                   SkBitmap::kARGB_8888_Config,
                                   SkImageDecoder::kDecodePixels_Mode, NULL)) {
        return compare_to_reference_image(name, bitmap,
                                          orig, diffPath,
                                          renderModeDescriptor);
    } else {
        fprintf(stderr, "FAILED to read %s\n", path.c_str());
        return ERROR_READING_REFERENCE_IMAGE;
    }
}

static ErrorBitfield handle_test_results(GM* gm,
                                         const ConfigData& gRec,
                                         const char writePath [],
                                         const char readPath [],
                                         const char diffPath [],
                                         const char renderModeDescriptor [],
                                         SkBitmap& bitmap,
                                         SkDynamicMemoryWStream* pdf,
                                         const SkBitmap* comparisonBitmap) {
    SkString name = make_name(gm->shortName(), gRec.fName);

    if (writePath) {
        return write_reference_image(gRec, writePath, renderModeDescriptor,
                                     name, bitmap, pdf);
    } else if (readPath && (
                   gRec.fBackend == kRaster_Backend ||
                   gRec.fBackend == kGPU_Backend ||
                   (gRec.fBackend == kPDF_Backend && CAN_IMAGE_PDF))) {
        return compare_to_reference_image(readPath, name, bitmap,
                                   diffPath, renderModeDescriptor);
    } else if (comparisonBitmap) {
        return compare_to_reference_image(name, bitmap,
                                   *comparisonBitmap, diffPath,
                                   renderModeDescriptor);
    } else {
        return ERROR_NONE;
    }
}

static SkPicture* generate_new_picture(GM* gm) {
    // Pictures are refcounted so must be on heap
    SkPicture* pict = new SkPicture;
    SkCanvas* cv = pict->beginRecording(1000, 1000);
    invokeGM(gm, cv);
    pict->endRecording();

    return pict;
}

static SkPicture* stream_to_new_picture(const SkPicture& src) {

    // To do in-memory commiunications with a stream, we need to:
    // * create a dynamic memory stream
    // * copy it into a buffer
    // * create a read stream from it
    // ?!?!

    SkDynamicMemoryWStream storage;
    src.serialize(&storage);

    int streamSize = storage.getOffset();
    SkAutoMalloc dstStorage(streamSize);
    void* dst = dstStorage.get();
    //char* dst = new char [streamSize];
    //@todo thudson 22 April 2011 when can we safely delete [] dst?
    storage.copyTo(dst);
    SkMemoryStream pictReadback(dst, streamSize);
    SkPicture* retval = new SkPicture (&pictReadback);
    return retval;
}

// Test: draw into a bitmap or pdf.
// Depending on flags, possibly compare to an expected image
// and possibly output a diff image if it fails to match.
static ErrorBitfield test_drawing(GM* gm,
                                  const ConfigData& gRec,
                                  const char writePath [],
                                  const char readPath [],
                                  const char diffPath [],
                                  GrContext* context,
                                  GrRenderTarget* rt,
                                  SkBitmap* bitmap) {
    SkDynamicMemoryWStream document;

    if (gRec.fBackend == kRaster_Backend ||
        gRec.fBackend == kGPU_Backend) {
        // Early exit if we can't generate the image.
        ErrorBitfield errors = generate_image(gm, gRec, context, rt, bitmap,
            false);
        if (ERROR_NONE != errors) {
            return errors;
        }
    } else if (gRec.fBackend == kPDF_Backend) {
        generate_pdf(gm, document);
#if CAN_IMAGE_PDF
        SkAutoDataUnref data(document.copyToData());
        SkMemoryStream stream(data.data(), data.size());
        SkPDFDocumentToBitmap(&stream, bitmap);
#endif
    } else if (gRec.fBackend == kXPS_Backend) {
        generate_xps(gm, document);
    }
    return handle_test_results(gm, gRec, writePath, readPath, diffPath,
                               "", *bitmap, &document, NULL);
}

static ErrorBitfield test_deferred_drawing(GM* gm,
                         const ConfigData& gRec,
                         const SkBitmap& comparisonBitmap,
                         const char diffPath [],
                         GrContext* context,
                         GrRenderTarget* rt) {
    SkDynamicMemoryWStream document;

    if (gRec.fBackend == kRaster_Backend ||
        gRec.fBackend == kGPU_Backend) {
        SkBitmap bitmap;
        // Early exit if we can't generate the image, but this is
        // expected in some cases, so don't report a test failure.
        if (!generate_image(gm, gRec, context, rt, &bitmap, true)) {
            return ERROR_NONE;
        }
        return handle_test_results(gm, gRec, NULL, NULL, diffPath,
                                   "-deferred", bitmap, NULL, &comparisonBitmap);
    }
    return ERROR_NONE;
}

static ErrorBitfield test_picture_playback(GM* gm,
                                           const ConfigData& gRec,
                                           const SkBitmap& comparisonBitmap,
                                           const char readPath [],
                                           const char diffPath []) {
    SkPicture* pict = generate_new_picture(gm);
    SkAutoUnref aur(pict);

    if (kRaster_Backend == gRec.fBackend) {
        SkBitmap bitmap;
        generate_image_from_picture(gm, gRec, pict, &bitmap);
        return handle_test_results(gm, gRec, NULL, NULL, diffPath,
                            "-replay", bitmap, NULL, &comparisonBitmap);
    } else {
        return ERROR_NONE;
    }
}

static ErrorBitfield test_picture_serialization(GM* gm,
                                                const ConfigData& gRec,
                                                const SkBitmap& comparisonBitmap,
                                                const char readPath [],
                                                const char diffPath []) {
    SkPicture* pict = generate_new_picture(gm);
    SkAutoUnref aurp(pict);
    SkPicture* repict = stream_to_new_picture(*pict);
    SkAutoUnref aurr(repict);

    if (kRaster_Backend == gRec.fBackend) {
        SkBitmap bitmap;
        generate_image_from_picture(gm, gRec, repict, &bitmap);
        return handle_test_results(gm, gRec, NULL, NULL, diffPath,
                            "-serialize", bitmap, NULL, &comparisonBitmap);
    } else {
        return ERROR_NONE;
    }
}

static void usage(const char * argv0) {
    SkDebugf(
        "%s [-w writePath] [-r readPath] [-d diffPath] [--noreplay]\n"
        "    [--serialize] [--forceBWtext] [--nopdf] [--nodeferred]\n"
        "    [--match substring]"
#if SK_MESA
        " [--mesagl]"
#endif
        "\n\n", argv0);
    SkDebugf("    writePath: directory to write rendered images in.\n");
    SkDebugf(
"    readPath: directory to read reference images from;\n"
"        reports if any pixels mismatch between reference and new images\n");
    SkDebugf("    diffPath: directory to write difference images in.\n");
    SkDebugf("    --noreplay: do not exercise SkPicture replay.\n");
    SkDebugf(
"    --serialize: exercise SkPicture serialization & deserialization.\n");
    SkDebugf("    --forceBWtext: disable text anti-aliasing.\n");
    SkDebugf("    --nopdf: skip the pdf rendering test pass.\n");
    SkDebugf("    --nodeferred: skip the deferred rendering test pass.\n");
    SkDebugf("    --match foo will only run tests that substring match foo.\n");
#if SK_MESA
    SkDebugf("    --mesagl will run using the osmesa sw gl rasterizer.\n");
#endif
}

static const ConfigData gRec[] = {
    { SkBitmap::kARGB_8888_Config, kRaster_Backend, "8888" },
    { SkBitmap::kARGB_4444_Config, kRaster_Backend, "4444" },
    { SkBitmap::kRGB_565_Config,   kRaster_Backend, "565" },
#ifdef SK_SCALAR_IS_FLOAT
    { SkBitmap::kARGB_8888_Config, kGPU_Backend,    "gpu" },
#endif
#ifdef SK_SUPPORT_PDF
    { SkBitmap::kARGB_8888_Config, kPDF_Backend,    "pdf" },
#endif
#ifdef SK_SUPPORT_XPS
    { SkBitmap::kARGB_8888_Config, kXPS_Backend,    "xps" },
#endif
};

static bool skip_name(const SkTDArray<const char*> array, const char name[]) {
    if (0 == array.count()) {
        // no names, so don't skip anything
        return false;
    }
    for (int i = 0; i < array.count(); ++i) {
        if (strstr(name, array[i])) {
            // found the name, so don't skip
            return false;
        }
    }
    return true;
}

namespace skiagm {
static GrContext* gGrContext;
GrContext* GetGr() {
    return gGrContext;
}
}

int main(int argc, char * const argv[]) {
    SkAutoGraphics ag;
    // we don't need to see this during a run
    gSkSuppressFontCachePurgeSpew = true;

    const char* writePath = NULL;   // if non-null, where we write the originals
    const char* readPath = NULL;    // if non-null, were we read from to compare
    const char* diffPath = NULL;    // if non-null, where we write our diffs (from compare)

    SkTDArray<const char*> fMatches;
    
    bool doPDF = true;
    bool doReplay = true;
    bool doSerialize = false;
    bool useMesa = false;
    bool doDeferred = true;
    
    const char* const commandName = argv[0];
    char* const* stop = argv + argc;
    for (++argv; argv < stop; ++argv) {
        if (strcmp(*argv, "-w") == 0) {
            argv++;
            if (argv < stop && **argv) {
                writePath = *argv;
            }
        } else if (strcmp(*argv, "-r") == 0) {
            argv++;
            if (argv < stop && **argv) {
                readPath = *argv;
            }
        } else if (strcmp(*argv, "-d") == 0) {
            argv++;
            if (argv < stop && **argv) {
                diffPath = *argv;
            }
        } else if (strcmp(*argv, "--forceBWtext") == 0) {
            gForceBWtext = true;
        } else if (strcmp(*argv, "--noreplay") == 0) {
            doReplay = false;
        } else if (strcmp(*argv, "--nopdf") == 0) {
            doPDF = false;
        } else if (strcmp(*argv, "--nodeferred") == 0) {
            doDeferred = false;
        } else if (strcmp(*argv, "--serialize") == 0) {
            doSerialize = true;
        } else if (strcmp(*argv, "--match") == 0) {
            ++argv;
            if (argv < stop && **argv) {
                // just record the ptr, no need for a deep copy
                *fMatches.append() = *argv;
            }
#if SK_MESA
        } else if (strcmp(*argv, "--mesagl") == 0) {
            useMesa = true;
#endif
        } else {
          usage(commandName);
          return -1;
        }
    }
    if (argv != stop) {
      usage(commandName);
      return -1;
    }

    int maxW = -1;
    int maxH = -1;
    Iter iter;
    GM* gm;
    while ((gm = iter.next()) != NULL) {
        SkISize size = gm->getISize();
        maxW = SkMax32(size.width(), maxW);
        maxH = SkMax32(size.height(), maxH);
    }
    // setup a GL context for drawing offscreen
    SkAutoTUnref<SkGLContext> glContext;
#if SK_MESA
    if (useMesa) {
        glContext.reset(new SkMesaGLContext());
    } else
#endif
    {
        glContext.reset(new SkNativeGLContext());
    }

    GrPlatformRenderTargetDesc rtDesc;
    if (glContext.get()->init(maxW, maxH)) {
        GrPlatform3DContext ctx =
            reinterpret_cast<GrPlatform3DContext>(glContext.get()->gl());
        gGrContext = GrContext::Create(kOpenGL_Shaders_GrEngine, ctx);
        if (NULL != gGrContext) {
            rtDesc.fConfig = kSkia8888_PM_GrPixelConfig;
            rtDesc.fStencilBits = 8;
            rtDesc.fRenderTargetHandle = glContext.get()->getFBOID();
        }
    } else {
        fprintf(stderr, "could not create GL context.\n");
    }

    if (readPath) {
        fprintf(stderr, "reading from %s\n", readPath);
    } else if (writePath) {
        fprintf(stderr, "writing to %s\n", writePath);
    }

    // Accumulate success of all tests.
    int testsRun = 0;
    int testsPassed = 0;
    int testsFailed = 0;
    int testsMissingReferenceImages = 0;

    iter.reset();
    while ((gm = iter.next()) != NULL) {
        const char* shortName = gm->shortName();
        if (skip_name(fMatches, shortName)) {
            SkDELETE(gm);
            continue;
        }

        SkISize size = gm->getISize();
        SkDebugf("drawing... %s [%d %d]\n", shortName,
                 size.width(), size.height());
        SkBitmap forwardRenderedBitmap;

        // Above we created an fbo for the context at maxW x maxH size.
        // Here we lie about the size of the rt. We claim it is the size
        // desired by the test. The reason is that rasterization may change
        // slightly when the viewport dimensions change. Previously, whenever
        // a new test was checked in that bumped maxW or maxH several images
        // would slightly change.
        rtDesc.fWidth = size.width();
        rtDesc.fHeight = size.height();
        SkAutoTUnref<GrRenderTarget> rt;
        if (gGrContext) {
            rt.reset(gGrContext->createPlatformRenderTarget(rtDesc));
        }

        for (size_t i = 0; i < SK_ARRAY_COUNT(gRec); i++) {
            // Skip any tests that we don't even need to try.
            uint32_t gmFlags = gm->getFlags();
            if ((kPDF_Backend == gRec[i].fBackend) && 
                (!doPDF || (gmFlags & GM::kSkipPDF_Flag)))
            {
                continue;
            }

            // Now we know that we want to run this test and record its
            // success or failure.
            ErrorBitfield testErrors = ERROR_NONE;

            if ((ERROR_NONE == testErrors) &&
                (kGPU_Backend == gRec[i].fBackend) &&
                (NULL == rt.get())) {
                fprintf(stderr, "Could not create render target for gpu.\n");
                testErrors |= ERROR_NO_GPU_CONTEXT;
            }

            if (ERROR_NONE == testErrors) {
                testErrors |= test_drawing(gm, gRec[i],
                                           writePath, readPath, diffPath,
                                           gGrContext,
                                           rt.get(), &forwardRenderedBitmap);
            }

            if (doDeferred && !testErrors &&
                (kGPU_Backend == gRec[i].fBackend || 
                kRaster_Backend == gRec[i].fBackend)) {
                testErrors |= test_deferred_drawing(gm, gRec[i],
                                    forwardRenderedBitmap,
                                    diffPath, gGrContext, rt.get());
            }

            if ((ERROR_NONE == testErrors) && doReplay &&
                !(gmFlags & GM::kSkipPicture_Flag)) {
                testErrors |= test_picture_playback(gm, gRec[i],
                                                    forwardRenderedBitmap,
                                                    readPath, diffPath);
            }

            if ((ERROR_NONE == testErrors) && doSerialize) {
                testErrors |= test_picture_serialization(gm, gRec[i],
                                                         forwardRenderedBitmap,
                                                         readPath, diffPath);
            }

            // Update overall results.
            // We only tabulate the particular error types that we currently
            // care about (e.g., missing reference images). Later on, if we
            // want to also tabulate pixel mismatches vs dimension mistmatches
            // (or whatever else), we can do so.
            testsRun++;
            if (ERROR_NONE == testErrors) {
                testsPassed++;
            } else if (ERROR_READING_REFERENCE_IMAGE & testErrors) {
                testsMissingReferenceImages++;
            } else {
                testsFailed++;
            }
        }
        SkDELETE(gm);
    }
    printf("Ran %d tests: %d passed, %d failed, %d missing reference images\n",
           testsRun, testsPassed, testsFailed, testsMissingReferenceImages);
    return (0 == testsFailed) ? 0 : -1;
}