tests/ReadWriteAlphaTest.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.
 */

// This test is specific to the GPU backend.
#if SK_SUPPORT_GPU && !defined(SK_BUILD_FOR_ANDROID)

#include "GrContextFactory.h"
#include "SkGpuDevice.h"
#include "Test.h"

static const int X_SIZE = 12;
static const int Y_SIZE = 12;

DEF_GPUTEST(ReadWriteAlpha, reporter, factory) {
    for (int type = 0; type < GrContextFactory::kLastGLContextType; ++type) {
        GrContextFactory::GLContextType glType = static_cast<GrContextFactory::GLContextType>(type);
        if (!GrContextFactory::IsRenderingGLContext(glType)) {
            continue;
        }
        GrContext* context = factory->get(glType);
        if (NULL == context) {
            continue;
        }

        unsigned char textureData[X_SIZE][Y_SIZE];

        memset(textureData, 0, X_SIZE * Y_SIZE);

        GrTextureDesc desc;

        // let Skia know we will be using this texture as a render target
        desc.fFlags     = kRenderTarget_GrTextureFlagBit;
        // it is a single channel texture
        desc.fConfig    = kAlpha_8_GrPixelConfig;
        desc.fWidth     = X_SIZE;
        desc.fHeight    = Y_SIZE;

        // We are initializing the texture with zeros here
        GrTexture* texture = context->createUncachedTexture(desc, textureData, 0);
        if (!texture) {
            return;
        }

        SkAutoUnref au(texture);

        // create a distinctive texture
        for (int y = 0; y < Y_SIZE; ++y) {
            for (int x = 0; x < X_SIZE; ++x) {
                textureData[x][y] = x*Y_SIZE+y;
            }
        }

        // upload the texture
        texture->writePixels(0, 0, desc.fWidth, desc.fHeight, desc.fConfig,
                             textureData, 0);

        unsigned char readback[X_SIZE][Y_SIZE];

        // clear readback to something non-zero so we can detect readback failures
        memset(readback, 0x1, X_SIZE * Y_SIZE);

        // read the texture back
        texture->readPixels(0, 0, desc.fWidth, desc.fHeight, desc.fConfig,
                            readback, 0);

        // make sure the original & read back versions match
        bool match = true;

        for (int y = 0; y < Y_SIZE; ++y) {
            for (int x = 0; x < X_SIZE; ++x) {
                if (textureData[x][y] != readback[x][y]) {
                    match = false;
                }
            }
        }

        REPORTER_ASSERT(reporter, match);

        // Now try writing on the single channel texture
        SkAutoTUnref<SkBaseDevice> device(new SkGpuDevice(context, texture->asRenderTarget()));
        SkCanvas canvas(device);

        SkPaint paint;

        const SkRect rect = SkRect::MakeLTRB(-10, -10, X_SIZE + 10, Y_SIZE + 10);

        paint.setColor(SK_ColorWHITE);

        canvas.drawRect(rect, paint);

        texture->readPixels(0, 0, desc.fWidth, desc.fHeight, desc.fConfig,
                            readback, 0);

        match = true;

        for (int y = 0; y < Y_SIZE; ++y) {
            for (int x = 0; x < X_SIZE; ++x) {
                if (0xFF != readback[x][y]) {
                    match = false;
                }
            }
        }

        REPORTER_ASSERT(reporter, match);
    }
}

#endif