C++ ensureGlContext函数代码示例

void Texture::setRepeated(bool repeated)
{
    if (repeated != m_isRepeated)
    {
        m_isRepeated = repeated;

        if (m_texture)
        {
            ensureGlContext();

            // Make sure that the current texture binding will be preserved
            priv::TextureSaver save;

            if (!m_isRepeated && !GLEXT_texture_edge_clamp)
            {
                static bool warned = false;

                if (!warned)
                {
                    err() << "OpenGL extension SGIS_texture_edge_clamp unavailable" << std::endl;
                    err() << "Artifacts may occur along texture edges" << std::endl;
                    err() << "Ensure that hardware acceleration is enabled if available" << std::endl;

                    warned = true;
                }
            }

            glCheck(glBindTexture(GL_TEXTURE_2D, m_texture));
            glCheck(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, m_isRepeated ? GL_REPEAT : (GLEXT_texture_edge_clamp ? GLEXT_GL_CLAMP_TO_EDGE : GLEXT_GL_CLAMP)));
            glCheck(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, m_isRepeated ? GL_REPEAT : (GLEXT_texture_edge_clamp ? GLEXT_GL_CLAMP_TO_EDGE : GLEXT_GL_CLAMP)));
        }
    }
}

void Shader::bind(const Shader* shader)
{
    ensureGlContext();

    // Make sure that we can use shaders
    if (!isAvailable())
    {
        err() << "Failed to bind or unbind shader: your system doesn't support shaders "
              << "(you should test Shader::isAvailable() before trying to use the Shader class)" << std::endl;
        return;
    }

    if (shader && shader->m_shaderProgram)
    {
        // Enable the program
        glCheck(GLEXT_glUseProgramObject(castToGlHandle(shader->m_shaderProgram)));

        // Bind the textures
        shader->bindTextures();

        // Bind the current texture
        if (shader->m_currentTexture != -1)
            glCheck(GLEXT_glUniform1i(shader->m_currentTexture, 0));
    }
    else
    {
        // Bind no shader
        glCheck(GLEXT_glUseProgramObject(0));
    }
}

void Shader::setParameter(const std::string& name, const Texture& texture)
{
    if (m_shaderProgram)
    {
        ensureGlContext();

        // Find the location of the variable in the shader
        int location = glGetUniformLocationARB(m_shaderProgram, name.c_str());
        if (location == -1)
        {
            err() << "Texture \"" << name << "\" not found in shader" << std::endl;
            return;
        }

        // Store the location -> texture mapping
        TextureTable::iterator it = m_textures.find(location);
        if (it == m_textures.end())
        {
            // New entry, make sure there are enough texture units
            static const GLint maxUnits = getMaxTextureUnits();
            if (m_textures.size() + 1 >= static_cast<std::size_t>(maxUnits))
            {
                err() << "Impossible to use texture \"" << name << "\" for shader: all available texture units are used" << std::endl;
                return;
            }

            m_textures[location] = &texture;
        }
        else
        {
            // Location already used, just replace the texture
            it->second = &texture;
        }
    }
}

bool RenderTextureImplFBO::isAvailable()
{
    ensureGlContext();

    // Make sure that GLEW is initialized
    priv::ensureGlewInit();

    return GLEW_EXT_framebuffer_object != 0;
}

bool RenderTextureImplFBO::isAvailable()
{
    ensureGlContext();

    // Make sure that extensions are initialized
    priv::ensureExtensionsInit();

    return GLEXT_framebuffer_object != 0;
}

unsigned int Texture::getMaximumSize()
{
    ensureGlContext();

    GLint size;
    glCheck(glGetIntegerv(GL_MAX_TEXTURE_SIZE, &size));

    return static_cast<unsigned int>(size);
}

Image Texture::copyToImage() const
{
    // Easy case: empty texture
    if (!m_texture)
        return Image();

    ensureGlContext();

    // Make sure that the current texture binding will be preserved
    priv::TextureSaver save;

    // Create an array of pixels
    std::vector<Uint8> pixels(m_size.x * m_size.y * 4);

    if ((m_size == m_actualSize) && !m_pixelsFlipped)
    {
        // Texture is not padded nor flipped, we can use a direct copy
        glCheck(glBindTexture(GL_TEXTURE_2D, m_texture));
        glCheck(glGetTexImage(GL_TEXTURE_2D, 0, GL_RGBA, GL_UNSIGNED_BYTE, &pixels[0]));
    }
    else
    {
        // Texture is either padded or flipped, we have to use a slower algorithm

        // All the pixels will first be copied to a temporary array
        std::vector<Uint8> allPixels(m_actualSize.x * m_actualSize.y * 4);
        glCheck(glBindTexture(GL_TEXTURE_2D, m_texture));
        glCheck(glGetTexImage(GL_TEXTURE_2D, 0, GL_RGBA, GL_UNSIGNED_BYTE, &allPixels[0]));

        // Then we copy the useful pixels from the temporary array to the final one
        const Uint8* src = &allPixels[0];
        Uint8* dst = &pixels[0];
        int srcPitch = m_actualSize.x * 4;
        int dstPitch = m_size.x * 4;

        // Handle the case where source pixels are flipped vertically
        if (m_pixelsFlipped)
        {
            src += srcPitch * (m_size.y - 1);
            srcPitch = -srcPitch;
        }

        for (unsigned int i = 0; i < m_size.y; ++i)
        {
            std::memcpy(dst, src, dstPitch);
            src += srcPitch;
            dst += dstPitch;
        }
    }

    // Create the image
    Image image;
    image.create(m_size.x, m_size.y, &pixels[0]);

    return image;
}

bool Texture::create(unsigned int width, unsigned int height)
{
    // Check if texture parameters are valid before creating it
    if ((width == 0) || (height == 0))
    {
        err() << "Failed to create texture, invalid size (" << width << "x" << height << ")" << std::endl;
        return false;
    }

    // Compute the internal texture dimensions depending on NPOT textures support
    Vector2u actualSize(getValidSize(width), getValidSize(height));

    // Check the maximum texture size
    unsigned int maxSize = getMaximumSize();
    if ((actualSize.x > maxSize) || (actualSize.y > maxSize))
    {
        err() << "Failed to create texture, its internal size is too high "
              << "(" << actualSize.x << "x" << actualSize.y << ", "
              << "maximum is " << maxSize << "x" << maxSize << ")"
              << std::endl;
        return false;
    }

    // All the validity checks passed, we can store the new texture settings
    m_size.x        = width;
    m_size.y        = height;
    m_actualSize    = actualSize;
    m_pixelsFlipped = false;

    ensureGlContext();

    // Create the OpenGL texture if it doesn't exist yet
    if (!m_texture)
    {
        GLuint texture;
        glCheck(glGenTextures(1, &texture));
        m_texture = static_cast<unsigned int>(texture);
    }

    // Make sure that the current texture binding will be preserved
    priv::TextureSaver save;

    // Initialize the texture
    glCheck(glBindTexture(GL_TEXTURE_2D, m_texture));
    glCheck(glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, m_actualSize.x, m_actualSize.y, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL));
    glCheck(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, m_isRepeated ? GL_REPEAT : GL_CLAMP_TO_EDGE));
    glCheck(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, m_isRepeated ? GL_REPEAT : GL_CLAMP_TO_EDGE));
    glCheck(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, m_isSmooth ? GL_LINEAR : GL_NEAREST));
    glCheck(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, m_isSmooth ? GL_LINEAR_MIPMAP_LINEAR : GL_NEAREST));
	glCheck(glTexParameteri(GL_TEXTURE_2D, GL_GENERATE_MIPMAP_SGIS, GL_TRUE));
	glCheck(glTexEnvi(GL_TEXTURE_FILTER_CONTROL_EXT, GL_TEXTURE_LOD_BIAS_EXT, -1));
    m_cacheId = getUniqueId();

    return true;
}

        bool Shader::isAvailable()
        {
            ensureGlContext();

            // Make sure that GLEW is initialized
            priv::ensureGlewInit();
            return GLEW_ARB_shading_language_100 &&
                   GLEW_ARB_shader_objects       &&
                   GLEW_ARB_vertex_shader        &&
                   GLEW_ARB_fragment_shader;
        }

void Shader::bind() const
{
    if (m_shaderProgram)
    {
        ensureGlContext();

        // Enable the program
        glCheck(glUseProgramObjectARB(m_shaderProgram));

        // Bind the textures
        bindTextures();

        // Bind the current texture
        if (m_currentTexture != -1)
            glCheck(glUniform1iARB(m_currentTexture, 0));
    }
}

    ////////////////////////////////////////////////////////////
    /// \brief Constructor: set up state before uniform is set
    ///
    ////////////////////////////////////////////////////////////
    UniformBinder(Shader& shader, const std::string& name) :
    savedProgram(0),
    currentProgram(castToGlHandle(shader.m_shaderProgram)),
    location(-1)
    {
        if (currentProgram)
        {
            ensureGlContext();

            // Enable program object
            glCheck(savedProgram = GLEXT_glGetHandle(GLEXT_GL_PROGRAM_OBJECT));
            if (currentProgram != savedProgram)
                glCheck(GLEXT_glUseProgramObject(currentProgram));

            // Store uniform location for further use outside constructor
            location = shader.getUniformLocation(name);
        }
    }

void Shader::setParameter(const std::string& name, const sf::Transform& transform)
{
    if (m_shaderProgram)
    {
        ensureGlContext();

        // Enable program
        GLhandleARB program = glGetHandleARB(GL_PROGRAM_OBJECT_ARB);
        glCheck(glUseProgramObjectARB(m_shaderProgram));

        // Get parameter location and assign it new values
        GLint location = getParamLocation(name);
        if (location != -1)
            glCheck(glUniformMatrix4fvARB(location, 1, GL_FALSE, transform.getMatrix()));

        // Disable program
        glCheck(glUseProgramObjectARB(program));
    }
}

void Texture::update(const Uint8* pixels, unsigned int width, unsigned int height, unsigned int x, unsigned int y)
{
    assert(x + width <= m_size.x);
    assert(y + height <= m_size.y);

    if (pixels && m_texture)
    {
        ensureGlContext();

        // Make sure that the current texture binding will be preserved
        priv::TextureSaver save;

        // Copy pixels from the given array to the texture
        glCheck(glBindTexture(GL_TEXTURE_2D, m_texture));
        glCheck(glTexSubImage2D(GL_TEXTURE_2D, 0, x, y, width, height, GL_RGBA, GL_UNSIGNED_BYTE, pixels));
        m_pixelsFlipped = false;
        m_cacheId = getUniqueId();
    }
}

void Shader::setParameter(const std::string& name, const Transform& transform)
{
    if (m_shaderProgram)
    {
        ensureGlContext();

        // Enable program
        GLEXT_GLhandle program;
        glCheck(program = GLEXT_glGetHandle(GLEXT_GL_PROGRAM_OBJECT));
        glCheck(GLEXT_glUseProgramObject(castToGlHandle(m_shaderProgram)));

        // Get parameter location and assign it new values
        GLint location = getParamLocation(name);
        if (location != -1)
        {
            glCheck(GLEXT_glUniformMatrix4fv(location, 1, GL_FALSE, transform.getMatrix()));
        }

        // Disable program
        glCheck(GLEXT_glUseProgramObject(program));
    }
}