Test using multiple sampler objects with a single texture object

gistfile1.cpp

bool TestSamplers()
{
    GLuint c;
    glGenRenderbuffers(1, &c);
    glNamedRenderbufferStorageEXT(c, GL_RGBA8, 4, 1);

    GLuint f;
    glGenFramebuffers(1, &f);
    glNamedFramebufferRenderbufferEXT(f, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, c);

    glBindFramebuffer(GL_FRAMEBUFFER, f);
    glViewport(0, 0, 4, 1);
    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
    glClear(GL_COLOR_BUFFER_BIT);

    GLubyte input[8] = {
        255, 255, 255, 255,
        0, 0, 0, 255
    };

    GLuint t;
    glGenTextures(1, &t);
    glTextureImage2DEXT(t, GL_TEXTURE_2D, 0, GL_RGBA8, 2, 1, 0, GL_RGBA, GL_UNSIGNED_BYTE, input);

    glBindMultiTextureEXT(GL_TEXTURE0, GL_TEXTURE_2D, t);
    glBindMultiTextureEXT(GL_TEXTURE1, GL_TEXTURE_2D, t);

    GLuint s0;
    glGenSamplers(1, &s0);
    glSamplerParameteri(s0, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glSamplerParameteri(s0, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

    GLuint s1;
    glGenSamplers(1, &s1);
    glSamplerParameteri(s1, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glSamplerParameteri(s1, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

    glBindSampler(0, s0);
    glBindSampler(1, s1);

    GLuint p = glCreateProgram();

    const GLchar *vsSource = "attribute vec4 a_position; varying vec2 v_coord; void main() { gl_Position = a_position; v_coord = (a_position.xy + 1.0) / 2.0; }";
    GLuint vs = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vs, 1, &vsSource, NULL);
    glCompileShader(vs);
    glAttachShader(p, vs);
    glDeleteShader(vs);

    const GLchar *psSource = "varying vec2 v_coord; uniform sampler2D t0; uniform sampler2D t1; void main() { gl_FragColor = texture2D(t1, v_coord); }";
    GLuint ps = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(ps, 1, &psSource, NULL);
    glCompileShader(ps);
    glAttachShader(p, ps);
    glDeleteShader(ps);

    glBindAttribLocation(p, 0, "a_position");
    glLinkProgram(p);

    glUseProgram(p);
    glUniform1i(glGetUniformLocation(p, "t0"), 0);
    glUniform1i(glGetUniformLocation(p, "t1"), 1);

    GLfloat vertices[] = {
        -1.0f, -1.0f,
         3.0f, -1.0f,
        -1.0f,  3.0f,
    };

    glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, vertices);
    glEnableVertexAttribArray(0);
    glDrawArrays(GL_TRIANGLES, 0, 3);
    glDisableVertexAttribArray(0);

    GLubyte expected[4 * 4] = {
        255, 255, 255, 255, 
        255, 255, 255, 255,
        0, 0, 0, 255, 
        0, 0, 0, 255
    };

    GLubyte output[4 * 4];
    glReadPixels(0, 0, 4, 1, GL_RGBA, GL_UNSIGNED_BYTE, output);

    glDeleteRenderbuffers(1, &c);
    glDeleteFramebuffers(1, &f);
    glDeleteTextures(1, &t);
    glDeleteSamplers(1, &s0);
    glDeleteSamplers(1, &s1);
    glDeleteProgram(p);

    for (int i = 0; i < 4 * 4; i++) {
        if (output[i] != expected[i])
            return false;
    }

    glClearColor(0.0f, 1.0f, 0.0f, 1.0f);

    return true;
}