glsl: test loop unroll with uint overflow

[piglit.git] / tests / spec / ext_framebuffer_multisample / draw-buffers-common.cpp

/*
 * Copyright © 2012 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#include "draw-buffers-common.h"
using namespace piglit_util_fbo;

/**
 * \file draw-buffers-common.cpp
 *
 * This file provides utility functions to draw a test pattern to multiple draw
 * buffers attached to a FBO with GL_SAMPLE_ALPHA_TO_{COVERAGE, ONE}
 * enabled / disabled.
 *
 * Expected color values are computed for each draw buffer based on the enabled
 * GL_SAMPLE_ALPHA_TO_{COVERAGE, ONE} flags and coverage value used to draw the
 * test pattern.
 *
 * Reference image for each draw buffer is drawn in to right half of default
 * framebuffer. It is used to verify the accuracy of test image as well as to
 * visually compare the difference caused by enabling above flags.
 *
 * Test image is drawn with the same test pattern in multisample buffer with
 * GL_SAMPLE_ALPHA_TO_{COVERAGE, ONE} enabled. All multisample draw buffers
 * are sequentially resolved by  blitting them to a single sample FBO. resolve_fbo
 * is then blitted to left half of window system framebuffer with appropriate y
 * offset. This produces three test images in the left half, each corresponds to
 * a color attachment.
 *
 * Test image is verified by comparing it with the corresponding reference
 * image in the right half
 *
 * For sample coverage and sample alpha to coverage, test image should be
 * verified by probing the rectangles in left half of window system framebuffer
 * and comparing with expected color values. OpenGL 3.0 specification intends to
 * allow (but not require) the implementation to produce a dithering effect when
 * the coverage value is not a strict multiple of 1 / num_samples. We will skip
 * computing expected values and probing for such rectangles. They are drawn
 * just to look for dithering by human inspection.
 *
 * Note:
 * At present, the test always uses three draw buffers.  To test other
 * numbers of draw buffers, we would have to modify the fragment shader in
 * nontrivial ways at run time.
 *
 * Also, the test always uses GL_RGBA8I as integer format or GL_RGBA as float
 * format for draw buffer zero.
 *
 * Author: Anuj Phogat <anuj.phogat@gmail.com>
 */

static Fbo ms_fbo, resolve_fbo, resolve_int_fbo;
static GLbitfield buffer_to_test;

static float *coverage = NULL;
static float *color = NULL;
static float *depth = NULL;
static float *expected_color = NULL;
static float *expected_depth = NULL;

static int num_draw_buffers;
static int num_samples;
static int num_rects;
static int prog;
static int color_loc;
static int depth_loc;
static int frag_0_color_loc;
static int alpha_to_coverage_loc;
static int pattern_width;
static int pattern_height;

static bool is_buffer_zero_integer_format = false;
static bool is_dual_src_blending = false;
static GLenum draw_buffer_zero_format;

static const int num_components = 4; /* for RGBA formats */
static const int num_color_bits = 8; /* for GL_RGBA & GL_RGBA8I formats */

static const float bg_depth = 0.8;
static const float bg_color[4] = {
        0.0, 0.6, 0.0, 0.4 };

/* Testing for three draw buffers is supported */
static const GLenum draw_buffers[] = {
        GL_COLOR_ATTACHMENT0_EXT,
        GL_COLOR_ATTACHMENT1_EXT,
        GL_COLOR_ATTACHMENT2_EXT };

/* Offset the viewport transformation on depth value passed to the vertex
 * shader by setting it to (2 * depth - 1.0).
 */
static const char *vert_template =
        "#version %s\n"
        "attribute vec2 pos;\n"
        "uniform float depth;\n"
        "void main()\n"
        "{\n"
        "  vec4 eye_pos = gl_ModelViewProjectionMatrix * vec4(pos, 0.0, 1.0);\n"
        "  gl_Position = vec4(eye_pos.xy, 2 * depth - 1.0, 1.0);\n"
        "}\n";

/* Fragment shader generates three different color outputs. Different color
 * values are generated based on if sample_alpha_to_coverage / dual_src_blend
 * are enabled or not.
 */
static const char *frag_template =
        "#version %s\n"
        "#define NUM_ATTACHMENTS %d\n"
        "#define DUAL_SRC_BLEND %d\n"
        "#define ALPHA_TO_COVERAGE %d\n"
        "#define OUT_TYPE %s\n"
        "#define FRAG_OUT_ZERO_WRITE %d\n"
        "#if __VERSION__ == 130\n"
        "out OUT_TYPE frag_out_0;\n"
        "#if DUAL_SRC_BLEND\n"
        "out vec4 frag_out_1;\n"
        "#elif NUM_ATTACHMENTS > 1\n"
        "out vec4 frag_out_1;\n"
        "out vec4 frag_out_2;\n"
        "#endif\n"
        "#else\n"
        "#define frag_out_0 gl_FragData[0]\n"
        "#if NUM_ATTACHMENTS > 1\n"
        "#define frag_out_1 gl_FragData[1]\n"
        "#define frag_out_2 gl_FragData[2]\n"
        "#endif\n"
        "#endif\n"
        "uniform OUT_TYPE frag_0_color;\n"
        "uniform vec4 color;\n"
        "void main()\n"
        "{\n"
        "  #if FRAG_OUT_ZERO_WRITE\n"
        "    frag_out_0 = frag_0_color;\n"
        "  #endif\n"
        "  #if DUAL_SRC_BLEND\n"
        "    frag_out_1 = vec4(color.rgb, 1.0 - color.a / 2.0);\n"
        "  #elif ALPHA_TO_COVERAGE && NUM_ATTACHMENTS > 1\n"
        "    frag_out_1 = vec4(color.rgb, color.a / 2);\n"
        "    frag_out_2 = vec4(color.rgb, color.a / 4);\n"
        "  #elif NUM_ATTACHMENTS > 1\n"
        "    frag_out_1 = frag_out_2 = color;\n"
        "  #endif\n"
        "}\n";

const char *
get_out_type_glsl(void)
{
        if (is_buffer_zero_integer_format)
                return "ivec4";
        else
                return "vec4";
}
void
shader_compile(bool sample_alpha_to_coverage,
               bool dual_src_blend,
               bool frag_out_zero_write)
{
        bool need_glsl130 = is_buffer_zero_integer_format || dual_src_blend;

        if (need_glsl130) {
                piglit_require_gl_version(30);
        }

        is_dual_src_blending = dual_src_blend;

        /* Compile program */
        unsigned vert_alloc_len = strlen(vert_template) + 4;
        char *vert = (char *) malloc(vert_alloc_len);
        sprintf(vert, vert_template, need_glsl130 ? "130" : "120");
        GLint vs = piglit_compile_shader_text(GL_VERTEX_SHADER, vert);
        free(vert);

        /* Generate appropriate fragment shader program */
        const char *out_type_glsl = get_out_type_glsl();
        unsigned frag_alloc_len = strlen(frag_template) +
                                  strlen(out_type_glsl) + 4;
        char *frag = (char *) malloc(frag_alloc_len);
        sprintf(frag, frag_template, need_glsl130 ? "130" : "120",
                num_draw_buffers,
                is_dual_src_blending,
                sample_alpha_to_coverage,
                out_type_glsl,
                frag_out_zero_write);

        GLint fs = piglit_compile_shader_text(GL_FRAGMENT_SHADER, frag);
        prog = piglit_link_simple_program(vs, fs);

        if (!piglit_link_check_status(prog)) {
                piglit_report_result(PIGLIT_FAIL);
        }
        free(frag);

        if (need_glsl130) {
                if (is_dual_src_blending) {
                        glBindFragDataLocationIndexed(prog, 0, 0, "frag_out_0");
                        glBindFragDataLocationIndexed(prog, 0, 1, "frag_out_1");

                }
                else if (num_draw_buffers > 1) {
                        glBindFragDataLocation(prog, 0, "frag_out_0");
                        glBindFragDataLocation(prog, 1, "frag_out_1");
                        glBindFragDataLocation(prog, 2, "frag_out_2");
                }
                else
                        glBindFragDataLocation(prog, 0, "frag_out_0");
        }

        glBindAttribLocation(prog, 0, "pos");
        glEnableVertexAttribArray(0);

        /* Linking is required after glBindFragDataLocation */
        glLinkProgram(prog);

        /* Set up uniforms */
        glUseProgram(prog);
        color_loc = glGetUniformLocation(prog, "color");
        depth_loc = glGetUniformLocation(prog, "depth");
        frag_0_color_loc = glGetUniformLocation(prog, "frag_0_color");
        alpha_to_coverage_loc = glGetUniformLocation(prog, "alphatocoverage");
}

void
allocate_data_arrays(void)
{
        float alpha_scale;
        /* Draw 2N + 1 rectangles for N samples, each with a unique color
         * and coverage value
         */
        if (num_samples) {
                num_rects = 2 * num_samples + 1;
                alpha_scale = (1.0 / (2.0 * num_samples));
        }
        else {
                num_rects = 9;
                alpha_scale = 0.125;
        }

        /* Allocate data arrays based on number of samples used */
        color = (float *) malloc(num_rects *
                                 num_components *
                                 sizeof(float));
        expected_color = (float *) malloc(num_draw_buffers *
                                  num_rects *
                                  num_components *
                                  sizeof(float));
        depth = (float *) malloc(num_rects * sizeof(float));
        expected_depth = (float *) malloc(num_draw_buffers *
                                          num_rects *
                                          sizeof(float));
        coverage = (float *) malloc(num_rects * sizeof(float));

        for (int i = 0; i < num_rects; i++) {
                unsigned rect_idx = i * num_components;
                for (int j = 0; j < num_components - 1; j++) {
                        color[rect_idx + j] =
                        (sin((float)(rect_idx + j)) + 1) / 2;
                }

                /* In case of alpha-to-coverage enabled, alpha values will be
                 * directly used as coverage.
                 */
                if (buffer_to_test == GL_DEPTH_BUFFER_BIT)
                        /* For depth buffer testing with alpha-to-coverage,
                         * set more rects with alpha = 1.0.
                         */
                        color[rect_idx + 3] = 2 * i * alpha_scale;
                else
                        color[rect_idx + 3] = i * alpha_scale;

                depth[i] =  i * (alpha_scale / 2.0);
        }
}

void
free_data_arrays(void)
{
        free(color);
        color = NULL;
        free(depth);
        depth = NULL;
        free(coverage);
        coverage = NULL;
        free(expected_color);
        expected_color = NULL;
}

void
float_color_to_int_color(int *dst, float *src)
{
        float offset = 1 - (1 << (num_color_bits - 1));
        float scale = -2.0 * offset;

        for (int j = 0; j < num_rects; ++j) {
                for (int k = 0; k < num_components; ++k) {
                        dst[j * num_components + k] =
                        scale * src[j * num_components + k] + offset;
                }
        }
}

void
draw_pattern(bool sample_alpha_to_coverage,
             bool sample_alpha_to_one,
             bool is_reference_image,
             float *float_color)
{
        glUseProgram(prog);
        if (buffer_to_test == GL_COLOR_BUFFER_BIT)
                glClearColor(bg_color[0], bg_color[1],
                             bg_color[2], bg_color[3]);
        else if (buffer_to_test == GL_DEPTH_BUFFER_BIT)
                glClearDepth(bg_depth);
        glClear(buffer_to_test);

        if (!is_reference_image) {
                if (sample_alpha_to_coverage)
                        glEnable(GL_SAMPLE_ALPHA_TO_COVERAGE);
                if (sample_alpha_to_one)
                        glEnable(GL_SAMPLE_ALPHA_TO_ONE);
        }
        glUniform1i(alpha_to_coverage_loc, sample_alpha_to_coverage);

        unsigned indices[6] = {0, 1, 2, 0, 2, 3};
        int *integer_color = (int *) malloc(num_rects *
                                            num_components *
                                            sizeof(int));

        /* For integer color buffers convert the color data to integer format */
        if (is_buffer_zero_integer_format) {
                float_color_to_int_color(integer_color, float_color);
        }

        for (int i = 0; i < num_rects; ++i) {
                float vertices[4][2] = {
                { 0.0f, 0.0f + i * (pattern_height / num_rects) },
                { 0.0f, (i + 1.0f) * (pattern_height / num_rects) },
                { pattern_width, (i + 1.0f) * (pattern_height / num_rects) },
                { pattern_width, 0.0f + i * (pattern_height / num_rects) } };

                glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE,
                                      sizeof(vertices[0]),
                                      (void *) vertices);

                glUniform4fv(color_loc, 1, (float_color + i * num_components));
                if (is_buffer_zero_integer_format) {
                        glUniform4iv(frag_0_color_loc, 1,
                                     integer_color + i * num_components);
                }
                else {
                        glUniform4fv(frag_0_color_loc, 1,
                                     (float_color + i * num_components));
                }
                glUniform1f(depth_loc, depth[i]);
                glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT,
                               (void *) indices);
        }
        glDisable(GL_SAMPLE_ALPHA_TO_COVERAGE);
        glDisable(GL_SAMPLE_ALPHA_TO_ONE);
        free(integer_color);
}

float
get_alpha_blend_factor(float src0_alpha, float src1_alpha,
                       bool compute_src)
{
        GLint blend_func;
        if (compute_src)
                glGetIntegerv(GL_BLEND_SRC_RGB, &blend_func);
        else
                glGetIntegerv(GL_BLEND_DST_RGB, &blend_func);

        switch(blend_func) {
                case GL_SRC_ALPHA:
                        return src0_alpha;
                        break;
                case GL_ONE_MINUS_SRC_ALPHA:
                        return (1.0 - src0_alpha);
                        break;
                case GL_SRC1_ALPHA:
                        return src1_alpha;
                        break;
                case GL_ONE_MINUS_SRC1_ALPHA:
                        return (1.0 - src1_alpha);
                        break;
                default:
                        printf("Blend function is not supported"
                               " by test case\n");
        }
        return -1;
}

void
compute_blend_color(float *frag_color, int rect_count,
                    bool sample_alpha_to_one)
{
        float src_blend_factor, dst_blend_factor;
        /* Taking in to account alpha values output by
         * fragment shader.
         */
        float src0_alpha = color[rect_count * num_components + 3];
        float src1_alpha =  1.0 - src0_alpha / 2.0;

        if (sample_alpha_to_one && num_samples) {
                /* Set fragment src0_alpha, src1_alpha to 1.0 and use them
                 * to compute blending factors.
                 */
                src0_alpha = 1.0;
                src1_alpha = 1.0;
        }

        src_blend_factor = get_alpha_blend_factor(src0_alpha,
                                                  src1_alpha,
                                                  true);
        dst_blend_factor = get_alpha_blend_factor(src0_alpha,
                                                  src1_alpha,
                                                  false);
        /* Using default BlendEquation, blend_color is:
         * src0_color * src_blend_factor + dst_color * dst_blend_factor
         */
        for (int j = 0; j < num_components; j++) {
                float blend_color=
                color[rect_count * num_components + j] *
                src_blend_factor +
                bg_color[j] *
                dst_blend_factor;

                frag_color[rect_count * num_components + j] =
                        (blend_color > 1) ? 1.0 : blend_color;
        }
}

void
compute_expected_color(bool sample_alpha_to_coverage,
                       bool sample_alpha_to_one,
                       int draw_buffer_count)
{
        unsigned buffer_idx_offset = draw_buffer_count *
                                     num_rects *
                                     num_components;
        for (int i = 0; i < num_rects; i++) {

                float *frag_color = NULL;
                float samples_used = coverage[i] * num_samples;
                /* Expected color values are computed only for integer
                 * number of samples_used. Non-integer values may result
                 * in dithering effect.
                 */
                if (samples_used == (int) samples_used) {
                        int rect_idx_offset = buffer_idx_offset +
                                              i * num_components;
                        frag_color = (float *) malloc(num_rects *
                                                      num_components *
                                                      sizeof(float));

                        /* Do dual source blending computations */
                        if (is_dual_src_blending) {
                                compute_blend_color(frag_color,
                                                    i /* rect_count */,
                                                    sample_alpha_to_one);
                        }
                        else {
                                memcpy(frag_color, color,
                                       num_rects * num_components *
                                       sizeof(float));
                        }

                        /* Coverage value decides the number of samples in
                         * multisample buffer covered by an incoming fragment,
                         * which will then receive the fragment data. When the
                         * multisample buffer is resolved it gets blended with
                         * the background color which is written to the
                         * remaining samples. Page 254 (page 270 of the PDF) of
                         * the OpenGL 3.0 spec says: "The method of combination
                         * is not specified, though a simple average computed
                         * independently for each color component is recommended."
                         * This is followed by NVIDIA and AMD in their proprietary
                         * linux drivers.
                         */
                        for (int j = 0; j < num_components - 1 ; j++) {

                                expected_color[rect_idx_offset + j] =
                                frag_color[i * num_components + j] * coverage[i] +
                                bg_color[j] * (1 - coverage[i]);
                        }

                        /* Compute expected alpha values of draw buffers */
                        float frag_alpha = frag_color[i * num_components + 3];
                        int alpha_idx = rect_idx_offset + 3;

                        if ((!num_samples &&
                             !sample_alpha_to_coverage) ||
                            is_buffer_zero_integer_format) {
                                /* Taking in to account alpha values output by
                                 * fragment shader.
                                 */
                                expected_color[alpha_idx] =
                                        is_buffer_zero_integer_format ?
                                        frag_alpha / (1 << draw_buffer_count) :
                                        frag_alpha;
                        }
                        else if (sample_alpha_to_coverage) {
                                /* Taking in to account alpha values output by
                                 * fragment shader.
                                 */
                                frag_alpha /= (1 << draw_buffer_count);
                                if (sample_alpha_to_one) {
                                        expected_color[alpha_idx] =
                                        1.0 * coverage[i] +
                                        bg_color[3] * (1 - coverage[i]);
                                }
                                else {
                                        expected_color[alpha_idx] =
                                        frag_alpha * coverage[i] +
                                        bg_color[3] * (1 - coverage[i]);
                                }
                        }
                        else {
                                expected_color[alpha_idx] =
                                        sample_alpha_to_one ? 1.0 : frag_alpha;
                        }
                }
                free(frag_color);
        }

}

void
compute_expected_depth(void)
{
        /* Compute the expected depth values only for coverage value equal to
         * 0.0 and 1.0. Expected depth is not defined by OpenGL specification
         * when coverage value is between 0.0 and 1.0 */
        for (int i = 0; i < num_rects; i++) {
                if (coverage[i] == 0.0)
                        expected_depth[i] = bg_depth;
                else if (coverage[i] == 1.0)
                        expected_depth[i] = (depth[i] < 1.0) ? depth[i] : 1.0;
        }
}

void
compute_expected(bool sample_alpha_to_coverage,
                 bool sample_alpha_to_one,
                 int draw_buffer_count)
{
        int i;
        /* Compute the coverage value used in the test */
        if (num_samples &&
            sample_alpha_to_coverage &&
            !is_buffer_zero_integer_format) {

                for (i = 0; i < num_rects; i++) {
                        /* Coverage value for all the draw buffers comes from
                         * the fragment alpha values of draw buffer zero
                         */
                        float frag_alpha = color[i * num_components + 3];
                        coverage[i] = (frag_alpha < 1.0) ? frag_alpha : 1.0;
                }
        }
        else {
                for (i = 0; i < num_rects; i++)
                        coverage[i] = 1.0;
        }

        if (buffer_to_test == GL_COLOR_BUFFER_BIT) {
                /* Don't compute expected color for color buffer zero
                 * if no renderbuffer is attached to it.
                 */
                if (draw_buffer_count == 0 && draw_buffer_zero_format == GL_NONE)
                        return;
                compute_expected_color(sample_alpha_to_coverage,
                                       sample_alpha_to_one,
                                       draw_buffer_count);
        }
        else if (buffer_to_test == GL_DEPTH_BUFFER_BIT)
                compute_expected_depth();

}

/* This function probes all the draw buffers blitted to downsampled FBO
 * (resolve_fbo / resolve_int_fbo) and compare against expected color values.
 */
bool
probe_framebuffer_color(void)
{
        bool result = true;
        int * expected_int_color = NULL;
        int rect_width = pattern_width;
        int rect_height = pattern_height / num_rects;

        for (int i = 0; i < num_draw_buffers; i++) {
                /* Don't probe color buffer zero if no renderbuffer is
                 * attached to it.
                 */
                if (i == 0 && draw_buffer_zero_format == GL_NONE)
                        continue;
                bool is_integer_operation = is_buffer_zero_integer_format && !i;

                if (is_integer_operation) {
                        glBindFramebuffer(GL_READ_FRAMEBUFFER,
                                          resolve_int_fbo.handle);
                        expected_int_color = (int*) malloc(num_rects *
                                                           num_components *
                                                           sizeof(int));
                }
                else {
                        glBindFramebuffer(GL_READ_FRAMEBUFFER,
                                          resolve_fbo.handle);
                }

                for (int j = 0; j < num_rects; j++) {
                        float samples_used = coverage[j] * num_samples;
                        int rect_x = 0;
                        int rect_y = i * pattern_height +
                                     j * rect_height;
                        int rect_idx_offset = (i * num_rects + j) *
                                              num_components;

                        /* Only probe rectangles with coverage value which is a
                         * strict  multiple of 1 / num_samples.
                         */
                        if (samples_used == (int)samples_used) {
                                if (is_integer_operation) {
                                        float_color_to_int_color(expected_int_color,
                                                                 expected_color);
                                        result = piglit_probe_rect_rgba_int(
                                                 rect_x,
                                                 rect_y,
                                                 rect_width,
                                                 rect_height,
                                                 expected_int_color +
                                                 rect_idx_offset)
                                                 && result;
                                }
                                else {
                                        result = piglit_probe_rect_rgba(
                                                 rect_x,
                                                 rect_y,
                                                 rect_width,
                                                 rect_height,
                                                 expected_color + rect_idx_offset)
                                                 && result;
                                }
                        }
                }
        }
        if (expected_int_color)
                free(expected_int_color);
        return result;
}

bool
probe_framebuffer_depth(void)
{
        bool result = true;
        int rect_width = pattern_width;
        int rect_height = pattern_height / num_rects;

        glBindFramebuffer(GL_READ_FRAMEBUFFER, resolve_fbo.handle);
        for (int i = 0; i < num_rects; i++) {
                if (coverage[i] == 0.0 || coverage[i] == 1.0) {
                        int rect_x = 0;
                        int rect_y = i * rect_height;
                        int rect_idx = i;

                        result = piglit_probe_rect_depth(
                                 rect_x,
                                 rect_y,
                                 rect_width,
                                 rect_height,
                                 expected_depth[rect_idx])
                                 && result;
                }
                else {
                /*Skip probing polygons which are drawn with fractional
                * coverage value (between 0.0 and 1.0)*/
                       continue;
                }
        }
        return result;
}

void
draw_image_to_window_system_fb(int draw_buffer_count, bool rhs)
{
        unsigned rect_x = 0;
        unsigned rect_y = draw_buffer_count * pattern_height;
        unsigned array_size = num_components * pattern_width * pattern_height;
        float *image = (float *) malloc(sizeof(float) * array_size);

        if (is_buffer_zero_integer_format && draw_buffer_count == 0) {
                glBindFramebuffer(GL_READ_FRAMEBUFFER, resolve_int_fbo.handle);
                int *tmp = (int *) malloc(sizeof(int) * array_size);
                glReadPixels(rect_x, rect_y,
                             pattern_width, pattern_height,
                             GL_RGBA_INTEGER,
                             GL_INT, tmp);
                for (unsigned i = 0; i < array_size; ++i) {
                        image[i] = tmp[i];
                }

                /* Convert integer color data to float color data */
                float color_offset = 1.0 - (1 << (num_color_bits - 1));
                float color_scale = -2.0 * color_offset;

                for (unsigned i = 0; i < array_size; ++i) {
                        image[i] = (image[i] - color_offset) / color_scale;
                }
                free(tmp);
        }
        else{
                glBindFramebuffer(GL_READ_FRAMEBUFFER, resolve_fbo.handle);
                glReadPixels(rect_x, rect_y,
                             pattern_width,
                             pattern_height,
                             GL_RGBA,
                             GL_FLOAT, image);
        }

        /* Rendering using gldrawPixels() with dual source blending enabled
         * produces undefined results. So, disable blending in
         * piglit_visualize_image function to avoid undefined behavior.
         */
        GLboolean isBlending;
        glGetBooleanv(GL_BLEND, &isBlending);
        glDisable(GL_BLEND);
        piglit_visualize_image(image, GL_RGBA,
                               pattern_width, pattern_height,
                               draw_buffer_count + 1, rhs);
        if (isBlending)
                glEnable(GL_BLEND);
        free(image);
}

void
draw_test_image(bool sample_alpha_to_coverage, bool sample_alpha_to_one)
{
        /* Draw test pattern in multisample ms_fbo with
         * GL_SAMPLE_ALPHA_TO_COVERAGE enabled
         */
        glBindFramebuffer(GL_DRAW_FRAMEBUFFER, ms_fbo.handle);
        glDrawBuffers(num_draw_buffers, draw_buffers);
        ms_fbo.set_viewport();

        draw_pattern(sample_alpha_to_coverage,
                     sample_alpha_to_one,
                     false /* is_reference_image */,
                     color);

        for (int i = 0; i < num_draw_buffers; i++) {

                /* Blit ms_fbo to singlesample FBO to resolve multisample
                 * buffer.
                 */
                glBindFramebuffer(GL_READ_FRAMEBUFFER, ms_fbo.handle);
                if (buffer_to_test == GL_COLOR_BUFFER_BIT)
                        glReadBuffer(GL_COLOR_ATTACHMENT0_EXT + i);

                if (is_buffer_zero_integer_format && !i)
                        glBindFramebuffer(GL_DRAW_FRAMEBUFFER,
                                          resolve_int_fbo.handle);
                else
                        glBindFramebuffer(GL_DRAW_FRAMEBUFFER,
                                          resolve_fbo.handle);

                /* Blit all the draw buffers to resolve_fbo / resolve_int_fbo
                 * with different y_offset.
                 */
                unsigned y_offset = i * pattern_height;
                glBlitFramebuffer(0, 0,
                                  pattern_width, pattern_height,
                                  0, y_offset,
                                  pattern_width, pattern_height + y_offset,
                                  buffer_to_test, GL_NEAREST);

                if (buffer_to_test == GL_COLOR_BUFFER_BIT) {
                        draw_image_to_window_system_fb(i /* draw_buffer_count */,
                                                       false /* rhs */);
                }

                /* Expected color values for all the draw buffers are computed
                 * to aid probe_framebuffer_color() and probe_framebuffer_depth()
                 * in verification.
                 */
                if (sample_alpha_to_coverage || is_dual_src_blending) {
                        /* Expected color is different for different draw
                         * buffers
                         */
                        compute_expected(sample_alpha_to_coverage,
                                         sample_alpha_to_one,
                                         i /* draw_buffer_count */);
                }
        }
}

void
draw_reference_image(bool sample_alpha_to_coverage, bool sample_alpha_to_one)
{
        /* Draw test pattern in multisample ms_fbo with
         * GL_SAMPLE_ALPHA_TO_COVERAGE disabled.
         */
        glBindFramebuffer(GL_DRAW_FRAMEBUFFER, ms_fbo.handle);
        glDrawBuffers(num_draw_buffers, draw_buffers);
        ms_fbo.set_viewport();

        if (sample_alpha_to_coverage) {
                draw_pattern(sample_alpha_to_coverage,
                             sample_alpha_to_one,
                             true /* is_reference_image */,
                             color);
        }
        else {
                /* Value of draw_buffer_count doesn't matter in this case */
                compute_expected(sample_alpha_to_coverage,
                                 sample_alpha_to_one,
                                 0 /* draw_buffer_count */);
                draw_pattern(sample_alpha_to_coverage,
                             sample_alpha_to_one,
                             true /* is_reference_image */,
                             expected_color);
        }

        for (int i = 0; i < num_draw_buffers; i++) {

                /* Blit ms_fbo to resolve_fbo to resolve multisample buffer */
                glBindFramebuffer(GL_READ_FRAMEBUFFER, ms_fbo.handle);
                if (buffer_to_test == GL_COLOR_BUFFER_BIT)
                        glReadBuffer(GL_COLOR_ATTACHMENT0_EXT + i);
                if (is_buffer_zero_integer_format && !i) {
                        glBindFramebuffer(GL_DRAW_FRAMEBUFFER,
                                          resolve_int_fbo.handle);
                }
                else {
                        glBindFramebuffer(GL_DRAW_FRAMEBUFFER,
                                          resolve_fbo.handle);
                }

                /* Blit all the draw buffers to resolve_fbo with different
                 * y_offset.
                 */
                unsigned y_offset = i * pattern_height;
                glBlitFramebuffer(0, 0,
                                  pattern_width, pattern_height,
                                  0, y_offset,
                                  pattern_width, pattern_height + y_offset,
                                  buffer_to_test, GL_NEAREST);

                if (buffer_to_test == GL_COLOR_BUFFER_BIT) {
                        draw_image_to_window_system_fb(i /* draw_buffer_count */,
                                                       true /* rhs */);
                }
        }
}

void
ms_fbo_and_draw_buffers_setup(int samples,
                              int width,
                              int height,
                              int n_attachments,
                              GLenum test_buffer,
                              GLenum color_buffer_zero_format)
{
        int maxBuffers;
        glGetIntegerv(GL_MAX_COLOR_ATTACHMENTS, &maxBuffers);

        /* Ensure that requested number of color attachments are
         * supported by the implementation and fragment shader.
         */
        if (n_attachments <= (int) ARRAY_SIZE(draw_buffers) &&
            n_attachments <= maxBuffers)
                num_draw_buffers = n_attachments;
        else {
                printf("Number of attachments requested are not supported\n");
                piglit_report_result(PIGLIT_SKIP);
        }

        pattern_width = width;
        pattern_height = height;
        draw_buffer_zero_format = color_buffer_zero_format;

        /* Setup frame buffer objects with required configuration */
        FboConfig ms_config(samples, pattern_width, pattern_height);
        ms_config.color_internalformat = color_buffer_zero_format;
        ms_fbo.setup(ms_config);

        /* Create resolve_fbo with dimensions large enough to accommodate
         * all the draw buffers
         */
        FboConfig resolve_config(0, pattern_width,
                                 num_draw_buffers * pattern_height);
        resolve_config.color_internalformat = GL_RGBA;
        resolve_fbo.setup(resolve_config);

        /* Create resolve_int_fbo to store downsampled integer draw buffer */
        if (color_buffer_zero_format == GL_RGBA8I) {
                resolve_config.color_internalformat = GL_RGBA8I;
                /* Assuming single integer buffer */
                resolve_config.height = pattern_height;
                resolve_int_fbo.setup(resolve_config);
                is_buffer_zero_integer_format = true;
        }
        else if (color_buffer_zero_format != GL_RGBA &&
                 color_buffer_zero_format != GL_NONE) {
                printf("Draw buffer zero format is not"
                       " supported by test functions.\n");
                piglit_report_result(PIGLIT_FAIL);
        }

        if (!piglit_check_gl_error(GL_NO_ERROR)) {
                printf("Error setting up frame buffer objects\n");
                piglit_report_result(PIGLIT_FAIL);
        }

        /* Query the number of samples used in ms_fbo. OpenGL implementation
         * may create FBO with more samples per pixel than what is requested.
         */
        glBindFramebuffer(GL_DRAW_FRAMEBUFFER, ms_fbo.handle);
        glGetIntegerv(GL_SAMPLES, &num_samples);

        /* Attach additional color buffers to multisample FBO with default
         * non-integer format (GL_RGBA.)
         */
        GLuint *color_rb = (GLuint *)malloc((num_draw_buffers - 1) *
                                            sizeof(GLuint));
        glGenRenderbuffers(num_draw_buffers - 1, color_rb);

        for (int i = 0; i < num_draw_buffers - 1; i++) {
                glBindRenderbuffer(GL_RENDERBUFFER, color_rb[i]);
                glRenderbufferStorageMultisample(GL_RENDERBUFFER,
                                        ms_fbo.config.num_samples,
                                        GL_RGBA,
                                        ms_fbo.config.width,
                                        ms_fbo.config.height);

                glFramebufferRenderbuffer(GL_DRAW_FRAMEBUFFER,
                                          GL_COLOR_ATTACHMENT0 + (i + 1),
                                          GL_RENDERBUFFER,
                                          color_rb[i]);
        }

        GLenum status = glCheckFramebufferStatus(GL_DRAW_FRAMEBUFFER);
        if (status != GL_FRAMEBUFFER_COMPLETE) {
                printf("Error attaching additional color buffers\n");
                piglit_report_result(PIGLIT_FAIL);
        }
        buffer_to_test = test_buffer;
        free(color_rb);
}