msaa: Rewrite sample-alpha-to-coverage test to utilize the shared code

Lot of the functions defined in this test case are also shared by
draw-buffers-common.cpp. So this refactoring is done to avoid code
duplication.

Reviewed-by: Paul Berry<stereotype441@gmail.com>

2 files changed, 49 insertions, 326 deletions

diff --git a/tests/spec/ext_framebuffer_multisample/CMakeLists.gl.txt b/tests/spec/ext_framebuffer_multisample/CMakeLists.gl.txt
index cdf1db4d4..36b680056 100644
--- a/tests/spec/ext_framebuffer_multisample/CMakeLists.gl.txt
+++ b/tests/spec/ext_framebuffer_multisample/CMakeLists.gl.txt
@@ -48,7 +48,8 @@ piglit_add_executable (ext_framebuffer_multisample-renderbuffer-samples renderbu
 piglit_add_executable (ext_framebuffer_multisample-renderbufferstorage-samples renderbufferstorage-samples.c)
 piglit_add_executable (ext_framebuffer_multisample-samples samples.c)
 piglit_add_executable (ext_framebuffer_multisample-sample-coverage common.cpp sample-coverage.cpp)
-piglit_add_executable (ext_framebuffer_multisample-sample-alpha-to-coverage common.cpp sample-alpha-to-coverage.cpp)
+piglit_add_executable (ext_framebuffer_multisample-sample-alpha-to-coverage common.cpp
+		       draw-buffers-common.cpp sample-alpha-to-coverage.cpp)
 piglit_add_executable (ext_framebuffer_multisample-sample-alpha-to-one common.cpp sample-alpha-to-one.cpp)
 piglit_add_executable (ext_framebuffer_multisample-turn-on-off common.cpp turn-on-off.cpp)
 piglit_add_executable (ext_framebuffer_multisample-unaligned-blit common.cpp unaligned-blit.cpp)
diff --git a/tests/spec/ext_framebuffer_multisample/sample-alpha-to-coverage.cpp b/tests/spec/ext_framebuffer_multisample/sample-alpha-to-coverage.cpp
index 28ae63304..b8ccf5de1 100644
--- a/tests/spec/ext_framebuffer_multisample/sample-alpha-to-coverage.cpp
+++ b/tests/spec/ext_framebuffer_multisample/sample-alpha-to-coverage.cpp
@@ -21,311 +21,45 @@
  * IN THE SOFTWARE.
  */
 
-#include "common.h"
+#include "draw-buffers-common.h"
 
 /**
  * \file sample-alpha-to-coverage.cpp
  *
- * Verify GL_SAMPLE_ALPHA_TO_COVERAGE with multisample FBO.
+ * Verify sample alpha to coverage with multisample FBO
  *
- * This test operates by drawing a test pattern to multisample_fbo with
- * GL_SAMPLE_ALPHA_TO_COVERAGE disabled.
+ * When rendering to multiple draw buffers, fragment's alpha value should be
+ * used to determine the coverage value.
  *
- * Blit the multisample_fbo to top half of window system framebuffer. This
- * is used as reference image to visually compare the difference caused by
- * sample alpha to coverage value.
+ * This test operates by drawing a pattern in multisample FBO to generate
+ * reference and test image. Reference image is drawn to right half of window
+ * system frame buffer and test image to left half.
  *
- * Compute the expected color values based on the coverage value used to
- * draw the test pattern.
+ * Compute the expected color / depth values.
  *
- * Clear the multisample framebuffer to a unique color. Draw the same test
- * pattern in multisample buffer with GL_SAMPLE_ALPHA_TO_COVERAGE enabled.
- * Resolve the multisample FBO by  blitting it to a single sample FBO. Blit
- * the resolve_fbo to bottom half of window system framebuffer. This is our
- * test image.
- *
- * Probe the rectangles in bottom half of window system framebuffer and
- * compare 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.
- *
- * Repeat the above testing with GL_SAMPLE_ALPHA_TO_ONE enabled / disabled.
- * when both GL_SAMPLE_ALPHA_TO_ONE and GL_SAMPLE_ALPHA_TO_COVERAGE are
- * enabled, GL_SAMPLE_ALPHA_TO_COVERAGE takes effect first. i.e. the
- * coverage value is computed from the alpha value before the alpha value
- * is changed to 1.
- *
- * Note: glSampleCoverage() takes effect in the graphics pipeline before
- * the point where the output of the fragment shader is split into the
- * various buffers. So it's very likely that if glSampleCoverage() works
- * properly for color buffers, it will work properly for depth and stencil
- * buffers too.
+ * Probe color / depth buffer blitted to downsampled FBO (resolve_fbo) and
+ * compare against expected color values.
  *
  * Author: Anuj Phogat <anuj.phogat@gmail.com>
  */
 
 PIGLIT_GL_TEST_MAIN(512 /*window_width*/,
-		    256 /*window_height*/,
+		    768 /*window_height*/,
 		    GLUT_DOUBLE | GLUT_RGBA | GLUT_ALPHA)
 
-const int pattern_width = 512; const int pattern_height = 128;
-static Fbo ms_fbo, resolve_fbo;
-static GLbitfield buffer_to_test;
-
-static float *coverage = NULL;
-static float *color = NULL;
-static float *expected = NULL;
-
-static int num_samples;
-static int num_rects;
-static int prog;
-static int color_loc;
-static int depth_loc;
-
-static const float bg_color[4] = { 0.4, 0.6, 0.0, 0.8 };
-
-static const char *vert =
-	"#version 130\n"
-	"in 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, depth, 1.0);\n"
-	"}\n";
-
-static const char *frag =
-	"#version 130\n"
-	"uniform vec4 color;\n"
-	"void main()\n"
-	"{\n"
-	"  gl_FragColor = color;\n"
-	"}\n";
-
-void
-shader_compile()
-{
-	/* Compile program */
-	GLint vs = piglit_compile_shader_text(GL_VERTEX_SHADER, vert);
-	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);
-	}
-
-	glBindAttribLocation(prog, 0, "pos");
-	glEnableVertexAttribArray(0);
-
-	/* Set up uniforms */
-	glUseProgram(prog);
-	color_loc = glGetUniformLocation(prog, "color");
-	depth_loc = glGetUniformLocation(prog, "depth");
-}
-
-void
-draw_pattern(bool sample_alpha_to_coverage, bool sample_alpha_to_one)
-{
-	glUseProgram(prog);
-	glClearColor(bg_color[0], bg_color[1],
-		     bg_color[2], bg_color[3]);
-	glClear(buffer_to_test);
-
-	if (sample_alpha_to_coverage)
-		glEnable (GL_SAMPLE_ALPHA_TO_COVERAGE);
-
-	if (sample_alpha_to_one)
-		glEnable (GL_SAMPLE_ALPHA_TO_ONE);
-
-	unsigned int indices[6] = {0, 1, 2, 0, 2, 3};
-
-	for (int i = 0; i < num_rects; ++i) {
-
-		float vertex_data[4][2] = {
-		{ 0.0f + i * (pattern_width / num_rects),   0.0f	   },
-		{ 0.0f + i * (pattern_width / num_rects),   pattern_height },
-		{ (i + 1.0f) * (pattern_width / num_rects), pattern_height },
-		{ (i + 1.0f) * (pattern_width / num_rects), 0.0f	   } };
-
-		glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE,
-				      sizeof(vertex_data[0]),
-				      (void *) vertex_data);
-
-		glUniform4fv(color_loc, 1, (color + i * 4));
-		glUniform1f(depth_loc, 0.0f);
-		glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT,
-			       (void *) indices);
-	}
-	if (sample_alpha_to_coverage)
-		glDisable (GL_SAMPLE_ALPHA_TO_COVERAGE);
-
-	if (sample_alpha_to_one)
-		glDisable (GL_SAMPLE_ALPHA_TO_ONE);
-}
-
 void
 print_usage_and_exit(char *prog_name)
 {
-	printf("Usage: %s <num_samples>\n", prog_name);
+        printf("Usage: %s <num_samples>\n", prog_name);
 	piglit_report_result(PIGLIT_FAIL);
 }
 
 void
-compute_expected(bool sample_alpha_to_one)
-{
-	int i, j;
-
-	/* Sample alpha to coverage doesn't affect single sample FBO */
-	if(num_samples == 0) {
-		for(i = 0; i < 4; i++)
-			expected[i] = color[i];
-		return;
-	}
-
-	/* Fragment's alpha value is directly used as coverage value */
-	for (i = 0; i < num_rects; i++)
-		coverage[i] = color[i * 4 + 3];
-
-	/* 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 will be blended
-	 * with the background color which will be 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."
-	 */
-	if(buffer_to_test == GL_COLOR_BUFFER_BIT) {
-		for (i = 0; i < num_rects; i++) {
-
-			float samples_used = coverage[i] * num_samples;
-			/* Exepected color values are computed only for integer
-			 * number of samples_used
-			 */
-			if(samples_used == (int)samples_used) {
-
-				for(j =0; j < 4; j++)
-					expected[i * 4 + j] =
-					color[i * 4 + j] * coverage[i] +
-					bg_color[j] * (1 - coverage[i]);
-
-				if (sample_alpha_to_one)
-					expected[i * 4 + 3] =
-					1.0 * coverage[i] +
-					bg_color[3] * (1 - coverage[i]);
-			}
-		}
-	}
-}
-
-bool
-probe_framebuffer_color(bool sample_alpha_to_one)
-{
-	bool result = true;
-	glBindFramebuffer(GL_READ_FRAMEBUFFER, 0);
-
-	for (int i = 0; i < num_rects; i++) {
-		float samples_used = coverage[i] * num_samples;
-
-		/* Only probe rectangles with coverage value which is a strict
-		 *  multiple of 1 / num_samples.
-		 */
-		if(samples_used == (int)samples_used) {
-			result = piglit_probe_rect_rgba(
-				 i * (pattern_width / num_rects),
-				 0,
-				 pattern_width / num_rects,
-				 pattern_height,
-				 expected + i * 4)
-				 && result;
-		}
-	}
-	return result;
-}
-
-bool
-test_sample_alpha_to_coverage(bool sample_alpha_to_one)
-{
-	bool result = true;
-	compute_expected(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);
-	draw_pattern(true /* sample_alpha_to_coverage */ , sample_alpha_to_one);
-
-	/* Blit ms_fbo to resolve_fbo to resolve multisample buffer */
-	glBindFramebuffer(GL_READ_FRAMEBUFFER, ms_fbo.handle);
-	glBindFramebuffer(GL_DRAW_FRAMEBUFFER, resolve_fbo.handle);
-	glBlitFramebuffer(0, 0, pattern_width, pattern_height,
-			  0, 0, pattern_width, pattern_height,
-			  buffer_to_test, GL_NEAREST);
-
-	/* Blit resolve_fbo to the bottom half of window system framebuffer.
-	 * This is the test image.
-	 */
-	glBindFramebuffer(GL_READ_FRAMEBUFFER, resolve_fbo.handle);
-	glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);
-	glBlitFramebuffer(0, 0, pattern_width, pattern_height,
-			  0, 0, pattern_width, pattern_height,
-			  buffer_to_test, GL_NEAREST);
-
-	/* Probe the bottom half of default framebuffer and compare to the
-	 * expected values */
-	if (buffer_to_test == GL_COLOR_BUFFER_BIT)
-		result = probe_framebuffer_color(sample_alpha_to_one) && result;
-
-	result = piglit_check_gl_error(GL_NO_ERROR) && result;
-	return result;
-}
-
-void
-allocate_data_arrays(void)
-{
-	/* Draw 2N + 1 rectangles for N samples, each with a unique color
-	 * and coverage value
-	 */
-	num_rects = 2 * num_samples + 1;
-
-	/* Allocate data arrays based on number of samples used */
-	color = (float *) malloc(num_rects * 4 * sizeof(float));
-	coverage = (float *) malloc(num_rects * sizeof(float));
-	expected = (float *) malloc(num_rects * 4 * sizeof(float));
-
-	for(int i = 0; i < num_rects; i++) {
-		color[i * 4 + 0] = (sin((float)(i * 4 + 0)) + 1) / 2;
-		color[i * 4 + 1] = (sin((float)(i * 4 + 1)) + 1) / 2;
-		color[i * 4 + 2] = (sin((float)(i * 4 + 2)) + 1) / 2;
-
-		/* Alpha value will be used as coverage */
-		color[i * 4 + 3] = i * (1.0 / (2 * num_samples));
-	}
-}
-
-void
-free_data_arrays(void)
-{
-	if(color != NULL) {
-		free(color);
-		color = NULL;
-	}
-	if(coverage != NULL) {
-		free(coverage);
-		coverage = NULL;
-	}
-	if(expected != NULL) {
-		free(expected);
-		expected = NULL;
-	}
-}
-
-void
 piglit_init(int argc, char **argv)
 {
 	int samples;
+	int num_attachments = 1;
+
 	if (argc < 2)
 		print_usage_and_exit(argv[0]);
 	{
@@ -336,7 +70,13 @@ piglit_init(int argc, char **argv)
 	}
 
 	piglit_require_gl_version(30);
-	piglit_ortho_projection(pattern_width, pattern_height, GL_TRUE);
+
+	int pattern_width = piglit_width / 2;
+	int pattern_height = piglit_height / num_attachments;
+
+	piglit_ortho_projection(pattern_width,
+				pattern_height,
+				GL_TRUE);
 
 	/* Skip the test if samples > GL_MAX_SAMPLES */
 	GLint max_samples;
@@ -345,24 +85,12 @@ piglit_init(int argc, char **argv)
 	if (samples > max_samples)
 		piglit_report_result(PIGLIT_SKIP);
 
-	/* Setup frame buffer objects with required configuration */
-	ms_fbo.setup(FboConfig(samples, pattern_width, pattern_height));
-	resolve_fbo.setup(FboConfig(0, pattern_width, pattern_height));
-
-        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.
-	 */
-	glBindRenderbuffer(GL_RENDERBUFFER, ms_fbo.color_rb);
-	glGetRenderbufferParameteriv(GL_RENDERBUFFER,
-				     GL_RENDERBUFFER_SAMPLES,
-				     &num_samples);
-
-	buffer_to_test = GL_COLOR_BUFFER_BIT;
+	ms_fbo_and_draw_buffers_setup(samples,
+				      pattern_width,
+				      pattern_height,
+				      num_attachments,
+				      GL_COLOR_BUFFER_BIT,
+				      GL_RGBA);
 	shader_compile();
 }
 
@@ -370,43 +98,37 @@ enum piglit_result
 piglit_display()
 {
 	bool pass = true;
-	allocate_data_arrays();
-
 	glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);
 	glClearColor(0.0, 0.0, 0.0, 1.0);
-	glClear(buffer_to_test);
+	glClear(GL_COLOR_BUFFER_BIT);
+	allocate_data_arrays();
 
-	/* Draw test pattern in multisample ms_fbo with
-	 * GL_SAMPLE_ALPHA_TO_COVERAGE disabled.
+	/* Reference image drawn when sample_alpha_to_coverage is enabled,
+	 * doesn't represent an expected image. Reference image is drawn only
+	 * to visualize the image difference caused by enabling
+	 * sample_alpha_to_coverage
 	 */
-	glBindFramebuffer(GL_DRAW_FRAMEBUFFER, ms_fbo.handle);
-	ms_fbo.set_viewport();
-	draw_pattern(false /* sample_alpha_to_coverage */,
-		     false /* sample_alpha_to_one */ );
+	draw_reference_image(true /* sample_alpha_to_coverage */,
+			     false /* sample_alpha_to_one */);
 
-	/* Blit ms_fbo to the top half of window system framebuffer. This
-	 * is our reference image to visually compare the effect of MSAA
-	 * with sample alpha to coverage.
-	 */
-	glBindFramebuffer(GL_READ_FRAMEBUFFER, ms_fbo.handle);
-	glBindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);
-	glBlitFramebuffer(0, 0,
-			  pattern_width, pattern_height,
-			  0, pattern_height,
-			  pattern_width, 2 * pattern_height,
-			  buffer_to_test, GL_NEAREST);
+	draw_test_image(true /* sample_alpha_to_coverage */,
+			false /* sample_alpha_to_one */);
 
-	/* Test with sample_alpha_to_one = false */
-	pass = test_sample_alpha_to_coverage(false) && pass;
+	pass = piglit_check_gl_error(GL_NO_ERROR) && pass;
 
-	/* Test sample alpha to coverage with sample_alpha_to_one = true */
-	pass = test_sample_alpha_to_coverage(true) && pass;
+	/* Probe all the test image blitted to resolve fbo and compare with
+	 * expected color values.  This method of verification is appropriate
+	 * for tests with sample-alpha-to-coverage enabled. Possibility of
+	 * dithering effect when the coverage value is not a strict multiple
+	 * of 1 / num_samples makes image compare (test / reference image)
+	 * unsuitable for this test.
+	 */
+	pass = probe_framebuffer_color() && pass;
 
 	/* Free the memory allocated for data arrays */
 	free_data_arrays();
 
-	if (!piglit_automatic &&
-	    buffer_to_test != GL_DEPTH_BUFFER_BIT)
+	if (!piglit_automatic)
 		piglit_present_results();
 
 	return pass ? PIGLIT_PASS : PIGLIT_FAIL;