/*
 * Copyright (C) 2015 Ilia Mirkin
 *
 * 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.
 */

/**
 * \file draw.c
 *
 * Test that GL_EXT_polygon_offset_clamp actually applies the
 * clamp. The polygon is set up between z = 1 and z = 0.1 (so under
 * depth = 0.5).
 *
 * 1. Clear the depth buffer to 0.5 (leaving the depth func as LESS)
 * 2. Draw the polygon with red, clamping the offset to -0.05. This
 *    ensures that even the z=0.1 end (i.e. depth = 0.55) does not go
 *    below the value in the depth buffer.
 * 3. Draw the polygon again with green, clamping the offset at -0.51,
 *    ensuring that every point of the polygon can end up being offset to
 *    a depth value below 0.5.
 */

#include "piglit-util-gl.h"

GLint prog, color, zflip;

static const struct piglit_gl_test_config * piglit_config;
static const float blue[4] = {0, 0, 1, 1};
static const float red[4] = {1, 0, 0, 1};
static const float green[4] = {0, 1, 0, 1};

/* NOTE: It appears that at least nvidia hw will end up wrapping around if the
 * final z value goes below 0 (or something). This can come up when testing
 * without the clamp.
 */

static enum piglit_result
test_negative_clamp(void * unused)
{
	bool pass = true;

	/* Draw red rectangle that slopes between 1 and 0.1. Use a
	 * polygon offset with a high factor but small clamp
	 */
	glPolygonOffsetClampEXT(-1000, 0, -0.05);
	glUniform4fv(color, 1, red);
	glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
	if (!piglit_probe_rect_rgba(0, 0, piglit_width, piglit_height, blue)) {
		printf("  FAIL: red rect peeks over blue rect\n");
		pass = false;
	}

	/* And now set the clamp such that all parts of the polygon
	 * can pass the depth test.
	 */
	glPolygonOffsetClampEXT(-1000, 0, -0.51);
	glUniform4fv(color, 1, green);
	glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
	if (!piglit_probe_rect_rgba(0, 0, piglit_width, piglit_height, green)) {
		printf("  FAIL: green rect does not cover blue rect\n");
		pass = false;
	}

	return pass ? PIGLIT_PASS : PIGLIT_FAIL;
}

static enum piglit_result
test_positive_clamp(void * unused)
{
	bool pass = true;

	/* Now try this again with the inverse approach and a positive
	 * clamp value. The polygon will now slope between -1 and
	 * -0.1. Everything is reversed, so just negate all the
	 * previous values.
	 */

	glUniform1f(zflip, -1.0);
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glDepthFunc(GL_GREATER);

	glPolygonOffsetClampEXT(1000, 0, 0.05);
	glUniform4fv(color, 1, red);
	glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
	if (!piglit_probe_rect_rgba(0, 0, piglit_width, piglit_height, blue)) {
		printf("  FAIL: red rect peeks over blue rect\n");
		pass = false;
	}

	/* And now set the clamp so that all parts of the polygon pass
	 * the depth test.
	 */
	glPolygonOffsetClampEXT(1000, 0, 0.51);
	glUniform4fv(color, 1, green);
	glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
	if (!piglit_probe_rect_rgba(0, 0, piglit_width, piglit_height, green)) {
		printf("  FAIL: green rect does not cover blue rect\n");
		pass = false;
	}

	return pass ? PIGLIT_PASS : PIGLIT_FAIL;
}

static const struct piglit_subtest tests[] = {
	{
		"negative clamp",
		"neg_clamp",
		test_negative_clamp,
		NULL
	},
	{
		"positive clamp",
		"pos_clamp",
		test_positive_clamp,
		NULL
	},
	{ NULL }
};

PIGLIT_GL_TEST_CONFIG_BEGIN
	piglit_config = &config;
	config.subtests = tests;
#if PIGLIT_USE_OPENGL
	config.supports_gl_compat_version = 21;
#else
	config.supports_gl_es_version = 20;
#endif
	config.window_visual = PIGLIT_GL_VISUAL_RGB | PIGLIT_GL_VISUAL_DEPTH | PIGLIT_GL_VISUAL_DOUBLE;

PIGLIT_GL_TEST_CONFIG_END

enum piglit_result
piglit_display(void)
{
	glUseProgram(prog);

	glViewport(0, 0, piglit_width, piglit_height);
	glEnable(GL_DEPTH_TEST);
	glEnable(GL_POLYGON_OFFSET_FILL);

	glUniform1f(zflip, 1.0);
	glClearColor(0, 0, 1, 1);
#ifdef PIGLIT_USE_OPENGL
	glClearDepth(0.5);
#else
	glClearDepthf(0.5);
#endif
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

	enum piglit_result result = PIGLIT_PASS;
	result = piglit_run_selected_subtests(
		tests,
		piglit_config->selected_subtests,
		piglit_config->num_selected_subtests,
		result);
	piglit_present_results();

	return result;
}

void
piglit_init(int argc, char **argv)
{
	static const float verts[4][4] = {
		/* x   y   z   w */
		{ -1, -1, 1.0, 1 },
		{  1, -1, 1.0, 1 },
		{ -1,  1, 0.1, 1 },
		{  1,  1, 0.1, 1 }
	};

	GLuint bo;

	piglit_require_extension("GL_EXT_polygon_offset_clamp");

	prog = piglit_build_simple_program(
#ifdef PIGLIT_USE_OPENGL
			"#version 120\n"
#else
			"#version 100\n"
			"attribute vec4 vertex;\n"
			"#define gl_Vertex vertex\n"
#endif
			"uniform float zflip;\n"
			"void main() { gl_Position = gl_Vertex * vec4(1, 1, zflip, 1); }\n",

#ifdef PIGLIT_USE_OPENGL
			"#version 120\n"
#else
			"#version 100\n"
			"precision highp float;\n"
#endif
			"uniform vec4 color;\n"
			"void main() { gl_FragColor = color; }\n");
	color = glGetUniformLocation(prog, "color");
	zflip = glGetUniformLocation(prog, "zflip");

	glEnableVertexAttribArray(0);
	glGenBuffers(1, &bo);
	glBindBuffer(GL_ARRAY_BUFFER, bo);
	glBufferData(GL_ARRAY_BUFFER, sizeof(verts), verts, GL_STATIC_DRAW);
	glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, (GLvoid const *)0);
}