Attachment 123239 Details for Bug 95130 – Test program

Test program

colour_derivatives.cc (text/plain), 3.46 KB, created by James Legg on 2016-04-25 11:26:46 UTC

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Creator: James Legg

Created: 2016-04-25 11:26:46 UTC

Size: 3.46 KB

patch

obsolete

>// Compile with c++ -std=c++14 [filepath] -Wall $(pkg-config --cflags --libs sdl2 gl)
>
>#define GL_GLEXT_PROTOTYPES
>#include <GL/gl.h>
>#include <SDL.h>
>#include <SDL_video.h>
>#include <cassert>
>#include <cstdlib>
>#include <iostream>
>#include <memory>
>
>namespace
>{
>const GLchar * const vertex_shader_source =
>R"(
>#version 130
>
>uniform float rotation;
>
>void main()
>{
>	// Draw a triangle.
>	// Avoid having edges aligned to even numbered pixels so all
>	// edges reproduce the bug.
>	float angle = float(gl_VertexID) * 2.094395102 + rotation;
>	gl_Position = vec4(sin(angle), -cos(angle), 0.5, 1.0);
>
>	// Constant across triangle
>	gl_FrontColor = vec4(0.5);
>	
>}
>)";
>
>const GLchar * const fragment_shader_source =
>R"(
>#version 130
>#extension GL_ARB_explicit_attrib_location : enable
>layout(location = 0) out vec4 colour;
>
>void main()
>{
>	// gl_Color is constant, so the derivative should be 0, but it is not at
>	// the edges of the triangle.
>	// The bug also reproduces with gl_FrontSecondaryColor in the vertex
>	// shader and gl_SecondaryColor here.
>	colour = fwidth(gl_Color);
>}
>)";
>
>void attach_shader(GLuint program, const char * const source, GLenum type)
>{
>	const GLuint shader = glCreateShader(type);
>	glShaderSource(shader, 1, const_cast<const GLchar**>(&source), 0);
>	glCompileShader(shader);
>	GLint is_compiled;
>	glGetShaderiv(shader, GL_COMPILE_STATUS, &is_compiled);
>	if (is_compiled == GL_FALSE)
>	{
>		GLint max_length;
>		glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &max_length);
>		const auto info_log = std::make_unique<char[]>(max_length);
>		glGetShaderInfoLog(shader, max_length, &max_length, info_log.get());
>		std::cerr << "Error compiling vertex shader:\n"
>		          << info_log.get();
>		std::exit(1);
>	}
>	glAttachShader(program, shader);
>	glDeleteShader(shader);
>}
>
>}
>
>int main()
>{
>	SDL_Init(SDL_INIT_VIDEO);
>	SDL_Window * const window = SDL_CreateWindow(
>		"Test",
>		SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 256, 256,
>		SDL_WINDOW_OPENGL);
>	if (!window)
>	{
>		std::cerr << "Could not create window: "
>		          << SDL_GetError() << '\n';
>		return 1;
>	}
>
>	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 2);
>	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 1);
>	SDL_GLContext gl_context = SDL_GL_CreateContext(window);
>	if (gl_context == NULL)
>	{
>		std::cerr << "Could not create OpenGL 2.1 context: "
>		          << SDL_GetError() << '\n';
>		return 1;
>	}
>
>	// Since we only write the front colour, be certain the back colour
>	// won't be used.
>	glEnable(GL_CULL_FACE);
>
>	GLuint vertex_array;
>	glGenVertexArrays(1, &vertex_array);
>	glBindVertexArray(vertex_array);
>
>	const GLuint program = glCreateProgram();
>	attach_shader(program, fragment_shader_source, GL_FRAGMENT_SHADER);
>	attach_shader(program, vertex_shader_source, GL_VERTEX_SHADER);
>	glLinkProgram(program);
>	GLint is_linked;
>	glGetProgramiv(program, GL_LINK_STATUS, &is_linked);
>	if (is_linked == GL_FALSE)
>	{
>		GLint max_length;
>		glGetProgramiv(program, GL_INFO_LOG_LENGTH, &max_length);
>		const auto info_log = std::make_unique<char[]>(max_length);
>		glGetProgramInfoLog(program, max_length, &max_length, info_log.get());
>		std::cerr << "Error linking shader:\n"
>		          << info_log.get();
>		return 1;
>	}
>	glUseProgram(program);
>
>	// Draw a triangle rotating for a while, then pause.
>	for (unsigned int i = 0; i < 120; i++)
>	{
>		glClear(GL_COLOR_BUFFER_BIT);
>		glUniform1f(0, i * 0.02);
>		glDrawArrays(GL_TRIANGLES,  0, 3);
>		SDL_GL_SwapWindow(window);
>	}
>	SDL_Delay(1500);
>
>	SDL_GL_DeleteContext(gl_context);
>	SDL_DestroyWindow(window);
>	SDL_Quit();
>}
>

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Attachments on bug 95130: 123239 | 123240 | 123241

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