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/*
* Copyright 2018 The Emscripten Authors. All rights reserved.
* Emscripten is available under two separate licenses, the MIT license and the
* University of Illinois/NCSA Open Source License. Both these licenses can be
* found in the LICENSE file.
*/
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <emscripten/emscripten.h>
#include <emscripten/html5.h>
#include <GLES2/gl2.h>
#include <GLES3/gl3.h>
GLuint compile_shader(GLenum shaderType, const char *src)
{
GLuint shader = glCreateShader(shaderType);
glShaderSource(shader, 1, &src, NULL);
glCompileShader(shader);
GLint isCompiled = 0;
glGetShaderiv(shader, GL_COMPILE_STATUS, &isCompiled);
if (!isCompiled)
{
GLint maxLength = 0;
glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &maxLength);
char *buf = (char*)malloc(maxLength+1);
glGetShaderInfoLog(shader, maxLength, &maxLength, buf);
printf("%s\n", buf);
free(buf);
return 0;
}
return shader;
}
GLuint create_program(GLuint vertexShader, GLuint fragmentShader)
{
GLuint program = glCreateProgram();
glAttachShader(program, vertexShader);
glAttachShader(program, fragmentShader);
glBindAttribLocation(program, 0, "apos");
glBindAttribLocation(program, 1, "acolor");
glLinkProgram(program);
return program;
}
int main()
{
EmscriptenWebGLContextAttributes attr;
emscripten_webgl_init_context_attributes(&attr);
attr.majorVersion = 2;
EMSCRIPTEN_WEBGL_CONTEXT_HANDLE ctx = emscripten_webgl_create_context("#canvas", &attr);
emscripten_webgl_make_context_current(ctx);
static const char vertex_shader[] =
"#version 300 es\n"
"in vec4 apos;\n"
"in int idx;\n"
"struct S { vec4 color; };\n"
"uniform S colors[3];\n"
"out vec4 color;\n"
"void main() {\n"
"color = colors[idx].color;\n"
"gl_Position = apos;\n"
"}\n";
GLuint vs = compile_shader(GL_VERTEX_SHADER, vertex_shader);
static const char fragment_shader[] =
"#version 300 es\n"
"precision lowp float;\n"
"in vec4 color;\n"
"out vec4 fragColor;\n"
"void main() {\n"
"fragColor = color;\n"
"}\n";
GLuint fs = compile_shader(GL_FRAGMENT_SHADER, fragment_shader);
GLuint program = create_program(vs, fs);
glUseProgram(program);
struct P
{
float x, y;
int idx;
};
static const struct P pos_and_idx[] = {
{ -0.6f, -0.6f, 0 },
{ 0.6f, -0.6f, 1 },
{ 0.f, 0.6f, 2 }
};
GLuint vbo;
glGenBuffers(1, &vbo);
glBindBuffer(GL_ARRAY_BUFFER, vbo);
glBufferData(GL_ARRAY_BUFFER, sizeof(pos_and_idx), pos_and_idx, GL_STATIC_DRAW);
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 12, 0);
glVertexAttribIPointer(1, 1, GL_INT, 12, (void*)8);
glEnableVertexAttribArray(0);
glEnableVertexAttribArray(1);
float red[4] = { 1.0f, 0.f, 0.0f, 1.0f };
float green[4] = { 0.0f, 1.f, 0.0f, 1.0f };
float blue[4] = { 0.0f, 0.f, 1.0f, 1.0f };
int loc = glGetUniformLocation(program, "colors[0].color");
assert(loc >= 0);
glUniform4fv(loc, 1, red);
loc = glGetUniformLocation(program, "colors[1].color");
assert(loc >= 0);
glUniform4fv(loc, 1, green);
loc = glGetUniformLocation(program, "colors[2].color");
assert(loc >= 0);
glUniform4fv(loc, 1, blue);
glClearColor(0.3f,0.3f,0.3f,1);
glClear(GL_COLOR_BUFFER_BIT);
glDrawArrays(GL_TRIANGLES, 0, 3);
return 0;
}
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