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emscripten glfw3 or webgl sample
CMAKE_MINIMUM_REQUIRED(VERSION 3.0.0)
PROJECT(em_gl VERSION 0.1.0)
LINK_DIRECTORIES(
$ENV{VCPKG_ROOT}/installed/x64-windows/lib
)
FILE(GLOB SRC
*.cpp
*.h
)
ADD_EXECUTABLE(${PROJECT_NAME} ${SRC})
TARGET_INCLUDE_DIRECTORIES(${PROJECT_NAME} PUBLIC
$ENV{VCPKG_ROOT}/installed/x64-windows/include
${CMAKE_CURRENT_LIST_DIR}/../emsdk/fastcomp/emscripten/system/include
)
TARGET_LINK_LIBRARIES(${PROJECT_NAME}
glad
glfw3dll
)
// emcc main.cpp -o index.html -s USE_WEBGL2=1 -s USE_GLFW=3 -s WASM=1 -std=c++1z
// base: https://www.glfw.org/docs/latest/quick.html#quick_example
// ref: https://gist.github.com/SuperV1234/5c5ad838fe5fe1bf54f9
#include <functional>
#include <vector>
#ifdef __EMSCRIPTEN__
#include <emscripten.h>
#define GL_GLEXT_PROTOTYPES
#define EGL_EGLEXT_PROTOTYPES
#else
#include <glad/glad.h>
#endif
#include <GLFW/glfw3.h>
#include "linmath.h"
#include <stdlib.h>
#include <stdio.h>
static const struct
{
float x, y;
float r, g, b;
} vertices[3] =
{
{-0.6f, -0.4f, 1.f, 0.f, 0.f},
{0.6f, -0.4f, 0.f, 1.f, 0.f},
{0.f, 0.6f, 0.f, 0.f, 1.f}};
static const char *vertex_shader_text =
"uniform mat4 MVP;\n"
"attribute vec3 vCol;\n"
"attribute vec2 vPos;\n"
"varying vec3 color;\n"
"void main()\n"
"{\n"
" gl_Position = MVP * vec4(vPos, 0.0, 1.0);\n"
" color = vCol;\n"
"}\n";
static const char *fragment_shader_text =
"precision mediump float;\n"
"varying vec3 color;\n"
"void main()\n"
"{\n"
" gl_FragColor = vec4(color, 1.0);\n"
"}\n";
static void error_callback(int error, const char *description)
{
fprintf(stderr, "Error: %s\n", description);
}
static void key_callback(GLFWwindow *window, int key, int scancode, int action, int mods)
{
if (key == GLFW_KEY_ESCAPE && action == GLFW_PRESS)
glfwSetWindowShouldClose(window, GLFW_TRUE);
}
std::function<void()> loop;
void main_loop() { loop(); }
void check_error(GLuint shader)
{
GLint result;
glGetShaderiv(shader, GL_COMPILE_STATUS, &result);
if (result == GL_FALSE)
{
GLint log_length;
glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &log_length);
std::vector<GLchar> log(log_length);
GLsizei length;
glGetShaderInfoLog(shader, log.size(), &length, log.data());
error_callback(0, log.data());
}
}
int main(void)
{
GLint mvp_location, vpos_location, vcol_location;
glfwSetErrorCallback(error_callback);
if (!glfwInit())
exit(EXIT_FAILURE);
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 2);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0);
auto window = glfwCreateWindow(640, 480, "Simple example", NULL, NULL);
if (!window)
{
glfwTerminate();
exit(EXIT_FAILURE);
}
glfwSetKeyCallback(window, key_callback);
glfwMakeContextCurrent(window);
#ifdef __EMSCRIPTEN__
#else
gladLoadGL();
#endif
glfwSwapInterval(1);
// NOTE: OpenGL error checks have been omitted for brevity
GLuint vertex_buffer;
glGenBuffers(1, &vertex_buffer);
glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
auto vertex_shader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertex_shader, 1, &vertex_shader_text, NULL);
glCompileShader(vertex_shader);
check_error(vertex_shader);
auto fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragment_shader, 1, &fragment_shader_text, NULL);
glCompileShader(fragment_shader);
check_error(fragment_shader);
auto program = glCreateProgram();
glAttachShader(program, vertex_shader);
glAttachShader(program, fragment_shader);
glLinkProgram(program);
mvp_location = glGetUniformLocation(program, "MVP");
vpos_location = glGetAttribLocation(program, "vPos");
vcol_location = glGetAttribLocation(program, "vCol");
glEnableVertexAttribArray(vpos_location);
glVertexAttribPointer(vpos_location, 2, GL_FLOAT, GL_FALSE,
sizeof(vertices[0]), (void *)0);
glEnableVertexAttribArray(vcol_location);
glVertexAttribPointer(vcol_location, 3, GL_FLOAT, GL_FALSE,
sizeof(vertices[0]), (void *)(sizeof(float) * 2));
loop = [&] {
float ratio;
int width, height;
mat4x4 m, p, mvp;
glfwGetFramebufferSize(window, &width, &height);
ratio = width / (float)height;
glViewport(0, 0, width, height);
glClear(GL_COLOR_BUFFER_BIT);
mat4x4_identity(m);
mat4x4_rotate_Z(m, m, (float)glfwGetTime());
mat4x4_ortho(p, -ratio, ratio, -1.f, 1.f, 1.f, -1.f);
mat4x4_mul(mvp, p, m);
glUseProgram(program);
glUniformMatrix4fv(mvp_location, 1, GL_FALSE, (const GLfloat *)mvp);
glDrawArrays(GL_TRIANGLES, 0, 3);
glfwSwapBuffers(window);
glfwPollEvents();
};
#ifdef __EMSCRIPTEN__
emscripten_set_main_loop(main_loop, 0, true);
#else
while (!glfwWindowShouldClose(window))
main_loop();
#endif
glfwDestroyWindow(window);
glfwTerminate();
exit(EXIT_SUCCESS);
}
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