multi_multi_thread.cpp

#include <glbinding/gl/gl.h>
#include <glbinding/glbinding.h>

#include <glfw_cpp/glfw_cpp.hpp>

#include <cmath>
#include <cstdlib>
#include <ctime>
#include <thread>

using namespace gl;    // from <glbinding/gl/g.h>

void window_thread(glfw_cpp::Window&& window)
{
    glfw_cpp::make_current(window.handle());
    glbinding::initialize(glfw_cpp::get_proc_address);

    const auto mul = 1.0F / static_cast<float>(std::rand() % 10 + 1);

    window.run([&, elapsed = 0.0F](const auto& events) mutable {
        events.visit(glfw_cpp::event::Overload{
            [&](const glfw_cpp::event::KeyPressed& e) {
                if (e.key == glfw_cpp::KeyCode::Q) {
                    window.request_close();
                }
            },
            [&](const glfw_cpp::event::FramebufferResized& e) { glViewport(0, 0, e.width, e.height); },
            [&](const auto&) { /* do nothing */ },
        });
        elapsed += (float)window.delta_time();

        // funny color cycle
        const auto r = (std::sin(mul * 23.0F / 8.0F * elapsed) + 1.0F) * 0.1F + 0.4F;
        const auto g = (std::cos(mul * 13.0F / 8.0F * elapsed) + 1.0F) * 0.2F + 0.3F;
        const auto b = (std::sin(mul * 41.0F / 8.0F * elapsed) + 1.5F) * 0.2F;

        glClearColor(r, g, b, 1.0F);
        glClear(GL_COLOR_BUFFER_BIT);
    });
}

int main()
{
    // forgive me for using rand and srand, I'm lazy :D
    std::srand(static_cast<unsigned>(std::time(nullptr)));

    auto glfw = glfw_cpp::init({});

    glfw->set_error_callback([](glfw_cpp::ErrorCode code, std::string_view msg) {
        fprintf(stderr, "glfw-cpp [%20s]: %s\n", to_string(code).data(), msg.data());
    });

    glfw->apply_hints({
        .api = glfw_cpp::api::OpenGL{
            .version_major = 3,
            .version_minor = 3,
            .profile       = glfw_cpp::gl::Profile::Core,
        },
    });

    auto window1 = glfw->create_window(800, 600, "Hello glfw-cpp 1");
    auto window2 = glfw->create_window(800, 600, "Hello glfw-cpp 2");
    auto window3 = glfw->create_window(800, 600, "Hello glfw-cpp 3");
    auto window4 = glfw->create_window(800, 600, "Hello glfw-cpp 4");

    auto thread1 = std::jthread{ window_thread, std::move(window1) };
    auto thread2 = std::jthread{ window_thread, std::move(window2) };
    auto thread3 = std::jthread{ window_thread, std::move(window3) };
    auto thread4 = std::jthread{ window_thread, std::move(window4) };

    while (glfw->has_window_opened()) {
        using glfw_cpp::operator""_fps;
        glfw->poll_events(120_fps);
    }
}