opengl_timing_example/main.cpp

#ifdef __APPLE__
    #include <OpenGL/gl.h>
    #include <OpenGL/gl3.h>
    #include <GLUT/glut.h>
#else
    #include <GL/glew.h>
    #include <GL/glut.h>
#endif
#include <chrono>
#include <cstdlib>
#include <iostream>
#include <string>
#include <arpa/inet.h>
#include <unistd.h>
#include "json/single_include/nlohmann/json.hpp"
#include <mutex>
#include <thread>
#include <condition_variable>

using namespace std;
using namespace std::chrono;
using namespace nlohmann;

volatile int DISPLAY_DURATION = 2000;
const int PORT = 8081;

steady_clock::time_point startTime;
bool shouldDisplayQuad = false;
mutex quadMutex;
condition_variable quadCondVar;

void displayQuad() {
    glClear(GL_COLOR_BUFFER_BIT);
    glEnable(GL_TEXTURE_2D);
    glViewport(0, 0, 500, 500);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(-1.0, 1.0, -1.0, 1.0, -1.0, 1.0);

    auto currentTime = steady_clock::now();
    auto elapsedTime = duration_cast<milliseconds>(currentTime - startTime).count();

    bool localShouldDisplayQuad;
    {
        unique_lock<mutex> lock(quadMutex);
        quadCondVar.wait(lock, [&] { return shouldDisplayQuad; });
        localShouldDisplayQuad = shouldDisplayQuad;
    }
    if (localShouldDisplayQuad && elapsedTime < DISPLAY_DURATION) {
        glColor3f(1.0f, 0.0f, 0.0f);
    } else {
        glColor3f(0.0f, 0.0f, 0.0f);
    }

    glBegin(GL_QUADS);
    glVertex2f(-0.5f, -0.5f);
    glVertex2f(-0.5f, 0.5f);
    glVertex2f(0.5f, 0.5f);
    glVertex2f(0.5f, -0.5f);
    glEnd();

    glutSwapBuffers();
}

void timer(int value) {
    glutPostRedisplay();
    glutTimerFunc(1, timer, 0);
}

void handleTCPConnection(int serverSocket) {
    struct sockaddr_in clientAddr;
    socklen_t clientAddrLen = sizeof(clientAddr);

    int clientSocket = accept(serverSocket, (struct sockaddr*)&clientAddr, &clientAddrLen);
    if (clientSocket < 0) {
        cerr << "Error accepting client connection" << endl;
        return;
    }

    char buffer[1024] = {0};
    int bytesRead = recv(clientSocket, buffer, sizeof(buffer) - 1, 0);
    if (bytesRead < 0) {
        cerr << "Error reading from client socket" << endl;
        close(clientSocket);
        return;
    }

    string jsonString(buffer, bytesRead);
    try {
        json jsonData = json::parse(jsonString);
        cout << "Received JSON: " << jsonData << endl;

        if (jsonData.contains("rgb")) {
            DISPLAY_DURATION = jsonData["rgb"];
            cout << "Set exposure time to " << DISPLAY_DURATION << "ms" << endl;
        }

        {
            lock_guard<mutex> lock(quadMutex);
            shouldDisplayQuad = true;
            startTime = steady_clock::now();
            quadCondVar.notify_all();
        }
    } catch (const exception& e) {
        cerr << "Error parsing JSON: " << e.what() << endl;
    }

    close(clientSocket);
}

void runTCPServer(int serverSocket) {
    while (true) {
        handleTCPConnection(serverSocket);
    }
}

int main(int argc, char** argv) {
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
    glutInitWindowSize(500, 500);
    glutCreateWindow("Red Quad");

    glutDisplayFunc(displayQuad);
    glutTimerFunc(0, timer, 0);
    
    startTime = steady_clock::now();

    int serverSocket = socket(AF_INET, SOCK_STREAM, 0);
    if (serverSocket < 0) {
        cerr << "Error creating socket" << endl;
        return 1;
    }

    struct sockaddr_in serverAddr;
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_addr.s_addr = INADDR_ANY;
    serverAddr.sin_port = htons(PORT);

    int bindResult = ::bind(serverSocket, reinterpret_cast<struct sockaddr*>(&serverAddr), sizeof(serverAddr));
    if (bindResult < 0) {
        std::cerr << "Error binding socket" << std::endl;
        close(serverSocket);
        return 1;
    }

    if (listen(serverSocket, 5) < 0) {
        cerr << "Error listening on socket" << endl;
        return 1;
    }

    cout << "TCP server listening on port " << PORT << endl;

    thread serverThread(runTCPServer, serverSocket);

    glutMainLoop();

    serverThread.join();
    close(serverSocket);

    return 0;
}