Code for https://stackoverflow.com/q/77230206/16582

so77230206.cpp

#include <string>
#include <fstream>
#include <sstream>
#include <iostream>
#include <vector>
#include <algorithm>
#include <wex.h>
#include "plot2d.h"
#include "cStarterGUI.h"

class cTrains
{
    std::vector<std::vector<std::string>> vHourlySchedule;
    std::vector<std::vector<int>> vSecsSchedule;
    int maxsecs;

public:
    cTrains()
    {
        generateHourlySchedule();
        convertScheduleToSecs();
    }
    void generateHourlySchedule()
    {
        vHourlySchedule = {
            {":35:00", ":38:18", ":45:06"},
            {":55:06", ":59:12", ":06:18"},
            {":12:00", ":18:12", ":23:18"}};
    }

    void convertScheduleToSecs()
    {
        maxsecs = 0;
        for (auto &train : vHourlySchedule)
        {
            std::vector<int> trainSchedule;
            for (std::string &minsec : train)
            {
                if (!trainSchedule.size())
                    trainSchedule.push_back(fms2secs(0, minsec));
                else
                {
                    int secs = fms2secs(trainSchedule[0], minsec);
                    trainSchedule.push_back(secs);
                    if (secs > maxsecs)
                        maxsecs = secs;
                }
            }
            vSecsSchedule.push_back(trainSchedule);
        }
    }
    int trainY(int train, int sec) const
    {
        if (0 > train || train >= trainCount())
            throw std::runtime_error("trainY bad train index");

        const int stationYinc = 100;
        const int stopsecs = 42;

        for (int station = 0; station < vSecsSchedule[train].size() - 1; station++)
        {
            int prev = 0;
            if (station > 0)
                prev = vSecsSchedule[train][station - 1];
            int arr = vSecsSchedule[train][station];
            int nxt = vSecsSchedule[train][station + 1];
            int stationY = (station + 1) * stationYinc;

            // check if train has not left the station yet
            if (sec < arr + stopsecs)
                return stationY + train;

            // check if train on way to next station
            if (sec < nxt)
            {
                // interpolate  between stations
                double f = ((float)(sec - arr - stopsecs)) / ((float)(nxt - arr - stopsecs));
                return stationY + f * stationYinc + train;
            }
        }

        // train has arrived at last station
        return vSecsSchedule[train].size() * stationYinc + train;
    }
    int trainCount() const
    {
        return vHourlySchedule.size();
    }

    std::vector<double> plot(int train)
    {
        const int secinc = 10;
        if (0 > train || train >= trainCount())
            throw std::runtime_error("plot bad train index");
        std::vector<double> ret;
        for (int s = 0; s < maxsecs; s += secinc)
            ret.push_back(trainY(train, s));
        return ret;
    }

private:
    int fms2secs(
        int secs1,                 // secs since epoch at station 1, 0 if not yet available
        const std::string &minsec) // time at station to be converted
    {
        int s = 60 * atoi(minsec.substr(1, 2).c_str()) + atoi(minsec.substr(4, 2).c_str());
        if (s < secs1) // check for hour wrap
            s = s + 60 * 60;
        return s;
    }
};

class cGUI : public cStarterGUI
{
public:
    cGUI()
        : cStarterGUI(
              "Trains",
              {50, 50, 1000, 500}),
          thePlot(wex::maker::make<wex::plot::plot>(fm))
    {

        thePlot.move({30, 30, 1200, 600});

        // construct plot traces
        wex::plot::trace &t1 = thePlot.AddStaticTrace();
        wex::plot::trace &t2 = thePlot.AddStaticTrace();
        wex::plot::trace &t3 = thePlot.AddStaticTrace();
        t1.color(0x0000FF);
        t2.color(0xFF0000);
        t3.color(0xAAFFAA);
        auto d1 = myTrains.plot(0);
        t1.set(d1);
        d1 = myTrains.plot(1);
        t2.set(d1);
        d1 = myTrains.plot(2);
        t3.set(d1);

        // resize plot when form resizes
        fm.events().resize(
            [&](int w, int h)
            {
                thePlot.move({30, 30, w, h});
                thePlot.update();
            });

        show();
        run();
    }

private:
    cTrains myTrains;
    wex::plot::plot &thePlot;
};

main()
{
    cGUI theGUI;
    return 0;
}