Draw graph with vertices located on a 2D grid https://stackoverflow.com/q/75725261/16582

main.cpp

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

class cGrid2D
{
public:
    typedef std::pair<int,int>  point_t;
    typedef std::pair<point_t,point_t> edge_t;

    cGrid2D()
    {
        reset();
    }
    void reset()
    {
        myColCount = -1;
        myRowCount = -1;
    }

    /// @brief Extend grid dimensions if neccessary to include point
    /// @param x zero based col
    /// @param y zero based row
    void extDim(int x, int y)
    {
        if (x < 0 || y < 0)
            throw std::runtime_error(
                "Bad cGrid2D co-ords");
        if (x > myColCount-1)
            myColCount = x+1;
        if (y > myRowCount-1)
            myRowCount = y+1;
    }
    void setDim(int colCount, int rowCount)
    {
        myColCount = colCount;
        myRowCount = rowCount;
    }

    void addEdge(int src, int dst)
    {
        vEdge.push_back(std::make_pair(src, dst));
    }
    void getDim(int &colCount, int &rowCount) const
    {
        colCount = myColCount;
        rowCount = myRowCount;
    }
    int index(int col, int row) const
    {
        return row * myColCount + col;
    }
    void coords(int &col, int &row, int index) const
    {
        row = index / myColCount;
        col = index - row * myColCount;
    }
    std::vector<std::pair<int, int>>
    getPoints() const
    {
        std::vector<std::pair<int, int>> ret;
        int x, y;
        for (int p = 0; p < myColCount * myRowCount; p++)
        {
            coords(x, y, p);
            ret.push_back(std::make_pair(x, y));
        }
        return ret;
    }
    std::vector<edge_t>
    getEdges() const
    {
        std::vector<edge_t> ret;
        for( auto& e : vEdge )
        {
            int x1,y1,x2,y2;
            coords(x1,y1,e.first);
            coords(x2,y2,e.second);
            ret.push_back(
                std::make_pair(
                    std::make_pair(x1,y1),std::make_pair(x2,y2)));
        }
        return ret;
    }
    private:
    int myColCount;
    int myRowCount;
    std::vector<std::pair<int,int>> vEdge;
};

cGrid2D theGrid;

class cGUI : public cStarterGUI
{
public:
    cGUI()
        : cStarterGUI(
              "Starter",
              {50, 50, 1000, 500})
    {

        readfile("../dat/input.txt");

        const int scale = 30;
        const int off = 50;

        fm.events().draw(
            [&](PAINTSTRUCT &ps)
            {
                wex::shapes S(ps);

                for( auto& e : theGrid.getEdges() ) {
                    S.line( {
                        scale * e.first.first + off, scale * e.first.second + off,
                        scale * e.second.first + off, scale * e.second.second + off});
                }

                for (auto &loc : theGrid.getPoints())
                    S.circle(
                        scale * loc.first + off,
                        scale * loc.second + off,
                        5);
            });

        show();
        run();
    }

private:
    void readfile(const std::string &fname);
};

void cGUI::readfile(const std::string &fname)
{
    std::ifstream ifs(fname);
    if (!ifs.is_open())
        exit(1);

    theGrid.reset();
    std::string line;

    // 1st pass to determine extent of grid
    while (getline(ifs, line))
    {
        int ob = -1;
        while (true)
        {
            ob = line.find("(", ob + 1);
            if (ob == -1)
                break;
            int x = atoi(line.substr(ob + 1).c_str());
            int cm = line.find(",", ob);
            int y = atoi(line.substr(cm + 1).c_str());
            theGrid.extDim(x, y);
        }
    }

    ifs.close();
    ifs.open(fname);

    // 2nd pass to get edges
    while (getline(ifs, line))
    {
        int src = -1;
        int ob = 0;
        while (true)
        {
            ob = line.find("(", ob + 1);
            if (ob == -1)
                break;
            int x = atoi(line.substr(ob + 1).c_str());
            int cm = line.find(",", ob);
            int y = atoi(line.substr(cm + 1).c_str());
            if (src < 0)
                src = theGrid.index(x, y);
            else
                theGrid.addEdge(src, theGrid.index(x, y));
        }
    }
}


main()
{
    cGUI theGUI;
    return 0;
}