问FLTK fl_line和fl_point不工作

EN

#include <FL/Fl.H>
#include <FL/Fl_Window.H>
#include <FL/fl_draw.H>
#include <FL/Fl_Button.H>
#include <Fl/fl_Input.H>
#include <Fl/fl_Output.H>
#include <Physics.h>
#include <string.h>
#include <stdlib.h>
#include <Windows.h>

using namespace std;

#define WINSIZE 700
#define TIMESTEP 0.02f

class Graph : public Fl_Widget
{
public:
    Graph(int X, int Y, int W, int H) : Fl_Widget(X, Y, W, H) {}

    void draw(void) 
    {
        fl_color(FL_RED);
        fl_point(pos_x, (500 - pos_y));
    }

    int pos_x, pos_y;
};
//------------------------------------------------------------------------    

class WindowReq : public Fl_Window
{
public:
    WindowReq(int W, int H, const char* Title);

    Fl_Input*   InVel;
    Fl_Input*   InDeg;
    Fl_Output*  OutT;
    Fl_Output*  OutX;
    Fl_Output*  OutY;
    Fl_Button*  Calc;
    Graph*      graph;

private:
    static void calc_cb(Fl_Widget* o, void* v);
    inline void copyValueToX(char* c);
    inline void copyValueToY(char* c);
    inline void copyValueToT(char* c);
};

WindowReq::WindowReq(int W, int H, const char* Title) : Fl_Window(W, H, Title)
{
    begin();
        Calc = new Fl_Button((WINSIZE - 150), 50, 100, 30, "Calculate path");
        Calc->callback(&WindowReq::calc_cb, this);

        InVel = new Fl_Input(70, 50, 100, 30, "Velocity:");

        InDeg = new Fl_Input(((WINSIZE / 3) + 50), 50, 100, 30, "Angle:");

        OutX = new Fl_Output(70, 100, 100, 30, "Distance:");

        OutY = new Fl_Output(((WINSIZE / 3) + 50), 100, 100, 30, "Height:");

        OutT = new Fl_Output((WINSIZE - 150), 100, 100, 30, "Time:");

        graph = new Graph(0, 150, 700, 500);

        redraw();
    end();

    show();
}

void WindowReq::calc_cb(Fl_Widget* o, void* v)
{
    Projectile Stone;
    WindowReq* win = (WindowReq*)v;
    Coordinates2D Position = { 0,500 }, Buffer = Position;
    double velocity;
    double Degree;
    double Time;
    char Stuff[1000];

    velocity = atof(win->InVel->value());
    Degree = atof(win->InDeg->value());

    Stone.initialize(velocity, Degree, TIMESTEP);

    for (int i = 0; i < 700; i++)
    {
        fl_point(i, 400);
    }

    do
    {
        Position = Stone.getpos();
        Time = Stone.gettime();
        sprintf(Stuff, "%.2f", Time);
        win->copyValueToT(Stuff);
        sprintf(Stuff, "%d", Position.x);
        win->copyValueToX(Stuff);
        sprintf(Stuff, "%d", Position.y);
        win->copyValueToY(Stuff);
        Stone.simulatestep();
        win->graph->pos_x = Position.x;
        win->graph->pos_y = Position.y;
        win->graph->draw();
        Fl::check();
        Sleep(100);
    }while(Position.y >= 0);
}

void WindowReq::copyValueToX(char c[1000])
{
    OutX->value(c);
}

void WindowReq::copyValueToY(char c[1000])
{
    OutY->value(c);
}

void WindowReq::copyValueToT(char c[1000])
{
    OutT->value(c);
}

//============================================================
int main()
{
    WindowReq win(WINSIZE, WINSIZE, "Balistics Simulator");
    Fl::run();
}