#include<stdio.h>

#include <FL/Fl.H>
#include <FL/Fl_Window.H>
#include <FL/Fl_Box.H>
#include <FL/Fl_Button.H>
#include <FL/Fl_Input.H>

class ImgBox: public Fl_Box
{
public:
    ImgBox(int x, int y, int w, int h);
protected:
    void draw();
    int handle(int e);
private:
};

#define MAX_X 399
#define MAX_Y 199

typedef struct
{
    Fl_Window *window;
        Fl_Group *bg;
            Fl_Button* ab;
            Fl_Button* bb;
        ImgBox* ibox;
} widgets;
widgets w;

typedef enum
{
    A_MODE,
    B_MODE,
} mode;

Fl_Input* intxt=0;
mode curr_mode = A_MODE;

void ab_callback(Fl_Widget* wd, void* data);
void bb_callback(Fl_Widget* wd, void* data);
void mainwin_callback(Fl_Widget* wd, void* data);
void reset_all_button_color();
void rem_input_box();
void create_input_box(int mouse_x, int mouse_y);
int main(int argc, char **argv);

//******************

void reset_all_button_color()
{
    w.ab->color(FL_BACKGROUND_COLOR);
    w.ab->redraw();
    w.bb->color(FL_BACKGROUND_COLOR);
    w.bb->redraw();
}

void create_input_box(int mouse_x, int mouse_y)
{
    intxt = new Fl_Input(w.ibox->x()+mouse_x, w.ibox->y()+mouse_y, 100, 24);
    Fl::focus(intxt);
    w.window->add(*intxt);
    intxt->redraw();
}

void rem_input_box()
{
    if(intxt != NULL)
    {
        ::w.window->remove(*intxt);

        //if mouse cursor is on the input box, it becomes I cursor.
        //when we type into input text box, mouse cursor I disappears.
        //if, while typing in input text box, we press escape button,
        //1. mouse cursor will anyway disappear for our typing,
        //2. input text box will disappear for escape key press,
        //then we have no cursor at all in the whole window.
        //so below code will help in restoring cursor for the window.

        //::w.window->cursor(FL_CURSOR_DEFAULT); //for cursor disappearing issue

        Fl::delete_widget(intxt);
        intxt = 0;
    }
}

//******************

ImgBox::ImgBox(int x, int y, int w, int h):Fl_Box(x, y, w, h)
{
}

int ImgBox::handle(int e)
{
    if (curr_mode == A_MODE)
    {
        if(e == FL_PUSH && Fl::event_button() == FL_LEFT_MOUSE)
        {
            int mouse_x = Fl::event_x() - Fl_Box::x();
            int mouse_y = Fl::event_y() - Fl_Box::y();

            rem_input_box();
            create_input_box(mouse_x, mouse_y);

            redraw();
            return 1;
        }
        if(e == FL_RELEASE && Fl::event_button() == FL_LEFT_MOUSE)
        {
            return 1;
        }
    }

    return(Fl_Box::handle(e));
}

void ImgBox::draw()
{
    Fl_Box::draw();
}

//******************

void ab_callback(Fl_Widget* wd, void* data)
{
    curr_mode = A_MODE;
    reset_all_button_color();

    w.ab->color(FL_BLUE);
    Fl::focus(w.ab);
    w.ab->redraw();
}

void bb_callback(Fl_Widget* wd, void* data)
{
    if(intxt != NULL)
    {
        rem_input_box();
        ::w.ibox->redraw();
    }

    curr_mode = B_MODE;
    reset_all_button_color();

    w.bb->color(FL_BLUE);
    Fl::focus(w.bb);
    w.bb->redraw();
}

void mainwin_callback(Fl_Widget* wd, void* data)
{
    if (Fl::event()==FL_SHORTCUT && Fl::event_key()==FL_Escape)
    {
        if(curr_mode == A_MODE)
        {
            bb_callback(0, 0);
        }
        else
        {
            ab_callback(0, 0);
        }

        w.ibox->redraw();

        return;
    }
    else
    {
        exit(0);
    }
}

//******************

int main(int argc, char **argv)
{
    int m=10;

    int bgw=MAX_X+1, bgh=25;
    int bw=75, bh=25;

    int ibw=MAX_X+1, ibh=MAX_Y+1;

    int ww=0;
    int wh=0;

    w.window = new Fl_Window(5, 5, ww, wh, "Test");
    {
        w.bg = new Fl_Group(m, m, bgw, bgh);
        {
            w.ab = new Fl_Button(w.bg->x() +(bw+m)*0, w.bg->y(), bw, bh, "A");
            w.ab->callback(ab_callback);
            w.ab->color(FL_BLUE);

            w.bb = new Fl_Button(w.bg->x() +(bw+m)*1, w.bg->y(), bw, bh, "B");
            w.bb->callback(bb_callback);

        } w.bg->end();

        w.ibox = new ImgBox(m, m+bgh+m, ibw, ibh);
        w.ibox->box(FL_FLAT_BOX);
        w.ibox->color(FL_WHITE);

        ww = m+bgw+m;
        wh = m+bgh+m+ibh+m;
        w.window->size(ww, wh);
    } w.window->end();

    w.window->callback(mainwin_callback);
    w.window->show();
    return Fl::run();
}