Hello!
I decided to try and learn some C++ programming with GTKmm the other day, i have programmed a little C++ a couple of years back but nothing fancy.
I have been able to draw some inputs and buttons on the window but that's about as far as i can get at this point.
As you can see i'm trying to make a basic calculator that just adds two numbers together and displays the result.

The question here is how do i access the values from numberone and numbertwo entries and put the sum of these in the label answerlabel. I tried passing some arguments to the function calculate() but that didn't work.
Any tips on good ways to do this would be appreciated.

Here is the code so far:

main.cpp
Makefile

You need to access the 'text' properties of numone and numtwo, and you will need to convert those text properties to floats (with atof maybe).

And since you want to access them from another function, you will have to move the declarations:

Gtk::Entry numone;
Gtk::Entry numtwo;

..outside function main.

For Gtk reference:
http://library.gnome.org/devel/gtk/u...GtkEntry--text

For an example of some similar code:
http://www.kplug.org/glade_tutorial/...l/gtemp_4.html

But you wanted C++? so maybe you could do something like...


#include <sstream>

....

std::stringstream ss;
float some_float, another_float;
string some_string;
....

// Get the string and Cast to float...
ss << numone.get_text();
ss >> some_float;
ss << numtwo.get_text();
ss >> another_float;
....

some_float = do something with some_float & another_float;

// Cast back to string...
ss << some_float;
ss >> some_string;

// and present the result in numthree

numthree.set_text(some_string)

Hello Magoot,

have you found out how to proceed yet? If not please find here one possible solution in C++ with classes and everything. I think it is best to look at the examples bundled with Gtkmm to learn how to make a structured program. I split up the code on three files and updated the makefile accordingly. Have fun!

//simple_calculator.h

#ifndef GTKMM_SIMPLE_CALCULATOR_H
#define GTKMM_SIMPLE_CALCULATOR_H

#include <gtkmm.h>

class Simple_Calculator : public Gtk::Window
{
public:
Simple_Calculator();
virtual ~Simple_Calculator();

protected:
//Signal handlers:
void calculate();


//Child widgets:
Gtk::VBox vbox;
Gtk::HBox hbox;

Gtk::Entry numone, numtwo;
Gtk::Button calcbutton;
Gtk::Label pluslabel, answerlabel;
};

#endif //GTKMM_SIMPLE_CALCULATOR_H



// simple_calculator.cc
#include "simple_calculator.h"
#include <iostream>
#include <sstream>
#include <string.h>
#include <string>


Simple_Calculator::Simple_Calculator()
: calcbutton("Calculate"),
pluslabel("+"),
answerlabel("=")
{
set_size_request(360, 100);
set_title("My simple Calculator");
set_border_width(10);

add(vbox);

hbox.pack_start(numone, false, false, 0);
hbox.pack_start(pluslabel, false, false, 5);
hbox.pack_start(numtwo, false, false, 0);
vbox.pack_start(hbox, false, false, 0);
vbox.pack_start(answerlabel, false, false, 5);
vbox.pack_start(calcbutton, false, false, 5);

calcbutton.signal_clicked().connect( sigc::mem_fun(*this,
&Simple_Calculator::calculate) );
calcbutton.set_flags(Gtk::CAN_DEFAULT);
calcbutton.grab_default();

show_all_children();
}

Simple_Calculator::~Simple_Calculator()
{
}

void Simple_Calculator::calculate()
{
std::stringstream ss, ss2, ss3;
float first, second;
std::string result;

ss << numone.get_text();
ss >> first;
ss2 << numtwo.get_text();
ss2 >> second;
first = first + second;
ss3 << first;
ss3 >> result;
answerlabel.set_text("=" + result);
}



//my_calculator.cc

#include <gtkmm/main.h>
#include "simple_calculator.h"

int main(int argc, char *argv[])
{
Gtk::Main kit(argc, argv);

Simple_Calculator calculator;
//Shows the window and returns when it is closed.
Gtk::Main::run(calculator);

return 0;
}



# Makefile

CFLAGS = `pkg-config gtkmm-2.4 --cflags --libs`
OPTIONS = -Wall

all:
g++ $(OPTIONS) -o my_calculator my_calculator.cc simple_calculator.cc $(CFLAGS)

Hi!
Sorry for a late reply, haven't had time to look at this latley.
Thanks a lot for your replys, it helps a lot starting to understand better how to structure programs now.

Your example was great m95vebj, however i had a question:
This row is a bit confusing for me:
Simple_Calculator::Simple_Calculator() : calcbutton("Calculate"), pluslabel("+"), answerlabel("=")
what exactly needs to be added to this row? As far as i can see it contains all widgets except numone and numtwo?
If i wanted to add more labels and stuff, do these go on this row as well?

Thanks.
// magoot

Hi again,

Those lines initiates the widgets and puts the initial text on them. I suppose you could have used e.g. answerlabel.add_text("="); later on in stead. You do however need to declare new widgets in the class declaration to be useful.

hi,

Thanks a lot for these.
It helped me do this function:

class topwindow : public Gtk::Window
{
public:
topwindow();
...
...


virtual void ADD();
Gtk::Entry result_entry;

...
...

protected:
...
...

Gtk::Entry input_1, input_2;

...
...

};

void topwindow::ADD()
{
std::stringstream ss, ss2, ss3;
double first, second, total;
std::string resulting;

ss << input_1.get_text();
ss >> first;
ss2 << input_2.get_text();
ss2 >> second;
total = first + second;
ss3 << total;
ss3 >> resulting;
result_entry.set_text(resulting);

}

Hope this helps.