Button and Textblock using Gtkmm-3.0 and C++

OOP in your GUI using GTKmm-3.0 and C++ (Button and Textblock)
From the previous post about setting up environment we build our first graphical user interface with "Hello world" as title, but in this one we will use object-oriented feature in C++ to create our window.
Let's get stated:

•  First create a class with Codeblocks in File -> New -> Class and name it "MainWindow". 

   #ifndef MAINWINDOW_H  
   #define MAINWINDOW_H   
     
   class MainWindow : public Gtk::Window  
   {  
     public:  
       MainWindow();  
       virtual ~MainWindow();  
     protected:  
     
   };  
     
   #endif // MAINWINDOW_H  
  

• Now second file with the name "MainWindow.cpp" content the body of the function above. Open it an type in the following lines of code.

   #include "mainwindow.h"  
     
   MainWindow::MainWindow():  
   {  
     set_title("Button and Text");  
     set_size_request(400,400);  
     
   }  
     
   MainWindow::~MainWindow()  
   {  
     //dtor  
   }  
  

Here the set_title and set_size_request functions are called without object of Gtk::Window because they are directly inherited. Now in the following we will push the boundary a little bit, by adding two button (one named "left" and the other "right") and a textblock for displaying message in response of the clicked events of the buttons. So, to do that let's add the following code to our header file.

  #ifndef MAINWINDOW_H  
 #define MAINWINDOW_H   
   
 class MainWindow : public Gtk::Window  
 {  
   public:  
     MainWindow();  
     virtual ~MainWindow();  
   protected:  
     Gtk::Box m_Vbox;
     Gtk::ButtonBox myButtonBox;
     Gtk::Button left, right;
     Gtk::Label textBlock;
   
 };  
   
 #endif // MAINWINDOW_H  

The variables above are quite self explanatory as in we have two containers, one for holder other element and the other for holding buttons. So here is how the code looks like:

 #include "mainwindow.h"  
   
 MainWindow::MainWindow():  
 m_Vbox(Gtk::ORIENTATION_VERTICAL), left("Left Button"), right("Right Button")  
 {  
   set_title("Button and Text");  
   set_size_request(400,400);  
   
   add(m_Vbox);  
   
   m_Vbox.pack_start(textBlock);  
   m_Vbox.pack_start(myButtonBox);  
   
   myButtonBox.pack_start(left);  
   myButtonBox.pack_start(right);  
   
   left.set_margin_left(100);  
   right.set_margin_right(100);  
   
   left.signal_clicked().connect(sigc::mem_fun(*this, &MainWindow::left_clicked));  
   right.signal_clicked().connect(sigc::mem_fun(*this, &MainWindow::right_clicked));  
   
   show_all_children();  
   
 }  
   
 MainWindow::~MainWindow()  
 {  
   //dtor  
 }  
   
   
 void MainWindow::left_clicked(){  
   textBlock.set_text("Left button clicked");  
 }  
   
 void MainWindow::right_clicked()  
 {  
   textBlock.set_text("Right button clicked");  
 }  

You can download the source code at https://github.com/Bakary-baktech/Gtkmm-3.0-tuto.

Next: Organizing UI Element