Free software, free society: Richard Stallman at TEDxGeneva 2014

It is the first TEDx talk of the founder of Free Software movement. Stallman, RMS for short, has changed the world with his vision of freedom for the digital age. He launched the GNU operating system, used with Linux as a component, and inspired the development of Creative Commons licences and Wikipedia project. In this talk, Stallman describes how nonfree programs give companies control of their users and what users can do in order to recover control over their computing.

Install Node.js on Ubuntu 14.04 via PPA

To install Node.js on Ubuntu 14.04, enter the command:
$ sudo add-apt-repository ppa:chris-lea/node.js
$ sudo apt-get update
$ sudo apt-get install nodejs

Linux command - tree, to list directories in a tree-like format

tree is a Linux command to list contents of directories in a tree-like format.

To install tree on Ubuntu:
$ sudo apt-get install tree

nomacs, a free, small, fast and multi-format image viewer

nomacs is a free image viewer for windows, linux, and mac systems, which is licensed under the GNU General Public License v3. nomacs is small, fast and able to handle the most common image formats including RAW images. Additionally it is possible to synchronize multiple viewers. A synchronization of viewers running on the same computer or via LAN is possible. It allows to compare images and spot the differences (e.g. schemes of architects to show the progress).

To install nomacs on Ubuntu, add repository of ppa:nomacs/stable:
$ sudo add-apt-repository ppa:nomacs/stable

Then, enter the commands:
$ sudo apt-get update
$ sudo apt-get install nomacs

Linux command, lscpu, to get CPU architecture information

The Linux command lscpu  gathers  CPU  architecture  information  like  number  of  CPUs, threads, cores, sockets, NUMA nodes, information about CPU caches,  CPU family,  model,  bogoMIPS,  byte  order  and  stepping  from  sysfs and /proc/cpuinfo, and prints it in a human-readable format.   It  supports both online and offline CPUs.  It can also print out in a parsable for‐mat, including how different caches are shared by different CPUs, which can be fed to other programs.

Code::Blocks + wxWidgets + wxSmith, to open text file with wxFileDialog

This video show steps to create wxWidgets project in Code::Blocks, using wxSmith, to open text file with wxFileDialog.



The only programmatic code is in wxTextFileFrame::OnMenuOpenSelected() of the file wxTextFileMain.cpp.

void wxTextFileFrame::OnMenuOpenSelected(wxCommandEvent& event)
{
    wxTextFile file;
    wxString text;

    int result;
    result = FileDialog1->ShowModal();
    if(result==wxID_OK){
        SetTitle(FileDialog1->GetPath());

        file.Open(FileDialog1->GetPath());
        for(size_t i=0; i<file.GetLineCount(); i++){
            text << file.GetLine(i) << _T("\r\n");
        }
        file.Close();
        TextCtrl1->SetValue(text);
    }

}

And also include wx/textfile.h.

#include <wx/textfile.h>

Hello World of Code::Blocks with wxSmith

"wxSmith plugin is not loaded, can not continue" in Code::Blocks

If you try to New a wxWidgets Project in Code::Blocls, with GUI Builder of wxSmith; may be you will be complained with error of "wxSmith plugin is not loaded, can not continue".

You have to install codeblocks-contrib, it is a contrib plugins for Code::Blocks IDE. To install it on Ubuntu, enter the command:

$ sudo apt-get install codeblocks-contrib

And then restart Code::Blocks.

Add Button to wxWidgets project

Create wxWidgets Project with Code::Blocks, as shown in last post.

To add a Buuton, modify HelloWxMain.h and HelloWxMain.h.cpp.

/***************************************************************
 * Name:      HelloWxMain.h
 * Purpose:   Defines Application Frame
 * Author:    Buddy ()
 * Created:   2014-08-21
 * Copyright: Buddy (linux-buddy.blogspot.com)
 * License:
 **************************************************************/

#ifndef HELLOWXMAIN_H
#define HELLOWXMAIN_H

#ifndef WX_PRECOMP
    #include <wx/wx.h>
#endif

#include "HelloWxApp.h"

class HelloWxFrame: public wxFrame
{
    public:
        HelloWxFrame(wxFrame *frame, const wxString& title);
        ~HelloWxFrame();
    private:

        //add for "Hello Button"
        static const long idButtonHello;
        wxBoxSizer* m_MainBox;
        wxButton* m_ButtonHello;
        void onClickHello(wxCommandEvent& event);
        //end of "Hello Button"

        enum
        {
            idMenuQuit = 1000,
            idMenuAbout
        };
        void OnClose(wxCloseEvent& event);
        void OnQuit(wxCommandEvent& event);
        void OnAbout(wxCommandEvent& event);
        DECLARE_EVENT_TABLE()
};


#endif // HELLOWXMAIN_H

/***************************************************************
 * Name:      HelloWxMain.cpp
 * Purpose:   Code for Application Frame
 * Author:    Buddy ()
 * Created:   2014-08-21
 * Copyright: Buddy (linux-buddy.blogspot.com)
 * License:
 **************************************************************/

#ifdef WX_PRECOMP
#include "wx_pch.h"
#endif

#ifdef __BORLANDC__
#pragma hdrstop
#endif //__BORLANDC__

#include "HelloWxMain.h"

//helper functions
enum wxbuildinfoformat {
    short_f, long_f };

wxString wxbuildinfo(wxbuildinfoformat format)
{
    wxString wxbuild(wxVERSION_STRING);

    if (format == long_f )
    {
#if defined(__WXMSW__)
        wxbuild << _T("-Windows");
#elif defined(__WXMAC__)
        wxbuild << _T("-Mac");
#elif defined(__UNIX__)
        wxbuild << _T("-Linux");
#endif

#if wxUSE_UNICODE
        wxbuild << _T("-Unicode build");
#else
        wxbuild << _T("-ANSI build");
#endif // wxUSE_UNICODE
    }

    return wxbuild;
}

const long HelloWxFrame::idButtonHello = ::wxNewId();   //Hello Button

BEGIN_EVENT_TABLE(HelloWxFrame, wxFrame)
    EVT_CLOSE(HelloWxFrame::OnClose)
    EVT_MENU(idMenuQuit, HelloWxFrame::OnQuit)
    EVT_MENU(idMenuAbout, HelloWxFrame::OnAbout)
    EVT_BUTTON(idButtonHello, HelloWxFrame::onClickHello) //Hello Button
END_EVENT_TABLE()

HelloWxFrame::HelloWxFrame(wxFrame *frame, const wxString& title)
    : wxFrame(frame, -1, title)
{
#if wxUSE_MENUS
    // create a menu bar
    wxMenuBar* mbar = new wxMenuBar();
    wxMenu* fileMenu = new wxMenu(_T(""));
    fileMenu->Append(idMenuQuit, _("&Quit\tAlt-F4"), _("Quit the application"));
    mbar->Append(fileMenu, _("&File"));

    wxMenu* helpMenu = new wxMenu(_T(""));
    helpMenu->Append(idMenuAbout, _("&About\tF1"), _("Show info about this application"));
    mbar->Append(helpMenu, _("&Help"));

    SetMenuBar(mbar);
#endif // wxUSE_MENUS

#if wxUSE_STATUSBAR
    // create a status bar with some information about the used wxWidgets version
    CreateStatusBar(2);
    SetStatusText(_("Hello Code::Blocks user!"),0);
    SetStatusText(wxbuildinfo(short_f), 1);
#endif // wxUSE_STATUSBAR

    //Hello Button
    this->SetSizeHints(wxDefaultSize, wxDefaultSize);
    m_MainBox = new wxBoxSizer(wxHORIZONTAL);

    m_ButtonHello = new wxButton(
                            this,
                            idButtonHello,
                            _T("Hello...!"),
                            wxDefaultPosition,
                            wxDefaultSize,
                            0);
    m_MainBox->Add(m_ButtonHello,
                    0,
                    wxALL,
                    5);

    this->SetSizer(m_MainBox);
    this->Layout();
}


HelloWxFrame::~HelloWxFrame()
{
}

void HelloWxFrame::OnClose(wxCloseEvent &event)
{
    Destroy();
}

void HelloWxFrame::OnQuit(wxCommandEvent &event)
{
    Destroy();
}

void HelloWxFrame::OnAbout(wxCommandEvent &event)
{
    wxString msg = wxbuildinfo(long_f);
    wxMessageBox(msg, _("Welcome to..."));
}

//Hello Button Clicked
void HelloWxFrame::onClickHello(wxCommandEvent &event)
{
    wxString msg = _T("Hello World");
    wxString info = _T("linux-buddy");
    wxMessageBox(msg,
                info,
                wxOK | wxICON_INFORMATION,
                this);
}

No modify on HelloWxApp.h and HelloWxApp.cpp

/***************************************************************
 * Name:      HelloWxApp.h
 * Purpose:   Defines Application Class
 * Author:    Buddy ()
 * Created:   2014-08-21
 * Copyright: Buddy (linux-buddy.blogspot.com)
 * License:
 **************************************************************/

#ifndef HELLOWXAPP_H
#define HELLOWXAPP_H

#include <wx/app.h>

class HelloWxApp : public wxApp
{
    public:
        virtual bool OnInit();
};

#endif // HELLOWXAPP_H

/***************************************************************
 * Name:      HelloWxApp.cpp
 * Purpose:   Code for Application Class
 * Author:    Buddy ()
 * Created:   2014-08-21
 * Copyright: Buddy (linux-buddy.blogspot.com)
 * License:
 **************************************************************/

#ifdef WX_PRECOMP
#include "wx_pch.h"
#endif

#ifdef __BORLANDC__
#pragma hdrstop
#endif //__BORLANDC__

#include "HelloWxApp.h"
#include "HelloWxMain.h"

IMPLEMENT_APP(HelloWxApp);

bool HelloWxApp::OnInit()
{
    HelloWxFrame* frame = new HelloWxFrame(0L, _("wxWidgets Application Template"));
    
    frame->Show();
    
    return true;
}

Create wxWidgets Project with Code::Blocks

With Code::Blocks installed, you can create wxWidgets Project by new a wxWidgets project (File > Project... > Category GUI > wxWidgets Project).

If you have error of:
fatal error: wx/app.h: No such file or directory

You need to install wx-common, and also libwxgtk2.8-dev or libwxgtk3.0-dev.

$ sudo apt-get install wx-common
$ sudo apt-get install libwxgtk2.8-dev
$ sudo apt-get install libwxgtk3.0-dev

The videos show how to install and run, on Ubuntu Linux.




Next:
- Add Button to wxWidgets project

Install Code::Blocks on Ubuntu

Code::Blocks is a cross-platform Integrated Development Environment (IDE). To install Code::Blocks on Ubuntu, simple search Code::Blocks in Ubuntu Software Center, or click this link.

Create Hello World (hello.cpp) using Code::Blocks


Create Hello World Project using Code::Blocks


Hello World Project with multiple files, Code::Blocks



- With Code::Blocks installed, you can create wxWidgets Project.

Display info kernel module of with modinfo command

To display info kernel module, enter the command:

$ modinfo hello.ko

where hello.ko is the kernel object file.

Develop Hello World of Linux Kernel Module

To create Linux Kernel Module, install the development tools:

$ sudo apt-get install gcc
$ sudo apt-get install kernel-package
$ sudo apt-get install make

Make and switch to a fold for your works. Create a c program, hello.c, and Makefile file. Please notice that both hello.c and Makefile have to be in the same folder.

hello.c

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/sched.h>

static int __init hello_init(void)
{
 printk(KERN_INFO "Hello World! pid = %d\n", current->pid);
 return 0;
}

static void __exit hello_exit(void)
{
 printk(KERN_INFO "Hello Bye!\n");
}

module_init(hello_init);
module_exit(hello_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Linux-Buddy: linux-buddy.blogspot.com");
MODULE_DESCRIPTION("Test Module: Hello World");
MODULE_VERSION("1.0");

Makefile

obj-m += hello.o

all:
 make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules

clean:
 make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

Make the kernel module by enter the command:
$ make

Then insert the module with:
$ sudo insmod hello.ko

You can use the dmesg to view the kermel message printed by the code printk() in c program.
$ dmesg

List installed modules:
$ lsmod

To remove the module:
$ sudo rmmod hello.ko

Install Adobe Reader on Ubuntu 14.04

To install Adobe Reader (version 9.5.5) on Ubuntu 14.04, download from http://ardownload.adobe.com/pub/adobe/reader/unix/9.x/9.5.5/enu/AdbeRdr9.5.5-1_i386linux_enu.deb, then install with Ubuntu Software Center by right clicking on the file.

Adobe Reader run on Ubuntu 14.04

Flashback Ubuntu 14.04 to legacy desktop

To flashback Ubuntu 14.04 to use legacy desktop, to remove the 3D effect and animation, enter the command:

$ sudo apt-get install gnome-session-flashback

Log-out after installed. Click the Ubuntu button when log-in, select GNOME Flashback (Metacity).

Install Node.js on Ubuntu

From Ubuntu 12.04 to 13.04, an old version (0.6.x) of Node is in the standard repository. To install, just run:

$ sudo apt-get install nodejs

Obtaining a recent version of Node or installing on older Ubuntu and other apt-based distributions may require a few extra steps. Example install:

$ sudo apt-get update
$ sudo apt-get install -y python-software-properties python g++ make
$ sudo add-apt-repository ppa:chris-lea/node.js
$ sudo apt-get update
$ sudo apt-get install nodejs

source: https://github.com/joyent/node/wiki/Installing-Node.js-via-package-manager#ubuntu-mint

Get my Process ID and Parent Process ID in C, by calling getpid() and getppid()

Example to Get my Process ID (PID) and Parent Process ID (PPID) by calling getpid() and getppid().

#include <stdio.h>
#include <sys/types.h>

main(){
 pid_t mypid;
 pid_t myppid;
 
 mypid = getpid();
 myppid = getppid();
 printf("My PID: %ld\n", (long)mypid);
 printf("My PPID: %ld\n", (long)myppid);
}

getpid() and getppid()

Get GNU libc version at run-time using C

To get GNU libc version in C language at run-time, you can call gnu_get_libc_version() and gnu_get_libc_release().

- gnu_get_libc_version() returns string that identifies the glibc version available on the system.
- gnu_get_libc_release() returns string indicates the release status of the glibc version available on the system.

And, you can retrieve _CS_GNU_LIBC_VERSION with confstr().

Here is example, test_version.c:

#include <stdio.h>
#include <gnu/libc-version.h>
#include <stdlib.h>
#include <unistd.h>

main(){
    printf("GNU libc version: %s\n", gnu_get_libc_version());
    printf("GNU libc release: %s\n", gnu_get_libc_release());
    
    char *buf; size_t n;
    n = confstr(_CS_GNU_LIBC_VERSION, NULL, (size_t)0);
    if ((buf = malloc(n)) == NULL) 
        abort();
    confstr(_CS_GNU_LIBC_VERSION, buf, n);

    printf("_CS_GNU_LIBC_VERSION: %s\n", buf );
    free( buf );
}

Get GNU libc version at run-time using C

cal - Linux command to display calendar

cal command

cal is a Linux command run on Terminal, to display built-in calendar on Terminal in text mode.

GtkColorChooser example

GtkColorChooser

#include <gtk/gtk.h>

static void 
chooser_color_activated(GtkColorChooser *chooser, 
 GdkRGBA *color, gpointer user_data)
{
 GtkLabel *label = user_data;
 gtk_label_set_text (label, gdk_rgba_to_string(color));
}

int main( int argc, char *argv[])
{
    GtkWidget *window;
    GtkWidget *box;
    GtkWidget *label;
    GtkWidget *chooser;

    gtk_init(&argc, &argv);
    window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    gtk_window_set_default_size(GTK_WINDOW(window), 400, 250);
    gtk_window_set_title(GTK_WINDOW(window), "Linux-buddy.blogspot.com");

    box = gtk_box_new(GTK_ORIENTATION_VERTICAL, 5);

 label = gtk_label_new("label");
    gtk_box_pack_start(GTK_BOX(box), label, FALSE, FALSE, 3);

 //Create GtkColorChooser
    chooser = gtk_color_chooser_widget_new();
    gtk_box_pack_start(GTK_BOX(box), chooser, FALSE, FALSE, 3);
    g_signal_connect (GTK_COLOR_CHOOSER(chooser),
                    "color-activated", 
                    G_CALLBACK (chooser_color_activated), 
                    label);

    g_signal_connect(G_OBJECT(window), "destroy", 
        G_CALLBACK(gtk_main_quit), NULL);

    gtk_container_add(GTK_CONTAINER(window), box);
    gtk_widget_show_all(window);
    gtk_main();

    return 0;
}

Note: double click the color buttons to activate color change.

View hiden file start with a "."

Filenames which start with a "." (dot) are normally not shown. Use 'ls .*' or 'ls -a ...' to see them.

GTK+ example: Scale

GTK+ example: Scale

#include <gtk/gtk.h>

static gboolean
scale_changed (GtkRange *range, gpointer data)
{
    gchar *text;
    gdouble value;
    GtkLabel *label;

    label = data;
    value = gtk_range_get_value (range);
    text = g_strdup_printf ("%.1f", value);
    gtk_label_set_text (label, text);
    g_free (text);

    return TRUE;
}

int main( int argc, char *argv[])
{
    GtkWidget *window;
    GtkWidget *box;
    GtkWidget *label;
    GtkWidget *spinButton;
    GtkWidget *scale;

    gtk_init(&argc, &argv);
    window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    gtk_window_set_default_size(GTK_WINDOW(window), 400, 250);
    gtk_window_set_title(GTK_WINDOW(window), "Linux-buddy.blogspot.com");

    box = gtk_box_new(GTK_ORIENTATION_VERTICAL, 5);

    //Create Label
    label = gtk_label_new("label");
    gtk_box_pack_start(GTK_BOX(box), label, FALSE, FALSE, 3);

    //Create Scale
    scale = gtk_scale_new_with_range (
        GTK_ORIENTATION_HORIZONTAL, 
        0,      //gdouble min
        10,     //gdouble max
        0.5);     //gdouble step
    gtk_widget_set_hexpand (scale, TRUE);
    g_signal_connect(G_OBJECT(scale), "value-changed", 
        G_CALLBACK(scale_changed), label);

    gtk_box_pack_start(GTK_BOX(box), scale, FALSE, FALSE, 3);

    //Connects GCallback function gtk_main_quit to "destroy" signal for "window"
    g_signal_connect(G_OBJECT(window), "destroy", 
        G_CALLBACK(gtk_main_quit), NULL);

    gtk_container_add(GTK_CONTAINER(window), box);
    gtk_widget_show_all(window);
    gtk_main();

    return 0;
}

GTK+ example: SpinButton

SpinButton displayed on Ubuntu

#include <gtk/gtk.h>

static gboolean
spinButton_changed (GtkSpinButton *spin, gpointer data)
{
    gchar *text;
    int value;
    GtkLabel *label;

    label = data;
    value = gtk_spin_button_get_value_as_int (spin);
    text = g_strdup_printf ("%02d", value);
    gtk_label_set_text (label, text);
    g_free (text);

    return TRUE;
}

int main( int argc, char *argv[])
{
    GtkWidget *window;
    GtkWidget *box;
    GtkWidget *label;
    GtkWidget *spinButton;

    gtk_init(&argc, &argv);
    window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    gtk_window_set_default_size(GTK_WINDOW(window), 400, 250);
    gtk_window_set_title(GTK_WINDOW(window), "Linux-buddy.blogspot.com");

    box = gtk_box_new(GTK_ORIENTATION_VERTICAL, 5);

    //Create Label
    label = gtk_label_new("label");
    gtk_box_pack_start(GTK_BOX(box), label, FALSE, FALSE, 3);

    //Create SpinButton
    spinButton = gtk_spin_button_new_with_range  (
        0,      //gdouble min
        10,     //gdouble max
        2);     //gdouble step
    gtk_widget_set_hexpand (spinButton, TRUE);
    g_signal_connect(G_OBJECT(spinButton), "value-changed", 
        G_CALLBACK(spinButton_changed), label);

    gtk_box_pack_start(GTK_BOX(box), spinButton, FALSE, FALSE, 3);

    //Connects GCallback function gtk_main_quit to "destroy" signal for "window"
    g_signal_connect(G_OBJECT(window), "destroy", 
        G_CALLBACK(gtk_main_quit), NULL);

    gtk_container_add(GTK_CONTAINER(window), box);
    gtk_widget_show_all(window);
    gtk_main();

    return 0;
}

Remark: wrong icon displayed on Lubuntu:

SpinButton with wrong icon displayed on Lubuntu

Download file using SSH with scp command

The Linux command scp, securely copying files, uses ssh for data transfer, to copy file to, from, or between different hosts.

To download file from server using ssh, using the command:

$ scp user@hostname:file local-directory

example:
$ scp pi@192.168.111.109:~/log1 ~/PiLog
where pi is user name in server with IP 192.168.111.109, copy ~/log1 from server to local directory ~/PiLog.

scp

Redirect command output to both stdout and file

The linux command tee read from standard input and write to standard output and files.

Example:
$ ls | tee filelist.txt

GTK+ example: Button

GTK+ example: Button

#include <gtk/gtk.h>

static void
button_toggled (GtkWidget *button, gpointer data)
{
    GtkLabel *label = data;

    if (gtk_toggle_button_get_active (GTK_TOGGLE_BUTTON(button)))
        gtk_label_set_text (label, "Active");
    else {
        gtk_label_set_text (label, "In-Active");
    }
}

int main( int argc, char *argv[])
{
    GtkWidget *window;
    GtkWidget *box;
    GtkWidget *label;
    GtkWidget *button;

    gtk_init(&argc, &argv);
    window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    gtk_window_set_default_size(GTK_WINDOW(window), 400, 250);
    gtk_window_set_title(GTK_WINDOW(window), "Linux-buddy.blogspot.com");

    box = gtk_box_new(GTK_ORIENTATION_VERTICAL, 5);

    //Create Label
    label = gtk_label_new("label");
    gtk_box_pack_start(GTK_BOX(box), label, FALSE, FALSE, 3);

    //Create Button
    button = gtk_toggle_button_new_with_label ("Button");
    gtk_box_pack_start(GTK_BOX(box), button, FALSE, FALSE, 3);

    g_signal_connect (GTK_TOGGLE_BUTTON (button), "toggled", 
                    G_CALLBACK (button_toggled), label);

    //Connects GCallback function gtk_main_quit to "destroy" signal for "window"
    g_signal_connect(G_OBJECT(window), "destroy", 
        G_CALLBACK(gtk_main_quit), NULL);

    gtk_container_add(GTK_CONTAINER(window), box);
    gtk_widget_show_all(window);
    gtk_main();

    return 0;
}

GTK+ example: Switch

GTK+ example: Switch

#include <gtk/gtk.h>

static void
switch_active (GtkSwitch *myswitch, GParamSpec *pspec, GtkLabel *label)
{
    if (gtk_switch_get_active (myswitch)){
        gtk_label_set_text (label, "Active");
    }else{
        gtk_label_set_text (label, "In-Active");
    }
}

int main( int argc, char *argv[])
{
    GtkWidget *window;
    GtkWidget *box;
    GtkWidget *label1;
    GtkWidget *label2;
    GtkWidget *switch1;
    GtkWidget *switch2;

    GObject *context_object;

    gtk_init(&argc, &argv);
    window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    gtk_window_set_default_size(GTK_WINDOW(window), 400, 250);
    gtk_window_set_title(GTK_WINDOW(window), "Linux-buddy.blogspot.com");

    box = gtk_box_new(GTK_ORIENTATION_VERTICAL, 5);

    //Create labels
    label1 = gtk_label_new("label1");
    gtk_box_pack_start(GTK_BOX(box), label1, FALSE, FALSE, 3);
    label2 = gtk_label_new("label2");
    gtk_box_pack_start(GTK_BOX(box), label2, FALSE, FALSE, 3);

    //Create Switchs
    //switch1 with default actived
    switch1 = gtk_switch_new ();
    gtk_switch_set_active (GTK_SWITCH (switch1), TRUE);
    gtk_box_pack_start(GTK_BOX(box), switch1, FALSE, FALSE, 3);
    //switch2 with default in-actived
    switch2 = gtk_switch_new ();
    gtk_switch_set_active (GTK_SWITCH (switch2), FALSE);
    gtk_box_pack_start(GTK_BOX(box), switch2, FALSE, FALSE, 3);

    g_signal_connect(GTK_SWITCH (switch1), "notify::active", 
        G_CALLBACK (switch_active), label1);
    g_signal_connect(GTK_SWITCH (switch2), "notify::active", 
        G_CALLBACK (switch_active), label2);

    //Connects GCallback function gtk_main_quit to "destroy" signal for "window"
    g_signal_connect(G_OBJECT(window), "destroy", 
        G_CALLBACK(gtk_main_quit), NULL);

    gtk_container_add(GTK_CONTAINER(window), box);
    gtk_widget_show_all(window);
    gtk_main();

    return 0;
}

GTK+ example: pass more data to callback using g_object_set_data()

This example show how to attach data to GTK+ object, then pass to callback function.

pass more data to callback using g_object_set_data()

#include <gtk/gtk.h>

static void
accept_clicked (GtkButton *button, GObject *context_object)
{
    GtkLabel *accept_lable1 = g_object_get_data (context_object, "label1");
    GtkLabel *accept_lable2 = g_object_get_data (context_object, "label2");
    GtkEntry *accept_entry1 = g_object_get_data (context_object, "entry1");
    GtkEntry *accept_entry2 = g_object_get_data (context_object, "entry2");

    const char *entry1_in = gtk_entry_get_text (accept_entry1);
    gtk_label_set_text (accept_lable1, entry1_in);
    const char *entry2_in = gtk_entry_get_text (accept_entry2);
    gtk_label_set_text (accept_lable2, entry2_in);
}

int main( int argc, char *argv[])
{
    GtkWidget *window;
    GtkWidget *box;
    GtkWidget *label1;
    GtkWidget *label2;
    GtkWidget *entry1;
    GtkWidget *entry2;
    GtkWidget *buttonAccept;

    GObject *context_object;

    gtk_init(&argc, &argv);
    window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    gtk_window_set_default_size(GTK_WINDOW(window), 400, 250);
    gtk_window_set_title(GTK_WINDOW(window), "Linux-buddy.blogspot.com");

    box = gtk_box_new(GTK_ORIENTATION_VERTICAL, 5);

    //Create label
    label1 = gtk_label_new("label1");
    gtk_box_pack_start(GTK_BOX(box), label1, FALSE, FALSE, 3);
    label2 = gtk_label_new("label2");
    gtk_box_pack_start(GTK_BOX(box), label2, FALSE, FALSE, 3);

    //Create entryBox
    entry1 = gtk_entry_new ();
    gtk_box_pack_start(GTK_BOX(box), entry1, FALSE, FALSE, 3);
    entry2 = gtk_entry_new ();
    gtk_box_pack_start(GTK_BOX(box), entry2, FALSE, FALSE, 3);
    
    buttonAccept = gtk_button_new_with_label ("Accept");
    gtk_box_pack_start(GTK_BOX(box), buttonAccept, FALSE, FALSE, 3);
    g_object_set_data(G_OBJECT(buttonAccept), "label1", label1);
    g_object_set_data(G_OBJECT(buttonAccept), "label2", label2);
    g_object_set_data(G_OBJECT(buttonAccept), "entry1", entry1);
    g_object_set_data(G_OBJECT(buttonAccept), "entry2", entry2);
    g_signal_connect(GTK_BUTTON (buttonAccept), "clicked", 
        G_CALLBACK (accept_clicked), buttonAccept);

    //Connects GCallback function gtk_main_quit to "destroy" signal for "window"
    g_signal_connect(G_OBJECT(window), "destroy", 
        G_CALLBACK(gtk_main_quit), NULL);

    gtk_container_add(GTK_CONTAINER(window), box);
    gtk_widget_show_all(window);
    gtk_main();

    return 0;
}

GTK+ example: Entry

Entry is EditText for GTK+

GTK+ example: Entry

#include <gtk/gtk.h>

static void
entry_activate (GtkEntry *entry, GtkLabel *label)
{
    const char *entry_in = gtk_entry_get_text (entry);
    gtk_label_set_text (label, entry_in);
}

int main( int argc, char *argv[])
{
    GtkWidget *window;
    GtkWidget *box;
    GtkWidget *label;
    GtkWidget *entry;

    gtk_init(&argc, &argv);
    window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    gtk_window_set_default_size(GTK_WINDOW(window), 400, 250);
    gtk_window_set_title(GTK_WINDOW(window), "Linux-buddy.blogspot.com");

    box = gtk_box_new(GTK_ORIENTATION_VERTICAL, 5);

    //Create label
    label = gtk_label_new("label");
    gtk_box_pack_start(GTK_BOX(box), label, FALSE, FALSE, 3);

    //Create entryBox
    entry = gtk_entry_new ();
    gtk_box_pack_start(GTK_BOX(box), entry, FALSE, FALSE, 3);
    g_signal_connect (GTK_ENTRY(entry), "activate", 
        G_CALLBACK(entry_activate), label);
    
    //Connects GCallback function gtk_main_quit to "destroy" signal for "window"
    g_signal_connect(G_OBJECT(window), "destroy", 
        G_CALLBACK(gtk_main_quit), NULL);

    gtk_container_add(GTK_CONTAINER(window), box);
    gtk_widget_show_all(window);
    gtk_main();

    return 0;
}

GTK+ example: handle "toggled" signal of RadioButton and determine the active selected RadioButton in group

This example implement radioButton_toggled() to handle the "toggled" signal from RadioButtons. Inside radioButton_toggled(), check if the button is active by calling gtk_toggle_button_get_active(), to determine the active selected RadioButton in group, then display on Label.

handle "toggled" signal of RadioButton

#include <gtk/gtk.h>

static void
radioButton_toggled (GtkWidget *button, GtkLabel  *label)
{
    char *button_state;
    const char *button_label = 
        gtk_button_get_label (GTK_BUTTON (button));

    if (gtk_toggle_button_get_active (GTK_TOGGLE_BUTTON (button))){
        button_state = "on";
        gtk_label_set_text (label, button_label);
    }
    else {
        button_state = "off";
    }

    g_print ("%s : %s\n", button_label, button_state);
}

int main( int argc, char *argv[])
{
    GtkWidget *window;
    GtkWidget *box;
    GtkWidget *label;

    GtkWidget *radioButton1;
    GtkWidget *radioButton2;
    GtkWidget *radioButton3;

    GtkWidget *radioButton4;
    GtkWidget *radioButton5;
    GSList *groupB;

    gtk_init(&argc, &argv);
    window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    gtk_window_set_default_size(GTK_WINDOW(window), 400, 250);
    gtk_window_set_title(GTK_WINDOW(window), "Linux-buddy.blogspot.com");
    box = gtk_box_new(GTK_ORIENTATION_VERTICAL, 5);

    label = gtk_label_new ("");
    gtk_box_pack_start(GTK_BOX(box), label, FALSE, FALSE, 3);

    //new RadioButton1, 2, 3 in same group
    radioButton1 = gtk_radio_button_new_with_label (
        NULL, "Radio Button 1");
    radioButton2 = gtk_radio_button_new_with_label_from_widget (
        GTK_RADIO_BUTTON (radioButton1), "Radio Button 2");
    radioButton3 = gtk_radio_button_new_with_label_from_widget (
        GTK_RADIO_BUTTON (radioButton1), "Radio Button 3");
    g_signal_connect (GTK_TOGGLE_BUTTON (radioButton1), "toggled", 
        G_CALLBACK (radioButton_toggled), label);
    g_signal_connect (GTK_TOGGLE_BUTTON (radioButton2), "toggled", 
        G_CALLBACK (radioButton_toggled), label);
    g_signal_connect (GTK_TOGGLE_BUTTON (radioButton3), "toggled", 
        G_CALLBACK (radioButton_toggled), label);
    gtk_box_pack_start(GTK_BOX(box), radioButton1, FALSE, FALSE, 3);
    gtk_box_pack_start(GTK_BOX(box), radioButton2, FALSE, FALSE, 3);
    gtk_box_pack_start(GTK_BOX(box), radioButton3, FALSE, FALSE, 3);

    //new RadioButton4, 5 in another group
    radioButton4 = gtk_radio_button_new_with_label (
        NULL, "Group B Button 4");
    groupB = gtk_radio_button_get_group (GTK_RADIO_BUTTON (radioButton4));
    radioButton5 = gtk_radio_button_new_with_label (
        groupB, "Group B Button 5");
    gtk_box_pack_start(GTK_BOX(box), radioButton4, FALSE, FALSE, 3);
    gtk_box_pack_start(GTK_BOX(box), radioButton5, FALSE, FALSE, 3);
    g_signal_connect (radioButton4, "toggled", 
        G_CALLBACK (radioButton_toggled), label);
    g_signal_connect (radioButton5, "toggled", 
        G_CALLBACK (radioButton_toggled), label);

    //Connects GCallback function gtk_main_quit to "destroy" signal for "window"
    g_signal_connect(G_OBJECT(window), "destroy", 
        G_CALLBACK(gtk_main_quit), NULL);

    gtk_container_add(GTK_CONTAINER(window), box);
    gtk_widget_show_all(window);
    gtk_main();

    return 0;
}