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| - | In this part of the GTK+ programming tutorial, we will create our first programs in GTK+
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| - | == Simple example ==
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| - |
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| - | We start with a very simple example. We will show a basic window.
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| - |
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| - | <source lang="cpp">
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| - | #include <gtk/gtk.h>
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| - |
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| - | int main( int argc, char *argv[])
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| - | {
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| - | GtkWidget *window;
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| - |
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| - | gtk_init(&argc, &argv);
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| - |
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| - | window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
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| - | gtk_widget_show(window);
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| - |
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| - | gtk_main();
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| - |
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| - | return 0;
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| - | }
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| - | </source>
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| - | This example will show a basic window on screen.
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| - |
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| - | <source lang="cpp">
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| - | gcc -o simple simple.c `pkg-config --libs --cflags gtk+-2.0`
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| - | </source>
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| - |
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| - | This is how we compile the example.
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| - | <source lang="cpp">
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| - | gtk_init(&argc, &argv);
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| - | </source>
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| - |
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| - | Here we initiate the GTK+ library.
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| - | <source lang="cpp">
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| - | window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
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| - | </source>
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| - |
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| - | We create a <b>GTK_WINDOW_TOPLEVEL</b>.
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| - | Toplevel windows have a titlebar and a border. They are managed by the window manager.
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| - | <source lang="cpp">
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| - | gtk_widget_show(window);
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| - | </source>
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| - | After we have created a widget, we must show it.
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| - | <source lang="cpp">
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| - | gtk_main();
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| - | </source>
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| - | This code enters the GTK+ main loop. From this point, the application sits and waits for events to happen.
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| - | [[image: gtk_faq_simple.png | center]]
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| - |
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| - | == Centering the window ==
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| - | If we do not position the window ourselves, the window manager will position it for us.
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| - | In the next example, we will center the window.
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| - |
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| - | <source lang="cpp">
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| - | #include <gtk/gtk.h>
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| - | int main( int argc, char *argv[])
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| - | {
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| - | GtkWidget *window;
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| - | gtk_init(&argc, &argv);
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| - | window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
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| - | gtk_window_set_title(GTK_WINDOW(window), "Center");
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| - | gtk_window_set_default_size(GTK_WINDOW(window), 230, 150);
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| - | gtk_window_set_position(GTK_WINDOW(window), GTK_WIN_POS_CENTER);
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| - | gtk_widget_show(window);
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| - | g_signal_connect_swapped(G_OBJECT(window), "destroy",
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| - | G_CALLBACK(gtk_main_quit), NULL);
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| - |
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| - | gtk_main();
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| - |
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| - | return 0;
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| - | }
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| - | </source>
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| - |
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| - | In our example, we center the window, set a title and size for the window.
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| - | <source lang="cpp">
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| - | gtk_window_set_title(GTK_WINDOW(window), "Center");
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| - | </source>
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| - | The <b>gtk_window_set_title()</b> function will set a window title. If we do not set a title ourselves, the GTK+ will use a name of a source file as a title.
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| - | <source lang="cpp">
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| - | gtk_window_set_default_size(GTK_WINDOW(window), 230, 150);
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| - | </source>
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| - | This code sets the size of the window to 230x150 pixels. Note, that we are talking about the client area, excluding the decorations provided by the window manager.
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| - |
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| - | <source lang="cpp">
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| - | gtk_window_set_position(GTK_WINDOW(window), GTK_WIN_POS_CENTER);
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| - | </source>
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| - | This code centers the window.
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| - |
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| - | <source lang="cpp">
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| - | g_signal_connect_swapped(G_OBJECT(window), "destroy",
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| - | G_CALLBACK(gtk_main_quit), NULL);
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| - | </source>
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| - | In the previous example, the window was not completely destroyed, when we clicked on the x button. We can see it, if we lauch the example from the command line. The window does not react to the <b>destroy</b> signal by default. We must explicitely terminate the application by connecting the destroy signal to the <b>gtk_main_quit()</b> function.
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| - |
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| - | == The application icon ==
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| - |
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| - | In the next example, we show the application icon. Most window managers display the icon in the left corner of the titlebar and also on the taskbar.
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| - |
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| - | <source lang="cpp">
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| - | #include <gtk/gtk.h>
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| - | GdkPixbuf *create_pixbuf(const gchar * filename)
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| - | {
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| - | GdkPixbuf *pixbuf;
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| - | GError *error = NULL;
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| - | pixbuf = gdk_pixbuf_new_from_file(filename, &error);
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| - | if(!pixbuf) {
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| - | fprintf(stderr, "%s\n", error->message);
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| - | g_error_free(error);
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| - | }
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| - | return pixbuf;
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| - | }
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| - | int main( int argc, char *argv[])
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| - | {
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| - | GtkWidget *window;
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| - | gtk_init(&argc, &argv);
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| - | window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
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| - | gtk_window_set_title(GTK_WINDOW(window), "icon");
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| - | gtk_window_set_default_size(GTK_WINDOW(window), 230, 150);
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| - | gtk_window_set_position(GTK_WINDOW(window), GTK_WIN_POS_CENTER);
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| - | gtk_window_set_icon(GTK_WINDOW(window), create_pixbuf("web.png"));
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| - | gtk_widget_show(window);
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| - | g_signal_connect_swapped(G_OBJECT(window), "destroy",
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| - | G_CALLBACK(gtk_main_quit), NULL);
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| - | gtk_main();
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| - | return 0;
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| - | }
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| - | </source>
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| - | The code example shows the application icon.
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| - | <source lang="cpp">
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| - | gtk_window_set_icon(GTK_WINDOW(window), create_pixbuf("web.png"));
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| - | </source>
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| - | The <b>gtk_window_set_icon()</b> displays the icon for our window. The <b>GdkPixbuf</b> from a png file.
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| - | <source lang="cpp">
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| - | pixbuf = gdk_pixbuf_new_from_file(filename, &error);
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| - | </source>
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| - | According to the documentation, the <b>gdk_pixbuf_new_from_file()</b> function creates a new pixbuf by loading an image from a file. The file format is detected automatically. If NULL is returned, then error will be set.
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| - | [[image: gtk_faq_icon.png | center]]
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| - | [[image: gtk_faq_taskbar.png | center]]
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| - | == Increase - Decrease ==
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| - | We finish the first chapter of the GTK+ programming tutorial with an example, where we have three child widgets.
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| - | Two buttons and one label. The label will hold an integer number. The buttons will increase or decrease this number.
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| - | <source lang="cpp">
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| - | #include <gtk/gtk.h>
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| - | gint count = 0;
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| - | char buf[5];
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| - | void increase(GtkWidget *widget, gpointer label)
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| - | {
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| - | count++;
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| - | sprintf(buf, "%d", count);
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| - | gtk_label_set_text(label, buf);
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| - | }
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| - | void decrease(GtkWidget *widget, gpointer label)
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| - | {
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| - | count--;
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| - | sprintf(buf, "%d", count);
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| - | gtk_label_set_text(label, buf);
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| - | }
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| - | int main(int argc, char** argv) {
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| - | GtkWidget *label;
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| - | GtkWidget *window;
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| - | GtkWidget *frame;
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| - | GtkWidget *plus;
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| - | GtkWidget *minus;
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| - | gtk_init(&argc, &argv);
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| - | window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
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| - | gtk_window_set_position(GTK_WINDOW(window), GTK_WIN_POS_CENTER);
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| - | gtk_window_set_default_size(GTK_WINDOW(window), 250, 180);
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| - | gtk_window_set_title(GTK_WINDOW(window), "+-");
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| - | frame = gtk_fixed_new();
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| - | gtk_container_add(GTK_CONTAINER(window), frame);
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| - | plus = gtk_button_new_with_label("+");
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| - | gtk_widget_set_size_request(plus, 80, 35);
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| - | gtk_fixed_put(GTK_FIXED(frame), plus, 50, 20);
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| - | minus = gtk_button_new_with_label("-");
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| - | gtk_widget_set_size_request(minus, 80, 35);
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| - | gtk_fixed_put(GTK_FIXED(frame), minus, 50, 80);
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| - | label = gtk_label_new("0");
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| - | gtk_fixed_put(GTK_FIXED(frame), label, 190, 58);
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| - | gtk_widget_show_all(window);
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| - | g_signal_connect(window, "destroy",
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| - | G_CALLBACK (gtk_main_quit), NULL);
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| - | g_signal_connect(plus, "clicked",
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| - | G_CALLBACK(increase), label);
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| - | g_signal_connect(minus, "clicked",
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| - | G_CALLBACK(decrease), label);
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| - | gtk_main();
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| - | return 0;
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| - | }
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| - | </source>
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| - | The code example increases or decreases a value in a GtkLabel.
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| - | <source lang="cpp">
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| - | g_signal_connect(plus, "clicked",
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| - | G_CALLBACK(increase), label);
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| - | </source>
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| - | We connect the <b>increase()</b> callback to the plus button. Note that we send a label as a parameter to the callback. We will work on this label inside the callback function.
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| - | <source lang="cpp">
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| - | count++;
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| - | sprintf(buf, "%d", count);
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| - | gtk_label_set_text(label, buf);
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| - | </source>
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| - | Inside the increase callback, we increase the counter. Make textual data out of the number value and update the label.
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| - | [[image: gtk_faq_plusminus.png | center]]
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| - | [[Категория:GTK+]]
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