<page xmlns="http://projectmallard.org/1.0/" xmlns:its="http://www.w3.org/2005/11/its" xmlns:xi="http://www.w3.org/2001/XInclude" type="guide" style="task" id="scale.c" xml:lang="de">

  <info>

    <title type="text">Scale (C)</title>

    <link type="guide" xref="c#entry"/>

    <link type="seealso" xref="grid.c"/>

    <link type="seealso" xref="label.c"/>

    <revision version="0.2" date="2012-07-04" status="draft"/>

    <credit type="author copyright">

      <name>Monica Kochofar</name>

      <email its:translate="no">monicakochofar@gmail.com</email>

      <years>2012</years>

    </credit>

    <desc>A slider widget for selecting a value from a range</desc>

    <mal:credit xmlns:mal="http://projectmallard.org/1.0/" type="translator copyright">

      <mal:name>Mario Blättermann</mal:name>

      <mal:email>mario.blaettermann@gmail.com</mal:email>

      <mal:years>2011, 2013</mal:years>

    </mal:credit>

  </info>

  <title>Scale</title>

  <media type="image" mime="image/png" src="media/scale2.png"/>

  
Slide the scales!

#include <gtk/gtk.h>

/* This is the callback function. 

 * It is a handler function which reacts to the signal. 

 * In this case, it will notify the user the value of their scale as a label.

 */

static void

hscale_moved (GtkRange *range,

              gpointer  user_data)

{

   GtkWidget *label = user_data;

   /* Get the value of the range, and convert it into a string which will be

    * used as a new label for the horizontal scale.

    * %.0f - stands for a double that will have 0 decimal places.

    */

   gdouble pos = gtk_range_get_value (range);

   /* Note: Using g_strdup_printf returns a string that must be freed. 

    * (In which is done below)

    */

   gchar *str = g_strdup_printf ("Horizontal scale is %.0f", pos);

   gtk_label_set_text (GTK_LABEL (label), str);

   g_free(str);

}

/* This is the second callback function. It is a handler function which 

 * reacts to the signal. It does the same thing as the function above, except with

 * the vertical scale.

 */

vscale_moved (GtkRange *range,

              gpointer  user_data)

{

   GtkWidget *label = user_data;

   gdouble pos = gtk_range_get_value (range);

   /* %.1f - stands for a double that will have 1 decimal place */

   gchar *str = g_strdup_printf ("Vertical scale is %.1f", pos);

   gtk_label_set_text (GTK_LABEL (label), str);

   g_free (str);

}

static void

activate (GtkApplication *app,

          gpointer        user_data)

{

  /* Declare variables */

  GtkWidget *window;

  GtkWidget *h_scale;

  GtkWidget *v_scale;

  GtkWidget *hlabel;

  GtkWidget *vlabel;

  GtkWidget *grid;

  /* The Adjustment object represents a value 

   * which has an associated lower and upper bound.

   */

  GtkAdjustment *hadjustment;

  GtkAdjustment *vadjustment;

  /* Create a window with a title and a default size */

  window = gtk_application_window_new (app);

  gtk_window_set_title (GTK_WINDOW (window), "Scale Example");

  gtk_window_set_default_size (GTK_WINDOW (window), 400, 300);

  gtk_container_set_border_width (GTK_CONTAINER (window), 5);

  /* Two labels to be shown in the window */

  hlabel = gtk_label_new ("Move the scale handle...");

  vlabel = gtk_label_new ("Move the scale handle...");

  /* gtk_adjustment_new takes six parameters, three of which 

   * may be difficult to understand:

   * step increment- move the handle with the arrow keys on your keyboard to see.

   * page increment - move the handle by clicking away from it 

   * on the scale to see.

   * page size - not used here.

   */

  hadjustment = gtk_adjustment_new (0, 0, 100, 5, 10, 0);

  vadjustment = gtk_adjustment_new (50, 0, 100, 5, 10, 0); 

  /* Create the Horizontal scale, making sure the 

   * digits used have no decimals.

   */

  h_scale = gtk_scale_new (GTK_ORIENTATION_HORIZONTAL, hadjustment);

  gtk_scale_set_digits (GTK_SCALE (h_scale), 0); 

  /* Allow it to expand horizontally (if there's space), and 

   * set the vertical alignment

   */

  gtk_widget_set_hexpand (h_scale, TRUE);

  gtk_widget_set_valign (h_scale, GTK_ALIGN_START);

  /* Connecting the "value-changed" signal for the horizontal scale 

   * to the appropriate callback function. 

   * take note that GtkRange is part of GtkScale's Object Hierarchy.

   */

  g_signal_connect (h_scale, 

                    "value-changed", 

                    G_CALLBACK (hscale_moved), 

                    hlabel);

  /* Create the Vertical scale. This time, we will see what happens 

   * when the digits arent initially set.

   */

  v_scale = gtk_scale_new (GTK_ORIENTATION_VERTICAL, vadjustment);

  gtk_widget_set_vexpand (v_scale, TRUE);

  /* Connecting the "value-changed" signal for the vertical scale to 

   * the appropriate callback function.

   */

  g_signal_connect (v_scale, 

                    "value-changed", 

                    G_CALLBACK (vscale_moved), 

                    vlabel);

  /* Create a grid and arrange everything accordingly */

  grid = gtk_grid_new ();

  gtk_grid_set_column_spacing (GTK_GRID (grid), 10);

  gtk_grid_set_column_homogeneous (GTK_GRID (grid), TRUE);

  gtk_grid_attach (GTK_GRID (grid), h_scale, 0, 0, 1, 1);

  gtk_grid_attach (GTK_GRID (grid), v_scale, 1, 0, 1, 1);

  gtk_grid_attach (GTK_GRID (grid), hlabel, 0, 1, 1, 1);

  gtk_grid_attach (GTK_GRID (grid), vlabel, 1, 1, 1, 1);

  gtk_container_add (GTK_CONTAINER (window), grid);

  gtk_widget_show_all (window);

}

int

main (int argc, char **argv)

{

  GtkApplication *app;

  int status;

  app = gtk_application_new ("org.gtk.example", G_APPLICATION_FLAGS_NONE);

  g_signal_connect (app, "activate", G_CALLBACK (activate), NULL);

  status = g_application_run (G_APPLICATION (app), argc, argv);

  g_object_unref (app);

  return status;

}

  In this sample we used the following:

<list>

  <item>
<link href="http://developer.gnome.org/gtk3/3.4/GtkApplication.html">GtkApplication</link>
</item>

  <item>
<link href="http://developer.gnome.org/gtk3/3.4/GtkWindow.html">GtkWindow</link>
</item>

  <item>
<link href="http://developer.gnome.org/gtk3/stable/GtkScale.html">GtkScale</link>
</item>

  <item>
<link href="http://developer.gnome.org/gtk3/stable/GtkRange.html">GtkRange</link>
</item>

  <item>
<link href="http://developer.gnome.org/gtk3/stable/GtkAdjustment.html">GtkAdjustment</link>
</item>

  <item>
<link href="http://developer.gnome.org/glib/stable/glib-String-Utility-Functions.html#g-strdup-printf">String Utility Functions</link>
</item>

</list>

</page>