<?xml version="1.0" encoding="utf-8"?>
<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="ca">
<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>
</info>
<title>Scale</title>
<media type="image" mime="image/png" src="media/scale2.png"/>
<p>Slide the scales!</p>
<code mime="text/x-csrc" style="numbered">
#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;
}
</code>
<p>
In this sample we used the following:
</p>
<list>
<item><p><link href="http://developer.gnome.org/gtk3/3.4/GtkApplication.html">GtkApplication</link></p></item>
<item><p><link href="http://developer.gnome.org/gtk3/3.4/GtkWindow.html">GtkWindow</link></p></item>
<item><p><link href="http://developer.gnome.org/gtk3/stable/GtkScale.html">GtkScale</link></p></item>
<item><p><link href="http://developer.gnome.org/gtk3/stable/GtkRange.html">GtkRange</link></p></item>
<item><p><link href="http://developer.gnome.org/gtk3/stable/GtkAdjustment.html">GtkAdjustment</link></p></item>
<item><p><link href="http://developer.gnome.org/glib/stable/glib-String-Utility-Functions.html#g-strdup-printf">String Utility Functions</link></p></item>
</list>
</page>