# Scale (C)

Monica Kochofar
monicakochofar@gmail.com 2012
A slider widget for selecting a value from a range
Rafael Fontenelle
rafaelff@gnome.org 2013, 2018

# Scale

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. */ static void 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 aren't 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:

GtkApplication

GtkWindow

GtkScale

GtkRange

GtkAdjustment

String Utility Functions