GTK#

Miscellaneous Widgets

Ruler

Ruler widgets are used to indicate the location of the mouse pointer in a given window. A window can have a vertical ruler spanning across the width and a horizontal ruler spanning down the height. A small triangular indicator on the ruler shows the exact location of the pointer relative to the ruler.

A ruler must first be created. Horizontal and vertical rulers are created using

HRuler hruler1 = new HRuler();    /* horizontal ruler */
VRuler vruler1 = new VRuler();    /* vertical ruler   */
Once a ruler is created, we can define the unit of measurement. Units of measure for rulers can be Gtk.Pixels, Gtk.Inches or Gtk.Centimeters. This is set using
hruler1.Metric = MetricType  metric;
The default measure is Gtk.Pixels.
hruler1.Metric = Gtk.Pixels;
Other important characteristics of a ruler are how to mark the units of scale and where the position indicator is initially placed. These are set for a ruler using
hruler.SetRange(          double   lower,
                          double   upper,
                          double   position,
                          double   max_size );
The lower and upper arguments define the extent of the ruler, and max_size is the largest possible number that will be displayed. Position defines the initial position of the pointer indicator within the ruler.

A vertical ruler can span an 800 pixel wide window thus

hruler.SetRange(0, 800, 0, 800);
The markings displayed on the ruler will be from 0 to 800, with a number for every 100 pixels. If instead we wanted the ruler to range from 7 to 16, we would code
hruler.SetRange(7, 16, 0, 20);
The indicator on the ruler is a small triangular mark that indicates the position of the pointer relative to the ruler. If the ruler is used to follow the mouse pointer, the motion_notify_event signal should be connected to the motion_notify_event method of the ruler. To follow all mouse movements within a window area, we would use
#define EVENT_METHOD(i, x) GTK_WIDGET_GET_CLASS(i)->x

    g_signal_connect_swapped (G_OBJECT (area),
"motion_notify_event",
           G_CALLBACK (EVENT_METHOD (ruler, motion_notify_event)),
           G_OBJECT (ruler));
The following example creates a drawing area with a horizontal ruler above it and a vertical ruler to the left of it. The size of the drawing area is 600 pixels wide by 400 pixels high. The horizontal ruler spans from 7 to 13 with a mark every 100 pixels, while the vertical ruler spans from 0 to 400 with a mark every 100 pixels. Placement of the drawing area and the rulers is done using a table.

#include >gtk/gtk.h<

#define EVENT_METHOD(i, x) GTK_WIDGET_GET_CLASS(i)->x

#define XSIZE  600
#define YSIZE  400

/* This routine gets control when the close button is clicked */
static gboolean close_application( GtkWidget *widget,
                                   GdkEvent  *event,
                                   gpointer   data )
{
    gtk_main_quit ();
    return FALSE;
}

/* The main routine */
int main( int   argc,
          char *argv[] ) {
    GtkWidget *window, *table, *area, *hrule, *vrule;

    /* Initialize GTK and create the main window */
    gtk_init (&argc, &argv);

    window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
    g_signal_connect (G_OBJECT (window), "delete_event",
                      G_CALLBACK (close_application), NULL);
    gtk_container_set_border_width (GTK_CONTAINER (window), 10);

    /* Create a table for placing the ruler and the drawing area */
    table = gtk_table_new (3, 2, FALSE);
    gtk_container_add (GTK_CONTAINER (window), table);

    area = gtk_drawing_area_new ();
    gtk_widget_set_size_request (GTK_WIDGET (area), XSIZE, YSIZE);
    gtk_table_attach (GTK_TABLE (table), area, 1, 2, 1, 2,
                      GTK_EXPAND|GTK_FILL, GTK_FILL, 0, 0);
    gtk_widget_set_events (area, GDK_POINTER_MOTION_MASK |
                                 GDK_POINTER_MOTION_HINT_MASK);

    /* The horizontal ruler goes on top. As the mouse moves across
the
     * drawing area, a motion_notify_event is passed to the
     * appropriate event handler for the ruler. */
    hrule = gtk_hruler_new ();
    gtk_ruler_set_metric (GTK_RULER (hrule), GTK_PIXELS);
    gtk_ruler_set_range (GTK_RULER (hrule), 7, 13, 0, 20);
    g_signal_connect_swapped (G_OBJECT (area),
"motion_notify_event",
                              G_CALLBACK (EVENT_METHOD (hrule,
motion_notify_event)),
                              G_OBJECT (hrule));
    gtk_table_attach (GTK_TABLE (table), hrule, 1, 2, 0, 1,
                      GTK_EXPAND|GTK_SHRINK|GTK_FILL, GTK_FILL, 0,
0);
    
    /* The vertical ruler goes on the left. As the mouse moves
across
     * the drawing area, a motion_notify_event is passed to the
     * appropriate event handler for the ruler. */
    vrule = gtk_vruler_new ();
    gtk_ruler_set_metric (GTK_RULER (vrule), GTK_PIXELS);
    gtk_ruler_set_range (GTK_RULER (vrule), 0, YSIZE, 10, YSIZE );
    g_signal_connect_swapped (G_OBJECT (area),
"motion_notify_event",
                              G_CALLBACK (EVENT_METHOD (vrule,
motion_notify_event)),
                              G_OBJECT (vrule));
    gtk_table_attach (GTK_TABLE (table), vrule, 0, 1, 1, 2,
                      GTK_FILL, GTK_EXPAND|GTK_SHRINK|GTK_FILL, 0,
0);

    /* Now show everything */
    gtk_widget_show (area);
    gtk_widget_show (hrule);
    gtk_widget_show (vrule);
    gtk_widget_show (table);
    gtk_widget_show (window);
    gtk_main ();

    return 0;
}