<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/loose.dtd">
<HTML
><HEAD
><TITLE
>Rulers</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK
REL="HOME"
TITLE="GTK+ 2.0 Tutorial"
HREF="book1.html"><LINK
REL="UP"
TITLE="Miscellaneous Widgets"
HREF="c753.html"><LINK
REL="PREVIOUS"
TITLE="Dialogs"
HREF="x861.html"><LINK
REL="NEXT"
TITLE="Statusbars"
HREF="x919.html"></HEAD
><BODY
CLASS="SECT1"
BGCOLOR="#FFFFFF"
TEXT="#000000"
LINK="#0000FF"
VLINK="#840084"
ALINK="#0000FF"
><DIV
CLASS="NAVHEADER"
><TABLE
SUMMARY="Header navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="3"
ALIGN="center"
>GTK+ 2.0 Tutorial</TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="bottom"
><A
HREF="x861.html"
ACCESSKEY="P"
><<< Previous</A
></TD
><TD
WIDTH="80%"
ALIGN="center"
VALIGN="bottom"
>Miscellaneous Widgets</TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="bottom"
><A
HREF="x919.html"
ACCESSKEY="N"
>Next >>></A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="SEC-RULERS"
>Rulers</A
></H1
><P
>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 height and a horizontal ruler spanning down the width. A small
triangular indicator on the ruler shows the exact location of the
pointer relative to the ruler.</P
><P
>A ruler must first be created. Horizontal and vertical rulers are
created using</P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>GtkWidget *gtk_hruler_new( void ); /* horizontal ruler */
GtkWidget *gtk_vruler_new( void ); /* vertical ruler */</PRE
></TD
></TR
></TABLE
><P
>Once a ruler is created, we can define the unit of measurement. Units
of measure for rulers can be <TT
CLASS="LITERAL"
>GTK_PIXELS</TT
>, <TT
CLASS="LITERAL"
>GTK_INCHES</TT
> or
<TT
CLASS="LITERAL"
>GTK_CENTIMETERS</TT
>. This is set using</P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>void gtk_ruler_set_metric( GtkRuler *ruler,
GtkMetricType metric );</PRE
></TD
></TR
></TABLE
><P
>The default measure is <TT
CLASS="LITERAL"
>GTK_PIXELS</TT
>.</P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
> gtk_ruler_set_metric( GTK_RULER(ruler), GTK_PIXELS );</PRE
></TD
></TR
></TABLE
><P
>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</P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>void gtk_ruler_set_range( GtkRuler *ruler,
gdouble lower,
gdouble upper,
gdouble position,
gdouble max_size );</PRE
></TD
></TR
></TABLE
><P
>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.</P
><P
>A vertical ruler can span an 800 pixel wide window thus</P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
> gtk_ruler_set_range( GTK_RULER(vruler), 0, 800, 0, 800);</PRE
></TD
></TR
></TABLE
><P
>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</P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
> gtk_ruler_set_range( GTK_RULER(vruler), 7, 16, 0, 20);</PRE
></TD
></TR
></TABLE
><P
>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</P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>#define EVENT_METHOD(i, x) GTK_WIDGET_GET_CLASS(i)->x
g_signal_connect_swapped (area, "motion_notify_event",
G_CALLBACK (EVENT_METHOD (ruler, motion_notify_event)),
ruler);</PRE
></TD
></TR
></TABLE
><P
>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.</P
><P
><SPAN
CLASS="INLINEMEDIAOBJECT"
><IMG
SRC="images/rulers.png"></SPAN
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
> #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 (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 (area, "motion_notify_event",
G_CALLBACK (EVENT_METHOD (hrule, motion_notify_event)),
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 (area, "motion_notify_event",
G_CALLBACK (EVENT_METHOD (vrule, motion_notify_event)),
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;
}</PRE
></TD
></TR
></TABLE
></DIV
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="x861.html"
ACCESSKEY="P"
><<< Previous</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="book1.html"
ACCESSKEY="H"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="x919.html"
ACCESSKEY="N"
>Next >>></A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>Dialogs</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="c753.html"
ACCESSKEY="U"
>Up</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>Statusbars</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>