GTK v1.2 Tutorial(英文)

来源：Linux-cn.com 作者：Webmaster 时间：2007-05-05 点击： [收藏] [投稿]

　　To make the wheelbarrow image sensitive, we could attach the button press event signal to make it do something. The following few lines would make the picture sensitive to a mouse button being pressed which makes the application terminate.


gtk_widget_set_events( window,
gtk_widget_get_events( window ) |
GDK_BUTTON_PRESS_MASK );
gtk_signal_connect( GTK_OBJECT(window), "button_press_event",
GTK_SIGNAL_FUNC(close_application), NULL );

9.7 Rulers

　　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


GtkWidget *gtk_hruler_new( void );/* horizontal ruler */
GtkWidget *gtk_vruler_new( void );/* vertical ruler */

　　Once a ruler is created, we can define the unit of measurement. Units of measure for rulers can beGTK_PIXELS, GTK_INCHES or GTK_CENTIMETERS. This is set using


void gtk_ruler_set_metric( GtkRuler*ruler,GtkMetricTypemetric );

　　The default measure is GTK_PIXELS.


gtk_ruler_set_metric( GTK_RULER(ruler), 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


void gtk_ruler_set_range( GtkRuler *ruler,
gfloatlower,gfloatupper,gfloatposition,gfloatmax_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


gtk_ruler_set_range( GTK_RULER(vruler), 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


gtk_ruler_set_range( GTK_RULER(vruler), 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_CLASS(GTK_OBJECT(i)->klass)->x
gtk_signal_connect_object( GTK_OBJECT(area), "motion_notify_event",
(GtkSignalFunc)EVENT_METHOD(ruler, motion_notify_event),
GTK_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.


/* example-start rulers rulers.c */
#include <gtk/gtk.h>
#define EVENT_METHOD(i, x) GTK_WIDGET_CLASS(GTK_OBJECT(i)->klass)->x
#define XSIZE600
#define YSIZE400
/* This routine gets control when the close button is clicked */
gint 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 );
gtk_signal_connect (GTK_OBJECT (window), "delete_event",
GTK_SIGNAL_FUNC( 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_drawing_area_size( (GtkDrawingArea *)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 );
gtk_signal_connect_object( GTK_OBJECT(area), "motion_notify_event",
 (GtkSignalFunc)EVENT_METHOD(hrule,
motion_notify_event),
 GTK_OBJECT(hrule) );
/*GTK_WIDGET_CLASS(GTK_OBJECT(hrule)->klass)->motion_notify_event,*/
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 );
gtk_signal_connect_object( GTK_OBJECT(area), "motion_notify_event",
 (GtkSignalFunc)
GTK_WIDGET_CLASS(GTK_OBJECT(vrule)->klass)->
 motion_notify_event,
 GTK_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);
}
/* example-end */

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