Re: Please, Give me advise about my first line draw program.

[Paolo Costabel <paolo imageworks com>]

Donggyoo Lee wrote:
> Sorry, Oh my misktake. Here is source.
> Please give me advise.
>
>   ------------------------------------------------------------------------
>
>    myline.cName: myline.c
>            Type: text/x-csrc

GtkDrawingArea is a widget. You can't just draw directly into it.
Instead, you have to provide a callback for expose events. Tis will be
called
every time the widget needs refreshing.
I have attached a modified version that works.
However, in general you will want to use a back buffer pixmap for your
drawing operations
and copy it in the drawing area inside the expose callback. See
scribble-simple in
the example directory of gtk source tree.
-- 
---------------------------------------------------------------------
Paolo Costabel                Visit The Internet Comic Books Database 
Sony Imageworks                           http://www.comicsdb.com

#include <gtk/gtk.h>

#define XSIZE  600
#define YSIZE  400

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

/* Redraw the screen from the backing pixmap */
static gint
expose_event (GtkWidget *widget, GdkEventExpose *event)
{
        gdk_draw_line(widget->window, widget->style->black_gc, 0, 0, 300, 300);
        return FALSE;
}


/* The main routine */
int main( int argc, char *argv[] )
{
        GtkWidget       *window, *drawing_area;

        /* 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);


        drawing_area = gtk_drawing_area_new ();
        gtk_container_add (GTK_CONTAINER (window), drawing_area);
        gtk_signal_connect (GTK_OBJECT (drawing_area), "expose_event",
                          GTK_SIGNAL_FUNC (expose_event), NULL);
        gtk_drawing_area_size (drawing_area, XSIZE, YSIZE);
        gtk_widget_show (drawing_area);
        gtk_widget_set_events (drawing_area, GDK_EXPOSURE_MASK);

        /* Now show everything */
        gtk_widget_show (window);
        gtk_main ();

        return 0;
}