Re: Got my statusbar displaying locations HURRAY THANKS, next

[Deborah Swayne <dfs research att com>]

> Could someone please enligntenment on the proper procedure for doing the
> following.
> 1. create pixmap size of screen (done i think);
> 2. put all data into pixmap. (maybe done)
> 3. blit to screen ???
> 4. if resize destroy current pixmap and rebuild

I handle these myself, though some people prefer to use a canvas.  I
end up using two pixmaps, one for the basic drawing, and one for the
drawing plus some decorations which may change frequently, as the
mouse is moved.

---- Questions 1 and 4  ----

Attach a callback to your drawing area:

  gtk_signal_connect (GTK_OBJECT (sp->da),
                      "configure_event",
                      (GtkSignalFunc) splot_configure_cb,
                      (gpointer) sp);

In the configure event handler, create or resize the pixmap:

static gint
splot_configure_cb (GtkWidget *w, GdkEventConfigure *event, splotd *sp)
{
  if (w->allocation.width == 1 || w->allocation.height == 1)
    return false;

  /*-- Create new backing pixmaps of the appropriate size --*/
  if (sp->pixmap0 != NULL)
    gdk_pixmap_unref (sp->pixmap0);
  if (sp->pixmap1 != NULL)
    gdk_pixmap_unref (sp->pixmap1);

  sp->pixmap0 = gdk_pixmap_new (w->window,
    w->allocation.width, w->allocation.height, -1);
  sp->pixmap1 = gdk_pixmap_new (w->window,
    w->allocation.width, w->allocation.height, -1);

  gtk_widget_queue_draw (sp->da);

  return false;
}

---- Question 3  ----

Blit pixmap to screen:

The basic routines are as
follows:

  /* clear the pixmap */
  gdk_gc_set_foreground (gg->plot_GC, &gg->bg_color);
  gdk_draw_rectangle (sp->pixmap0, gg->plot_GC,
                      TRUE, 0, 0,
                      da->allocation.width,
                      da->allocation.height);

  /* draw to the pixmap; code not shown */

  /* copy pixmap0 to pixmap1 */
  gdk_draw_pixmap (sp->pixmap1, gg->plot_GC, sp->pixmap0,
                   0, 0, 0, 0,
                   w->allocation.width,
                   w->allocation.height);

  /* copy pixmap1 to the window */
  w = sp->da;
  gdk_draw_pixmap (w->window, gg->plot_GC, sp->pixmap1,
                   0, 0, 0, 0,
                   w->allocation.width,
                   w->allocation.height);

  
Debby