Very slow gdk_draw_pixbuf

[Barry Demchak <vendors tpsoft com>]

Hi --

I am trying to use gdk_draw_pixbuf to render a .PNG into a window via a 
pixmap. (Actually, this is a much simplified case of trying to use librsvg 
to render into a window.)

To make it as simple as possible, I grafted a gdk_draw_pixbuf call into 
scribble. When the rendering occurs, it takes about 2 seconds and I'm 
watching wild network activity ... probably a bunch of calls between an X 
client and an X server ... my guess.

What could be going on here?? And how can I avoid this delay?? (The reason 
I'm pushing this through pixbuf is that librsvg will be leaving its result 
in a pixbuf.)

I have included the scribble code below ... my changes are marked by a 
DRAW_PIXBUF conditional. The problem is very obvious when one resizes the 
window.

Can someone shed light on this??

Thanks!!!

--------------

/* GTK - The GIMP Toolkit
 * Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#include <stdlib.h>
#include <gtk/gtk.h>

#define DRAW_PIXBUF

#ifdef DRAW_PIXBUF
GdkPixbuf* pixbuf = NULL;
#endif

/* Backing pixmap for drawing area */
static GdkPixmap *pixmap = NULL;

/* Create a new backing pixmap of the appropriate size */
static gboolean configure_event( GtkWidget         *widget,
                                 GdkEventConfigure *event )
{
  if (pixmap)
    g_object_unref (pixmap);

  pixmap = gdk_pixmap_new (widget->window,
                           widget->allocation.width,
                           widget->allocation.height,
                           -1);

#ifdef DRAW_PIXBUF
  if (pixbuf == NULL)
    pixbuf = gdk_pixbuf_new_from_file((gchar *) "mapserv.png", NULL);

  if (pixbuf)
    gdk_draw_pixbuf(pixmap, NULL, pixbuf, 0, 0, 0, 0, -1, -1, 
GDK_RGB_DITHER_NORMAL, 0, 0);
  else
    g_print("No pixbuf!\n");
#else
  gdk_draw_rectangle (pixmap,
                      widget->style->white_gc,
                      TRUE,
                      0, 0,
                      widget->allocation.width,
                      widget->allocation.height);
#endif

  g_print("configure_event\n");

  return TRUE;
}

/* Redraw the screen from the backing pixmap */
static gboolean expose_event( GtkWidget      *widget,
                              GdkEventExpose *event )
{
  gdk_draw_drawable (widget->window,
                     widget->style->fg_gc[GTK_WIDGET_STATE (widget)],
                     pixmap,
                     event->area.x, event->area.y,
                     event->area.x, event->area.y,
                     event->area.width, event->area.height);

  g_print("expose_event\n");
  return FALSE;
}

/* Draw a rectangle on the screen */
static void draw_brush( GtkWidget *widget,
                        gdouble    x,
                        gdouble    y)
{
  GdkRectangle update_rect;

  update_rect.x = (int) (x - 5);
  update_rect.y = (int) (y - 5);
  update_rect.width = 10;
  update_rect.height = 10;
  gdk_draw_rectangle (pixmap,
                      widget->style->black_gc,
                      TRUE,
                      update_rect.x, update_rect.y,
                      update_rect.width, update_rect.height);
  gtk_widget_queue_draw_area (widget,
                              update_rect.x, update_rect.y,
                              update_rect.width, update_rect.height);
}

static gboolean button_press_event( GtkWidget      *widget,
                                    GdkEventButton *event )
{
  if (event->button == 1 && pixmap != NULL)
    draw_brush (widget, event->x, event->y);

  return TRUE;
}

static gboolean motion_notify_event( GtkWidget *widget,
                                     GdkEventMotion *event )
{
  int x, y;
  GdkModifierType state;

  if (event->is_hint)
    gdk_window_get_pointer (event->window, &x, &y, &state);
  else
    {
      x = (int) event->x;
      y = (int) event->y;
      state = (GdkModifierType) event->state;
    }

  if (state & GDK_BUTTON1_MASK && pixmap != NULL)
    draw_brush (widget, x, y);

  return TRUE;
}

void quit ()
{
  exit (0);
}

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

  GtkWidget *button;

  gtk_init (&argc, &argv);

  window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
  gtk_widget_set_name (window, "Test Input");

  vbox = gtk_vbox_new (FALSE, 0);
  gtk_container_add (GTK_CONTAINER (window), vbox);
  gtk_widget_show (vbox);

  g_signal_connect (G_OBJECT (window), "destroy",
                    G_CALLBACK (quit), NULL);

  /* Create the drawing area */

  drawing_area = gtk_drawing_area_new ();
  gtk_widget_set_size_request (GTK_WIDGET (drawing_area), 200, 200);
  gtk_box_pack_start (GTK_BOX (vbox), drawing_area, TRUE, TRUE, 0);

  gtk_widget_show (drawing_area);

  /* Signals used to handle backing pixmap */

  g_signal_connect (G_OBJECT (drawing_area), "expose_event",
                    G_CALLBACK (expose_event), NULL);
  g_signal_connect (G_OBJECT (drawing_area),"configure_event",
                    G_CALLBACK (configure_event), NULL);

  /* Event signals */

  g_signal_connect (G_OBJECT (drawing_area), "motion_notify_event",
                    G_CALLBACK (motion_notify_event), NULL);
  g_signal_connect (G_OBJECT (drawing_area), "button_press_event",
                    G_CALLBACK (button_press_event), NULL);

  gtk_widget_set_events (drawing_area, GDK_EXPOSURE_MASK
                        | GDK_LEAVE_NOTIFY_MASK
                        | GDK_BUTTON_PRESS_MASK
                        | GDK_POINTER_MOTION_MASK
                        | GDK_POINTER_MOTION_HINT_MASK);

  /* .. And a quit button */
  button = gtk_button_new_with_label ("Quit");
  gtk_box_pack_start (GTK_BOX (vbox), button, FALSE, FALSE, 0);

  g_signal_connect_swapped (G_OBJECT (button), "clicked",
                            G_CALLBACK (gtk_widget_destroy),
                            G_OBJECT (window));
  gtk_widget_show (button);

  gtk_widget_show (window);

  gtk_main ();

  return 0;
}