gtk/demos/gtk-demo/images.c

/* Images
 *
 * GtkImage is used to display an image; the image can be in a number of formats.
 * Typically, you load an image into a GdkPixbuf, then display the pixbuf.
 *
 * This demo code shows some of the more obscure cases, in the simple
 * case a call to gtk_image_new_from_file() is all you need.
 *
 * If you want to put image data in your program as a C variable,
 * use the make-inline-pixbuf program that comes with GTK+.
 * This way you won't need to depend on loading external files, your
 * application binary can be self-contained.
 */

#include <gtk/gtk.h>
#include <stdio.h>
#include <errno.h>

static GtkWidget *window = NULL;
static GdkPixbufLoader *pixbuf_loader = NULL;
static guint load_timeout = 0;
static FILE* image_stream = NULL;

static void
progressive_prepared_callback (GdkPixbufLoader *loader,
			       gpointer		data)
{
  GdkPixbuf *pixbuf;
  GtkWidget *image;

  image = GTK_WIDGET (data);
  
  pixbuf = gdk_pixbuf_loader_get_pixbuf (loader);

  /* Avoid displaying random memory contents, since the pixbuf
   * isn't filled in yet.
   */
  gdk_pixbuf_fill (pixbuf, 0xaaaaaaff);
  
  gtk_image_set_from_pixbuf (GTK_IMAGE (image), pixbuf);
}

static void progressive_updated_callback (GdkPixbufLoader *loader,
					  gint		   x,
					  gint		   y,
					  gint		   width,
					  gint		   height,
					  gpointer	   data)
{
  GtkWidget *image;
  
  image = GTK_WIDGET (data);

  /* We know the pixbuf inside the GtkImage has changed, but the image
   * itself doesn't know this; so queue a redraw.  If we wanted to be
   * really efficient, we could use a drawing area or something
   * instead of a GtkImage, so we could control the exact position of
   * the pixbuf on the display, then we could queue a draw for only
   * the updated area of the image.
   */
  
  gtk_widget_queue_draw (image);
}

static gint
progressive_timeout (gpointer data)
{
  GtkWidget *image;

  image = GTK_WIDGET (data);
  
  /* This shows off fully-paranoid error handling, so looks scary.
   * You could factor out the error handling code into a nice separate
   * function to make things nicer.
   */
  
  if (image_stream)
    {
      size_t bytes_read;
      guchar buf[256];
      GError *error = NULL;
      
      bytes_read = fread (buf, 1, 256, image_stream);

      if (ferror (image_stream))
	{
	  GtkWidget *dialog;
	  
	  dialog = gtk_message_dialog_new (GTK_WINDOW (window),
					   GTK_DIALOG_DESTROY_WITH_PARENT,
					   GTK_MESSAGE_ERROR,
					   GTK_BUTTONS_CLOSE,
					   "Failure reading image file 'alphatest.png': %s",
					   g_strerror (errno));

	  gtk_signal_connect (GTK_OBJECT (dialog),
			      "response",
			      GTK_SIGNAL_FUNC (gtk_widget_destroy),
			      NULL);

	  fclose (image_stream);
	  image_stream = NULL;

	  gtk_widget_show (dialog);
	  
	  load_timeout = 0;

	  return FALSE; /* uninstall the timeout */
	}

      if (!gdk_pixbuf_loader_write (pixbuf_loader,
				    buf, bytes_read,
				    &error))
	{
	  GtkWidget *dialog;
	  
	  dialog = gtk_message_dialog_new (GTK_WINDOW (window),
					   GTK_DIALOG_DESTROY_WITH_PARENT,
					   GTK_MESSAGE_ERROR,
					   GTK_BUTTONS_CLOSE,
					   "Failed to load image: %s",
					   error->message);

	  g_error_free (error);
	  
	  gtk_signal_connect (GTK_OBJECT (dialog),
			      "response",
			      GTK_SIGNAL_FUNC (gtk_widget_destroy),
			      NULL);

	  fclose (image_stream);
	  image_stream = NULL;
	  
	  gtk_widget_show (dialog);

	  load_timeout = 0;

	  return FALSE; /* uninstall the timeout */
	}

      if (feof (image_stream))
	{
	  fclose (image_stream);
	  image_stream = NULL;

	  /* Errors can happen on close, e.g. if the image
	   * file was truncated we'll know on close that
	   * it was incomplete.
	   */
	  error = NULL;
	  if (!gdk_pixbuf_loader_close (pixbuf_loader,
					&error))
	    {
	      GtkWidget *dialog;
	      
	      dialog = gtk_message_dialog_new (GTK_WINDOW (window),
					       GTK_DIALOG_DESTROY_WITH_PARENT,
					       GTK_MESSAGE_ERROR,
					       GTK_BUTTONS_CLOSE,
					       "Failed to load image: %s",
					       error->message);
	      
	      g_error_free (error);
	      
	      gtk_signal_connect (GTK_OBJECT (dialog),
				  "response",
				  GTK_SIGNAL_FUNC (gtk_widget_destroy),
				  NULL);
	      
	      gtk_widget_show (dialog);

	      g_object_unref (G_OBJECT (pixbuf_loader));
	      pixbuf_loader = NULL;
	      
	      load_timeout = 0;
	      
	      return FALSE; /* uninstall the timeout */
	    }
	  
	  g_object_unref (G_OBJECT (pixbuf_loader));
	  pixbuf_loader = NULL;
	}
    }
  else
    {
      const gchar *filename;

      if (g_file_test ("./alphatest.png", G_FILE_TEST_EXISTS))
	filename = "./alphatest.png";
      else
	filename = DEMOCODEDIR"/alphatest.png";
      
      image_stream = fopen (filename, "r");

      if (image_stream == NULL)
	{
	  GtkWidget *dialog;
	  
	  dialog = gtk_message_dialog_new (GTK_WINDOW (window),
					   GTK_DIALOG_DESTROY_WITH_PARENT,
					   GTK_MESSAGE_ERROR,
					   GTK_BUTTONS_CLOSE,
					   "Unable to open image file 'alphatest.png': %s",
					   g_strerror (errno));

	  gtk_signal_connect (GTK_OBJECT (dialog),
			      "response",
			      GTK_SIGNAL_FUNC (gtk_widget_destroy),
			      NULL);
	  
	  gtk_widget_show (dialog);

	  load_timeout = 0;

	  return FALSE; /* uninstall the timeout */
	}

      if (pixbuf_loader)
	{
	  gdk_pixbuf_loader_close (pixbuf_loader, NULL);
	  g_object_unref (G_OBJECT (pixbuf_loader));
	  pixbuf_loader = NULL;
	}
      
      pixbuf_loader = gdk_pixbuf_loader_new ();
      
      g_signal_connect (G_OBJECT (pixbuf_loader),
			"area_prepared",
			G_CALLBACK (progressive_prepared_callback),
			image);
      
      g_signal_connect (G_OBJECT (pixbuf_loader),
			"area_updated",
			G_CALLBACK (progressive_updated_callback),
			image);
    }

  /* leave timeout installed */
  return TRUE;
}

static void
start_progressive_loading (GtkWidget *image)
{
  /* This is obviously totally contrived (we slow down loading
   * on purpose to show how incremental loading works).
   * The real purpose of incremental loading is the case where
   * you are reading data from a slow source such as the network.
   * The timeout simply simulates a slow data source by inserting
   * pauses in the reading process.
   */
  load_timeout = g_timeout_add (150,
				progressive_timeout,
				image);
}

static void
cleanup_callback (GtkObject *object,
		  gpointer   data)
{
  if (load_timeout)
    {
      g_source_remove (load_timeout);
      load_timeout = 0;
    }
  
  if (pixbuf_loader)
    {
      gdk_pixbuf_loader_close (pixbuf_loader, NULL);
      g_object_unref (G_OBJECT (pixbuf_loader));
      pixbuf_loader = NULL;
    }

  if (image_stream)
    fclose (image_stream);
  image_stream = NULL;
}

GtkWidget *
do_images (void)
{
  GtkWidget *frame;
  GtkWidget *vbox;
  GtkWidget *image;
  GtkWidget *label;
  GtkWidget *align;
  
  if (!window)
    {
      window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
      gtk_window_set_title (GTK_WINDOW (window), "Images");

      gtk_signal_connect (GTK_OBJECT (window), "destroy", GTK_SIGNAL_FUNC (gtk_widget_destroyed), &window);
      gtk_signal_connect (GTK_OBJECT (window), "destroy", GTK_SIGNAL_FUNC (cleanup_callback), NULL);

      gtk_container_set_border_width (GTK_CONTAINER (window), 8);

      vbox = gtk_vbox_new (FALSE, 8);
      gtk_container_set_border_width (GTK_CONTAINER (vbox), 8);
      gtk_container_add (GTK_CONTAINER (window), vbox);

      label = gtk_label_new (NULL);
      gtk_label_set_markup (GTK_LABEL (label),
			    "<u>Image loaded from a file</u>");
      gtk_box_pack_start (GTK_BOX (vbox), label, FALSE, FALSE, 0);
      
      frame = gtk_frame_new (NULL);
      gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_IN);
      /* The alignment keeps the frame from growing when users resize
       * the window
       */
      align = gtk_alignment_new (0.5, 0.5, 0, 0);
      gtk_container_add (GTK_CONTAINER (align), frame);
      gtk_box_pack_start (GTK_BOX (vbox), align, FALSE, FALSE, 0);

      /* We look for the image in the current directory first,
       * so you can run gtk-demo without installing GTK
       */
      if (g_file_test ("./gtk-logo-rgb.gif", G_FILE_TEST_EXISTS))
	{
	  /* This code shows off error handling. You can just use
	   * gtk_image_new_from_file() instead if you don't want to report
	   * errors to the user. If the file doesn't load when using
	   * gtk_image_new_from_file(), a "missing image" icon will
	   * be displayed instead.
	   */
	  GdkPixbuf *pixbuf;
	  GError *error = NULL;
	  
	  pixbuf = gdk_pixbuf_new_from_file ("./gtk-logo-rgb.gif",
					     &error);
	  if (error)
	    {
	      GtkWidget *dialog;

	      dialog = gtk_message_dialog_new (GTK_WINDOW (window),
					       GTK_DIALOG_DESTROY_WITH_PARENT,
					       GTK_MESSAGE_ERROR,
					       GTK_BUTTONS_CLOSE,
					       "Unable to open image file 'gtk-logo-rgb.gif': %s",
					       error->message);
	      g_error_free (error);
	      
	      gtk_signal_connect (GTK_OBJECT (dialog),
				  "response",
				  GTK_SIGNAL_FUNC (gtk_widget_destroy),
				  NULL);
	      
	      gtk_widget_show (dialog);
	    }
	  
	  image = gtk_image_new_from_pixbuf (pixbuf);
	}
      else
	{
	  /* This is the simpler code, with no error handling.
	   * Here we're loading the installed gtk-logo-rgb.gif instead
	   * of the one in the current directory.
	   */
	  image = gtk_image_new_from_file (DEMOCODEDIR"/gtk-logo-rgb.gif");
	}

      gtk_container_add (GTK_CONTAINER (frame), image);


      /* Animation */

      label = gtk_label_new (NULL);
      gtk_label_set_markup (GTK_LABEL (label),
			    "<u>Animation loaded from a file</u>");
      gtk_box_pack_start (GTK_BOX (vbox), label, FALSE, FALSE, 0);
      
      frame = gtk_frame_new (NULL);
      gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_IN);
      /* The alignment keeps the frame from growing when users resize
       * the window
       */
      align = gtk_alignment_new (0.5, 0.5, 0, 0);
      gtk_container_add (GTK_CONTAINER (align), frame);
      gtk_box_pack_start (GTK_BOX (vbox), align, FALSE, FALSE, 0);

      /* We look for the image in the current directory first,
       * so you can run gtk-demo without installing GTK
       */
      if (g_file_test ("./floppybuddy.gif", G_FILE_TEST_EXISTS))
	image = gtk_image_new_from_file ("./floppybuddy.gif");
      else
	image = gtk_image_new_from_file (DEMOCODEDIR"/floppybuddy.gif");

      gtk_container_add (GTK_CONTAINER (frame), image);
      

      /* Progressive */
      
      
      label = gtk_label_new (NULL);
      gtk_label_set_markup (GTK_LABEL (label),
			    "<u>Progressive image loading</u>");
      gtk_box_pack_start (GTK_BOX (vbox), label, FALSE, FALSE, 0);
      
      frame = gtk_frame_new (NULL);
      gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_IN);
      /* The alignment keeps the frame from growing when users resize
       * the window
       */
      align = gtk_alignment_new (0.5, 0.5, 0, 0);
      gtk_container_add (GTK_CONTAINER (align), frame);
      gtk_box_pack_start (GTK_BOX (vbox), align, FALSE, FALSE, 0);

      /* Create an empty image for now; the progressive loader
       * will create the pixbuf and fill it in.
       */
      image = gtk_image_new_from_pixbuf (NULL);
      gtk_container_add (GTK_CONTAINER (frame), image);

      start_progressive_loading (image);
    }

  if (!GTK_WIDGET_VISIBLE (window))
    {
      gtk_widget_show_all (window);
    }
  else
    {
      gtk_widget_destroy (window);
      window = NULL;
    }

  return window;
}