/* Text Widget/Automatic scrolling

 *

 * This example demonstrates how to use the gravity of 

 * GtkTextMarks to keep a text view scrolled to the bottom

 * while appending text.

 */

#include <gtk/gtk.h>

#include "demo-common.h"

/* Scroll to the end of the buffer.

 */

static gboolean

scroll_to_end (GtkTextView *textview)

{

  GtkTextBuffer *buffer;

  GtkTextIter iter;

  GtkTextMark *mark;

  char *spaces;

  static int count;

  buffer = gtk_text_view_get_buffer (textview);

  /* Get "end" mark. It's located at the end of buffer because 

   * of right gravity

   */

  mark = gtk_text_buffer_get_mark (buffer, "end");

  gtk_text_buffer_get_iter_at_mark (buffer, &iter, mark);

  /* and insert some text at its position, the iter will be 

   * revalidated after insertion to point to the end of inserted text

   */

  spaces = g_strnfill (count++, ' ');

  gtk_text_buffer_insert (buffer, &iter, "\n", -1);

  gtk_text_buffer_insert (buffer, &iter, spaces, -1);

  gtk_text_buffer_insert (buffer, &iter,

                          "Scroll to end scroll to end scroll "

                          "to end scroll to end ",

                          -1);

  g_free (spaces);

  /* Now scroll the end mark onscreen.

   */

  gtk_text_view_scroll_mark_onscreen (textview, mark);

  /* Emulate typewriter behavior, shift to the left if we 

   * are far enough to the right.

   */

  if (count > 150)

    count = 0;

  return TRUE;

}

/* Scroll to the bottom of the buffer.

 */

static gboolean

scroll_to_bottom (GtkTextView *textview)

{

  GtkTextBuffer *buffer;

  GtkTextIter iter;

  GtkTextMark *mark;

  char *spaces;

  static int count;

  buffer = gtk_text_view_get_buffer (textview);

  /* Get end iterator */

  gtk_text_buffer_get_end_iter (buffer, &iter);

  /* and insert some text at it, the iter will be revalidated

   * after insertion to point to the end of inserted text

   */

  spaces = g_strnfill (count++, ' ');

  gtk_text_buffer_insert (buffer, &iter, "\n", -1);

  gtk_text_buffer_insert (buffer, &iter, spaces, -1);

  gtk_text_buffer_insert (buffer, &iter,

                          "Scroll to bottom scroll to bottom scroll "

                          "to bottom scroll to bottom",

                          -1);

  g_free (spaces);

  /* Move the iterator to the beginning of line, so we don't scroll 

   * in horizontal direction 

   */

  gtk_text_iter_set_line_offset (&iter, 0);

  /* and place the mark at iter. the mark will stay there after we

   * insert some text at the end because it has right gravity.

   */

  mark = gtk_text_buffer_get_mark (buffer, "scroll");

  gtk_text_buffer_move_mark (buffer, mark, &iter);

  /* Scroll the mark onscreen.

   */

  gtk_text_view_scroll_mark_onscreen (textview, mark);

  /* Shift text back if we got enough to the right.

   */

  if (count > 40)

    count = 0;

  return TRUE;

}

static guint

setup_scroll (GtkTextView *textview,

              gboolean     to_end)

{

  GtkTextBuffer *buffer;

  GtkTextIter iter;

  buffer = gtk_text_view_get_buffer (textview);

  gtk_text_buffer_get_end_iter (buffer, &iter);

  if (to_end)

  {

    /* If we want to scroll to the end, including horizontal scrolling,

     * then we just create a mark with right gravity at the end of the 

     * buffer. It will stay at the end unless explicitely moved with 

     * gtk_text_buffer_move_mark.

     */

    gtk_text_buffer_create_mark (buffer, "end", &iter, FALSE);

    /* Add scrolling timeout. */

    return g_timeout_add (50, (GSourceFunc) scroll_to_end, textview);

  }

  else

  {

    /* If we want to scroll to the bottom, but not scroll horizontally, 

     * then an end mark won't do the job. Just create a mark so we can 

     * use it with gtk_text_view_scroll_mark_onscreen, we'll position it

     * explicitely when needed. Use left gravity so the mark stays where 

     * we put it after inserting new text.

     */

    gtk_text_buffer_create_mark (buffer, "scroll", &iter, TRUE);

    /* Add scrolling timeout. */

    return g_timeout_add (100, (GSourceFunc) scroll_to_bottom, textview);

  }

}

static void

remove_timeout (GtkWidget *window,

                gpointer   timeout)

{

  g_source_remove (GPOINTER_TO_UINT (timeout));

}

static void

create_text_view (GtkWidget *hbox,

                  gboolean   to_end)

{

  GtkWidget *swindow;

  GtkWidget *textview;

  guint timeout;

  swindow = gtk_scrolled_window_new (NULL, NULL);

  gtk_box_pack_start (GTK_BOX (hbox), swindow, TRUE, TRUE, 0);

  textview = gtk_text_view_new ();

  gtk_container_add (GTK_CONTAINER (swindow), textview);

  timeout = setup_scroll (GTK_TEXT_VIEW (textview), to_end);

  /* Remove the timeout in destroy handler, so we don't try to

   * scroll destroyed widget. 

   */

  g_signal_connect (textview, "destroy",

                    G_CALLBACK (remove_timeout),

                    GUINT_TO_POINTER (timeout));

}

GtkWidget *

do_textscroll (GtkWidget *do_widget)

{

  static GtkWidget *window = NULL;

  if (!window)

    {

      GtkWidget *hbox;

      window = gtk_window_new (GTK_WINDOW_TOPLEVEL);

      g_signal_connect (window, "destroy",

			G_CALLBACK (gtk_widget_destroyed), &window);

      gtk_window_set_default_size (GTK_WINDOW (window), 600, 400);

      hbox = gtk_hbox_new (TRUE, 6);

      gtk_container_add (GTK_CONTAINER (window), hbox);

      create_text_view (hbox, TRUE);

      create_text_view (hbox, FALSE);

    }

  if (!gtk_widget_get_visible (window))

      gtk_widget_show_all (window);

  else

      gtk_widget_destroy (window);

  return window;

}