/* Text Widget/Hypertext * * Usually, tags modify the appearance of text in the view, e.g. making it  * bold or colored or underlined. But tags are not restricted to appearance.  * They can also affect the behavior of mouse and key presses, as this demo  * shows. */#include <gtk/gtk.h>#include <gdk/gdkkeysyms.h>/* Inserts a piece of text into the buffer, giving it the usual * appearance of a hyperlink in a web browser: blue and underlined. * Additionally, attaches some data on the tag, to make it recognizable * as a link.  */static void insert_link (GtkTextBuffer *buffer, 	     GtkTextIter   *iter, 	     gchar         *text, 	     gint           page){  GtkTextTag *tag;    tag = gtk_text_buffer_create_tag (buffer, NULL, 				    "foreground", "blue", 				    "underline", PANGO_UNDERLINE_SINGLE, 				    NULL);  g_object_set_data (G_OBJECT (tag), "page", GINT_TO_POINTER (page));  gtk_text_buffer_insert_with_tags (buffer, iter, text, -1, tag, NULL);}/* Fills the buffer with text and interspersed links. In any real * hypertext app, this method would parse a file to identify the links. */static voidshow_page (GtkTextBuffer *buffer, 	   gint           page){  GtkTextIter iter;  gtk_text_buffer_set_text (buffer, "", 0);  gtk_text_buffer_get_iter_at_offset (buffer, &iter, 0);  if (page == 1)    {      gtk_text_buffer_insert (buffer, &iter, "Some text to show that simple ", -1);      insert_link (buffer, &iter, "hypertext", 3);      gtk_text_buffer_insert (buffer, &iter, " can easily be realized with ", -1);      insert_link (buffer, &iter, "tags", 2);      gtk_text_buffer_insert (buffer, &iter, ".", -1);    }  else if (page == 2)    {      gtk_text_buffer_insert (buffer, &iter, 			      "A tag is an attribute that can be applied to some range of text. "			      "For example, a tag might be called \"bold\" and make the text inside "			      "the tag bold. However, the tag concept is more general than that; "			      "tags don't have to affect appearance. They can instead affect the "			      "behavior of mouse and key presses, \"lock\" a range of text so the "			      "user can't edit it, or countless other things.\n", -1);      insert_link (buffer, &iter, "Go back", 1);    }  else if (page == 3)     {      GtkTextTag *tag;        tag = gtk_text_buffer_create_tag (buffer, NULL, 					"weight", PANGO_WEIGHT_BOLD, 					NULL);      gtk_text_buffer_insert_with_tags (buffer, &iter, "hypertext:\n", -1, tag, NULL);      gtk_text_buffer_insert (buffer, &iter, 			      "machine-readable text that is not sequential but is organized "			      "so that related items of information are connected.\n", -1);      insert_link (buffer, &iter, "Go back", 1);    }}/* Looks at all tags covering the position of iter in the text view,  * and if one of them is a link, follow it by showing the page identified * by the data attached to it. */static voidfollow_if_link (GtkWidget   *text_view, 		GtkTextIter *iter){  GSList *tags = NULL, *tagp = NULL;  tags = gtk_text_iter_get_tags (iter);  for (tagp = tags;  tagp != NULL;  tagp = tagp->next)    {      GtkTextTag *tag = tagp->data;      gint page = GPOINTER_TO_INT (g_object_get_data (G_OBJECT (tag), "page"));      if (page != 0)        {	  show_page (gtk_text_view_get_buffer (GTK_TEXT_VIEW (text_view)), page);	  break;        }    }  if (tags)     g_slist_free (tags);}/* Links can be activated by pressing Enter. */static gbooleankey_press_event (GtkWidget *text_view,		 GdkEventKey *event){  GtkTextIter iter;  GtkTextBuffer *buffer;  switch (event->keyval)    {      case GDK_Return:       case GDK_KP_Enter:        buffer = gtk_text_view_get_buffer (GTK_TEXT_VIEW (text_view));        gtk_text_buffer_get_iter_at_mark (buffer, &iter,                                           gtk_text_buffer_get_insert (buffer));        follow_if_link (text_view, &iter);        break;      default:        break;    }  return FALSE;}/* Links can also be activated by clicking. */static gbooleanevent_after (GtkWidget *text_view,	     GdkEvent  *ev){  GtkTextIter start, end, iter;  GtkTextBuffer *buffer;  GdkEventButton *event;  gint x, y;  if (ev->type != GDK_BUTTON_RELEASE)    return FALSE;  event = (GdkEventButton *)ev;  if (event->button != 1)    return FALSE;  buffer = gtk_text_view_get_buffer (GTK_TEXT_VIEW (text_view));  /* we shouldn't follow a link if the user has selected something */  gtk_text_buffer_get_selection_bounds (buffer, &start, &end);  if (gtk_text_iter_get_offset (&start) != gtk_text_iter_get_offset (&end))    return FALSE;  gtk_text_view_window_to_buffer_coords (GTK_TEXT_VIEW (text_view),                                          GTK_TEXT_WINDOW_WIDGET,                                         event->x, event->y, &x, &y);  gtk_text_view_get_iter_at_location (GTK_TEXT_VIEW (text_view), &iter, x, y);  follow_if_link (text_view, &iter);  return FALSE;}gboolean hovering_over_link = FALSE;GdkCursor *hand_cursor = NULL;GdkCursor *regular_cursor = NULL;/* Looks at all tags covering the position (x, y) in the text view,  * and if one of them is a link, change the cursor to the "hands" cursor * typically used by web browsers. */static voidset_cursor_if_appropriate (GtkTextView    *text_view,                           gint            x,                           gint            y){  GSList *tags = NULL, *tagp = NULL;  GtkTextBuffer *buffer;  GtkTextIter iter;  gboolean hovering = FALSE;  buffer = gtk_text_view_get_buffer (text_view);  gtk_text_view_get_iter_at_location (text_view, &iter, x, y);    tags = gtk_text_iter_get_tags (&iter);  for (tagp = tags;  tagp != NULL;  tagp = tagp->next)    {      GtkTextTag *tag = tagp->data;      gint page = GPOINTER_TO_INT (g_object_get_data (G_OBJECT (tag), "page"));      if (page != 0)         {          hovering = TRUE;          break;        }    }  if (hovering != hovering_over_link)    {      hovering_over_link = hovering;      if (hovering_over_link)        gdk_window_set_cursor (gtk_text_view_get_window (text_view, GTK_TEXT_WINDOW_TEXT), hand_cursor);      else        gdk_window_set_cursor (gtk_text_view_get_window (text_view, GTK_TEXT_WINDOW_TEXT), regular_cursor);    }  if (tags)     g_slist_free (tags);}/* Update the cursor image if the pointer moved.  */static gbooleanmotion_notify_event (GtkWidget      *text_view,		     GdkEventMotion *event){  gint x, y;  gtk_text_view_window_to_buffer_coords (GTK_TEXT_VIEW (text_view),                                          GTK_TEXT_WINDOW_WIDGET,                                         event->x, event->y, &x, &y);  set_cursor_if_appropriate (GTK_TEXT_VIEW (text_view), x, y);  gdk_window_get_pointer (text_view->window, NULL, NULL, NULL);  return FALSE;}/* Also update the cursor image if the window becomes visible * (e.g. when a window covering it got iconified). */static gbooleanvisibility_notify_event (GtkWidget          *text_view,			 GdkEventVisibility *event){  gint wx, wy, bx, by;    gdk_window_get_pointer (text_view->window, &wx, &wy, NULL);    gtk_text_view_window_to_buffer_coords (GTK_TEXT_VIEW (text_view),                                          GTK_TEXT_WINDOW_WIDGET,                                         wx, wy, &bx, &by);  set_cursor_if_appropriate (GTK_TEXT_VIEW (text_view), bx, by);  return FALSE;}GtkWidget *do_hypertext (GtkWidget *do_widget){  static GtkWidget *window = NULL;  if (!window)    {      GtkWidget *view;      GtkWidget *sw;      GtkTextBuffer *buffer;      hand_cursor = gdk_cursor_new (GDK_HAND2);      regular_cursor = gdk_cursor_new (GDK_XTERM);            window = gtk_window_new (GTK_WINDOW_TOPLEVEL);      gtk_window_set_screen (GTK_WINDOW (window),			     gtk_widget_get_screen (do_widget));      gtk_window_set_default_size (GTK_WINDOW (window),				   450, 450);            g_signal_connect (window, "destroy",			G_CALLBACK (gtk_widget_destroyed), &window);      gtk_window_set_title (GTK_WINDOW (window), "Hypertext");      gtk_container_set_border_width (GTK_CONTAINER (window), 0);      view = gtk_text_view_new ();      gtk_text_view_set_wrap_mode (GTK_TEXT_VIEW (view), GTK_WRAP_WORD);      g_signal_connect (view, "key-press-event", 			G_CALLBACK (key_press_event), NULL);      g_signal_connect (view, "event-after", 			G_CALLBACK (event_after), NULL);      g_signal_connect (view, "motion-notify-event", 			G_CALLBACK (motion_notify_event), NULL);      g_signal_connect (view, "visibility-notify-event", 			G_CALLBACK (visibility_notify_event), NULL);      buffer = gtk_text_view_get_buffer (GTK_TEXT_VIEW (view));            sw = gtk_scrolled_window_new (NULL, NULL);      gtk_scrolled_window_set_policy (GTK_SCROLLED_WINDOW (sw),				      GTK_POLICY_AUTOMATIC,				      GTK_POLICY_AUTOMATIC);      gtk_container_add (GTK_CONTAINER (window), sw);      gtk_container_add (GTK_CONTAINER (sw), view);      show_page (buffer, 1);      gtk_widget_show_all (sw);    }  if (!GTK_WIDGET_VISIBLE (window))    {      gtk_widget_show (window);    }  else    {      gtk_widget_destroy (window);      window = NULL;    }  return window;}