Add a "Hypertext" demo.

demos/gtk-demo/Makefile.am

@@ -21,7 +21,8 @@ demos =						\
 	sizegroup.c				\
 	stock_browser.c				\
 	textview.c				\
-	tree_store.c
+	tree_store.c				\
+	hypertext.c
 
 INCLUDES = \
 	-DDEMOCODEDIR="\"$(democodedir)\""		\

demos/gtk-demo/hypertext.c

@@ -0,0 +1,315 @@
+/* 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 void
+show_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 void
+follow_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 gboolean
+key_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 gboolean
+event_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 void
+set_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 gboolean
+motion_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 gboolean
+visibility_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 (void)
+{
+  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_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 (G_OBJECT (view), "key-press-event", 
+			G_CALLBACK (key_press_event), NULL);
+      g_signal_connect (G_OBJECT (view), "event-after", 
+			G_CALLBACK (event_after), NULL);
+      g_signal_connect (G_OBJECT (view), "motion-notify-event", 
+			G_CALLBACK (motion_notify_event), NULL);
+      g_signal_connect (G_OBJECT (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;
+}
+

demos/gtk-demo/textview.c

@@ -1,4 +1,4 @@
-/* Text Widget
+/* Text Widget/Multiple Views
  *
  * The GtkTextView widget displays a GtkTextBuffer. One GtkTextBuffer
  * can be displayed by multiple GtkTextViews. This demo has two views