Bug #600533 zenity --text-info should have an auto scroll option

This is a request to add a auto-scroll option.
For now it's only works when text-info is getting the
text from stdin.
Example usage:
cat file.txt | zenity --text-info --auto-scroll

src/option.c

@@ -106,6 +106,8 @@ static gboolean zenity_question_default_cancel;
 static gboolean zenity_text_active;
 static gchar   *zenity_text_font;
 static gchar   *zenity_text_checkbox;
+static gboolean zenity_text_auto_scroll;
+
 #ifdef HAVE_WEBKITGTK
 static gboolean zenity_text_enable_html;
 static gchar   *zenity_text_url;
@@ -878,6 +880,15 @@ static GOptionEntry text_options[] = {
     N_("URL")
   },
 #endif
+  {
+    "auto-scroll",
+    '\0',
+    G_OPTION_FLAG_NOALIAS,
+    G_OPTION_ARG_NONE,
+    &zenity_text_auto_scroll,
+    N_("Auto scroll the text to the end. Only when text is captured from stdin"),
+    NULL
+  },
   { 
     NULL 
   }
@@ -1531,6 +1542,7 @@ zenity_text_pre_callback (GOptionContext *context,
   zenity_text_active = FALSE;
   zenity_text_font = NULL;
   zenity_text_checkbox = NULL;
+  zenity_text_auto_scroll = FALSE;
 #ifdef HAVE_WEBKITGTK
   zenity_text_enable_html = FALSE;
   zenity_text_url = NULL;
@@ -1944,6 +1956,7 @@ zenity_text_post_callback (GOptionContext *context,
     results->text_data->no_wrap = zenity_general_dialog_no_wrap;
     results->text_data->font = zenity_text_font;
     results->text_data->checkbox = zenity_text_checkbox;
+    results->text_data->auto_scroll = zenity_text_auto_scroll;
 #ifdef HAVE_WEBKITGTK
     results->text_data->html = zenity_text_enable_html;
     results->text_data->url = zenity_text_url;

src/text.c

@@ -134,11 +134,13 @@ zenity_text_handle_stdin (GIOChannel  *channel,
                           gpointer     data)
 {
   static GtkTextBuffer *buffer;
+  static GtkTextView *text_view;
   gchar buf[1024];
 
   gsize len;
 
-  buffer = GTK_TEXT_BUFFER (data);
+  text_view = GTK_TEXT_VIEW (data);
+  buffer = gtk_text_view_get_buffer (text_view);
 
   if ((condition & G_IO_IN) || (condition & (G_IO_IN | G_IO_HUP))) {
     GError *error = NULL;
@@ -179,6 +181,12 @@ zenity_text_handle_stdin (GIOChannel  *channel,
       } else {
         gtk_text_buffer_insert (buffer, &end, buf, len);
       }
+      if (zen_text_data->auto_scroll) {
+        GtkTextMark *mark = NULL;
+        mark = gtk_text_buffer_get_insert (buffer);
+        if (mark != NULL)
+          gtk_text_view_scroll_to_mark (text_view, mark, 0.0, FALSE, 0, 0);
+      }
     }
   }
 
@@ -186,14 +194,14 @@ zenity_text_handle_stdin (GIOChannel  *channel,
 }
 
 static void
-zenity_text_fill_entries_from_stdin (GtkTextBuffer *text_buffer)
+zenity_text_fill_entries_from_stdin (GtkTextView *text_view)
 {
   GIOChannel *channel; 
 
   channel = g_io_channel_unix_new (0);
   g_io_channel_set_encoding (channel, NULL, NULL);
   g_io_channel_set_flags (channel, G_IO_FLAG_NONBLOCK, NULL);
-  g_io_add_watch (channel, G_IO_IN | G_IO_HUP, zenity_text_handle_stdin, text_buffer);
+  g_io_add_watch (channel, G_IO_IN | G_IO_HUP, zenity_text_handle_stdin, text_view);
 }
 
 void
@@ -257,7 +265,7 @@ zenity_text (ZenityData *data, ZenityTextData *text_data)
   if (text_data->uri)
     zenity_util_fill_file_buffer (text_buffer, text_data->uri);
   else
-    zenity_text_fill_entries_from_stdin (GTK_TEXT_BUFFER (text_buffer));
+    zenity_text_fill_entries_from_stdin (GTK_TEXT_VIEW(text_view));
 
   if (text_data->editable)
     zen_text_data->buffer = text_buffer;
@@ -326,6 +334,7 @@ zenity_text (ZenityData *data, ZenityTextData *text_data)
     gtk_widget_show (GTK_WIDGET (web_kit));
   }
 #endif
+
   zenity_util_show_dialog (dialog, data->attach);
 
   g_object_unref (builder);

src/zenity.h

@@ -110,6 +110,7 @@ typedef struct {
   gchar         *uri;
   gboolean       editable;
   gboolean       no_wrap;
+  gboolean       auto_scroll;
   gchar         *font;
   GtkTextBuffer	*buffer;
   gchar         *checkbox;