[tepl] utils: copy str_middle_truncate() from gedit

[Sébastien Wilmet <swilmet src gnome org>]

commit 7407ac37fafd2992183303acce998e08bd1ce1ff
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Sun Aug 6 09:19:32 2017 +0200

    utils: copy str_middle_truncate() from gedit

 tepl/tepl-utils.c |   76 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 tepl/tepl-utils.h |    5 +++
 2 files changed, 81 insertions(+), 0 deletions(-)
---
diff --git a/tepl/tepl-utils.c b/tepl/tepl-utils.c
index eb4a020..be6ce77 100644
--- a/tepl/tepl-utils.c
+++ b/tepl/tepl-utils.c
@@ -33,6 +33,82 @@
  * Utility functions.
  */
 
+static gchar *
+str_truncate (const gchar *string,
+             guint        truncate_length,
+             gboolean     middle)
+{
+       GString *truncated;
+       guint length;
+       guint n_chars;
+       guint num_left_chars;
+       guint right_offset;
+       guint delimiter_length;
+       const gchar *delimiter = "\342\200\246";
+
+       g_return_val_if_fail (string != NULL, NULL);
+
+       length = strlen (string);
+
+       g_return_val_if_fail (g_utf8_validate (string, length, NULL), NULL);
+
+       /* It doesnt make sense to truncate strings to less than
+        * the size of the delimiter plus 2 characters (one on each
+        * side)
+        */
+       delimiter_length = g_utf8_strlen (delimiter, -1);
+       if (truncate_length < (delimiter_length + 2))
+       {
+               return g_strdup (string);
+       }
+
+       n_chars = g_utf8_strlen (string, length);
+
+       /* Make sure the string is not already small enough. */
+       if (n_chars <= truncate_length)
+       {
+               return g_strdup (string);
+       }
+
+       /* Find the 'middle' where the truncation will occur. */
+       if (middle)
+       {
+               num_left_chars = (truncate_length - delimiter_length) / 2;
+               right_offset = n_chars - truncate_length + num_left_chars + delimiter_length;
+
+               truncated = g_string_new_len (string,
+                                             g_utf8_offset_to_pointer (string, num_left_chars) - string);
+               g_string_append (truncated, delimiter);
+               g_string_append (truncated, g_utf8_offset_to_pointer (string, right_offset));
+       }
+       else
+       {
+               num_left_chars = truncate_length - delimiter_length;
+               truncated = g_string_new_len (string,
+                                             g_utf8_offset_to_pointer (string, num_left_chars) - string);
+               g_string_append (truncated, delimiter);
+       }
+
+       return g_string_free (truncated, FALSE);
+}
+
+gchar *
+_tepl_utils_str_middle_truncate (const gchar *str,
+                                guint        truncate_length)
+{
+       return str_truncate (str, truncate_length, TRUE);
+}
+
+#if 0
+/* Not yet used in Tepl. */
+gchar *
+_tepl_utils_str_end_truncate (const gchar *str,
+                            guint        truncate_length)
+{
+       return str_truncate (str, truncate_length, FALSE);
+}
+#endif
+
 /*
  * _tepl_utils_replace_home_dir_with_tilde:
  * @filename: the filename.
diff --git a/tepl/tepl-utils.h b/tepl/tepl-utils.h
index f88900d..c4a7684 100644
--- a/tepl/tepl-utils.h
+++ b/tepl/tepl-utils.h
@@ -28,6 +28,11 @@
 
 G_BEGIN_DECLS
 
+/* String utilities */
+
+gchar *                _tepl_utils_str_middle_truncate                 (const gchar *str,
+                                                                guint        truncate_length);
+
 /* File utilities */
 
 G_GNUC_INTERNAL