[gnome-builder] source-snippet-completion: fix text insertion

[Christian Hergert <chergert src gnome org>]

commit 3341dcb08e687998d5dcdfa1f2fe73157d7df3fd
Author: Christian Hergert <chergert redhat com>
Date:   Fri Nov 11 02:40:42 2016 -0800

    source-snippet-completion: fix text insertion
    
    We only need to handler our longest-common-substring case here, otherwise
    we just fallback to the default.
    
    Doing this improves our ability to use ctags while inside of a snippet
    without breaking things too much.

 plugins/ctags/ide-ctags-completion-provider.c |   42 ++++++++++--------------
 1 files changed, 18 insertions(+), 24 deletions(-)
---
diff --git a/plugins/ctags/ide-ctags-completion-provider.c b/plugins/ctags/ide-ctags-completion-provider.c
index 7e95dbb..765d98b 100644
--- a/plugins/ctags/ide-ctags-completion-provider.c
+++ b/plugins/ctags/ide-ctags-completion-provider.c
@@ -326,39 +326,33 @@ ide_ctags_completion_provider_activate_proposal (GtkSourceCompletionProvider *pr
 
   buffer = gtk_text_iter_get_buffer (iter);
 
+  /*
+   * NOTE:
+   *
+   * Try to reduce our insertion to just the new text. This avoids a delete
+   * which can be troublesome when we are working on a snippet. Ideally we
+   * would improve snippets, but due to various limitations in GtkTextBuffer
+   * and GtkTextView, we don't have an answer for that yet.
+   */
   if (_ide_source_iter_backward_visible_word_start (&begin))
     {
       g_autofree gchar *current_text = gtk_text_iter_get_slice (&begin, iter);
       g_autofree gchar *proposal_text = gtk_source_completion_proposal_get_text (proposal);
-      const gchar *c_iter = current_text;
-      const gchar *p_iter = proposal_text;
-      gint n_chars = 0;
 
-      /*
-       * Work our way through the common substring to see if we can reduce
-       * how much we replace in the final target;
-       */
-      while (*c_iter != '\0' && g_utf8_get_char (c_iter) == g_utf8_get_char (p_iter))
+      if (g_str_has_prefix (proposal_text, current_text))
         {
-          n_chars++;
-          c_iter = g_utf8_next_char (c_iter);
-          p_iter = g_utf8_next_char (p_iter);
+          gtk_text_buffer_begin_user_action (buffer);
+          gtk_text_buffer_insert (buffer,
+                                  iter,
+                                  proposal_text + strlen (current_text),
+                                  -1);
+          gtk_text_buffer_end_user_action (buffer);
+          return TRUE;
         }
-
-      begin = *iter;
-
-      gtk_text_iter_backward_chars (&begin, n_chars);
-
-      gtk_text_buffer_begin_user_action (buffer);
-      gtk_text_buffer_delete (buffer, &begin, iter);
-      gtk_text_buffer_insert (buffer, &begin, p_iter, strlen (p_iter));
-      gtk_text_buffer_end_user_action (buffer);
-
-      *iter = begin;
-
-      return TRUE;
     }
 
+  /* Fallback and let the default handler take care of things */
+
   return FALSE;
 }