Smarter decision about setting up expandtab.

Previously we assumed hard tabs upon finding just
one hard tab in the file.

1 files changed, 39 insertions, 2 deletions

diff --git a/autotab.c b/autotab.c
index 5c38446..9d709f2 100644
--- a/autotab.c
+++ b/autotab.c
@@ -4,8 +4,8 @@
  * it as a Vim command to set up the tabstop, shiftwidth and expandtab
  * parameters.
  *
- * Copyright 2012 
- * Kaz Kylheku <kaz@kylheku.com>
+ * Copyright 2014
+ * Kaz Kylheku <kkylheku@gmail.com>
  * Vancouver, Canada
  *
  * To use this, compile to an executable called "autotab".
@@ -710,6 +710,40 @@ static int compute_alignment_histogram(long (*array)[128], line_t *lines)
 }
 #endif
 
+int determine_expandtab(line_t *lines_in, int tabsize, int shiftwidth)
+{
+  line_t *lines = tab_munge(lines_in, tabsize);
+  int indented = 0, tabbed = 0;
+
+  for (; lines; lines = lines->next) {
+    char *str = lines->str;
+    long ind = strspn(str, ANYSP);
+
+    /* Count indented lines which require at least one tab,
+     * and count how many of these include a tab in that
+     * indentation.
+     */
+    if (ind % shiftwidth == 0 && ind >= tabsize) {
+      char *tab = strpbrk(str, INTAB LETAB);
+
+      indented++;
+      if (!tab)
+        continue;
+      if (tab - str > ind)
+        continue;
+      tabbed++;
+    }
+  }
+
+  free_lines(lines);
+
+  /* If 25% or fewer of the indented lines which should
+   * have tabs actually have tabs, then let's turn
+   * on expandtab mode.
+   */
+  return (tabbed <= indented / 4) ? 1 : 0;
+}
+
 int main(int argc, char **argv)
 {
   line_t *lines;
@@ -731,6 +765,9 @@ int main(int argc, char **argv)
   if ((shiftwidth = determine_shiftwidth(lines, tabsize, 0)) == 0)
     goto out;
 
+  if (!expandtabs)
+    expandtabs = determine_expandtab(lines, tabsize, shiftwidth);
+
 out_default:
   printf("tabstop=%d shiftwidth=%d %sexpandtab\n", tabsize, shiftwidth,
          expandtabs ? "" : "no");