Re: [PATCH] TUI: Expand TABs into spaces

[Eli Zaretskii <eliz@gnu.org>]

> From: Doug Evans <xdje42@gmail.com>
> Cc: gdb-patches@sourceware.org
> Date: Sat, 24 Jan 2015 13:26:47 -0800
> 
> For tui_register_format it used to be such a straightforward function,
> it's a shame to grow it by 2x for bitfiddly tab handling.
> 
> Let's add a helper routine that takes one string and returns
> another with tabs expanded, and put this helper routine in, say tui-io.c
> (this routine isn't tui-regs specific), and then call that routine from
> tui_register_format.

I did that below, but since tui_register_format is its only user,
keeping that function in tui-regs.c would have allowed us to make it
static.  Wouldn't that be slightly better?

Thanks for the review; updated patch attached.

2015-01-26  Eli Zaretskii  <eliz@gnu.org>

	* tui/tui-io.c (tui_expand_tabs): New function.
	(tui_puts, tui_redisplay_readline): Expand TABs into the
	appropriate number of spaces.
	* tui/tui-regs.c: Include tui-io.h.
	(tui_register_format): Call tui_expand_tabs to expand TABs into
	the appropriate number of spaces.
	* tui/tui-io.h: Add prototype for tui_expand_tabs.

--- tui/tui-io.c~0	Wed Oct 29 21:45:50 2014
+++ tui/tui-io.c	Mon Jan 26 09:10:34 2015
@@ -179,7 +179,20 @@ tui_puts (const char *string)
       else if (tui_skip_line != 1)
         {
           tui_skip_line = -1;
-          waddch (w, c);
+	  /* Expand TABs, since ncurses on MS-Windows doesn't.  */
+	  if (c == '\t')
+	    {
+	      int line, col;
+
+	      getyx (w, line, col);
+	      do
+		{
+		  waddch (w, ' ');
+		  col++;
+		} while ((col % 8) != 0);
+	    }
+	  else
+	    waddch (w, c);
         }
       else if (c == '\n')
         tui_skip_line = -1;
@@ -254,6 +269,16 @@ tui_redisplay_readline (void)
           waddch (w, '^');
           waddch (w, CTRL_CHAR (c) ? UNCTRL (c) : '?');
 	}
+      else if (c == '\t')
+	{
+	  /* Expand TABs, since ncurses on MS-Windows doesn't.  */
+	  getyx (w, line, col);
+	  do
+	    {
+	      waddch (w, ' ');
+	      col++;
+	    } while ((col % 8) != 0);
+	}
       else
 	{
           waddch (w, c);
@@ -700,6 +725,58 @@ tui_getc (FILE *fp)
   return ch;
 }
 
+/* Utility function to expand TABs in a STRING into spaces.  STRING
+   will be displayed starting at column COL.  The returned expanded
+   string is malloc'ed.  */
+char *
+tui_expand_tabs (const char *string, int col)
+{
+  int n_adjust;
+  const char *s;
+  char *ret, *q;
+
+  /* 1. How many additional characters do we need?  */
+  for (n_adjust = 0, s = string; s; )
+    {
+      s = strpbrk (s, "\t");
+      if (s)
+	{
+	  col += (s - string) + n_adjust;
+	  /* Adjustment for the next tab stop, minus one for the TAB
+	     we replace with spaces.  */
+	  n_adjust += 8 - (col % 8) - 1;
+	  s++;
+	}
+    }
+
+  /* Allocate the copy.  */
+  ret = q = xmalloc (strlen (string) + n_adjust + 1);
+
+  /* 2. Copy the original string while replacing TABs with spaces.  */
+  for (s = string; s; )
+    {
+      char *s1 = strpbrk (s, "\t");
+      if (s1)
+	{
+	  if (s1 > s)
+	    {
+	      strncpy (q, s, s1 - s);
+	      q += s1 - s;
+	      col += s1 - s;
+	    }
+	  do {
+	    *q++ = ' ';
+	    col++;
+	  } while ((col % 8) != 0);
+	  s1++;
+	}
+      else
+	strcpy (q, s);
+      s = s1;
+    }
+
+  return ret;
+}
 
 /* Cleanup when a resize has occured.
    Returns the character that must be processed.  */


--- tui/tui-regs.c~0	Wed Oct 29 21:45:50 2014
+++ tui/tui-regs.c	Mon Jan 26 09:24:23 2015
@@ -37,6 +37,7 @@
 #include "tui/tui-wingeneral.h"
 #include "tui/tui-file.h"
 #include "tui/tui-regs.h"
+#include "tui/tui-io.h"
 #include "reggroups.h"
 #include "valprint.h"
 
@@ -694,7 +695,9 @@ tui_register_format (struct frame_info *
   if (s && s[1] == 0)
     *s = 0;
 
-  ret = xstrdup (p);
+  /* Expand tabs into spaces, since ncurses on MS-Windows doesn't.  */
+  ret = tui_expand_tabs (p, 0);
+
   do_cleanups (cleanups);
 
   return ret;


--- tui/tui-io.h~0	Wed Jun 11 19:34:41 2014
+++ tui/tui-io.h	Mon Jan 26 09:11:42 2015
@@ -41,6 +41,9 @@
    changed the edited text.  */
 extern void tui_redisplay_readline (void);
 
+/* Expand TABs into spaces.  */
+extern char *tui_expand_tabs (const char *, int);
+
 extern struct ui_out *tui_out;
 extern struct ui_out *tui_old_uiout;