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List:       busybox
Subject:    [RFC 1/2] vi: add expandtab option
From:       Ron Yorston <rmy () pobox ! com>
Date:       2021-04-16 12:47:03
Message-ID: 60798747.OVfU2EuCvM8P5mZ+%rmy () pobox ! com
[Download RAW message or body]

This implements the vim option expandtab in BusyBox vi.  From
vim help:

  In Insert mode: Use the appropriate number of spaces to insert a
  <Tab>.  Spaces are used in indents with the '>' and '<' commands and
  when 'autoindent' is on.  To insert a real tab when 'expandtab' is
  on, use CTRL-V<Tab>.

This implementation doesn't change how BusyBox vi handles autoindent:
it continues to copy the indentation from a neighbouring line.  If
that line has tabs in its indentation so too will the new line.

function                                             old     new   delta
char_insert                                          563     699    +136
do_cmd                                              4668    4716     +48
next_tabstop                                           -      26     +26
.rodata                                           105211  105236     +25
colon                                               3844    3855     +11
refresh                                             1000     995      -5
move_to_col                                           83      74      -9
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 4/2 up/down: 246/-14)           Total: 232 bytes
---
 editors/vi.c | 57 +++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 50 insertions(+), 7 deletions(-)

diff --git a/editors/vi.c b/editors/vi.c
index 6dd951421..261a5c075 100644
--- a/editors/vi.c
+++ b/editors/vi.c
@@ -289,11 +289,13 @@ struct globals {
 #if ENABLE_FEATURE_VI_SETOPTS
 	smallint vi_setops;     // set by setops()
 #define VI_AUTOINDENT (1 << 0)
-#define VI_ERR_METHOD (1 << 1)
-#define VI_IGNORECASE (1 << 2)
-#define VI_SHOWMATCH  (1 << 3)
-#define VI_TABSTOP    (1 << 4)
+#define VI_EXPANDTAB  (1 << 1)
+#define VI_ERR_METHOD (1 << 2)
+#define VI_IGNORECASE (1 << 3)
+#define VI_SHOWMATCH  (1 << 4)
+#define VI_TABSTOP    (1 << 5)
 #define autoindent (vi_setops & VI_AUTOINDENT)
+#define expandtab  (vi_setops & VI_EXPANDTAB )
 #define err_method (vi_setops & VI_ERR_METHOD) // indicate error with beep or flash
 #define ignorecase (vi_setops & VI_IGNORECASE)
 #define showmatch  (vi_setops & VI_SHOWMATCH )
@@ -301,6 +303,7 @@ struct globals {
 // order of constants and strings must match
 #define OPTS_STR \
 		"ai\0""autoindent\0" \
+		"et\0""expandtab\0" \
 		"fl\0""flash\0" \
 		"ic\0""ignorecase\0" \
 		"sm\0""showmatch\0" \
@@ -309,6 +312,7 @@ struct globals {
 #define clear_openabove() (vi_setops &= ~VI_TABSTOP)
 #else
 #define autoindent (0)
+#define expandtab  (0)
 #define err_method (0)
 #define openabove  (0)
 #define set_openabove() ((void)0)
@@ -758,6 +762,23 @@ static int next_tabstop(int col)
 	return col + ((tabstop - 1) - (col % tabstop));
 }
 
+#if ENABLE_FEATURE_VI_SETOPTS
+static int get_column(char *p)
+{
+	const char *r;
+	int co = 0;
+
+	for (r = begin_line(p); r < p; r++) {
+		if (*r == '\t')
+			co = next_tabstop(co);
+		else if ((unsigned char)*r < ' ' || *r == 0x7f)
+			co++; // display as ^X, use 2 columns
+		co++;
+	}
+	return co;
+}
+#endif
+
 //----- Erase the Screen[] memory ------------------------------
 static void screen_erase(void)
 {
@@ -2103,6 +2124,17 @@ static char *char_insert(char *p, char c, int undo) // insert the char c at 'p'
 			p--;
 			p = text_hole_delete(p, p, ALLOW_UNDO_QUEUED);
 		}
+	} else if (c == '\t' && expandtab) {	// expand tab
+		int col = get_column(p);
+		int next = next_tabstop(col);
+		for (; col <= next; ++col) {
+#if ENABLE_FEATURE_VI_UNDO
+			undo_push_insert(p, 1, undo);
+#else
+			modified_count++;
+#endif
+			p += 1 + stupid_insert(p, ' ');
+		}
 #endif
 	} else if (c == term_orig.c_cc[VERASE] || c == 8 || c == 127) { // Is this a BS
 		if (p > text) {
@@ -2870,11 +2902,13 @@ static void colon(char *buf)
 #  if ENABLE_FEATURE_VI_SETOPTS
 			status_line_bold(
 				"%sautoindent "
+				"%sexpandtab "
 				"%sflash "
 				"%signorecase "
 				"%sshowmatch "
 				"tabstop=%u",
 				autoindent ? "" : "no",
+				expandtab ? "" : "no",
 				err_method ? "" : "no",
 				ignorecase ? "" : "no",
 				showmatch ? "" : "no",
@@ -3752,7 +3786,7 @@ static void do_cmd(int c)
 		i = count_lines(p, q);	// # of lines we are shifting
 		for ( ; i > 0; i--, p = next_line(p)) {
 			if (c == '<') {
-				// shift left- remove tab or 8 spaces
+				// shift left- remove tab or tabstop spaces
 				if (*p == '\t') {
 					// shrink buffer 1 char
 					text_hole_delete(p, p, allow_undo);
@@ -3766,8 +3800,17 @@ static void do_cmd(int c)
 					}
 				}
 			} else /* if (c == '>') */ {
-				// shift right -- add tab or 8 spaces
-				char_insert(p, '\t', allow_undo);
+				// shift right -- add tab or tabstop spaces
+				if (expandtab) {
+					for (j = 0; j < tabstop; ++j) {
+						char_insert(p, ' ', allow_undo);
+#if ENABLE_FEATURE_VI_UNDO
+						allow_undo = ALLOW_UNDO_CHAIN;
+#endif
+					}
+				} else {
+					char_insert(p, '\t', allow_undo);
+				}
 			}
 #if ENABLE_FEATURE_VI_UNDO
 			allow_undo = ALLOW_UNDO_CHAIN;
-- 
2.30.2

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