Showing whitespace on minus lines of diff ouput

The colored diff output is quite helpful to show introductions of whitespace.

However, if whitespace has been removed, it's impossible to see in the
diff output since whitespace is colorized on '+' lines, but not '-'
lines.

I'm looking at diff.c, but wow. Can someone more familiar with this
file point me toward how I'd make a patch to colorize whitespace on
'-' lines as well?

Thanks,

j.

On Thu, Feb 4, 2010 at 8:47 PM, Jay Soffian [off-list ref] wrote:

I'm looking at diff.c, but wow. Can someone more familiar with this
file point me toward how I'd make a patch to colorize whitespace on
'-' lines as well?

Ah, got it. I think. Patch shortly. :-)

j.

On Thu, Feb 4, 2010 at 9:08 PM, Jay Soffian [off-list ref] wrote:

Ah, got it. I think. Patch shortly. :-)

Bah, still need help. Here's what I tried (apologizes for the gmail
munging of long lines):

diff --git a/diff.c b/diff.c
index 381cc8d..17133cd 100644
--- a/diff.c
+++ b/diff.c

@@ -331,6 +331,23 @@ static int new_blank_line_at_eof(struct

emit_callback *ecbdata, const char *line
 	return ws_blank_line(line, len, ecbdata->ws_rule);
 }

+static void emit_sub_line(const char *reset,
+			  struct emit_callback *ecbdata,
+			  const char *line, int len)
+{
+	const char *ws = diff_get_color(ecbdata->color_diff, DIFF_WHITESPACE);
+	const char *set = diff_get_color(ecbdata->color_diff, DIFF_FILE_OLD);
+
+	if (!*ws)
+		emit_line_0(ecbdata->file, set, reset, '-', line, len);
+	else {
+		/* Emit just the prefix, then the rest. */
+		emit_line_0(ecbdata->file, set, reset, '-', "", 0);
+		ws_check_emit(line, len, ecbdata->ws_rule,
+			      ecbdata->file, set, reset, ws);
+	}
+}
+
 static void emit_add_line(const char *reset,
 			  struct emit_callback *ecbdata,
 			  const char *line, int len)

@@ -434,7 +451,6 @@ static void emit_rewrite_lines(struct emit_callback *ecb,
 {
 	const char *endp = NULL;
 	static const char *nneof = " No newline at end of file\n";
-	const char *old = diff_get_color(ecb->color_diff, DIFF_FILE_OLD);
 	const char *reset = diff_get_color(ecb->color_diff, DIFF_RESET);

 	while (0 < size) {

@@ -444,8 +460,7 @@ static void emit_rewrite_lines(struct emit_callback *ecb,
 		len = endp ? (endp - data + 1) : size;
 		if (prefix != '+') {
 			ecb->lno_in_preimage++;
-			emit_line_0(ecb->file, old, reset, '-',
-				    data, len);
+			emit_sub_line(reset, ecb, data, len);
 		} else {
 			ecb->lno_in_postimage++;
 			emit_add_line(reset, ecb, data, len);

@@ -862,9 +877,12 @@ static void fn_out_consume(void *priv, char

*line, unsigned long len)
 			diff_get_color(ecbdata->color_diff,
 				       line[0] == '-' ? DIFF_FILE_OLD : DIFF_PLAIN);
 		ecbdata->lno_in_preimage++;
-		if (line[0] == ' ')
+		if (line[0] == ' ') {
 			ecbdata->lno_in_postimage++;
-		emit_line(ecbdata->file, color, reset, line, len);
+			emit_line(ecbdata->file, color, reset, line, len);
+		} else {
+			emit_sub_line(reset, ecbdata, line + 1, len - 1);
+		}
 	} else {
 		ecbdata->lno_in_postimage++;
 		emit_add_line(reset, ecbdata, line + 1, len - 1);


But for reasons I don't understand this screws up some of the diff
test cases. It's emitting "index" lines where it shouldn't, and "- No
newline at end of file" instead of "\ No newline at end of file".

I guess something is post-processing the output of the emit functions
and doesn't like the change?

Help appreciated. :-)

j.