Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> writes:
> From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Date: Wed, 16 Mar 2016 09:15:53 -0700
> Subject: [PATCH] pretty-print: de-tabify indented logs to make things line up properly
>
> This should all line up:
>
> Column 1 Column 2
> -------- --------
> A B
> ABCD EFGH
> SPACES Instead of Tabs
>
> Even with multi-byte UTF8 characters:
>
> Column 1 Column 2
> -------- --------
> Ä B
> åäö 100
> A Møøse once bit my sister..
>
> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> ---
>
> This seems to work for me, and while there is some cost, it's minimal.
> Doing a "git log > /dev/null" of the current git tree is about 1% slower
> because of the tab-finding. A tree with a lot of tabs in the commit
> messages would be more noticeable, because then you actually end up
> hitting the whole "how wide is this" issue.
>
> (But if the tabs are all at the beginning of a line, you'd still be ok
> and avoid the utf8 width calculations).
>
> Comments?
I stared at it for a while, and didn't spot anything wrong with it.
I did wonder about two things, though:
(1) if turning your "preparation; do { ... } while()" into
"while () { }" would make the result a bit easier to read;
(2) if we can somehow eliminate duplication of "tab + 1" (spelled
differently on the previous line as "1+tab"), the end result
may get easier to follow.
but both are minor.
> pretty.c | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 74 insertions(+), 2 deletions(-)
>
> diff --git a/pretty.c b/pretty.c
> index 92b2870a7eab..0b40457f99f0 100644
> --- a/pretty.c
> +++ b/pretty.c
> @@ -1629,6 +1629,76 @@ void pp_title_line(struct pretty_print_context *pp,
> strbuf_release(&title);
> }
>
> +static int pp_utf8_width(const char *start, const char *end)
> +{
> + int width = 0;
> + size_t remain = end - start;
> +
> + while (remain) {
> + int n = utf8_width(&start, &remain);
> + if (n < 0 || !start)
> + return -1;
> + width += n;
> + }
> + return width;
> +}
> +
> +/*
> + * pp_handle_indent() prints out the intendation, and
> + * perhaps the whole line (without the final newline)
> + *
> + * Why "perhaps"? If there are tabs in the indented line
> + * it will print it out in order to de-tabify the line.
> + *
> + * But if there are no tabs, we just fall back on the
> + * normal "print the whole line".
> + */
> +static int pp_handle_indent(struct strbuf *sb, int indent,
> + const char *line, int linelen)
> +{
> + const char *tab;
> +
> + strbuf_addchars(sb, ' ', indent);
> +
> + tab = memchr(line, '\t', linelen);
> + if (!tab)
> + return 0;
> +
> + do {
> + int width = pp_utf8_width(line, tab);
> +
> + /*
> + * If it wasn't well-formed utf8, or it
> + * had characters with badly defined
> + * width (control characters etc), just
> + * give up on trying to align things.
> + */
> + if (width < 0)
> + break;
> +
> + /* Output the data .. */
> + strbuf_add(sb, line, tab - line);
> +
> + /* .. and the de-tabified tab */
> + strbuf_addchars(sb, ' ', 8-(width & 7));
> +
> + /* Skip over the printed part .. */
> + linelen -= 1+tab-line;
> + line = tab + 1;
> +
> + /* .. and look for the next tab */
> + tab = memchr(line, '\t', linelen);
> + } while (tab);
> +
> + /*
> + * Print out everything after the last tab without
> + * worrying about width - there's nothing more to
> + * align.
> + */
> + strbuf_add(sb, line, linelen);
> + return 1;
> +}
> +
> void pp_remainder(struct pretty_print_context *pp,
> const char **msg_p,
> struct strbuf *sb,
> @@ -1652,8 +1722,10 @@ void pp_remainder(struct pretty_print_context *pp,
> first = 0;
>
> strbuf_grow(sb, linelen + indent + 20);
> - if (indent)
> - strbuf_addchars(sb, ' ', indent);
> + if (indent) {
> + if (pp_handle_indent(sb, indent, line, linelen))
> + linelen = 0;
> + }
> strbuf_add(sb, line, linelen);
> strbuf_addch(sb, '\n');
> }
--
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