[pacman-dev] [PATCH] util.c: table_print_line: properly align texts involving CJK

[Andrew Gregory]

On 09/12/20 at 04:25pm, Chih-Hsuan Yen wrote:
> Fixes FS#59229
> 
> Signed-off-by: Chih-Hsuan Yen <yan12125 at gmail.com>
> ---
>  src/pacman/util.c | 20 +++++++++++++++-----
>  1 file changed, 15 insertions(+), 5 deletions(-)
> 
> diff --git a/src/pacman/util.c b/src/pacman/util.c
> index e9187529..b45ca22d 100644
> --- a/src/pacman/util.c
> +++ b/src/pacman/util.c
> @@ -516,22 +516,32 @@ static void table_print_line(const alpm_list_t *line, short col_padding,
>  			i++, curcell = alpm_list_next(curcell)) {
>  		const struct table_cell_t *cell = curcell->data;
>  		const char *str = (cell->label ? cell->label : "");
> -		int cell_width;
> +		int padding_width;
>  
>  		if(!has_data[i]) {
>  			continue;
>  		}
>  
> -		cell_width = (cell->mode & CELL_RIGHT_ALIGN ? (int)widths[i] : -(int)widths[i]);
> -
>  		if(need_padding) {
>  			printf("%*s", col_padding, "");
>  		}
>  
>  		if(cell->mode & CELL_TITLE) {
> -			printf("%s%*s%s", config->colstr.title, cell_width, str, config->colstr.nocolor);
> +			printf("%s", config->colstr.title);
> +		}
> +		/* Handle alignment manually here - for printf in C, "If the
> +		 * precision is specified, no more than that many bytes are
> +		 * written." [1]
> +		 * [1] Section 7.21.6, N2176, final draft for ISO/IEC 9899:2017 (C18)
> +		 * Fixes FS#59229. */

I appreciate a reference to a spec, but this is a bit verbose for
a source comment.  This information is better suited to the commit
message with a shorter comment in the source about printf width being
in bytes instead of characters.

I think this solution is more complex than necessary though.  It
should be sufficient to just adjust the above cell_width to be in
bytes rather than characters.  Something like:

        /* calculate cell width adjusting for multi-byte character strings */
		cell_width = (int)widths[i] + strlen(str) - string_length(str);
		cell_width = cell->mode & CELL_RIGHT_ALIGN ? cell_width : -cell_width;

> +		padding_width = (int)(widths[i] - string_length(str));
> +		if (cell->mode & CELL_RIGHT_ALIGN) {
> +			printf("%*s%s", padding_width, "", str);
>  		} else {
> -			printf("%*s", cell_width, str);
> +			printf("%s%*s", str, padding_width, "");
> +		}
> +		if(cell->mode & CELL_TITLE) {
> +			printf("%s", config->colstr.nocolor);
>  		}
>  		need_padding = 1;
>  	}
> -- 
> 2.28.0