Hide empty columns in table package list display

On -R operations, the "New Version" column is always empty, taking up
space and not really showing the user anything valuable. The same is
true on -S or -U operations for the "Old Version" column when packages
are only being installed and not upgraded.

Remove this column so we get a few screen columns back, especially now
that we show repo/packagename style output. This also makes some
adjustment to the padding logic. We no longer include padding in column
widths but it is included in the total table width. We also ensure the
last displayed column is always right aligned, even if this is not the
actual rightmost column.

Example output, before:
    $ sudo pacman -R eclipse
    checking dependencies...

    Targets (1):

    Name     Old Version  New Version   Net Change

    eclipse  3.7-1                     -194.02 MiB

    Total Removed Size:     194.02 MiB

And after:
    $ sudo pacman -R eclipse
    checking dependencies...

    Targets (1):

    Name     Old Version   Net Change

    eclipse  3.7-1        -194.02 MiB

    Total Removed Size:     194.02 MiB

Signed-off-by: Dan McGee <dan@archlinux.org>

src/pacman/util.c

@@ -487,52 +487,86 @@ void string_display(const char *title, const char *string)
 	printf("\n");
 }
 
-static void table_print_line(const alpm_list_t *line,
+static void table_print_line(const alpm_list_t *line, short col_padding,
-		size_t colcount, size_t *widths)
+		size_t colcount, size_t *widths, int *has_data)
 {
-	size_t i;
+	size_t i, lastcol = 0;
+	int need_padding = 0;
 	const alpm_list_t *curcell;
 
+	for(i = colcount; i > 0; i--) {
+		if(has_data[i - 1]) {
+			lastcol = i - 1;
+			break;
+		}
+	}
+
 	for(i = 0, curcell = line; curcell && i < colcount;
 			i++, curcell = alpm_list_next(curcell)) {
-		const char *value = curcell->data;
+		const char *value;
-		size_t len = string_length(value);
+		int cell_padding;
+
+		if(!has_data[i]) {
+			continue;
+		}
+
+		value = curcell->data;
 		/* silly printf requires padding size to be an int */
-		int padding = (int)widths[i] - (int)len;
+		cell_padding = (int)widths[i] - (int)string_length(value);
-		if(padding < 0) {
+		if(cell_padding < 0) {
-			padding = 0;
+			cell_padding = 0;
+		}
+		if(need_padding) {
+			printf("%*s", col_padding, "");
 		}
 		/* left-align all but the last column */
-		if(i + 1 < colcount) {
+		if(i != lastcol) {
-			printf("%s%*s", value, padding, "");
+			printf("%s%*s", value, cell_padding, "");
 		} else {
-			printf("%*s%s", padding, "", value);
+			printf("%*s%s", cell_padding, "", value);
 		}
+		need_padding = 1;
 	}
 
 	printf("\n");
 }
 
-/* find the max string width of each column */
+
+
+/**
+ * Find the max string width of each column. Also determines whether values
+ * exist in the column and sets the value in has_data accordingly.
+ * @param header a list of header strings
+ * @param rows a list of lists of rows as strings
+ * @param padding the amount of padding between columns
+ * @param totalcols the total number of columns in the header and each row
+ * @param widths a pointer to store width data
+ * @param has_data a pointer to store whether column has data
+ *
+ * @return the total width of the table; 0 on failure
+ */
 static size_t table_calc_widths(const alpm_list_t *header,
-		const alpm_list_t *rows, size_t totalcols, size_t **widths)
+		const alpm_list_t *rows, short padding, size_t totalcols,
+		size_t **widths, int **has_data)
 {
 	const alpm_list_t *i;
-	const unsigned short padding = 2;
+	size_t curcol, totalwidth = 0, usefulcols = 0;
-	size_t curcol, totalwidth = 0;
 	size_t *colwidths;
+	int *coldata;
 
 	if(totalcols <= 0) {
 		return 0;
 	}
 
 	colwidths = malloc(totalcols * sizeof(size_t));
-	if(!colwidths) {
+	coldata = calloc(totalcols, sizeof(int));
+	if(!colwidths || !coldata) {
 		return 0;
 	}
 	/* header determines column count and initial values of longest_strs */
 	for(i = header, curcol = 0; i; i = alpm_list_next(i), curcol++) {
 		colwidths[curcol] = string_length(i->data);
+		/* note: header does not determine whether column has data */
 	}
 
 	/* now find the longest string in each column */
@@ -546,18 +580,27 @@ static size_t table_calc_widths(const alpm_list_t *header,
 			if(str_len > colwidths[curcol]) {
 				colwidths[curcol] = str_len;
 			}
+			if(str_len > 0) {
+				coldata[curcol] = 1;
+			}
 		}
 	}
 
 	for(i = header, curcol = 0; i; i = alpm_list_next(i), curcol++) {
-		/* pad everything but the last column */
+		/* only include columns that have data */
-		if(curcol + 1 < totalcols) {
+		if(coldata[curcol]) {
-			colwidths[curcol] += padding;
+			usefulcols++;
-		}
 			totalwidth += colwidths[curcol];
 		}
+	}
+
+	/* add padding between columns */
+	if(usefulcols > 0) {
+		totalwidth += padding * (usefulcols - 1);
+	}
 
 	*widths = colwidths;
+	*has_data = coldata;
 	return totalwidth;
 }
 
@@ -574,21 +617,24 @@ static size_t table_calc_widths(const alpm_list_t *header,
 int table_display(const char *title, const alpm_list_t *header,
 		const alpm_list_t *rows)
 {
+	const unsigned short padding = 2;
 	const alpm_list_t *i;
 	size_t *widths = NULL, totalcols, totalwidth;
+	int *has_data = NULL;
 
 	if(rows == NULL || header == NULL) {
 		return 0;
 	}
 
 	totalcols = alpm_list_count(header);
-	totalwidth = table_calc_widths(header, rows, totalcols, &widths);
+	totalwidth = table_calc_widths(header, rows, padding, totalcols,
+			&widths, &has_data);
 	/* return -1 if terminal is not wide enough */
 	if(totalwidth > getcols()) {
 		fprintf(stderr, _("insufficient columns available for table display\n"));
 		return -1;
 	}
-	if(!totalwidth || !widths) {
+	if(!totalwidth || !widths || !has_data) {
 		return -1;
 	}
 
@@ -596,14 +642,15 @@ int table_display(const char *title, const alpm_list_t *header,
 		printf("%s\n\n", title);
 	}
 
-	table_print_line(header, totalcols, widths);
+	table_print_line(header, padding, totalcols, widths, has_data);
 	printf("\n");
 
 	for(i = rows; i; i = alpm_list_next(i)) {
-		table_print_line(i->data, totalcols, widths);
+		table_print_line(i->data, padding, totalcols, widths, has_data);
 	}
 
 	free(widths);
+	free(has_data);
 	return 0;
 }