New sort option: mtime

Sort filelist by modification time, newer files first. Useful for
perusing a directory of images by most recently added or changed.

5 files changed, 36 insertions, 5 deletions

diff --git a/man/feh.pre b/man/feh.pre
index f24729d..cecc58f 100644
--- a/man/feh.pre
+++ b/man/feh.pre
@@ -532,10 +532,15 @@ in paused mode.
 .It Cm -S , --sort Ar sort_type
 .
 The file list may be sorted according to image parameters.  Allowed sort
-types are: name, filename, width, height, pixels, size, format.  For sort
-modes other than name or filename, a preload run will be necessary,
+types are: name, filename, mtime, width, height, pixels, size, format.  For sort
+modes other than name, filename, or mtime, a preload run will be necessary,
 causing a delay proportional to the number of images in the list.
 .
+.Pp
+.
+The mtime sort mode sorts images by most recently modified. To sort by oldest
+first, reverse the filelist with --reverse.
+.
 .It Cm -| , --start-at Ar filename
 .
 Start the filelist at
diff --git a/src/filelist.c b/src/filelist.c
index 542dbdf..8f3bfe9 100644
--- a/src/filelist.c
+++ b/src/filelist.c
@@ -354,6 +354,25 @@ int feh_cmp_name(void *file1, void *file2)
 	return(strcmp(FEH_FILE(file1)->name, FEH_FILE(file2)->name));
 }
 
+/* Return -1 if file1 is _newer_ than file2 */
+int feh_cmp_mtime(void *file1, void *file2)
+{
+	struct stat s1, s2;
+
+	if (stat(FEH_FILE(file1)->filename, &s1)) {
+		feh_print_stat_error(FEH_FILE(file1)->filename);
+		return(-1);
+	}
+
+	if (stat(FEH_FILE(file2)->filename, &s2)) {
+		feh_print_stat_error(FEH_FILE(file2)->filename);
+		return(-1);
+	}
+
+	/* gib_list_sort is not stable, so explicitly return 0 as -1 */
+	return(s1.st_mtime >= s2.st_mtime ? -1 : 1);
+}
+
 int feh_cmp_width(void *file1, void *file2)
 {
 	return((FEH_FILE(file1)->info->width - FEH_FILE(file2)->info->width));
@@ -381,7 +400,7 @@ int feh_cmp_format(void *file1, void *file2)
 
 void feh_prepare_filelist(void)
 {
-	if (opt.list || opt.customlist || (opt.sort > SORT_FILENAME)
+	if (opt.list || opt.customlist || (opt.sort > SORT_MTIME)
 			|| opt.preload || opt.min_width || opt.min_height
 			|| (opt.max_width != UINT_MAX) || (opt.max_height != UINT_MAX)) {
 		/* For these sort options, we have to preload images */
@@ -407,6 +426,9 @@ void feh_prepare_filelist(void)
 	case SORT_FILENAME:
 		filelist = gib_list_sort(filelist, feh_cmp_filename);
 		break;
+	case SORT_MTIME:
+		filelist = gib_list_sort(filelist, feh_cmp_mtime);
+		break;
 	case SORT_WIDTH:
 		filelist = gib_list_sort(filelist, feh_cmp_width);
 		break;
diff --git a/src/filelist.h b/src/filelist.h
index 00e36e8..7bfd518 100644
--- a/src/filelist.h
+++ b/src/filelist.h
@@ -56,7 +56,7 @@ struct __feh_file_info {
 
 enum filelist_recurse { FILELIST_FIRST, FILELIST_CONTINUE, FILELIST_LAST };
 
-enum sort_type { SORT_NONE, SORT_NAME, SORT_FILENAME, SORT_WIDTH,
+enum sort_type { SORT_NONE, SORT_NAME, SORT_FILENAME, SORT_MTIME, SORT_WIDTH,
 	SORT_HEIGHT,
 	SORT_PIXELS,
 	SORT_SIZE, SORT_FORMAT
@@ -82,6 +82,7 @@ void feh_save_filelist();
 
 int feh_cmp_name(void *file1, void *file2);
 int feh_cmp_filename(void *file1, void *file2);
+int feh_cmp_mtime(void *file1, void *file2);
 int feh_cmp_width(void *file1, void *file2);
 int feh_cmp_height(void *file1, void *file2);
 int feh_cmp_pixels(void *file1, void *file2);
diff --git a/src/help.raw b/src/help.raw
index 27e3b6c..462e715 100644
--- a/src/help.raw
+++ b/src/help.raw
@@ -46,7 +46,8 @@ OPTIONS
  -U, --loadable            List all loadable files. No image display
  -u, --unloadable          List all unloadable files. No image display
  -S, --sort SORT_TYPE      Sort files by:
-                           name, filename, width, height, pixels, size or format
+                           name, filename, mtime, width, height, pixels, size,
+                           or format
  -n, --reverse             Reverse sort order
  -A, --action ACTION       Specify action to perform when pressing <return>.
                            Executed by /bin/sh, may contain FORMAT SPECIFIERS
diff --git a/src/options.c b/src/options.c
index cdd37d1..469115e 100644
--- a/src/options.c
+++ b/src/options.c
@@ -501,6 +501,8 @@ static void feh_parse_option_array(int argc, char **argv, int finalrun)
 				opt.sort = SORT_NAME;
 			else if (!strcasecmp(optarg, "filename"))
 				opt.sort = SORT_FILENAME;
+			else if (!strcasecmp(optarg, "mtime"))
+				opt.sort = SORT_MTIME;
 			else if (!strcasecmp(optarg, "width"))
 				opt.sort = SORT_WIDTH;
 			else if (!strcasecmp(optarg, "height"))