WIP Reverse sorting in Open & Slideshows dialog

...via --reversesort option.  WIP; need docs updated.
(Also need Tux Paint Config. changes, but that's another repo)

docs/CHANGES.txt

@@ -150,6 +150,12 @@ http://www.tuxpaint.org/
       (the top of the list).
       Bill Kendrick <bill@newbreedsoftware.com>
 
+    * WIP Added an option to sort the "Open" and "Slideshow" dialogs
+      by newest-images-first, rather than the default oldest-first.
+      (For https://sourceforge.net/p/tuxpaint/feature-requests/206/)
+      Pere Pujal i Carabantes <perepujal@gmail.com> and
+      Bill Kendrick <bill@newbreedsoftware.com>
+
   * Localization Updates:
     ---------------------
     * Albanian translation

src/parse.gperf

@@ -139,6 +139,7 @@ print,               NEGBOOL(disable_print)
 printcfg,            POSBOOL(use_print_config)
 printcommand,        MULTI(printcommand)
 printdelay,          MULTI(print_delay)
+reversesort,         POSBOOL(reversesort)
 quit,                NEGBOOL(disable_quit)
 save,                NEGBOOL(disable_save)
 savedir,             MULTI(savedir)

src/parse.h

@@ -48,6 +48,7 @@ struct cfginfo
   const char *colors_rows;
   const char *print_delay;
   const char *printcommand;
+  const char *reversesort;
 //  const char *promptless_save;
   const char *_promptless_save_over;
   const char *_promptless_save_over_new;

src/tuxpaint-completion.bash

@@ -3,7 +3,7 @@
 # Bill Kendrick <bill@newbreedsoftware.com>; http://www.tuxpaint.org/
 # Based on inkscape's completion file, by allali@univ-mlv.fr
 #
-# Last modified 2022-01-18
+# Last modified 2022-05-15
 #
 # $Id$
 
@@ -67,6 +67,7 @@ _tuxpaint()
 			--nosave --save \
 			--autosave --noautosave \
 			--savedir --datadir --exportdir \
+			--reversesort --noreversesort \
 			--printdelay= \
 			--altprintmod --altprintalways --altprintnever \
 			--printcommand --altprintcommand \

src/tuxpaint.c

@@ -1269,6 +1269,7 @@ static int ok_to_use_lockfile = 1;
 static int start_blank;
 static int autosave_on_quit;
 static int no_prompt_on_quit = 0;
+static int reversesort = 0;
 
 static int dont_do_xor;
 static int dont_load_stamps;
@@ -2035,6 +2036,7 @@ static void disable_avail_tools(void);
 static void enable_avail_tools(void);
 static void reset_avail_tools(void);
 static int compare_dirent2s(struct dirent2 *f1, struct dirent2 *f2);
+static int compare_dirent2s_invert(struct dirent2 *f1, struct dirent2 *f2);
 static void redraw_tux_text(void);
 static void draw_tux_text(int which_tux, const char *const str, int want_right_to_left);
 static void draw_tux_text_ex(int which_tux, const char *const str, int want_right_to_left, Uint8 locale_text);
@@ -7349,6 +7351,7 @@ void show_usage(int exitcode)
           "  [--savedir DIRECTORY]\n"
           "  [--nosave | --save]\n"
           "  [--autosave | --noautosave]\n"
+          "  [--reversesort | --noreversesort]\n"
           "\n"
           " Data:\n"
           "  [--nolockfile]\n"
@@ -11624,6 +11627,16 @@ static int compare_dirent2s(struct dirent2 *f1, struct dirent2 *f2)
 }
 
 
+/**
+ * FIXME
+ */
+/* For qsort() call in do_open()... */
+static int compare_dirent2s_invert(struct dirent2 *f1, struct dirent2 *f2)
+{
+  return compare_dirent2s(f2, f1);
+}
+
+
 /**
  * FIXME
  */
@@ -15554,7 +15567,10 @@ static int do_open(void)
 
       /* Sort: */
 
-      qsort(fs, num_files_in_dirs, sizeof(struct dirent2), (int (*)(const void *, const void *))compare_dirent2s);
+      if (!reversesort)
+        qsort(fs, num_files_in_dirs, sizeof(struct dirent2), (int (*)(const void *, const void *))compare_dirent2s);
+      else
+        qsort(fs, num_files_in_dirs, sizeof(struct dirent2), (int (*)(const void *, const void *))compare_dirent2s_invert);
 
 
       /* Read directory of images and build thumbnails: */
@@ -16692,7 +16708,10 @@ static int do_slideshow(void)
 
   /* Sort: */
 
-  qsort(fs, num_files_in_dir, sizeof(struct dirent2), (int (*)(const void *, const void *))compare_dirent2s);
+  if (!reversesort)
+    qsort(fs, num_files_in_dir, sizeof(struct dirent2), (int (*)(const void *, const void *))compare_dirent2s);
+  else
+    qsort(fs, num_files_in_dir, sizeof(struct dirent2), (int (*)(const void *, const void *))compare_dirent2s_invert);
 
 
   /* Read directory of images and build thumbnails: */
@@ -20597,6 +20616,7 @@ static int do_new_dialog(void)
 
   /* Sort: */
 
+  /* (N.B. "New" dialog not affected by 'reversesort' option) */
   qsort(fs, num_files_in_dirs, sizeof(struct dirent2), (int (*)(const void *, const void *))compare_dirent2s);
 
 
@@ -25889,6 +25909,7 @@ static void setup_config(char *argv[])
 #define SETBOOL(x) do{ if(tmpcfg.x) x = (tmpcfg.x==PARSE_YES); }while(0)
   SETBOOL(all_locale_fonts);
   SETBOOL(autosave_on_quit);
+  SETBOOL(reversesort);
   SETBOOL(disable_label);
   SETBOOL(disable_brushspacing);
   SETBOOL(disable_magic_controls);