Ability to specify fonts on a per-locale basis

Add to the list found in `src/fonts.c` (use language IDs
found in `src/i18n.h`, e.g. "LANG_DE" for German).
h/t Shin-ichi for the suggestion

Closes https://sourceforge.net/p/tuxpaint/feature-requests/240/

docs/CHANGES.txt

@@ -70,6 +70,13 @@ https://tuxpaint.org/
       Closes https://sourceforge.net/p/tuxpaint/feature-requests/146/
       Bill Kendrick <bill@newbreedsoftware.com>
 
+    * WIP Different default fonts may be set on a per-locale basis
+      (hard-coded into Tux Paint).  Most locales still use "DejaVu Sans",
+      if available.  As of 0.9.31, things are configured as:
+      + Japanese: TBD
+      Closes https://sourceforge.net/p/tuxpaint/feature-requests/240/
+      Bill Kendrick <bill@newbreedsoftware.com> (code)
+
   * Bug Fixes:
     ----------
     * In some window size / button size combinations, Eraser

src/fonts.c

@@ -19,7 +19,7 @@
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   (See COPYING.txt)
 
-  Last modified: June 1, 2023
+  Last modified: June 8, 2023
 */
 
 #include <stdio.h>
@@ -173,6 +173,16 @@ int button_label_y_nudge;
 static void reliable_read(int fd, void *buf, size_t count);
 #endif
 
+const char * PANGO_DEFAULT_FONT = "DejaVu Sans";
+
+default_locale_font_t default_local_fonts[] = {
+  {
+   LANG_JA,
+   "TakaoPGothic" /* Included in Ubuntu "fonts-takao-gothic" package */
+   // FIXME: Shin-ichi recommend something, please! -bjk 2023.06.08
+  },
+  {-1, NULL},
+}; 
 
 void TuxPaint_Font_CloseFont(TuxPaint_Font * tpf)
 {

src/fonts.h

@@ -19,7 +19,7 @@
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   (See COPYING.txt)
 
-  Last updated: May 31, 2023
+  Last updated: June 8, 2023
 */
 
 #ifndef FONTS_H
@@ -39,11 +39,23 @@
 #include "SDL_ttf.h"
 #include "SDL2_Pango.h"
 
+#include "i18n.h"
+
 /* UI font, which as of 0.9.31, can be overridden by "uifont"
    setting (also, this will be used if "uifont=default" is specified,
-   e.g. to override a config. file option using a command-line option) */
+   e.g. to override a config. file option using a command-line option).
 
-#define PANGO_DEFAULT_FONT "DejaVu Sans"
+   Also, starting in 0.9.31, we can specify different preferred fonts
+   based on locale.
+*/
+
+typedef struct default_locale_font_s {
+  int locale_id;
+  const char * font_name;
+} default_locale_font_t;
+
+extern default_locale_font_t default_local_fonts[];
+extern const char * PANGO_DEFAULT_FONT;
 
 #include "compiler.h"
 

src/tuxpaint.c

@@ -27921,6 +27921,7 @@ static void setup_config(char *argv[])
 {
   char str[128];
   char *picturesdir;
+  int i;
 
 #if !defined(_WIN32) && !defined(__ANDROID__)
   const char *home = getenv("HOME");
@@ -28097,6 +28098,15 @@ static void setup_config(char *argv[])
     tmpcfg.parsertmp_locale = NULL;
   button_label_y_nudge = setup_i18n(tmpcfg.parsertmp_lang, tmpcfg.parsertmp_locale, &num_wished_langs);
 
+  /* Determine the referred font for the current locale */
+  for (i = 0; default_local_fonts[i].locale_id != -1; i++)
+  {
+    if (default_local_fonts[i].locale_id == get_current_language())
+    {
+      PANGO_DEFAULT_FONT = default_local_fonts[i].font_name;
+    }
+  }
+
   if (tmpcfg.tp_ui_font)
   {
     char * tmp_str;