(Font) One copy of the language-to-font decision

The same switch existed five times - twice in ozone, once each in
materialui, gfx_widgets and file_path_special - mapping Arabic and
Persian to fallback-font.ttf, Chinese to chinese-fallback-font.ttf,
Korean to korean-fallback-font.ttf, and everything else to the
caller's own default. Character for character the same, differing only
in which variable held the assets directory.

font_driver_language_font_file() returns the file name, or NULL when
the language has no special requirement. The name rather than a full
path, because the callers do genuinely differ on the directory:
ozone and materialui build it from directory_assets, widgets keep
assets_pkg_dir already, file_path_special has its own. The default
branch stays with the caller too - bold.ttf, regular.ttf,
FILE_PATH_TTF_FONT and the xmb theme directory are all different.

Adding a language was five edits and is now one. That matters
immediately: Thai renders as tofu today because it is not in the
switch, and neither shipped fallback font contains Thai - checking the
cmap tables, fallback-font.ttf covers Arabic but not U+0E01. So Thai
needs a font as well as a case, and when one arrives there is now a
single place to put it.

This is also the piece the language switch was missing.
font_driver_reload_fonts() rebuilds each font from the path it was
created with, which re-reads the same face; making a language change
take effect without a restart needs the path re-resolved, and that
needs one function to ask. It exists now.

samples/gfx/font_lifecycle grows a msg_hash_get_uint() stub, since
font_driver.c now asks which language is selected. English there - the
tests are about the lifecycle, not the mapping. Clean under ASan,
UBSan, LeakSanitizer and TSan.

file_path_special.c

@@ -381,35 +381,21 @@ size_t fill_pathname_application_special(char *s,
             {
                char tmp_dir[DIR_MAX_LENGTH];
 
-               switch (*msg_hash_get_uint(MSG_HASH_USER_LANGUAGE))
+               const char *lang_font = font_driver_language_font_file();
+
+               if (lang_font)
                {
-                  case RETRO_LANGUAGE_ARABIC:
-                  case RETRO_LANGUAGE_PERSIAN:
-                     fill_pathname_join_special(tmp_dir,
-                           settings->paths.directory_assets, "pkg", sizeof(tmp_dir));
-                     _len = fill_pathname_join_special(s, tmp_dir, "fallback-font.ttf", len);
-                     break;
-                  case RETRO_LANGUAGE_CHINESE_SIMPLIFIED:
-                  case RETRO_LANGUAGE_CHINESE_TRADITIONAL:
-                     fill_pathname_join_special(tmp_dir,
-                           settings->paths.directory_assets, "pkg", sizeof(tmp_dir));
-                     _len = fill_pathname_join_special(s, tmp_dir, "chinese-fallback-font.ttf", len);
-                     break;
-                  case RETRO_LANGUAGE_KOREAN:
-                     fill_pathname_join_special(tmp_dir,
-                           settings->paths.directory_assets, "pkg", sizeof(tmp_dir));
-                     _len = fill_pathname_join_special(s, tmp_dir, "korean-fallback-font.ttf", len);
-                     break;
-                  default:
-                     {
-                        char tmp_dir2[DIR_MAX_LENGTH];
-                        settings_t *settings     = config_get_ptr();
-                        const char *dir_assets   = settings->paths.directory_assets;
-                        fill_pathname_join_special(tmp_dir2, dir_assets, "xmb", sizeof(tmp_dir2));
-                        fill_pathname_join_special(tmp_dir, tmp_dir2, xmb_theme_ident(), sizeof(tmp_dir));
-                        _len = fill_pathname_join_special(s, tmp_dir, FILE_PATH_TTF_FONT, len);
-                     }
-                     break;
+                  fill_pathname_join_special(tmp_dir,
+                        settings->paths.directory_assets, "pkg", sizeof(tmp_dir));
+                  _len = fill_pathname_join_special(s, tmp_dir, lang_font, len);
+               }
+               else
+               {
+                  char tmp_dir2[DIR_MAX_LENGTH];
+                  const char *dir_assets = settings->paths.directory_assets;
+                  fill_pathname_join_special(tmp_dir2, dir_assets, "xmb", sizeof(tmp_dir2));
+                  fill_pathname_join_special(tmp_dir, tmp_dir2, xmb_theme_ident(), sizeof(tmp_dir));
+                  _len = fill_pathname_join_special(s, tmp_dir, FILE_PATH_TTF_FONT, len);
                }
             }
          }

gfx/font_driver.c

@@ -24,6 +24,7 @@
 #include "../config.h"
 #endif
 
+#include "../msg_hash.h"
 #include "font_driver.h"
 #include "video_thread_wrapper.h"
 
@@ -68,6 +69,25 @@ static void font_driver_cache_metrics(font_data_t *font)
    }
 }
 
+const char *font_driver_language_font_file(void)
+{
+   switch (*msg_hash_get_uint(MSG_HASH_USER_LANGUAGE))
+   {
+      case RETRO_LANGUAGE_ARABIC:
+      case RETRO_LANGUAGE_PERSIAN:
+         return "fallback-font.ttf";
+      case RETRO_LANGUAGE_CHINESE_SIMPLIFIED:
+      case RETRO_LANGUAGE_CHINESE_TRADITIONAL:
+         return "chinese-fallback-font.ttf";
+      case RETRO_LANGUAGE_KOREAN:
+         return "korean-fallback-font.ttf";
+      default:
+         break;
+   }
+
+   return NULL;
+}
+
 unsigned font_driver_reload_fonts(void)
 {
    font_data_t *font;

gfx/font_driver.h

@@ -150,6 +150,15 @@ void font_driver_free(font_data_t *font);
  * left alone. Returns the number rebuilt. */
 unsigned font_driver_reload_fonts(void);
 
+/* The font file the current menu language needs, relative to the
+ * assets pkg directory, or NULL when it has no special requirement
+ * and the caller's own default should be used.
+ *
+ * One copy of this decision. It was four - ozone, materialui,
+ * gfx_widgets and file_path_special each carried the same switch -
+ * which is three places to forget when a language is added. */
+const char *font_driver_language_font_file(void);
+
 /* Returns a monotonic counter incremented on every font free;
  * see font_driver.c for rationale. Used to validate externally
  * cached per-font derived data */

gfx/gfx_widgets.c

@@ -1015,22 +1015,15 @@ static void gfx_widgets_layout(
             is_threaded, p_dispwidget->ozone_bold_font_path, BASE_FONT_SIZE);
 
       /* Create msg_queue font */
-      switch (*msg_hash_get_uint(MSG_HASH_USER_LANGUAGE))
       {
-         case RETRO_LANGUAGE_ARABIC:
-         case RETRO_LANGUAGE_PERSIAN:
-            fill_pathname_join_special(font_file, p_dispwidget->assets_pkg_dir, "fallback-font.ttf", sizeof(font_file));
-            break;
-         case RETRO_LANGUAGE_CHINESE_SIMPLIFIED:
-         case RETRO_LANGUAGE_CHINESE_TRADITIONAL:
-            fill_pathname_join_special(font_file, p_dispwidget->assets_pkg_dir, "chinese-fallback-font.ttf", sizeof(font_file));
-            break;
-         case RETRO_LANGUAGE_KOREAN:
-            fill_pathname_join_special(font_file, p_dispwidget->assets_pkg_dir, "korean-fallback-font.ttf", sizeof(font_file));
-            break;
-         default:
-            strlcpy(font_file, p_dispwidget->ozone_regular_font_path, sizeof(font_file));
-            break;
+         const char *lang_font = font_driver_language_font_file();
+
+         if (lang_font)
+            fill_pathname_join_special(font_file,
+                  p_dispwidget->assets_pkg_dir, lang_font, sizeof(font_file));
+         else
+            strlcpy(font_file, p_dispwidget->ozone_regular_font_path,
+                  sizeof(font_file));
       }
       gfx_widgets_font_init(p_disp, p_dispwidget,
             &p_dispwidget->gfx_widget_fonts.msg_queue,

menu/drivers/materialui.c

@@ -9327,33 +9327,22 @@ static void materialui_init_font(gfx_display_t *p_disp,
       font_data->font = NULL;
    }
 
-   switch (*msg_hash_get_uint(MSG_HASH_USER_LANGUAGE))
    {
-      case RETRO_LANGUAGE_ARABIC:
-      case RETRO_LANGUAGE_PERSIAN:
+      const char *lang_font = font_driver_language_font_file();
+
+      if (lang_font)
+      {
          fill_pathname_join_special(tmp_dir,
                settings->paths.directory_assets, "pkg", sizeof(tmp_dir));
-         fill_pathname_join_special(fontpath, tmp_dir, "fallback-font.ttf",
+         fill_pathname_join_special(fontpath, tmp_dir, lang_font,
                sizeof(fontpath));
-         break;
-      case RETRO_LANGUAGE_CHINESE_SIMPLIFIED:
-      case RETRO_LANGUAGE_CHINESE_TRADITIONAL:
-         fill_pathname_join_special(tmp_dir,
-               settings->paths.directory_assets, "pkg", sizeof(tmp_dir));
-         fill_pathname_join_special(fontpath, tmp_dir, "chinese-fallback-font.ttf",
-               sizeof(fontpath));
-         break;
-      case RETRO_LANGUAGE_KOREAN:
-         fill_pathname_join_special(tmp_dir,
-               settings->paths.directory_assets, "pkg", sizeof(tmp_dir));
-         fill_pathname_join_special(fontpath, tmp_dir, "korean-fallback-font.ttf",
-               sizeof(fontpath));
-         break;
-      default:
+      }
+      else
+      {
          fill_pathname_join_special(tmp_dir, dir_assets, "glui", sizeof(tmp_dir));
          fill_pathname_join_special(fontpath, tmp_dir, FILE_PATH_TTF_FONT,
                sizeof(fontpath));
-         break;
+      }
    }
 
    font_data->font = gfx_display_font_file(p_disp,

menu/drivers/ozone.c

@@ -10114,25 +10114,16 @@ static void ozone_set_layout(
    ozone->pointer_active_delta = CURSOR_ACTIVE_DELTA * scale_factor;
 
    /* Initialise fonts */
-   switch (*msg_hash_get_uint(MSG_HASH_USER_LANGUAGE))
    {
-      case RETRO_LANGUAGE_ARABIC:
-      case RETRO_LANGUAGE_PERSIAN:
+      const char *lang_font = font_driver_language_font_file();
+
+      if (lang_font)
+      {
          fill_pathname_join_special(tmp_dir, path_directory_assets, "pkg", sizeof(tmp_dir));
-         fill_pathname_join_special(font_path, tmp_dir, "fallback-font.ttf", sizeof(font_path));
-         break;
-      case RETRO_LANGUAGE_CHINESE_SIMPLIFIED:
-      case RETRO_LANGUAGE_CHINESE_TRADITIONAL:
-         fill_pathname_join_special(tmp_dir, path_directory_assets, "pkg", sizeof(tmp_dir));
-         fill_pathname_join_special(font_path, tmp_dir, "chinese-fallback-font.ttf", sizeof(font_path));
-         break;
-      case RETRO_LANGUAGE_KOREAN:
-         fill_pathname_join_special(tmp_dir, path_directory_assets, "pkg", sizeof(tmp_dir));
-         fill_pathname_join_special(font_path, tmp_dir, "korean-fallback-font.ttf", sizeof(font_path));
-         break;
-      default:
+         fill_pathname_join_special(font_path, tmp_dir, lang_font, sizeof(font_path));
+      }
+      else
          fill_pathname_join_special(font_path, ozone->assets_path, "bold.ttf", sizeof(font_path));
-         break;
    }
 
    if (path_menu_font && *path_menu_font)
@@ -10143,25 +10134,16 @@ static void ozone_set_layout(
    if (!(((ozone->flags & OZONE_FLAG_HAS_ALL_ASSETS) > 0) && font_inited))
       ozone->flags &= ~OZONE_FLAG_HAS_ALL_ASSETS;
 
-   switch (*msg_hash_get_uint(MSG_HASH_USER_LANGUAGE))
    {
-      case RETRO_LANGUAGE_ARABIC:
-      case RETRO_LANGUAGE_PERSIAN:
+      const char *lang_font = font_driver_language_font_file();
+
+      if (lang_font)
+      {
          fill_pathname_join_special(tmp_dir, path_directory_assets, "pkg", sizeof(tmp_dir));
-         fill_pathname_join_special(font_path, tmp_dir, "fallback-font.ttf", sizeof(font_path));
-         break;
-      case RETRO_LANGUAGE_CHINESE_SIMPLIFIED:
-      case RETRO_LANGUAGE_CHINESE_TRADITIONAL:
-         fill_pathname_join_special(tmp_dir, path_directory_assets, "pkg", sizeof(tmp_dir));
-         fill_pathname_join_special(font_path, tmp_dir, "chinese-fallback-font.ttf", sizeof(font_path));
-         break;
-      case RETRO_LANGUAGE_KOREAN:
-         fill_pathname_join_special(tmp_dir, path_directory_assets, "pkg", sizeof(tmp_dir));
-         fill_pathname_join_special(font_path, tmp_dir, "korean-fallback-font.ttf", sizeof(font_path));
-         break;
-      default:
+         fill_pathname_join_special(font_path, tmp_dir, lang_font, sizeof(font_path));
+      }
+      else
          fill_pathname_join_special(font_path, ozone->assets_path, "regular.ttf", sizeof(font_path));
-         break;
    }
 
    if (path_menu_font && *path_menu_font)

samples/gfx/font_lifecycle/stubs_retroarch.c

@@ -26,6 +26,15 @@ bool filestream_read_file(const char *path, void **buf, int64_t *len)
    return *buf != NULL;
 }
 
+/* font_driver_language_font_file() asks which language is selected.
+ * English here: the tests are about the lifecycle, not the mapping. */
+unsigned *msg_hash_get_uint(enum msg_hash_action type)
+{
+   static unsigned lang = 0;   /* RETRO_LANGUAGE_ENGLISH */
+   (void)type;
+   return ⟨
+}
+
 static video_driver_state_t vst;
 video_driver_state_t *video_state_get_ptr(void) { return &vst; }