UI: Improved Font Thumbnails

Thumbnails of fonts that better show design, shapes, contents, intent,
and intended language. Previews almost every known language - living
and dead - and symbol, specialty fonts, etc.

See D12032 for more details and samples.

Differential Revision: https://developer.blender.org/D12032

Reviewed by Campbell Barton

9 files changed, 374 insertions, 189 deletions

diff --git a/source/blender/blenfont/BLF_api.h b/source/blender/blenfont/BLF_api.h
index 992107a30e9..af2e4fd1784 100644
--- a/source/blender/blenfont/BLF_api.h
+++ b/source/blender/blenfont/BLF_api.h
@@ -290,16 +290,8 @@ void BLF_dir_free(char **dirs, int count) ATTR_NONNULL();
  *
  * \note called from a thread, so it bypasses the normal BLF_* api (which isn't thread-safe).
  */
-void BLF_thumb_preview(const char *filepath,
-                       const char **draw_str,
-                       const char **i18n_draw_str,
-                       unsigned char draw_str_lines,
-                       const float font_color[4],
-                       int font_size,
-                       unsigned char *buf,
-                       int w,
-                       int h,
-                       int channels) ATTR_NONNULL();
+bool BLF_thumb_preview(const char *filename, unsigned char *buf, int w, int h, int channels)
+    ATTR_NONNULL();
 
 /* blf_default.c */
 
diff --git a/source/blender/blenfont/intern/blf_font.c b/source/blender/blenfont/intern/blf_font.c
index 3d7e83bc22f..9ea7e529df2 100644
--- a/source/blender/blenfont/intern/blf_font.c
+++ b/source/blender/blenfont/intern/blf_font.c
@@ -1146,38 +1146,6 @@ void blf_font_draw_buffer__wrap(FontBLF *font,
 /** \} */
 
 /* -------------------------------------------------------------------- */
-/** \name Text Evaluation: Count Missing Characters
- * \{ */
-
-int blf_font_count_missing_chars(FontBLF *font,
-                                 const char *str,
-                                 const size_t str_len,
-                                 int *r_tot_chars)
-{
-  int missing = 0;
-  size_t i = 0;
-
-  *r_tot_chars = 0;
-  while (i < str_len) {
-    uint c;
-
-    if ((c = str[i]) < GLYPH_ASCII_TABLE_SIZE) {
-      i++;
-    }
-    else {
-      c = BLI_str_utf8_as_unicode_step(str, str_len, &i);
-      if (blf_get_char_index(font, c) == 0) {
-        missing++;
-      }
-    }
-    (*r_tot_chars)++;
-  }
-  return missing;
-}
-
-/** \} */
-
-/* -------------------------------------------------------------------- */
 /** \name Font Query: Attributes
  * \{ */
 
diff --git a/source/blender/blenfont/intern/blf_internal.h b/source/blender/blenfont/intern/blf_internal.h
index e1001cfc1ba..28f433a3018 100644
--- a/source/blender/blenfont/intern/blf_internal.h
+++ b/source/blender/blenfont/intern/blf_internal.h
@@ -149,11 +149,6 @@ void blf_font_boundbox_foreach_glyph(struct FontBLF *font,
                                      void *user_data,
                                      struct ResultBLF *r_info);
 
-int blf_font_count_missing_chars(struct FontBLF *font,
-                                 const char *str,
-                                 size_t str_len,
-                                 int *r_tot_chars);
-
 void blf_font_free(struct FontBLF *font);
 
 struct GlyphCacheBLF *blf_glyph_cache_acquire(struct FontBLF *font);
diff --git a/source/blender/blenfont/intern/blf_thumbs.c b/source/blender/blenfont/intern/blf_thumbs.c
index cba4bb96f73..8ad880edf30 100644
--- a/source/blender/blenfont/intern/blf_thumbs.c
+++ b/source/blender/blenfont/intern/blf_thumbs.c
@@ -8,16 +8,20 @@
  * Isolate since this needs to be called by #ImBuf code (bad level call).
  */
 
-#include <stdio.h>
 #include <stdlib.h>
-#include <string.h>
 
 #include <ft2build.h>
 
 #include FT_FREETYPE_H
+#include FT_ADVANCES_H        /* For FT_Get_Advance */
+#include FT_TRUETYPE_IDS_H    /* Codepoint coverage constants. */
+#include FT_TRUETYPE_TABLES_H /* For TT_OS2 */
 
 #include "BLI_listbase.h"
+#include "BLI_math_bits.h"
 #include "BLI_rect.h"
+#include "BLI_string.h"
+#include "BLI_string_utf8.h"
 #include "BLI_threads.h"
 #include "BLI_utildefines.h"
 
@@ -25,89 +29,378 @@
 #include "blf_internal_types.h"
 
 #include "BLF_api.h"
-#include "BLT_translation.h"
 
 #include "BLI_strict_flags.h"
 
-void BLF_thumb_preview(const char *filepath,
-                       const char **draw_str,
-                       const char **i18n_draw_str,
-                       const uchar draw_str_lines,
-                       const float font_color[4],
-                       const int font_size,
-                       uchar *buf,
-                       const int w,
-                       const int h,
-                       const int channels)
+/* Maximum length of text sample in char32_t, including NULL terminator. */
+#define BLF_SAMPLE_LEN 5
+
+typedef struct UnicodeSample {
+  char32_t sample[BLF_SAMPLE_LEN];
+  char field; /* ‘OS/2’ table ulUnicodeRangeX field (1-4). */
+  long mask;  /* ‘OS/2’ table ulUnicodeRangeX bit mask. */
+} UnicodeSample;
+
+/* The seemingly arbitrary order that follows is to help quickly find the most-likely designed
+ * intent of the font. Many feature-specific fonts contain Latin, Greek, & Coptic characters so
+ * those need to be checked last. */
+static const UnicodeSample unicode_samples[] = {
+    /* Chinese, Japanese, Korean, ordered specific to general. */
+    {U"\uc870\uc120\uae00", 2, TT_UCR_HANGUL},                 /* 조선글 */
+    {U"\u3042\u30a2\u4e9c", 2, TT_UCR_HIRAGANA},               /* あア亜 */
+    {U"\u30a2\u30a4\u4e9c", 2, TT_UCR_KATAKANA},               /* アイ亜 */
+    {U"\u1956\u195b\u1966", 3, TT_UCR_TAI_LE},                 /* ᥖᥛᥦ */
+    {U"\u3105\u3106\u3107", 2, TT_UCR_BOPOMOFO},               /* ㄅㄆㄇ */
+    {U"\ua840\ua841\ua85d", 2, TT_UCR_PHAGSPA},                /* ꡀꡁꡝ */
+    {U"\u5e03\u4e01\u4f53", 2, TT_UCR_CJK_UNIFIED_IDEOGRAPHS}, /* 布丁体 */
+    /* Languages in the BMP with a coverage bit. */
+    {U"\u05d0\u05da\u05e4", 1, TT_UCR_HEBREW},
+    {U"\ua500\ua502\ua549", 1, TT_UCR_VAI},
+    {U"\ufee6\ufef4\ufeb3", 1, TT_UCR_ARABIC},
+    {U"\u07C1\u07C2\u07C3", 1, TT_UCR_NKO},
+    {U"\u0905\u093f\u092a", 1, TT_UCR_DEVANAGARI},
+    {U"\u0986\u0987\u098c", 1, TT_UCR_BENGALI},
+    {U"\u0a05\u0a16\u0a30", 1, TT_UCR_GURMUKHI},
+    {U"\u0aaa\u0aaf\u0ab8", 1, TT_UCR_GUJARATI},
+    {U"\u0b2a\u0b30\u0b37", 1, TT_UCR_ORIYA},
+    {U"\u0b85\u0b88\u0b8f", 1, TT_UCR_TAMIL},
+    {U"\u0c05\u0c0c\u0c36", 1, TT_UCR_TELUGU},
+    {U"\u0c85\u0c87\u0c8e", 1, TT_UCR_KANNADA},
+    {U"\u0d05\u0d09\u0d3d", 1, TT_UCR_MALAYALAM},
+    {U"\u0e05\u0e06\u0e07", 1, TT_UCR_THAI},
+    {U"\u0e81\u0e82\u0e84", 1, TT_UCR_LAO},
+    {U"\u10a0\u10a1\u10a2", 1, TT_UCR_GEORGIAN},
+    {U"\u1B05\u1B07\u1B09", 1, TT_UCR_BALINESE},
+    {U"\u0f00\u0f04\u0f08", 3, TT_UCR_TIBETAN},
+    {U"\u0710\u0717\u071c", 3, TT_UCR_SYRIAC},
+    {U"\u0784\u0783\u0798", 3, TT_UCR_THAANA},
+    {U"\u0d85\u0d89\u0daf", 3, TT_UCR_SINHALA},
+    {U"\u1000\u1001\u1014", 3, TT_UCR_MYANMAR},
+    {U"\u1202\u1207\u1250", 3, TT_UCR_ETHIOPIC},
+    {U"\u13a3\u13a4\u13a8", 3, TT_UCR_CHEROKEE},
+    {U"\u1401\u144d\u156e", 3, TT_UCR_CANADIAN_ABORIGINAL_SYLLABICS},
+    {U"\u1681\u1687\u168b", 3, TT_UCR_OGHAM},
+    {U"\u16A0\u16A4\u16AA", 3, TT_UCR_RUNIC},
+    {U"\u1780\u1781\u1783", 3, TT_UCR_KHMER},
+    {U"\u1820\u1826\u1845", 3, TT_UCR_MONGOLIAN},
+    {U"\ua188\ua320\ua4bf", 3, TT_UCR_YI},
+    {U"\u1900\u1901\u1902", 3, TT_UCR_LIMBU},
+    {U"\u1950\u1951\u1952", 3, TT_UCR_TAI_LE},
+    {U"\u1980\u1982\u1986", 3, TT_UCR_NEW_TAI_LUE},
+    {U"\u1A00\u1A01\u1A02", 4, TT_UCR_BUGINESE},
+    {U"\u2c01\u2c05\u2c0c", 4, TT_UCR_GLAGOLITIC},
+    {U"\u2d31\u2d33\u2d37", 4, TT_UCR_TIFINAGH},
+    {U"\u2d31\u2d33\u2d37", 4, TT_UCR_YIJING},
+    {U"\u1B83\u1B84\u1B88", 4, TT_UCR_SUNDANESE},
+    {U"\u1C00\u1C01\u1C02", 4, TT_UCR_LEPCHA},
+    {U"\u1C50\u1C51\u1C52", 4, TT_UCR_OL_CHIKI},
+    {U"\uA800\uA801\uA805", 4, TT_UCR_SYLOTI_NAGRI},
+    {U"\uA882\uA88a\uA892", 4, TT_UCR_SAURASHTRA},
+    {U"\uA901\uA902\uA904", 4, TT_UCR_KAYAH_LI},
+    {U"\uA930\uA932\uA943", 4, TT_UCR_REJANG},
+    {U"\uaa00\uaa02\uaa05", 4, TT_UCR_CHAM},
+    /* Indexed languages in the Supplementary Multilingual Plane. */
+    {U"\U00010000\U00010001\U00010002", 4, TT_UCR_LINEAR_B},
+    {U"\U00010300\U00010301\U00010302", 3, TT_UCR_OLD_ITALIC},
+    {U"\U00010330\U00010331\U00010332", 3, TT_UCR_GOTHIC},
+    {U"\U00010380\U00010381\U00010382", 4, TT_UCR_UGARITIC},
+    {U"\U000103A0\U000103A1\U000103A2", 4, TT_UCR_OLD_PERSIAN},
+    {U"\U00010400\U00010401\U00010402", 3, TT_UCR_DESERET},
+    {U"\U00010450\U00010451\U00010452", 4, TT_UCR_SHAVIAN},
+    {U"\U00010480\U00010481\U00010482", 4, TT_UCR_OSMANYA},
+    {U"\U00010800\U00010803\U00010805", 4, TT_UCR_CYPRIOT_SYLLABARY},
+    {U"\U00010900\U00010901\U00010902", 2, TT_UCR_PHOENICIAN},
+    {U"\U00010A10\U00010A11\U00010A12", 4, TT_UCR_KHAROSHTHI},
+    {U"\U00012000\U00012001\U00012002", 4, TT_UCR_CUNEIFORM},
+    /* Philippine languages use a single OS2 coverage bit. */
+    {U"\u1700\u1701\u1702", 3, TT_UCR_PHILIPPINE}, /* Tagalog */
+    {U"\u1720\u1721\u1722", 3, TT_UCR_PHILIPPINE}, /* Hanunoo */
+    {U"\u1740\u1741\u1742", 3, TT_UCR_PHILIPPINE}, /* Buhid */
+    {U"\u1760\u1761\u1762", 3, TT_UCR_PHILIPPINE}, /* Tagbanwa */
+    /* Anatolian languages use a single OS2 coverage bit. */
+    {U"\U000102A3\U000102A8\U000102CB", 4, TT_UCR_OLD_ANATOLIAN}, /* Carian */
+    {U"\U00010280\U00010281\U00010282", 4, TT_UCR_OLD_ANATOLIAN}, /* Lycian */
+    {U"\U00010920\U00010921\U00010922", 4, TT_UCR_OLD_ANATOLIAN}, /* Lydian */
+    /* Symbol blocks. */
+    {U"\U0001f600\U0001f638", 0, 0}, /* Emoticons 😀😸 */
+    {U"\uf021\uf022\uf023", 0, 0},   /* MS Symbols */
+    {U"\u280f\u2815\u283f", 3, TT_UCR_BRAILLE},
+    {U"\U0001D11e\U0001D161\U0001D130", 3, TT_UCR_MUSICAL_SYMBOLS},
+    {U"\u2700\u2708\u2709", 2, TT_UCR_DINGBATS},
+    {U"\u2600\u2601\u2602", 2, TT_UCR_MISCELLANEOUS_SYMBOLS},
+    {U"\ue000\ue001\ue002", 2, TT_UCR_PRIVATE_USE},
+    {U"\ue702\ue703\ue704", 2, TT_UCR_PRIVATE_USE},
+    {U"\U000F0001\U000F0002\U000F0003", 2, TT_UCR_PRIVATE_USE_SUPPLEMENTARY},
+    /* Languages in the Supplementary Multilingual Plane. */
+    {U"\U00010350\U00010352\U00010353", 2, TT_UCR_NON_PLANE_0}, /* Old Permic */
+    {U"\U000104B0\U000104B6\U000104B8", 2, TT_UCR_NON_PLANE_0}, /* Osage */
+    {U"\U00010500\U00010501\U00010502", 2, TT_UCR_NON_PLANE_0}, /* Elbasan */
+    {U"\U00010530\U00010531\U00010532", 2, TT_UCR_NON_PLANE_0}, /* Caucasian Albanian */
+    {U"\U00010600\U00010601\U00010602", 2, TT_UCR_NON_PLANE_0}, /* Linear A */
+    {U"\U00010840\U00010841\U00010842", 2, TT_UCR_NON_PLANE_0}, /* Imperial Aramaic */
+    {U"\U00010860\U00010861\U00010862", 2, TT_UCR_NON_PLANE_0}, /* Palmyrene */
+    {U"\U00010880\U00010881\U00010882", 2, TT_UCR_NON_PLANE_0}, /* Nabataean */
+    {U"\U000108E0\U000108E3\U000108E4", 2, TT_UCR_NON_PLANE_0}, /* Hatran */
+    {U"\U00010980\U00010983\U00010989", 2, TT_UCR_NON_PLANE_0}, /* Meroitic Hieroglyphs */
+    {U"\U000109A0\U000109A1\U000109A2", 2, TT_UCR_NON_PLANE_0}, /* Meroitic Cursive */
+    {U"\U00010A60\U00010A61\U00010A62", 2, TT_UCR_NON_PLANE_0}, /* Old South Arabian */
+    {U"\U00010A80\U00010A81\U00010A82", 2, TT_UCR_NON_PLANE_0}, /* Old North Arabian */
+    {U"\U00010ac0\U00010ac3\U00010ac6", 2, TT_UCR_NON_PLANE_0}, /* Manichaean */
+    {U"\U00010B00\U00010B04\U00010B08", 2, TT_UCR_NON_PLANE_0}, /* Avestan */
+    {U"\U00010B40\U00010B41\U00010B42", 2, TT_UCR_NON_PLANE_0}, /* Inscriptional Parthian */
+    {U"\U00010B60\U00010B61\U00010B62", 2, TT_UCR_NON_PLANE_0}, /* Inscriptional Pahlavi */
+    {U"\U00010B80\U00010B84\U00010B87", 2, TT_UCR_NON_PLANE_0}, /* Psalter Pahlavi */
+    {U"\U00010C00\U00010C01\U00010C02", 2, TT_UCR_NON_PLANE_0}, /* Old Turkic */
+    {U"\U00010C80\U00010C81\U00010C82", 2, TT_UCR_NON_PLANE_0}, /* Old Hungarian */
+    {U"\U00010D00\U00010D07\U00010D0D", 2, TT_UCR_NON_PLANE_0}, /* Hanifi Rohingya */
+    {U"\U00010E80\U00010E81\U00010E82", 2, TT_UCR_NON_PLANE_0}, /* Yezidi */
+    {U"\U00010F00\U00010F01\U00010F02", 2, TT_UCR_NON_PLANE_0}, /* Old Sogdian */
+    {U"\U00010F30\U00010F32\U00010F34", 2, TT_UCR_NON_PLANE_0}, /* Sogdian */
+    {U"\U00010F70\U00010F71\U00010F72", 2, TT_UCR_NON_PLANE_0}, /* Old Uyghur */
+    {U"\U00010FB0\U00010FB1\U00010FB2", 2, TT_UCR_NON_PLANE_0}, /* Chorasmian */
+    {U"\U00010FE0\U00010FE1\U00010FE2", 2, TT_UCR_NON_PLANE_0}, /* Elymaic */
+    {U"\U00011003\U00011004\U00011005", 2, TT_UCR_NON_PLANE_0}, /* Brahmi */
+    {U"\U00011083\U00011085\U00011087", 2, TT_UCR_NON_PLANE_0}, /* Kaithi */
+    {U"\U000110D0\U000110D1\U000110D2", 2, TT_UCR_NON_PLANE_0}, /* Sora Sompeng */
+    {U"\U00011103\U00011104\U00011105", 2, TT_UCR_NON_PLANE_0}, /* Chakma */
+    {U"\U00011150\U00011151\U00011152", 2, TT_UCR_NON_PLANE_0}, /* Mahajani */
+    {U"\U00011183\U00011185\U0001118b", 2, TT_UCR_NON_PLANE_0}, /* Sharada */
+    {U"\U00011200\U00011201\U00011202", 2, TT_UCR_NON_PLANE_0}, /* Khojki */
+    {U"\U00011280\U00011281\U00011282", 2, TT_UCR_NON_PLANE_0}, /* Multani */
+    {U"\U000112B0\U000112B2\U000112B4", 2, TT_UCR_NON_PLANE_0}, /* Khudawadi */
+    {U"\U00011305\U00011309\U0001130b", 2, TT_UCR_NON_PLANE_0}, /* Grantha */
+    {U"\U00011400\U00011404\U00011409", 2, TT_UCR_NON_PLANE_0}, /* Newa */
+    {U"\U00011480\U00011481\U00011482", 2, TT_UCR_NON_PLANE_0}, /* Tirhuta */
+    {U"\U00011580\U00011582\U00011589", 2, TT_UCR_NON_PLANE_0}, /* Siddham */
+    {U"\U00011600\U00011604\U00011609", 2, TT_UCR_NON_PLANE_0}, /* Modi */
+    {U"\U00011680\U00011682\U0001168A", 2, TT_UCR_NON_PLANE_0}, /* Takri */
+    {U"\U00011700\U00011701\U00011702", 2, TT_UCR_NON_PLANE_0}, /* Ahom */
+    {U"\U00011800\U00011801\U00011802", 2, TT_UCR_NON_PLANE_0}, /* Dogri */
+    {U"\U000118A0\U000118A1\U000118AA", 2, TT_UCR_NON_PLANE_0}, /* Warang Citi */
+    {U"\U00011900\U00011901\U00011902", 2, TT_UCR_NON_PLANE_0}, /* Dives Akuru */
+    {U"\U00011A00\U00011A10\U00011A15", 2, TT_UCR_NON_PLANE_0}, /* Zanabazar Square */
+    {U"\U00011A50\U00011A5C\U00011A6B", 2, TT_UCR_NON_PLANE_0}, /* Soyombo */
+    {U"\U00011AC0\U00011AC1\U00011AC2", 2, TT_UCR_NON_PLANE_0}, /* Pau Cin Hau */
+    {U"\U00011C00\U00011C01\U00011C02", 2, TT_UCR_NON_PLANE_0}, /* Bhaiksuki */
+    {U"\U00011C70\U00011C71\U00011C72", 2, TT_UCR_NON_PLANE_0}, /* Marchen */
+    {U"\U00011D00\U00011D02\U00011D08", 2, TT_UCR_NON_PLANE_0}, /* Masaram Gondi */
+    {U"\U00011D60\U00011D62\U00011D6c", 2, TT_UCR_NON_PLANE_0}, /* Gunjala Gondi */
+    {U"\U00011FC1\U00011FC2\U00011FC8", 2, TT_UCR_NON_PLANE_0}, /* Tamil Supplement */
+    {U"\U00012F90\U00012F91\U00012F92", 2, TT_UCR_NON_PLANE_0}, /* Cypro-Minoan */
+    {U"\U00013000\U00013076\U0001307f", 2, TT_UCR_NON_PLANE_0}, /* Egyptian Hieroglyphs */
+    {U"\U00014400\U00014409\U00014447", 2, TT_UCR_NON_PLANE_0}, /* Anatolian Hieroglyphs */
+    {U"\U00016A40\U00016A41\U00016A42", 2, TT_UCR_NON_PLANE_0}, /* Mro */
+    {U"\U00016A70\U00016A71\U00016A72", 2, TT_UCR_NON_PLANE_0}, /* Tangsa */
+    {U"\U00016AD0\U00016AD2\U00016ADA", 2, TT_UCR_NON_PLANE_0}, /* Bassa Vah */
+    {U"\U00016B00\U00016B01\U00016B02", 2, TT_UCR_NON_PLANE_0}, /* Pahawh Hmong */
+    {U"\U00016F01\U00016F05\U00016F09", 2, TT_UCR_NON_PLANE_0}, /* Miao */
+    {U"\U0001BC19\U0001BC1f\U0001BC0e", 2, TT_UCR_NON_PLANE_0}, /* Duployan */
+    {U"\U0001D2E0\U0001D2E6\U0001D2f3", 2, TT_UCR_NON_PLANE_0}, /* Mayan Numerals */
+    {U"\U0001E800\U0001E80A\U0001E80F", 2, TT_UCR_NON_PLANE_0}, /* Mende Kikakui */
+    {U"\U0001E900\U0001E902\U0001E907", 2, TT_UCR_NON_PLANE_0}, /* Adlam */
+    {U"\U0001E2C0\U0001E2C2\U0001E2C7", 2, TT_UCR_NON_PLANE_0}, /* Wancho */
+    {U"\U0001EC71\U0001EC72\U0001EC73", 2, TT_UCR_NON_PLANE_0}, /* Indic Siyaq Numbers */
+    /* Basic Multilingual Plane but are not indexed with an OS2 coverage bit. */
+    {U"\u0638\u0630\u0633", 0, 0}, /* Urdu */
+    {U"\u0800\u0801\u0802", 0, 0}, /* Samaritan */
+    {U"\u0841\u0842\u084c", 0, 0}, /* Mandaic */
+    {U"\u1A20\u1A21\u1A22", 0, 0}, /* Tai Tham */
+    {U"\u1BC0\u1BC1\u1BC2", 0, 0}, /* Batak */
+    {U"\uA4EF\uA4E8\uA4ED", 0, 0}, /* Lisu */
+    {U"\uA6A0\uA6A1\uA6A2", 0, 0}, /* Bamum */
+    {U"\ua983\ua984\ua98d", 0, 0}, /* Javanese */
+    {U"\uaa80\uaa81\uaa82", 0, 0}, /* Tai Viet */
+    {U"\uABC0\uABC1\uABC2", 0, 0}, /* Meetei Mayek */
+    /* Near the end since many fonts contain these. */
+    {U"\u03e2\u03e4\u03e8", 1, TT_UCR_COPTIC},
+    {U"\u1f08\u03a6\u03a8", 1, TT_UCR_GREEK},
+    {U"\u0518\u0409\u040f", 1, TT_UCR_CYRILLIC},
+    {U"\u0533\u0537\u0539", 1, TT_UCR_ARMENIAN},
+};
+
+static const char32_t *blf_get_sample_text(FT_Face face)
 {
-  const int font_size_min = 6;
-  int font_size_curr;
-  /* shrink 1/th each line */
-  int font_shrink = 4;
+  /* First check for fonts with MS Symbol character map. */
+  if (face->charmap->encoding == FT_ENCODING_MS_SYMBOL) {
+    /* Many of these have characters starting from F020. */
+    if (FT_Get_Char_Index(face, U'\uf041') != 0) {
+      return U"\uf041\uf044\uf048";
+    }
+    if (FT_Get_Char_Index(face, U'\uf030') != 0) {
+      return U"\uf030\uf031\uf032";
+    }
+    return U"ADH";
+  }
 
-  /* While viewing thumbnails in font directories this function can be called simultaneously from a
-   * greater number of threads than we want the FreeType cache to keep open at a time. Therefore
-   * pass own FT_Library to font creation so that it is not managed by the FreeType cache system.
-   */
+  const char32_t *def = U"Aabg";
+  const char32_t *sample = def;
 
-  FT_Library ft_library = NULL;
-  if (FT_Init_FreeType(&ft_library) != FT_Err_Ok) {
-    return;
+  /* Fonts too old to have a Unicode character map. */
+  if (face->charmap->encoding != FT_ENCODING_UNICODE) {
+    return def;
   }
 
-  FontBLF *font = blf_font_new_ex("thumb_font", filepath, NULL, 0, ft_library);
-  if (!font) {
-    printf("Info: Can't load font '%s', no preview possible\n", filepath);
-    FT_Done_FreeType(ft_library);
-    return;
+  /* TrueType table with bits to quickly test most Unicode block coverage. */
+  TT_OS2 *os2_table = (TT_OS2 *)FT_Get_Sfnt_Table(face, FT_SFNT_OS2);
+  if (!os2_table) {
+    return def;
+  }
+
+  /* Detect "Last resort" fonts. They have everything, except the last 5 bits.  */
+  if (os2_table->ulUnicodeRange1 == 0xffffffffU && os2_table->ulUnicodeRange2 == 0xffffffffU &&
+      os2_table->ulUnicodeRange3 == 0xffffffffU && os2_table->ulUnicodeRange4 >= 0x7FFFFFFU) {
+    return U"\xE000\xFFFF";
+  }
+
+  int language_count = count_bits_i((uint)os2_table->ulUnicodeRange1) +
+                       count_bits_i((uint)os2_table->ulUnicodeRange2) +
+                       count_bits_i((uint)os2_table->ulUnicodeRange3) +
+                       count_bits_i((uint)os2_table->ulUnicodeRange4);
+
+  for (uint i = 0; i < ARRAY_SIZE(unicode_samples); ++i) {
+    UnicodeSample s = unicode_samples[i];
+    if (os2_table && s.field && s.mask) {
+      /* OS/2 Table contains 4 contiguous integers of script coverage bit flags. */
+      FT_ULong *field = &(os2_table->ulUnicodeRange1) + (s.field - 1);
+      if (!(*field & (FT_ULong)s.mask)) {
+        continue;
+      }
+    }
+    if (FT_Get_Char_Index(face, s.sample[0]) != 0) {
+      sample = s.sample;
+      break;
+    }
   }
 
-  /* Would be done via the BLF API, but we're not using a fontid here */
-  font->buf_info.cbuf = buf;
-  font->buf_info.ch = channels;
-  font->buf_info.dims[0] = w;
-  font->buf_info.dims[1] = h;
+  bool has_latin = (os2_table && (os2_table->ulUnicodeRange1 & TT_UCR_BASIC_LATIN) &&
+                    (FT_Get_Char_Index(face, U'A') != 0));
+  bool has_cjk = (os2_table && (os2_table->ulUnicodeRange2 & TT_UCR_CJK_UNIFIED_IDEOGRAPHS));
 
-  /* Always create the image with a white font,
-   * the caller can theme how it likes */
-  memcpy(font->buf_info.col_init, font_color, sizeof(font->buf_info.col_init));
-  font->pos[1] = h;
+  if (has_latin && ((has_cjk && language_count > 40) || (!has_cjk && language_count > 5))) {
+    return def;
+  }
 
-  font_size_curr = font_size;
+  return sample;
+}
 
-  blf_draw_buffer__start(font);
+bool BLF_thumb_preview(
+    const char *filename, unsigned char *buf, int w, int h, int UNUSED(channels))
+{
+  /* Use own FT_Library and direct FreeType calls as this is called from multiple threads. */
+  FT_Library ft_lib = NULL;
+  if (FT_Init_FreeType(&ft_lib) != FT_Err_Ok) {
+    return false;
+  }
 
-  for (int i = 0; i < draw_str_lines; i++) {
-    const char *draw_str_i18n = i18n_draw_str[i] != NULL ? i18n_draw_str[i] : draw_str[i];
-    const size_t draw_str_i18n_len = strlen(draw_str_i18n);
-    int draw_str_i18_count = 0;
+  FT_Face face;
+  if (FT_New_Face(ft_lib, filename, 0, &face) != FT_Err_Ok) {
+    FT_Done_FreeType(ft_lib);
+    return false;
+  }
 
-    CLAMP_MIN(font_size_curr, font_size_min);
-    if (!blf_font_size(font, (float)font_size_curr)) {
-      break;
+  if (!(face->face_flags & FT_FACE_FLAG_SCALABLE)) {
+    return false;
+  }
+
+  FT_Error err = FT_Select_Charmap(face, FT_ENCODING_UNICODE);
+  if (err) {
+    err = FT_Select_Charmap(face, FT_ENCODING_MS_SYMBOL);
+  }
+  if (err) {
+    err = FT_Select_Charmap(face, FT_ENCODING_APPLE_ROMAN);
+  }
+  if (err && face->num_charmaps > 0) {
+    err = FT_Select_Charmap(face, face->charmaps[0]->encoding);
+  }
+  if (err != FT_Err_Ok) {
+    FT_Done_Face(face);
+    FT_Done_FreeType(ft_lib);
+    return false;
+  }
+
+  const char32_t *codepoints = blf_get_sample_text(face);
+  uint glyph_ids[BLF_SAMPLE_LEN] = {0};
+
+  /* A large initial font size for measuring. Nothing will be rendered this size. */
+  if (FT_Set_Char_Size(face, w * 64, 0, 72, 72) != FT_Err_Ok) {
+    FT_Done_Face(face);
+    FT_Done_FreeType(ft_lib);
+    return false;
+  }
+
+  /* Approximate length of the sample. Uses only advances, ignores bearings. */
+  int width = 0;
+  for (uint i = 0; i < BLF_SAMPLE_LEN && codepoints[i]; i++) {
+    glyph_ids[i] = FT_Get_Char_Index(face, codepoints[i]);
+    /* If sample glyph is not found, use another. */
+    if (!glyph_ids[i]) {
+      glyph_ids[i] = (uint)(face->num_glyphs / (BLF_SAMPLE_LEN + 1)) * (i + 1);
     }
+    /* Get advance without loading the glyph. */
+    FT_Fixed advance;
+    FT_Get_Advance(face, glyph_ids[i], FT_LOAD_NO_HINTING, &advance);
+    /* Advance is returned in 16.16 format, so divide by 65536 for pixels. */
+    width += (int)(advance >> 16);
+  }
+
+  int height = ft_pix_to_int((ft_pix)face->size->metrics.ascender -
+                             (ft_pix)face->size->metrics.descender);
+  width = MAX2(width, height);
+
+  /* Fill up to 96% horizontally or vertically. */
+  float font_size = MIN3((float)w,
+                         ((float)w * 0.96f / (float)width * (float)w),
+                         (float)h * 0.96f / (float)height * (float)h);
 
-    /* decrease font size each time */
-    font_size_curr -= (font_size_curr / font_shrink);
-    font_shrink += 1;
+  if (font_size < 1 || FT_Set_Char_Size(face, (int)(font_size * 64.0f), 0, 72, 72) != FT_Err_Ok) {
+    /* Sizing can fail, but very rarely. */
+    FT_Done_Face(face);
+    FT_Done_FreeType(ft_lib);
+    return false;
+  }
+
+  /* Horizontally center, line up baselines vertically. */
+  int left = (int)(((float)w - ((float)width * (font_size / (float)w))) / 2.0f);
+  int top = (int)((float)h * 0.7f);
+
+  /* Print out to buffer. */
 
-    font->pos[1] -= (int)((float)blf_font_ascender(font) * 1.1f);
+  FT_Pos advance_x = 0;
+  int glyph_count = 0; /* How many are successfully loaded and rendered. */
 
-    /* We fallback to default English strings in case not enough chars are available in current
-     * font for given translated string (useful in non-Latin i18n context, like Chinese,
-     * since many fonts will then show nothing but ugly 'missing char' in their preview).
-     * Does not handle all cases, but much better than nothing.
-     */
-    if (blf_font_count_missing_chars(font, draw_str_i18n, draw_str_i18n_len, &draw_str_i18_count) >
-        (draw_str_i18_count / 2)) {
-      blf_font_draw_buffer(font, draw_str[i], strlen(draw_str[i]), NULL);
+  for (int i = 0; i < BLF_SAMPLE_LEN && glyph_ids[i]; i++) {
+    if (FT_Load_Glyph(face, glyph_ids[i], FT_LOAD_TARGET_NORMAL | FT_LOAD_NO_HINTING) !=
+        FT_Err_Ok) {
+      break;
     }
-    else {
-      blf_font_draw_buffer(font, draw_str_i18n, draw_str_i18n_len, NULL);
+
+    if (FT_Render_Glyph(face->glyph, FT_RENDER_MODE_NORMAL) != FT_Err_Ok ||
+        face->glyph->format != FT_GLYPH_FORMAT_BITMAP) {
+      break;
     }
+
+    glyph_count++;
+
+    for (int y = 0; y < (int)face->glyph->bitmap.rows; y++) {
+      int dest_row = (h - y - 1 + (int)face->glyph->bitmap_top - top);
+      if (dest_row >= 0 && dest_row < h) {
+        for (int x = 0; x < (int)face->glyph->bitmap.width; x++) {
+          int dest_col = (x + ft_pix_to_int((ft_pix)advance_x) + face->glyph->bitmap_left + left);
+          if (dest_col >= 0 && dest_col < w) {
+            uchar *source = &face->glyph->bitmap.buffer[y * (int)face->glyph->bitmap.width + x];
+            uchar *dest = &buf[dest_row * w * 4 + (dest_col * 4 + 3)];
+            *dest = (uchar)MIN2(((uint)*dest + (uint)*source), 255u);
+          }
+        }
+      }
+    }
+
+    advance_x += face->glyph->advance.x;
   }
 
-  blf_draw_buffer__end();
-  blf_font_free(font);
-  FT_Done_FreeType(ft_library);
+  FT_Done_Face(face);
+  FT_Done_FreeType(ft_lib);
+
+  /* Return success if we printed at least one glyph. */
+  return glyph_count > 0;
 }
diff --git a/source/blender/blentranslation/intern/blt_lang.c b/source/blender/blentranslation/intern/blt_lang.c
index cb04b3ac0dc..0662adfb9ed 100644
--- a/source/blender/blentranslation/intern/blt_lang.c
+++ b/source/blender/blentranslation/intern/blt_lang.c
@@ -263,7 +263,6 @@ void BLT_lang_set(const char *str)
 #else
   (void)str;
 #endif
-  IMB_thumb_clear_translations();
 }
 
 const char *BLT_lang_get(void)
diff --git a/source/blender/editors/space_file/filelist.cc b/source/blender/editors/space_file/filelist.cc
index daf04aa5f41..20c74f04319 100644
--- a/source/blender/editors/space_file/filelist.cc
+++ b/source/blender/editors/space_file/filelist.cc
@@ -1642,9 +1642,6 @@ static void filelist_cache_init(FileListEntryCache *cache, size_t cache_size)
   cache->flags = FLC_IS_INIT;
 
   cache->previews_todo_count = 0;
-
-  /* We cannot translate from non-main thread, so init translated strings once from here. */
-  IMB_thumb_ensure_translations();
 }
 
 static void filelist_cache_free(FileListEntryCache *cache)
diff --git a/source/blender/imbuf/IMB_thumbs.h b/source/blender/imbuf/IMB_thumbs.h
index b55a6f653b8..ac287856fa9 100644
--- a/source/blender/imbuf/IMB_thumbs.h
+++ b/source/blender/imbuf/IMB_thumbs.h
@@ -87,8 +87,6 @@ struct ImBuf *IMB_thumb_load_blend(const char *blen_path,
  */
 struct ImBuf *IMB_thumb_load_font(const char *filepath, unsigned int x, unsigned int y);
 bool IMB_thumb_load_font_get_hash(char *r_hash);
-void IMB_thumb_clear_translations(void);
-void IMB_thumb_ensure_translations(void);
 
 /* Threading */
 
diff --git a/source/blender/imbuf/intern/thumbs_font.c b/source/blender/imbuf/intern/thumbs_font.c
index 65848bfb55e..0f18e9dd4cb 100644
--- a/source/blender/imbuf/intern/thumbs_font.c
+++ b/source/blender/imbuf/intern/thumbs_font.c
@@ -6,94 +6,40 @@
 
 #include "BLI_fileops.h"
 #include "BLI_hash_md5.h"
-#include "BLI_string.h"
 #include "BLI_utildefines.h"
 
 #include "IMB_imbuf.h"
 #include "IMB_imbuf_types.h"
 
-#include "IMB_thumbs.h"
+#include "IMB_thumbs.h" /* own include. */
 
 /* XXX, bad level call */
 #include "../../blenfont/BLF_api.h"
-#include "../../blentranslation/BLT_translation.h"
 
-#define THUMB_TXT_ITEMS \
-  N_("AaBbCc"), N_("The quick"), N_("brown fox"), N_("jumps over"), N_("the lazy dog"),
+/* Only change if we need to update the previews in the on-disk cache. */
+#define FONT_THUMB_VERSION "1.0.0"
 
-static const char *thumb_str[] = {THUMB_TXT_ITEMS};
-
-static const char *i18n_thumb_str[] = {THUMB_TXT_ITEMS};
-
-#undef THUMB_TXT_ITEMS
-
-void IMB_thumb_clear_translations(void)
-{
-  for (int i = ARRAY_SIZE(thumb_str); i-- > 0;) {
-    i18n_thumb_str[i] = NULL;
-  }
-}
-
-void IMB_thumb_ensure_translations(void)
-{
-  for (int i = ARRAY_SIZE(thumb_str); i-- > 0;) {
-    i18n_thumb_str[i] = BLT_translate_do(BLT_I18NCONTEXT_DEFAULT, thumb_str[i]);
-  }
-}
-
-struct ImBuf *IMB_thumb_load_font(const char *filepath, uint x, uint y)
+struct ImBuf *IMB_thumb_load_font(const char *filename, unsigned int x, unsigned int y)
 {
-  const int font_size = y / 4;
+  struct ImBuf *ibuf = IMB_allocImBuf(x, y, 32, IB_rect | IB_metadata);
 
-  struct ImBuf *ibuf;
-  float font_color[4];
+  /* fill with white and zero alpha */
+  const float col[4] = {1.0f, 1.0f, 1.0f, 0.0f};
+  IMB_rectfill(ibuf, col);
 
-  /* create a white image (theme color is used for drawing) */
-  font_color[0] = font_color[1] = font_color[2] = 1.0f;
-
-  /* fill with zero alpha */
-  font_color[3] = 0.0f;
-
-  ibuf = IMB_allocImBuf(x, y, 32, IB_rect | IB_metadata);
-  IMB_rectfill(ibuf, font_color);
-
-  /* draw with full alpha */
-  font_color[3] = 1.0f;
-
-  BLF_thumb_preview(filepath,
-                    thumb_str,
-                    i18n_thumb_str,
-                    ARRAY_SIZE(thumb_str),
-                    font_color,
-                    font_size,
-                    (uchar *)ibuf->rect,
-                    ibuf->x,
-                    ibuf->y,
-                    ibuf->channels);
+  if (!BLF_thumb_preview(
+          filename, (unsigned char *)ibuf->rect, ibuf->x, ibuf->y, ibuf->channels)) {
+    IMB_freeImBuf(ibuf);
+    ibuf = NULL;
+  }
 
   return ibuf;
 }
 
 bool IMB_thumb_load_font_get_hash(char *r_hash)
 {
-  char buf[1024];
-  char *str = buf;
-  size_t len = 0;
-
-  int draw_str_lines = ARRAY_SIZE(thumb_str);
-  int i;
-
-  uchar digest[16];
-
-  len += BLI_strncpy_rlen(str + len, THUMB_DEFAULT_HASH, sizeof(buf) - len);
-
-  for (i = 0; (i < draw_str_lines) && (len < sizeof(buf)); i++) {
-    len += BLI_strncpy_rlen(str + len,
-                            i18n_thumb_str[i] != NULL ? i18n_thumb_str[i] : thumb_str[i],
-                            sizeof(buf) - len);
-  }
-
-  BLI_hash_md5_buffer(str, len, digest);
+  unsigned char digest[16];
+  BLI_hash_md5_buffer(FONT_THUMB_VERSION, sizeof(FONT_THUMB_VERSION), digest);
   r_hash[0] = '\0';
   BLI_hash_md5_to_hexdigest(digest, r_hash);
 
diff --git a/source/blender/windowmanager/intern/wm_init_exit.c b/source/blender/windowmanager/intern/wm_init_exit.c
index 7ab2e67e4b6..e5ab876e75f 100644
--- a/source/blender/windowmanager/intern/wm_init_exit.c
+++ b/source/blender/windowmanager/intern/wm_init_exit.c
@@ -310,9 +310,6 @@ void WM_init(bContext *C, int argc, const char **argv)
   /* For file-system. Called here so can include user preference paths if needed. */
   ED_file_init();
 
-  /* That one is generated on demand, we need to be sure it's clear on init. */
-  IMB_thumb_clear_translations();
-
   if (!G.background) {
     GPU_render_begin();