[gnome-characters] libgc: Perform full canonical decomposition for Hangul syllables

[Daiki Ueno <dueno src gnome org>]

commit 70e5e05a8f8cbf24a122680dbc943e90ec8fd4f9
Author: DaeHyun Sung <sungdh86+git gmail com>
Date:   Sun Nov 19 10:28:51 2017 +0100

    libgc: Perform full canonical decomposition for Hangul syllables
    
    Previously, the code finding related characters only took into account
    of composed characters built from a base character and combining
    characters (such as Latin, Hiragana, and Katakana).  However, Hangul
    syllables are composed of two or three Hangul jamo characters, all of
    which should be considered as a base character.  This patch handles
    that case properly.
    
    For the implementation, uc_canonical_decomposition() is not capable of
    decomposing Hangul syllables.  Instead of the function, this patch
    uses u32_normalize() with UNINORM_NFD, as suggested by Bruno Haible in:
    https://lists.gnu.org/archive/html/bug-libunistring/2017-11/msg00002.html
    
    https://bugzilla.gnome.org/show_bug.cgi?id=790391

 lib/gc.c |   69 +++++++++++++++++++++++++++++++++++++++++--------------------
 1 files changed, 46 insertions(+), 23 deletions(-)
---
diff --git a/lib/gc.c b/lib/gc.c
index 46bb0df..ad27d27 100644
--- a/lib/gc.c
+++ b/lib/gc.c
@@ -839,34 +839,57 @@ populate_related_characters (GcCharacterIter *iter)
 
   if (uc_is_general_category (iter->uc, UC_CATEGORY_L))
     {
-      ucs4_t decomposition[UC_DECOMPOSITION_MAX_LENGTH];
-      int decomposition_length;
-      ucs4_t decomposition_base;
       const uc_script_t *script;
 
-      decomposition_length =
-        uc_canonical_decomposition (iter->uc, decomposition);
-      if (decomposition_length > 0)
-        {
-          decomposition_base = decomposition[0];
-          if (decomposition_base != iter->uc)
-            g_array_append_val (result, decomposition_base);
-        }
-      else
-        decomposition_base = iter->uc;
-
       script = uc_script (iter->uc);
       if (script)
         {
-          if (strcmp (script->name, "Latin") == 0)
-            add_composited (result, decomposition_base,
-                            latin_blocks, latin_block_count);
-          else if (strcmp (script->name, "Hiragana") == 0)
-            add_composited (result, decomposition_base,
-                            hiragana_blocks, hiragana_block_count);
-          else if (strcmp (script->name, "Katakana") == 0)
-            add_composited (result, decomposition_base,
-                            katakana_blocks, katakana_block_count);
+          if (strcmp (script->name, "Hangul") == 0)
+            {
+              /* For Hangul, do full canonical decomposition.  */
+              uint32_t s = (uint32_t) iter->uc;
+              uint32_t decomposition[3];
+              size_t decomposition_length = 3;
+
+              if (u32_normalize (UNINORM_NFD, &s, 1,
+                                 decomposition, &decomposition_length))
+                for (i = 0; i < decomposition_length; i++)
+                  {
+                    ucs4_t hangul_jamo = (ucs4_t) decomposition[i];
+                    g_array_append_val (result, hangul_jamo);
+                  }
+            }
+          else
+            {
+              /* For Latin, Hiragana, and Katakana, first find out the
+                 base character, and then find all composited
+                 characters whose base character is the one identified
+                 by the first step.  */
+              ucs4_t decomposition[UC_DECOMPOSITION_MAX_LENGTH];
+              int decomposition_length;
+              ucs4_t decomposition_base;
+
+              decomposition_length =
+                uc_canonical_decomposition (iter->uc, decomposition);
+              if (decomposition_length > 0)
+                {
+                  decomposition_base = decomposition[0];
+                  if (decomposition_base != iter->uc)
+                    g_array_append_val (result, decomposition_base);
+                }
+              else
+                decomposition_base = iter->uc;
+
+              if (strcmp (script->name, "Latin") == 0)
+                add_composited (result, decomposition_base,
+                                latin_blocks, latin_block_count);
+              else if (strcmp (script->name, "Hiragana") == 0)
+                add_composited (result, decomposition_base,
+                                hiragana_blocks, hiragana_block_count);
+              else if (strcmp (script->name, "Katakana") == 0)
+                add_composited (result, decomposition_base,
+                                katakana_blocks, katakana_block_count);
+            }
         }
     }