[[ Grapheme Handling ]] Implement grapheme cluster break rules

livecodeali · livecodeali · commit 6dabce12d1ee · 2016-01-19T12:22:00.000Z
diff --git a/libfoundation/include/foundation-unicode.h b/libfoundation/include/foundation-unicode.h
@@ -716,6 +716,8 @@ inline uinteger_t MCUnicodeMapFromNative_ISO8859_1(char_t p_native)
 
 ////////////////////////////////////////////////////////////////////////////////
 
+bool MCUnicodeIsGraphemeClusterBoundary(codepoint_t p_left, codepoint_t p_right);
 
+////////////////////////////////////////////////////////////////////////////////
 
 #endif  /* ifndef __MC_FOUNDATION_UNICODE__ */
diff --git a/libfoundation/src/foundation-unicode.cpp b/libfoundation/src/foundation-unicode.cpp
@@ -2407,3 +2407,97 @@ bool MCUnicodeWildcardMatch(const void *source_chars, uindex_t source_length, bo
     
     return true;
 }
+
+////////////////////////////////////////////////////////////////////////////////
+
+// Implement rules GB 6 - 8 based on Hangul syllable type
+static bool __MCUnicodeIsHangulClusterBoundary(int32_t p_left, int32_t p_right)
+{
+    switch (p_left)
+    {
+        case U_GCB_L:
+            return p_right == U_GCB_T;
+        case U_GCB_LV:
+        case U_GCB_V:
+            return p_right != U_GCB_V && p_right != U_GCB_T;
+        case U_GCB_LVT:
+        case U_GCB_T:
+            return p_right != U_GCB_T;
+        default:
+            MCUnreachable();
+    }
+}
+
+static bool __MCUnicodeIsControl(int32_t p_gcb)
+{
+    return p_gcb == U_GCB_CR || p_gcb == U_GCB_LF || p_gcb == U_GCB_CONTROL;
+}
+
+static bool __MCUnicodeIsHangulSyllable(int32_t p_gcb)
+{
+    switch (p_gcb)
+    {
+        case U_GCB_L:
+        case U_GCB_LV:
+        case U_GCB_LVT:
+        case U_GCB_T:
+        case U_GCB_V:
+            return true;
+        default:
+            break;
+    }
+    
+    return false;
+}
+
+bool MCUnicodeIsGraphemeClusterBoundary(codepoint_t p_left, codepoint_t p_right)
+{
+    int32_t t_left_gcb;
+    t_left_gcb = MCUnicodeGetIntegerProperty(p_left, kMCUnicodePropertyGraphemeClusterBreak);
+    
+    int32_t t_right_gcb;
+    t_right_gcb = MCUnicodeGetIntegerProperty(p_right, kMCUnicodePropertyGraphemeClusterBreak);
+    
+    // We treat CR LF as 2 graphemes, contrary to GB 3
+    /*
+    if (t_left_gcb == U_GCB_CR && t_right_gcb == U_GCB_LF)
+        return false;
+    */
+    
+    // GB 4: Break after controls
+    if (__MCUnicodeIsControl(t_left_gcb))
+        return true;
+    
+    // GB 5: Break before controls
+    if (__MCUnicodeIsControl(t_right_gcb))
+        return true;
+    
+    // GB 6 - 8: Do not break Hangul syllable sequences.
+    if (__MCUnicodeIsHangulSyllable(t_left_gcb) && __MCUnicodeIsHangulSyllable(t_right_gcb))
+    {
+        if (!__MCUnicodeIsHangulClusterBoundary(t_left_gcb, t_right_gcb))
+            return false;
+    }
+    
+    // GB 8a: Do not break between regional indicator symbols.
+    if (t_left_gcb == U_GCB_REGIONAL_INDICATOR && t_right_gcb == U_GCB_REGIONAL_INDICATOR)
+        return false;
+    
+    // GB 9: Do not break before extending characters.
+    if (t_right_gcb == U_GCB_EXTEND)
+        return false;
+
+    // GB 9a: Do not break before SpacingMarks
+    if (t_right_gcb == U_GCB_SPACING_MARK)
+        return false;
+
+    // GB 9b: Do not break after Prepend characters
+    if (t_left_gcb == U_GCB_PREPEND)
+        return false;
+    
+    // GB 10: Otherwise, break everywhere.
+    return true;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
