Fix g_unichar_iswide for unassigned codepoints

There are a few blocks in Unicode (mainly ideographs)
which default to wide. These blocks are defined in the
header comment of EastAsianWidth.txt.

We have some tests which check that unassigned codepoints
in those blocks get reported as wide, so make sure we handle
this correctly.

glib/guniprop.c

@@ -477,6 +477,14 @@ g_unichar_iswide_bsearch (gunichar ch)
   return FALSE;
 }
 
+static const struct Interval default_wide_blocks[] = {
+  { 0x3400, 0x4dbf },
+  { 0x4e00, 0x9fff },
+  { 0xf900, 0xfaff },
+  { 0x20000, 0x2fffd },
+  { 0x30000, 0x3fffd }
+};
+
 /**
  * g_unichar_iswide:
  * @c: a Unicode character
@@ -491,8 +499,17 @@ g_unichar_iswide (gunichar c)
 {
   if (c < g_unicode_width_table_wide[0].start)
     return FALSE;
-  else
-    return g_unichar_iswide_bsearch (c);
+  else if (g_unichar_iswide_bsearch (c))
+    return TRUE;
+  else if (g_unichar_type (c) == G_UNICODE_UNASSIGNED &&
+           bsearch (GUINT_TO_POINTER (c),
+                    default_wide_blocks,
+                    G_N_ELEMENTS (default_wide_blocks),
+                    sizeof default_wide_blocks[0],
+                    interval_compare))
+    return TRUE;
+
+  return FALSE;
 }