Dictionary: disable fuzzy search when CJK words (#8458)

Fuzzy searching doesn't work with CJK text: with Japanese,
we get large numbers of useless results because sdcv
decides to strip off the wrong part of the word.
It seems unlikely that sdcv correctly handles Korean
or Chinese, so just disable fuzzy searching on all
CJK-containing word lookups.

frontend/apps/reader/modules/readerdictionary.lua

@@ -712,7 +712,6 @@ function ReaderDictionary:onShowDictionaryLookup()
 end
 
 function ReaderDictionary:rawSdcv(words, dict_names, fuzzy_search, lookup_progress_msg)
-    local all_results = {}
     -- Allow for two sdcv calls : one in the classic data/dict, and
     -- another one in data/dict_ext if it exists
     -- We could put in data/dict_ext dictionaries with a great number of words
@@ -728,6 +727,7 @@ function ReaderDictionary:rawSdcv(words, dict_names, fuzzy_search, lookup_progre
     if dictDirsEmpty(dict_dirs) then
         return false, nil
     end
+    local all_results = {}
     local lookup_cancelled = false
     for _, dict_dir in ipairs(dict_dirs) do
         if lookup_cancelled then
@@ -811,6 +811,22 @@ function ReaderDictionary:startSdcv(word, dict_names, fuzzy_search)
         end
     end
 
+    -- If every word contains a CJK character, every word candidate is
+    -- (probably) a CJK word. We don't want fuzzy searching in this case
+    -- because sdcv cannot handle CJK text properly when fuzzy searching (with
+    -- Japanese, it returns hundreds of useless results).
+    local shouldnt_fuzzy_search = true
+    for _, word in ipairs(words) do
+        if not util.hasCJKChar(word) then
+            shouldnt_fuzzy_search = false
+            break
+        end
+    end
+    if shouldnt_fuzzy_search then
+        logger.dbg("disabling fuzzy searching for all-CJK word search:", words)
+        fuzzy_search = false
+    end
+
     local lookup_cancelled, results = self:rawSdcv(words, dict_names, fuzzy_search, self.lookup_progress_msg or false)
     if results == nil then -- no dictionaries found
         return {